II. CONFERENCES

FISH AND SHELLFISH CULTURE IN THE LIM CANAL PRESENT AND FUTURE PILOT FARM REARING*

MR. Z. FILIC, Ms. M. HRS-BRENKO and I. IVANCIC

* Remark : The article has been published in “Food and Development”, edited in “La Yougoslavie en developpement”.

The exploitation of marine resources is becoming a technique of the present,due to the lack of energy. Apart from the fact that the sea is exploited, so as to obtain fuel, liquid and gas minerals, it has also become a food source. of much greater importance. In this report, we shall give a description of the technological aspects and the rearing techniques employed in the Lim Canal, as a possible example for intensive rearing in our part of the Adriatic.

1. INTRODUCTION

In comparison to the exploitation of land, the aquatic space area is rather poorly exploited, especially as the latter makes up 71 % of the terrestrial surface area (rivers, lakes, seas and oceans). While land exploitation. Only the surface is employed for production, in the sea the whole space area can be exploited, in other words, a three dimension system. It has been calculated that 1 to 1,5 of food comes from the sea while the rest is obtained from the land (1). In 1984, the production of consumable organisms from aquatic environments was 76 million ton (2). There exists two means if increasing the production and of satisfying the market requirement in sea protein : the promotion and intensification of fishing and the production of marine organisms through aquaculture (3). The problems arising in fishing are well known and it is not easy to introduce its intensification, as apart from the technological and technical problems and those of organization (the fishing activity), the principle obstacle is, in fact, the limited resources of the sea, due to the fact that the fishing zones bear very severe and complicated laws. Fishing, by which means 90 % of consumable organisms are product, has significant limits of development: Thus, we must increase the production through rational sea-exploitation, the most effective being fishculture with the employment of intensive rearing techniques in fresh and marine water. According to PILLAY (4), through aquaculture (fresh and brackish water), 67 % of fish, 16.5 % of molluscs, 16 % of algae and 0.5 % of crabs are produced.

Unpolluted protected coastal zones are reserved to rear consumable organisms for commercial purposes. With as objective an economic exploitation and the conservation of the quality of aquatic environment, the simultaneous rearing of two or several species such as fish-fish, fish-crustaceans and other combinations are employed more and more to-day. It has been remarked that the shells reared in polyculture, with different species of fish or shells, reach a commercial value more quickly and present a better quality meat. This is due to the surplus phytoplanktonic organisms and dissolved waste matter (faeces) from fish, plus the nutritive salts after decomposition of the food uneaten by the fish. In this way, the shells maintain, a biological and chemical balance of the aquatic environment, there where intensive rearing is employed. A permanent control of the organisms reared and of the aquatic environment is advisable, especially, in tanks and shallow closed -in regions with feeble exchange of water masses.

Our coast being well indented, with more than 6, 000 km of coastal strips, offers real possibilities to practice the mass rearing of different species of marine organisms which can satisfy our own requirements as well as those of exportation.

This sea-food production was introduced into the economy of our country. Shellfish rearing, after a long stagnation (300 – 500 t/y) shows a tendency to increase the production, with 1,200 ton in 1984 and 1985. (2, Statistic Institute of the Socialist Republic of Croatia). Commercial fish rearing (sea-bass, trout, salmon) was started in several localities along the coastline and on parallel intensive research was carried out on fish, shells and crabs while taking into account their ecology, their physiology and the rearing technologies (5, 6).

The Lim Canal, one of our prired regions has been dedicated in mussel and oyster rearing for a long time. Some years ago, after the successful results obtained with the experimental rearing of sea-bass (7), the building of a pilot farm was undertaken in the interior part of the canal, along with the research of the biological characteristics of the fish and shells, the fundamental hydrographical, chemical, and biological parameters of the marine environment (8). The pursuit of the control of the organisms and of the marine environment is scheduled. This has been included within the next national and international research programme

This report will not only take into account the description of the rearing techniques employed for fish and shellfish, but also, the actual state of the organisms in culture and of the environment, in comparing present data with that obtained through anterior research works.

2. THE LIM CANAL AS A REARING SITE

The Lim Canal was decreed as a special sea-reserve for intensive shellfish and fish culture. It is located on the West coast of Istria to the North of ROVINJ and measured around 11 km. The banks of the Canal are indented and covered with autochthonal vegetation. The width at the inlet is around 160 m and decreases little by little up to the extremity. The depth of one third of the canal is around 34 m while at its extremity it descends to 5 m.

The rearing site at present, occupies the interior half of the canal (Figure 1) and active rearing is carried out at surface level and at a depth of 3 to 4 m. In the shallow part of the Canal, can be seen fixed parts, consisting of a series of wooden poles which are embedded into the bottom soil and linked to one another by means of ropes, on which the shellfish rearing takes place (Ro “SKOLJKA”, POREC) (Figure 2). Towards the center of Canal, in the deep parts (more than 10 m in depth) is found the parks-floating longlines (series of plastic floats attached to one another by means of “Atlas” ropes (Figure 3). Next to the floating parks, we find the cages with fish nets, on the outside of which hang strings of beads (mussels) and plastic baskets (oysters) (RO “MIRNA”, ROVINJ) (Figure 7).

3. SHELLFISH CULTURE

It was in 1888 that oyster rearing on beechwood branches was first started in the inner part of the Canal. The success in the production of oysters (up to 7 million oyster/year) reared in floating parks, was ensured during the period between the two world wars (9). Towards the end of 1950, mussel rearing was introduced into the Lim Canal and other Adriatic sites along the coast and a greater production has always been obtained when compared to oysters, (2, 10). An important production of shells from the Lim Canal was finally obtained in 1984, 600 tons of mussels and 150 tons of oysters (Statistic Institute of the Socialist republic of Croatia).

3.1. The technology employed in mussel rearing, Mytilus gallo-provincialis

The rearing of mussels begins with the collection of spat from natural environments by means of collectors (flexible plaited ropes). The ropes are placed horizontally between the poles or the floats, in the park, at a depth of 10 to 30 cm below the surface of the sea (Figure 3 c).

Intensive collection of mussels lasts from March to the end of May (11). In Autumn, small mussels (2 – 4 cm in length are detached and threaded onto plastic tube-like nets (Figure 4). In the Lim Canal, the mussels reach commercial size in 1½ to 2 years (8, 12). It is possible to cultivate 8 to 15 kg of commercial size mussels in a tube-like net of 1,7 to 2 meters in length (figures 2 a, 4 b). Mortality is insignifiant during the rearing of the mussels but however it does increase in the hot season.

3.2. The technology employed in oyster rearing, Ostrea edulis

Bundles of branches (10 to 20 branches) are employed for the capture of oysters. These are connected to one another by means of nylon strings or beech or elm wood branches (figure 4 c, d). To-day, plastic plates are also employed (20 × 20 cm) through which a nylon rope is threaded and this is connected to the floting ropes or to the sides of the cages (Figures 3 a – 4 c).

The season for spat oyster collection lasts from June to October (11). If the collection is poor, the spat oysters are left on the branches which will be cut up into sticks of 20 to 30 cm and which are threaded onto a nylon string (Figure 4 F). When the collection is good, the oysters are selected out and detached from the branches or plates, and they are then cemented or placed into plastic baskets. The oysters are cemented, with quick setting cement, either to ropes or onto large strips of netting, in twos or in fours or again in twos at the end of each branch (figure 4 g, h, i, j). Oysters can also be cemented to nylon ropes which are attached to the park (Figure 2, b, c, d). The baskets containing the shells are suspended by means of ropes from the floating park, one by one or several at a time, one on top of the other (15) (Figure 3 b). Our oysters reach commercial size in 2 to 2 ½ years while the oyster reaches this size in less time. The oyster mortalities can reach up to % and from time to time, in certain sites, up to 70 % (12, 14). At the present, in our sites, a sufficient amount of spat oysters, can be collected for commercial rearing. Nevertheless, when necessary, the existing capacities of the fish hatchery can be employed to rear young oysters (15).

The shellfish culture methods carried out in the Lim Canal are also employed in our other rearing centers with some slight modifications. The perspectives are good for the development of shellfish culture, thanks to the advantage that we avail of and to the improved technologies in rearing, especially mussels, alone or with fish, leads to an increase in sea food along with an assured marketing supply for home and foreign markets, and the processing industry. The technology of oyster rearing which is expensive and more complicated, requires development in certain technological procedures so as to increase production.

4. THE PARAMETERS FOR THE CONTROL OF THE REARING ENVIRONMENT AND OF THE MUSSELS

In modern rearing, the knowledge of the basic physical, chemical and biological parameters of the aquatic world is absolutely necessary so as to control and adapt the rearing to the environmental conditions.

In addition to the standard hydrobiological measures for the requirements of the rearing and for the quality control of the organisms, it is advisable to control the quality of the water and of the commercial shells, as there is a potential danger of pollution due to the faecal bacteria fresh water.

4.1. Hydrography of the Lim Canal

The Lim Canal is a site which has important fresh water intakes. The fresh water flowing into it generally comes from shallow coastal sources ; the underground water of the central part of Western Istria, along with biologicaly purified waste water from restaurants located on the banks of the Canal. The influence of the fresh water is unpredictable and very changeable, from surface and time points of view, but generally this concerns only the upper layers (less the 2,5 m deep) where important variations in parameters and in the rearing have been remarked.

The hydrographical and chemical characteristics in the other side of the water column are much more homogeneous and undergo fewer variations in this layer, the hydrographical and chemical parameters vary in the characteristic divergences for oligotrophic coastal waters in ROVINJ (Table 1). However, in the superior layer of the Canal, when the sea water is freshened, the nitrated, the nitrate concentrations are rather high. The distribution of the superficial nitrate concentrations, in June 1986 (L-1 – L-5) indicated that this increase, remarked in the whole canal is greater in the last third where the salinity values at surface level are at their lowest level (Figure 8). However, in August 1986, the nitrate concentrations were equalled, even if they remained a little superior in the surface layer. The drop in the surface salinity, which was remarked in August, in comparison to the inferior layers, was not provoked by fresh water inflows, but was the consequence of a decrease in salinity, which at that period, was typical in the whole North Adriatic. The analysis of the report which has been followed up for years, between the salinity and the nitrate concentrations in the surface layer confirmed that the greatest part of these salts come from fresh water. The estimation of the nitrate concentration in the fresh waters which flow into the Lim Canal also shows that the quantity of these waters has greatly increased when compared to previous periods. This shows that the superior concentrations of nitrate in fresh water, recently remarked, are of anthropogenic origin. This, has been confirmed by the periodical apparition of a green superficial layer, provoked by the blooming of fresh water algae (FILIPIC, not edited). This has not been remarked for ammonia, nitrite and orthophosphate, which have the same divergences in concentrations in the superior layer as in the other part of the water column (Table 1).

4.2. The quality control of shells

To control the quality of the shells (meat content), we employ mussels (because they intensively filtrate sea water) of commercial size (between 55 and 65 cm in length) which at the end of Summer, reach a maximum value of Condition index (8). At the end of July, strings of commercial mussels were placed into 9 different sites, in the canal (Figure 1). Mussels, at points 5 and 6, were attached to the fish cages. We wanted to find out if the condition index for the mussel, increased on account of the fish food. The condition index is calculated by means of the volumetric method (20). Over a relatively short period (1.5 mois), the C.1 of the mussels located near the fish and those far away showed no difference (Table 2), as with the value obtained before (HRS BRENKO, 1967 ; BOHAC i sur, 1984).

The parameters of the marine environment and of the mussels did not demonstrate great changes during the period of stratification in Summer (June – August 1985). However, it is advisable to contain the same rearing capacity while assuring a permanent control of the marine environment which can be unpredictable and at certain periods, unexpected changes can have catastrophic consequences.

5. FISH REARING

Fish rearing, dates back to ancient times. The first doctorate written on aquaculture was presented in 475 B C by FAN LI (22, 23). The traditional extensive and semi-intensive fish rearing takes place in lagoons (Valliculture), near VENICE, in canals where many different species are reared: mullet (Mugil sp), Sea-bream (Sparus aurata), sea-bass (Dicentrarchus labrax) and eel (Anguilla anguilla) and according to RIEWAGEN (24) a production of 200 kg/year is obtained.

In the seventies, we witnessed the rapid development of fish rearing in the sea, with the introduction of cage rearing for salmonidae. The modern cages of to-day were first introduced in 1986, in Scotland, the best results were obtained by Japan with the yellowtail (Seriola quinqueradiata) and by Norway with the salmon (25, 26). In Norway, already 15,000 t/year of Salmonidae are produced and in 1990, it is scheduled that a production of 20,000 ton of trout and salmon will be obtained (Onchorhinchus kisutch, Salmo gairdneri, S. salar (27, 28).

Following the intensive research carried out in Yugoslavia, very important experiments in sea-bass cage rearing were performed at the end of the seventies and the beginning of the eighties, when the commercial rearing of sea-bass was introduced into the Lim Canal and at the Lamljani near ZADAR (3, 29, 30, 31). At the mouth of the river Krk and in the Bay of Zrnovnica, trout rearing was introduced, followed by salmon rearing (32, 33). At ZADAR, fish rearing in cages rapidly increased due, to the opening of the industrial hatchery for fish in NIN (34).

5.1. Cage-rearing of fish as a perspective for rearing in the Adriatic

Rapid progress was made in marine fish rearing after the first successful results obtained with the controlled reproduction of sea-bass and the juvenile rearing in France and Italy, at the beginning of the seventies (35, 36, 37).

In 1976, the first successes were obtained with the induced spawning of sea-bass, carried out at the Sea-research Center in ROVINJ, and the complete experimental hatchery production and cage rearing in the Lim Canal occured in 1978 (3).

5.2. Pilot farm for sea-bass rearing in the Lim Canal

As an example of cage rearing for marine fish in the Adriatic, let us consider the technical data on the sea-bass rearing farms which are employed by the marinculture Center of the“MIRNA”Society in ROVINJ, in the Lim Canal. The farms are built in accordance with the projects by FILIC/PLESE (1983) and FILIC/LEDERER (1984) (Figures 6, 7).

The typical characteristic of these plat-form cages is that they are very robust which makes them expensive. This is considered necessary for security reasons, as when a complete production is carried out, the value of the fish in the cages is 5 to 7 times greater than the value of each plat-form. The cages and farm, due to their form, construction and materials are adapted to the rearing technology employed for sea-bass and to the site.

TECHNICAL AND TECHNOLOGICAL CHARACTERISTICS OF THE FARM

The cages are formed of 4 segments which can be employed separately, and can be easily separated from the farm (Figures 6, 7). In addition, to its rectangular shape, the principal characteristic of the “MIRNA” farm model is its canals (free spaces between the segments). We think that this is important on a rearing with closed bays, where currents are feeble (4 to 5 cm/sec). In such conditions, the maximum quantity of sea-bass, according to the experiments carried out in the Lim Canal, is around 8 to 10 kg/m³. This is a fish, rearing where the environment is no different (surplus metabolites) from the marine environment outside the cages. The same density is obtained in cage rearings in Southern France (This pond) and in Japan (38, 39).

To obtain a continuous production of fish, over a two year cycle, it is necessary to have at disposal two of these systems for an annual production of 18 to 27 ton. The farm is equipped with a watchman's quarters, a warehouse and a platform pier, where the work can be carried out. Three people are quite sufficient to take charge of the fish rearing of the farm.

A particularly interesting possibility is the combination of shells and fish in rearing (polyculture) (Figure 7) which rationalizes time, space and work and leads to a quicker depreciation of the rearing facilities and as has been specified here above in the introduction, this type of rearing also improves the quality of the marine environment. The negative side of polyculture is that spat shells can catch on to the nets, especially when the environment is one for collection.

In addition to large system rearing, linked with industrial hatchery rearing, the farms can be individually, privately or cooperatively owned, all along the whole coast. The fry can be fished, or obtained from large hatcheries. At present we have but one hatchery in operation and it is located at NIN, while another one is being built in the Lim Canal.

The farms must be implanted in good sites and when possible, they must answer the following requirements : protection from waves and winds, good currents and deep bottoms.

This is why, sites of good potential required, their hydrographical and biological characteristics defined and the most favourable place determined.

An example of this space planning is shown in Figure 8, where shell culture is carried out in the shallow eutrophic part of the Lim Canal, and the fish rearing, in the deepest and vastest part, with the best water exchange. This space planning, scheduled for rearing, is the result among other things, of the previous ecological research of the site and the verifications of the technical and technological parameters of the rearing.

During the commercial rearing, it is essential that the parameters of the rearing environment be surveyed so as to remark possible changes before its too late and which could, in the later case, decrease the efficiency of the rearing (FUJIVA, 1976; LUCET et al., 1984).

We consider that the implantation of such a rearing or a similiar one along the coast, will lead to the more rapid development in sea-fish and shell rearing in Yugoslavia.

6. CONCLUSIONS AND RECOMMENDATIONS

Within the frame of sea fishing, in addition to the fishing development, based on the rational exploitation of fish populations, the rearing of sea organisms must also be developed and particularly fish and shellfish culture.

Fish and shellfish rearing represent a programmed and controlled view of fishing which could, trough its production, reach the results obtained in fresh water fishing (around 40,000 t/year).

The implementation of a rearing programme is possible, as far as, our knowledge and the technologies employed, are concerned. However, for this, it is necessary to organize an energetic economical and scientific public action for the promotion of the rearing (based on the economic indicators) by creating special financial organization conditions along with other conditions of development.

In addition to that, two important resources must be available, the human and natural resource. Thorough the intermediary of science, public instruction and economy, an efficient collaboration must be established, so as to form experts who will be capable of taking in charge, the production and development. The principal factor which limits the development, is the unavailability of marine sites of quality, which must be quickly protected and the harmonization of conflicting interests (urban environments, tourism, industry, rearing). Tourism and rearing can, for example, be directly complementary to one another as producer and consumer of high quality food and thus decrease the present importation of around 20,000 ton of white fish.

In addition to the direct financial effects of the increase in the consumption of fish and shellfish, there are important socio-economical and health reasons for the most rapid development of fishculture. Fish and shellfish are a very wholesome food and from a nutrition view-point a complete food which contains all the necessary materials for the development of the human organism, thus their consumption will lead to an improvement in the health of the population.

By encouraging fishculture and creating mass rearings, we shall influence the stabilization and improvement of the socio-economical and demographical structures of the coastal populations and Islanders.

Fish rearing, is an annual activity and not a seasonal one, it will thus decrease a part of the migrations (seasonal) of populations.

As fish rearing is a biotechnical activity in particular it is very complex and requires the permanent development of the rearing techniques which will influence the general level of instruction of the population concerned by fish rearing.

To conclude, by linking the economic existance of the population with rearing, people shall realize the necessity of conservation, promotion and rational exploitation of a healthy marine environment.

We think that this is absolutely necessary, not only because the Adriatic is considered as the “most beautiful sea”, but because we wish to save it from degradation and preserve it for future generations as we have not inherited this natural patrimony only for its exploitation during our short biological existance.

Figure 1 : Site of the Lim Canal Rearing site L-1 – L-5 Hydrography, 1 – 9 Mussel (Condition index)

Figure 2 : Fixed park (Italian)

Figure 3 - Part of a rearing park - Line

Figure 4: Shellfish culture combined with fish rearing

Figure 5: Pilot-farm for marine fishculture, “MIRNA” model.

Figure 6: General view of the farm
Legend

1. Elements of the farm
2. Warehouse
3. watchman's quarters
4. Shed
5. Wharf
6. Power press
7. Feeders
8. Stairs
9. Signal lights
10. Rails
11. Rope connections
12. Armouring for the fixation of the nets
13. Anchors and anchor armouring

Figure 7: Presentation of the urbanization of the rearing site in the Lim Canal

Figure 8: Distribution of the salinity and nitrate values in the site of the Lim Canal in June and August 1986.

DESCRIPTION OF THE FIGURES

Figure 1 : Site of the Lim Canal. Rearing site, Place from where the samples are taken:L-1 – L-5 (Hydrography), 1–9 (Condition index of the mussels).

Figure 2 : Fixed park (Italian make) (a - netbag with mussels, b, c, d - Cemented oysters).

Figure 3 : Floating park (a - oyster collector, b - oyster basket, c-mussel collector).

Figure 4 : Culture during the rearing of the shell (a, b, - mussels in the net-bag, c, d, e, - oyster collectors, f - spat oysters on branches, g, h, i, j - cemented oysters).

Figure 5 : Pilot farm of marine fishculture - “MIRNA” model (1 - watchman quarters and warehouse, 2 - Platform, 3 - boat, 4 - cages)

Figure 6 : General view of the farm (1 - elements of the farm, 2 - Warehouse, 3 - Watchman quarters, 4 - Shed, 5 - Wharf, 6 - Power press, 7 - Feeders, 8 - stairs, 9 - Signal lights, 10 - Rails, 11 - Rope-connections, 12 - Armouring for the fixation of the nets, 13 - Anchors and anchor armouring

Figure 7 : Presentation of the urbanization of the rearing site in the Lim Canal.

Table 1 - Value of the fundamental oceanographical parameters and of the nutritive salts in the Lim Canal and on the coastal region of ROVINJ.

+ Sal (‰) salinity, 0₂ % of oxygen saturation, PO₄ Ortophosphate,NH₄ Ammonia, NO₂ nitrate, NO₃ Nitrate, u μmol. 1^-1.

+ Data obtained from 1978 to 1985 on part 4 of the Lim Canal
1 - Surface layer, 2 - Rest of the water column.

- Data obtained from 1978 to 1983 on 8 places along the coast of ROVINJ, including the site in front of the port of ROVINJ.
1. Surface layer, 2 - Rest of the water column.

Table 2 - Biometrical characteristics and the condition index of mussels (between 55 and 65 mm in length), in the Lim Canal on the 21 August 1986.

⁺ The samples were taken from the park as the strings had disappeared.

BIBLIOGRAPHY

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MARINE FISH FARMING - THE C E N M A R EXPERIENCE

Sea-bass can be considered as the first marine fish species successfully cultured from egg to market size in the Mediterranean region. A young company, CENMAR, is amongst the first to have mastered the reproduction and intensive culture of sea-bass on a commercial scale. An outline of the steps leading to this, and a presentation of today's involvment in mariculture activities will be given.

HISTORY

In 1976, the Institute for Biotechnology in ZADAR began the first trials with cage culture for sea-bass employing imported hatchery fry. Results were good; the fish reached 300 g after 18 months culture, and the survival rate was 70 %. The trials were repeated successfully over the following years, with initial stocking of cages limited to a maximum of 50,000 fry of 3 cm due to low availability. Being one of the most valuable finfish in the Mediterranean (retailed at around 20 US dollars), sea-bass farming became an attractive financial venture. The Yugoslavian coastline with hundreds of Islands and deep bays is ideally suited for intensive cage culture both at industrial and family scale.

A prerequiste for the expansion of this activity is to ensure a reliable and steady supply of fry. To secure this, the construction of a hatchery was obligatory. A temporary company was formed to organize and carry out the construction of this building.

HATCHERY CONSTRUCTION

In 1980, the projects for a hatchery with a capacity of 1,400,000 sea-bass fry were completed. It was not until 1982 that the levelling of the site began, after all funds (loans and credits) were secured.

Constructing the hatchery and equipping it took almost a year and a half. This also involved adaptations and redesigning of original plans during the implementation. By Summer 1983: the building works were terminated, and the first culture phases of phytoplankton began. In January 1984, the hatchery was technologically functional and the first fish eggs were seeded. The hatchery was constructed and equipped entirely with domestic materials.

At the same time, CENMAR became an independant company. As such, it is entirely self-financed.

HATCHERY OUTLINE

The hatchery building covers an area of 5,000 m² and it is the largest marine hatchery in Europe. It is located within a reasonably-insulated building, to minimize heat loss during winter months. The sea water is heated above 20° C and recirculated within the hatchery for faster growth and energy conservation.

Operating the hatchery (totalizing 250 tanks) requires a strict control on sanitary and water quality parameters, timely balanced feeding, and a reliable live food culture. This can be achieved only by employing dependable manpower at the work and guidance/supervision levels. It also requires standby auxiliary equipment, such as pumps and electricity generators in the event of breakdowns, even of very brief duration.

PRODUCTION RESULTS

The first production season was completed in July 1984, with a production of 1,100,000 fry, which were almost all stocked in our own cages. During this running-in season, assistance was obtained from the F.A.O (Technical Cooperation Programme) through expert help and equipment for the chemistry and pathology laboratories.

The following year production increased to 2 million fry and another species, sea-bream, was included. This was a major step forward in our effort to double the hatchery production capacity through constant technological improvments.

It is planned to achieve was without any major new investments but through a more intensive exploitation and the introduction of other fish species.

A detailed analysis of the first two production seasons was made and the strategies for further development set up.

ONGROWING EXPERIENCE

On parallel to the invitation of the hatchery project, the experimental work with cage culture continued.

In 1980, a pilot facility was set up at a new location, in Lamjana Bay on the island of Ugljan. This site was chosen for its more favourable sea water temperature range (min, 11° C, max. 25° C), better water circulation, lower organic productivity and reasonable protection from high seas.

During this pilot phase (1980 – 1984), a number of biotechnological parameters affecting marine fish culture were investigated.

CAGE DESIGN

Fourteen different types of cages were tested thoroughly for characteristics of stability, wave-resistance, corrosion-resistance, ease of maintenance and repair, easy assembly, compatibility with husbandry requirements (communication between cages, net changing, safety). by the end of 1983, it was not difficult to decide on the present model for the merit of sea-worthiness coupled with confortable use and low maintenance. The cage platform is constructed with a modular frame of hot-galvanised tubes, styrofoam floats, wooden walkway all around, and can accomodate either one net of 9.5 × 9.5 m or four nets of 4.5 ×4.5 m. It was manufactured in a local shipyard to our specifications.

BIOTECHNOLOGICAL ASPECTS

A variety of fish species were cultured from hatchery and wild fry including Sparus aurata, Puntazzo puntazzo, Mugilidae, Diplodus sargus, Boops salpa, Diplodus vulgaris, Lithognathus mormyrus, apart from the initial Dicentrarchus labrax. Of the high value species, Puntazzo show the best growth and survival in cages, followed by S. aurata and D. labrax.

Both dry and wet feeds were tested, and e number of dry fees compared. There is often a greater variation between batches from the same producer than between different producers. This is shown by a mass mortality (over 80 %) of fish, in Summer 1982. The cause was a batch of food from a producer who had previously supplied a good quality product.

Fish density in cages is a fundamental factor in determining the bio-economy of a culture operation. We found that crowding fish to densities of 20 kg/m³ results in decreased growth rate and feed conversion efficiency. Pathological problems and risk of oxygen depletion increase when nets became fouled and in period of calm weather with little water circulation.

The major cause of mortality in cages were outbreaks of Vibrio. These were most pronounced at the beginning of Summer and in Autumn, affecting year old fish. 40% of the stock was sometimes lost. A Vibrio vaccine was tested, buy by 1984, a more effective treatment was found; properly timed prevention with sulphadrugs. The effectiveness of this is increased by good husbandry; varied food, clean nets, low stocking densities. Losses from Vibrio are now below 5 %.

The cage culture ongrowing complex was completed in 1984. The shore facility comprises a building (1,000 m²), housing a 50 ton freezer unit, a dry food store, net store, net repair shop, workshop, laboratory, offices, and social rooms. Ahead, is a jetty for landing boats, cleaning nets, feed preparation section, auxiliary services.

Presently, we have 150 cage platforms of 10 × 10 m, situated in two different locations of the bay, one for each year class. A third location will also be exploited, giving flexibility and possibility to allow regeneration of the sea substrate. The presence of almost 400 ton fish in the bay and the food input has led to the local increase in organic productivity, which is exploited by increased shellfish and wild fish biomass.

STAFFING

CENMAR employs ten full-time mariculture specialists. The production manager is backed by a hatchery and a cage manager. The hatchery is divided into four main sections: live food, reproduction and pathology, larvae and fry, water circulation quality, each headed by one specialist. The cage unit similarly has a fish production and pathology specialist. The research and development section is being formed, and presently employs one feed specialist. A minimum of two trainees are always employed, allowing key to undertake research and development activities.

COMMERCIAL ASPECTS

Market size fish are in preference sold abroad because of the higher prices obtained than on the domestic market. and the need to obtain foreign currency so to import dry foods and other materials. Apart from market size fish, we have export and import trade of live fish eggs, larvae and fry.

New regulations on foreign investments in Yugoslavia do not limit foreign participation in financing and management. The low cost of lobour and materials, coupled with a good technological basis, expertize, and favourable environmental conditions make the Yugoslavian coast an attractive site for joint ventures in mariculture production. One joint venture arrangement with a Norwegian company is already under way.

MARINE FISH HATCHERIES
SITE - PRODUCTION PROGRAMME - DIMENSIONING

Mr. L. BERG

1. SITE CHOICE

In most cases, the choice of the site for the construction of a hatchery is directly related with the existence or planning and relative requirements of an on-growing farm (sea-cages, extensive lagoon rearing, integrated intensive rearing projects).

Therefore the criteria for the choice of the site mostly depend on the on-growing stage. Criteria generally considered for the site choice of a marine hatchery are as following:

1.1 Socio-economic aspects

This is important in the particular case of an integrated project : hatchery + on-growing. Any new aquaculture activity must be perfectly adapted to the economic and social context of the country and area chosen for the project.

The market possibility and conditions must be taken into account in relation with the site :

-   Transport possibilities and costs to local fish markets or to foreign markets

-   Possibility of direct sale to consumers (I. E. restaurants)

-   Sale prices of the fish produced

-   Daily/Weekly/monthly quantities that can be absorbed by the market

-   Impact of costs of raw-materials and labour.

1.2. Water supply and water quality

The water quality is a basic factor for site choice and the productivity of a hatchery. The chemical and physical properties of the water directly influence the results of hatchery productions as well as the production costs of fingerlings. For the reproduction of marine species, marine water is needed, especially for gonadal maturation and so us to ensure high quality sexual products (fertilized and viable eggs).

Three kinds of water supply can be found, on general :

-   Direct supply from the sea

-   Supply from a marine lagoon

-   supply from an underground salt water sheet.

When a sea or lagoon water supply is employed, particular attention must be paid to the following factors : bathymetry (water depths, streams, tides).

When underground water is employed, the water flow capacity must be previous established. Frequently underground water is poor or completely void in oxygen and iron or ammonia concentrations are at lethal levels for fish.

Generally lagoon waters have to be avoided because of the high and fast variability of some basic factors : temperature, salinity, oxygen, pH, algae blooms.

On general, the following parameters have to be analysed and correspond to the specific requirements of fish,

-   temperature,

-   salinity,

-   oxygen,

-   ph,

-   ammonia, nitrites and nitrates,

-   phosphates and silicates,

-   eventual pollution sources (heavy metals, pesticides, insecticides).

Most of these factors can be easily controlled and manipulated at the entrance of the hatchery or at the water recirculating system level inside the hatchery.

1.3. Building permissions and eventual restrictions

The site must be chosen in accordance with the possibility of obtaining permission for the implementation of the hatchery building, the pumping station or any other construction works and the waste water discharge network systems.

The various restrictions connected with local or national rules and laws in matters of building projects have to be taken into consideration during the stage of site choice for a hatchery.

It can happen that buildings, which already exist, can be positively used for a hatchery project, thus reducing the requests of permissions and also the building costs.

1.4. Proximity of raw materials, labour supply and basic networks

The most direct and nearest supply of raw materials and spare parts for the hatchery is one of the most important criteria for the site choice. The management of the hatchery also takes advantage from the possibility of finding labour staff in the proximity of the hatchery, thus reducing travelling time losses for staff and facilitating emergency interventions when required.

Raw materials must be obtainable from the area where the project is to take place, thus increasing the availability efficiency and reducing production costs. The site must offer the possibility of good communication with the various networks : roads, electricity power, freshwater, telephone. The distance of the chosen site to the various networks will directly define the investment costs of the hatchery.

1.5. Proximity of the place of destination for fingerlings

When a site has been defined for the on-growing of fish, the hatchery must be built as close as possible to the on-growing site.

In all events, transport of fingerlings for a period of 24 hours doesn't present any difficulty and can be carried out while causing little or no harm to the fish.

The distance between the hatchery and farm will directly influence the costs of fingerlings for on-growing.

1.6. Environmental factors

Climatology and meteorology can also influence the choice of a hatchery site, even if the hatchery activity is carried out in sheltered buildings and therefore protected from the meteorological conditions. For example, the wind conditions and the annual air temperature evolution will determine the kind of building to be bulit (concrete, green-houses) and the degree of thermic insulation needed.

The topography and pedology must be studied for the preliminary ground preparation and the design of the hatchery building.

1.7. Eventual existence of economic or social facilities

Particular facilities can be offered by some local administrations or national plans for defined areas in order to improve and develop specific industrial activities.

2. PRODUCTION PROGRAMMES

A marine hatchery must be designed for the reproduction of various species, thus exploiting different periods during the year and increasing the production capacity of the hatchery.

At the present time, in the Mediterranean area, three marine species can be successfully reproduced on industrial scale in a hatchery while using the same basic frameworks :

-   Sea-bass (Dicentrarchus labrax) : December – March

-   Sea-bream (Sparus aurata) : October – February

-   Shrimp (Penaeus japonicus) : March – June.

For Sea-bass and Sea-bream, these are the natural reproduction periods. The hatchery production capacity can be furthermore increased and ensure staggered spawning. In employing these techniques which have been performed in France over the past years (See DEVAUCHELLE's paper), it is possible to obtain spawning during the whole year. The problems arising with fingerlings coming from staggered spawnings is that the juveniles are of small size when Winter arrives. In some Northern Mediterranean areas, small size juveniles will have to be kept in indoor tanks during Winter because of the low water temperatures. Shrimp reproduction can be carried out throughout the whole year, but generally hatchery programmes plan their spawnings in Spring time so that post-larvae can benefit by the maximum time of favourable thermic conditions for the on-growing stage (one season rearing cycle).

Figure 1 shows an example of a five cycle production programme for a marine hatchery in the Mediterranean. The spawning season begins in October (1st cycle) for sea-bream and fingerlings generally must be kept inside the hatchery until February – March, because of the low water temperatures (Northern Mediterranean). In December, the sea-bass spawning season begins and the hatchery programme can include sea-bass as well as sea-bream Fingerling production. (2nd cycle). During the second cycle, there will be a superposition of the nursery stages of 1st and 2nd cycle (January – February) and of 2nd and 3rd cycle (March). This aspect must be taken into consideration when calculating the number of tanks needed for the nursery (See part 3). In January, the 3rd cycle begins (sea-bass and/or sea-bream). In March, the hatchery programme can include sea-bass as well as shrimp reproduction (4th cycle). Generally, at this time, the natural spawning season has finished for sea-bream. A last cycle (5th) could be carried out with the staggered spawning techniques.

This programme is based on a specific hatchery technology and can therefore vary, in relation with the methodology used for the hatchery production. In the present case, larval rearing is carried out at 20° C in cylindro-conical tanks 2 m³ capacity) until the larvae reach 45 days of age. At this stage, the larvae are transferred from larval rearing tanks to nursery tanks (10 to 15 m³ capacity).

3. DIMENSIONING OF A HATCHERY

The main activity sectors of a marine hatchery are:

1. Breeder and spawning tanks
2. Phyto-zooplankton unit
3. Larval rearing tanks
4. Nursery tanks

The rest of the hatchery premisses consists in the technical and service units:

-   Heating-refrigeration unit

-   Electricity room, generator

-   Workshop and store-room

-   Food stocking and preparation unit

-   Laboratory and office

-   Services (we, bed-room, kitchen)

The figures below show the dimension of each sector in a hatchery having a production capacity of 2,000,000 sea-bass fingerlings/year.

The kind and size of technical and service premisses needed for a hatchery can vary in accordance with the specific conditions and requirements of a given project. For example, some of these premisses (workshop, generator, laboratory, office, kitchen) can be used in common by the rest of the farm or other facilities.

The size of both the larval rearing and nursery unit will be in proportion with the size of the hatchery (capacity), whereas, in percentage, the size of the breeding and plankton unit will increase if the hatchery capacity decreases.

3.1 Breeding and spawning unit.

This unit includes the following tanks:

1. Indoor and outdoor stocking (In Northern Mediterranean indoor stocking of sea-bream is necessary)
   50 – 100 m³ capacity tanks for stocking densities varying from 2 (Summer) to 5 kg/m³ (Winter).

   Broodstock needed (For each million Fingerlings/year capacity)

   * Sea-bass : 250 kg ; sex-ratio : 2 : 1

   * Sea-bream : 150 kg ; sex-ratio : 1 : 1

2. Conditioning tanks for staggered spawning (See DEVAUCHELLE's report)

3. Spawning tanks
   at least 4 tanks of 5–10 m³ capacity each.

3.2. Phyto-zooplankton unit

For each million of fingerlings/year capacity of the hatchery, the following daily plankton production capacities are needed (See table).

Example of the kind of culture containers and total volumes needed are also reported.

For algae and rotifers culture, large volumes (10 – 50 m³) can be used in addition to the normal containers. For this purpose un-used breeder tanks or nursery tanks can be temporarily used.

3.3 Larval rearing and nursery tanks

3.3.1. Initial figures

The following table shows the various figures involved in the calculation for the number of tanks needed for larval rearing and nursery. The initial and fixed figures are as following :

1. Yearly production of Fingerlings needed

   The present example is based on a production of 1,000,000 sea-bass fingerlings/year

2. Number of production cycles of the hatchery

   Example : 3 cycles/year(a staggered spawning cycle is not included here)

3. Survival rates of larvae and fingerlings

   -   For iarval rearing (from egg stage to 45 day old larvae) : 25 %

   -   For nursery stage (from 45 day old larvae to 1 g fingerlings) : 75 %

4. Stocking densities of larvae and fingerlings

   For the capacities calculations, the final density has to be considered :

   -   For 45 day old larvae : 10,000 individuals/m³

   -   For 1 g Fingerlings : 3,000 ind/m³

5. Unitary volumes of tanks

   In this example, we have chosen the following tanks :

   -   Larval rearing : 2 m³ capacity tanks

   -   Nursery : 10 m³ capacity tanks

3.3.2. Steps of calculation

-   Total yearly production : 1,000,000 fingerlings

-   Total production of fingerlings per cycle (3 cycles) :

-   Initial number of larvae in nursery per cycle (75 %) :

-   Final number of larvae in larval rearing tanks per cycle : 440,000

-   Initial number of eggs per cycle (25 %) :

-   Total number of eggs needed per year : 1,760.000 × 3 cycles = 5,280,000

-   Total larval rearing tank volume per cycle :

-   Total larval rearing tanks per cycle :

-   Total larval rearing tanks in the hatchery (separated cycles ) : 22

-   Total nursery tank volume per cycle :

-   Total nursery tanks per cycle :

-   Total nursery tanks in the hatchery (superposition of 2 cycles) : 11 × 2 = 22 tanks.

(1) If the exterior water temperatures permits the transfer of 1st cycle fry, the number of weaning tanks necessary will be 11 instead of 22.

Notes :

(1) Without staggered spawning

(2) At 20° C temperature

(3) End of larval rearing : 45 day old larvae
End of nursery stage : 90 – 120 day old (0.5 – 2 g of individual weight)

(4) Undervaluated - Normally twice the amount can be kept

(5) Separated cycles for larval rearing tanks
Eventual superposition of two cycles for nursery tanks

Figure 1 : Example of a five cycle production programme for a marine hatchery operating with sea-bream, sea-bass and shrimp (Total shrimp cycle is about 30–50 days). The last cycle (V) is obtained through staggered spawning. Periods between broken lines: superposition of two cycles for the nursery stage.

FISH HATCHERIES
STRUCTURES - EQUIPMENT - ECONOMICAL ASPECTS

Mr. G. BRUNEL

1. INTRODUCTION

The design of the hatcheries implemented:

-   The detail knowledge of the rearing techniques

-   The characteristics of the rearing site

-   The objective of production and/or of profitability.

In an economic context, there exists a compromise with this design phase between the technical and economical parameters.

2. DESIGN OF THE REARING STRUCTURE

This entails a succession of stages, from general to particular, which define the technico-economical functions and objectives.

2.1. Definition of the basic units for a hatchery

2.1.1. Definition of the three principle criteria of determination

-   Homogeneity in functioning

-   Identification of the environmental factors

-   Unity in management.

Let us define the following units (Each unit will have its own functional characteristics which will permit the detailed definition of its structure.

Sea-bass -Gilthead sea-bream

1. Stocking of breeders/spawning

2. Phyto/zooplankton unit

3. Larval rearing/first fattening

4. Technical unit (workshop, machine room, boiler room pumping unit)

5. Operation unit (laboratory, administration, storage)

2.1.2. Secondary design criteria

-   Operation standards - Repartition of risks

- Standardization of productions

-   Possibilities of extension

-   Reports between the units

Ex. : Breeders/spawning - Larval rearing

Phyto/zooplankton - Larval rearing

Technical buildings - Biological units.

2.2. The structure of the units for a hatchery

They are defined, when the site has be chosen, according to the following data :

-   Environmental parameters of the site,

-   Environmental parameters of the basic units,

-   Technical constraints,

-   Operational and security constraints,

-   Sanitary constraints.

2.2.1. Breeding/spawning unit

This unit generally comprises three parts:

1. The natural maturation tanks
   No particular structure is required here, as the environmental parameters are similar to those found in a natural environment. However, so as to facilitate the management of the tanks, and because, in these tanks, there is a much more confined environment than in an open environment, it is advisable to schedule a flexible covering, similar to that used in agriculture, which will have the role of:

   -   limiting the evaporation of the calories in Winter,

   -   limiting the algae growth and ensuring shelter from the sun in Summer

   -   limiting the variations in the salinity during heavy rainfalls.

2. The staggered maturation tanks
   These tanks which undergo different photo-period and thermic rhythms than those of a natural cycle, must obligatory have a covering which will allow no day light filtration to pass through and which will ensure good maintenance of the environmental conditions.

   The type of structure will depend on the site chosen and on the economic context and can range from a double wall greenhouse having an opaque lining in warm temperate regions, to the industrial type building, with eventually air conditioning/heating.

3. The spawning tanks
   This tank is employed indifferently for breeders which mature in natural conditions or in controlled conditions. It is thus confined to the most restrained conditions, in other words it has not the same kind of structure as the tank employed for staggered maturation.

   All these tanks, which have generally a capacity of more than 20 m³, can be built according to many different procedures. The choice will depend on the context in the country in question. The moulded reinforced concrete tanks, circular in shape, are the most advantageous in many cases.

2.2.2. Phyto/zooplankton unit

This unit is comprised of two rooms :

-   The phyto-plankton room, which requires a regular temperature of 22° C.

-   The zoo-plankton room (Rotifer, Artemia) which must ensure a temperature of around 26–28 ° C.

These two rooms are closely connected to one another, as most of the algae produced are distributed to the rotifer rearings. The choice of the structures will here again depend on the prices.

The phyto-plankton culture rooms are well known and have been described many times, by different authors. Therefore, we shall not enlarge on this subject. A more simple alternative, less expensive but also less efficient, is that the bloom be cultured in a semi-controlled environment. This solution can not be justified but in countries which do not have great drops in temperatures in Winter. They permit important economical realisations.

The rotifer room is equipped more of ton with polyester containers of cylinder-conical shape (1 to 2 m³) which are thermo-regulated. The temperature of the water having to be at around 20 ° C, special attention will be taken for the insulation of these containers, especially the upper parts. If this point is properly controlled, the rotifer culture containers can be placed in low costing structure (agricultural green house).

The Artemia room is divided into 3 parts:

-   The decapsulation zone, having three tanks, one for hydration, one for treatment, and a final one for rincing.

-   A set of polyester incubators.

-   A set of fattening tanks (2 to 4 m³) of Foster-Lucas type which can be built in reinforced concrete and have a polyester covering.

The two last sets are thermo-regulated (26. to 28 ° C) and must be perfectly insulated (idem rotifers).

2.2.3. Larval rearing and first fattening units

Generally, this unit is divided up into three parts (larval rearing, First, fattening, recycling circuit) constituting a rearing module.

a) Larval rearing tanks

The shape, dimension, construction method and operating principles vary a lot depending on the hatchery.

-   The shape : circular, subsquare, raceways, cylinder-conical : this latter shape is the most renown at the present.

-   The dimension : from 1 m³ to 45 m³. Today, there is a marked tendency to limit the use of big tanks in favour of smaller tanks.

-   The construction method: reinforced concrete polyester, polyethylene, plywood with a PVC canvas covering. Polyester is being employed more and more today.

-   The operation principle : this can range from very intensive (more than 150 eggs/liter) to extensive type (10 eggs/liter). Densities of 100 eggs/liter is the amount most of ten employed.

As far as we are concerned, we employ cylinder-conical polyester containers of 1 to 3 m³, which is a good compromise, ensuring a good physico-chemical regulator in the rearing tanks.

The larval rearing is carried out while employing the initial densities of around 100 eggs/liter.

b) First fattening tanks

They permit fry rearing from the beginning of its metamorphosis until it reaches an average size of 1 to 2 g. In practice from the 45^th day onwards, the sea-bass fry is transferred from the larval rearing to the fattening tank 60 to 65 days for the gilthead sea-bream).

The rearing, from this moment, concerns trout rearing and the structures are much similar to those defined for these species 9raceways, circular or sub-square tanks. Polyester is frequently employed along with reinforced concrete, with or without a polyester covering.

c) Recycling circuit

Recycling has as objective the limitation of energy consumption so as to maintain the temperature in the rearing environment and it combines the following elements:

-   Waste water recovery canals,

-   Detritus chambers (excreta trap, plate detritus chamber),

-   Scumming system,

-   Pumping station,

-   Regulated heat exchanger,

-   Biofilter having a polyester fluidized bottom,

-   U.V. Sterilization (for the larval rearing).

These rearing units can be sheltered depending on the climate, under green house or in industrial type hangars.

2.2.4. The technical building

The technical building is a unit which must be separated from the other facilities and sheltered in an industrial hangar.

It is separated from the other structures for the following reasons:

-   Technical : better conservation of the material located outside the rearing structures, the air of which is vapor-saturated. Indeed, the costly material is often prone to corrosion due to humidity, and sea-air.

-   Environmental: Indeed, the noise and vibration caused by the machines can have a negative affect on the rearing.

-   Management: As the personnel who intervene in this unit are specific (maintenance personnel) for sanitary reasons, access to the rearing zones is thus restricted to only the personnel concerned.

This building is generally divided up into the following compartments:

-   a “hatchery” pumping station along with a set of filters (one compartment)

-   an air-blower station

-   a water heating/cooling system

-   a electricity compartment divided into two distinct sections, which are the transformer and the emergency power-unit in one section and the general low voltage cupboard in the other section.

Remark: There exist many different heating/cooling production sources. For the fish in the Mediterranean, calories are more in demand than cooling methods. A mixed system is therefore generally employed which includes:

-   a principal source of heat, which can either be a fuel heater or a thermal drive - in situ combustion (geothermics)

-   an adjustable heating/cooling source which is the heat pump.

3. THE EQUIPMENT

3.1. Generalities

The choice and selection of the equipment is of prime importance in the concept of a hatchery, as it is necessary:

-   to answer to necessary requirements in the defined conditions, through the construction work studies for example, the electric motors must be perfectly insulated against humidity and the existing temperatures.

-   to minimize the operation costs of these devices: this always calls for an arrangement between the purchase price (investment) and operation cost.

-   to examine the maintenance problems which are always of importance as the work is carried out in humid environments, with high temperatures in a marine athmosphere.

-   to schedule the stand-by equipment; the principal devices (pumps, aerators …) will be scheduled on the double. Great attention must be paid to the choice of the material which should have a slightly superior capacity than required overestimation of security).

-   to schedule spare parts when purchasing the material thus enabling to intervene when break-downs occur.

-   to choose material which will limit upkeep and maintenance requirements.

It is only through experience that the correct choice can be made.

The principal equipment required for a hatchery are hydraulic, thermic and electric devices.

3.2. Hydraulic equipment

a) Pumps: Generally, they have feeble or average flow discharges, and a pressure permitting to combat the different head losses of the circuit (canalizations, connectors, filtration system… ). Sumerged or surface centrifugal pumps will be chosen. The material should not be corrodible by sea-water and should be non-toxic to the animals. Generally, Ni-Resist iron should be employed (iron/nickel alloy). However, corrosion by the sand can not be avoided (mechanical corrosion) and thus a stock of spare parts for all the mobile parts of the pumps must be scheduled.

Remark : It must be ensured, that all the hydraulic circuits, can be disassembled, separatly, so that when they require repair, cleaning or desinfection while employing toxic products, one is free to do so easily.

b) Filters: Swimming pool stable standard polyester filters are mostly employed, due to corrosion problems in sea-water. However, with the use of polyester, a pressure a problem arises (at present, we are practically limited to 3 bars).

Remark : All the sea-water pipes are made in PVC plastic of natural flow or pressure flow type.

c) Aeration: Two types of device can be employed; either the compressor, requiring a compressed air reservoir or blow tank storage or preferably, the superblower ensuring a feeble pressure but a great flow which requires to be permanently in operation (no storage).

3.3 The thermic equipment

a) The heating systems

They ensure the heating cooling requirements. The heat pump will suffice if the needs are well balanced. There exist many solutions for the heating system:

-   the fuel heater,

-   the geothermic recovery (+ heat pump),

-   the electric heater (resistor)

-   the industrial recovery of calories.

The material is selected depending on the price, in Kw/h and in fuel, which varies depending on the country. The feeble energies alone do not suffice for the hatchery tanks they are generally associated with the others so as to limit the running costs.

b) The exchangers

This is meeting point between warm and fresh water, generally Flowing from the heating systems (boiler, heat-pump, drilling, … ), and the sea water flowing from the rearing. For reasons of corrosion and toxicity, titanium plated exchangers are currently being used at present. They resist well to marine corrosion and have a remarkable thermic performance.

3.4. The electric equipment

They include emergency power units, switch cupboard, along with the control equipment. This is relatively current equipment. Let us pay special attention to the insulation and water tightness of these cupboards.

4. ECONOMIC ASPECTS

4.1. Investments

The construction costs of a hatchery depend on the side, the rearing technology chosen and the compromise between the technical considerations on one hand and economic on the other (relation between investment cost and running cost).

As an example, for a sea-bass/gilthead sea-bream hatchery, with a capacity of 1 million fry of 1 to 2 g/year, the repartition of the investments takes place as shown here following (Economic conditions, France 1985) (Total amount : 8,5 million F.F.).

4.2. Running costs

In the case of the fish hatchery seen here above (1 million sea-bass fry and 100 000 gilthead sea-bream fry) the cost price of the fry entails the following elements, in a routine year, in other words from the 4^th year onwards:

This repartition of the cost prices leads to the following comments:

1. The hatchery entails and will continue to do so, for a long time a high technological activity which requires qualified personnel. The personnel and technical assistance represents 45,5% of the cost price of the fry (which is nearly half). An effort for automatization must be undertaken so as to limit this important cost price factor; we shall also try and reduce certain tasks such as feeding (in avoiding live food, for example).

2. The energy costs are low (9.0%). Thus any technological efforts made here will not give a noticeable improvement on the production cost. The choice of the designer must concern moreover the reliability of the material rather than the economy of energy.

3. The amortization is high (20%). Consequently, it is necessary to find less expensive construction technologies which will be less sophiscated.

THE CONCEPTION OF “INTENSIVE TYPE” FISH HEARING FACILITIES WITH PARTIAL OR TOTAL WATER REGENERATION

M.J. PETIT

PREFACTORY NOTE

The lecturer has no experience in marine hatcheries. The method exposed here deals with all the different types of intensive fishculture where aquaculturist tries to free himself of the incidents of the environment (intensive). This applies to hatchery and fry rearing of Salmonidae and species whose growth speed must be accelerated by means of heat so as to reach economic profitability (eels).

Marine hatcheries are linked with this type of fishculture.

The description of the functions of the water and equipment which are necessary for a marine hatchery were exposed at MOTTA DI LIVENZA (MEDRAP, TD/86/03). This description permits the formulation of the contrat procedure for the building works of a facility.

The calculation methods for the equipment have been exposed in TUNIS during the engineering session organized by MEDRAP.

Let us propose here the examination of the relation between the technical choices and investment cost, which will be a guide for the conceiver. The analysis of the operating coasts and gains linked with each type of structure remains to be elaborated.

INTRODUCTION

The investment cost will closely depend on the choices taken concerning the rearing structures (tanks) and the water supplies (open circuit or recycled water).

The rearing VOLUME depends on the maximum stock of fish maintained during the cycle, which will thus require a management study of the stocks from their growth speed and dispersion.

The WATER SUPPLIES depend on the oxygen consumption and pollution thresholds which the fish support.

Although it may be possible to minimize greatly the investment by means of certain technical choices, the outcome of this, results generally in higher operating costs.

Thus the use of pure oxygen permits to decrease the SUPPLY, and to make important economics on the hydraulic network system and on the water treatment system : on the other hand, this will also lead to a supplementary operating cost entailed through the payment of gas.

Likewise that heating of the water will increase growth and will also reduce the volume of the tank necessary for a given production, but at the same time it will also entail a supplementary cost in energy.

The rearing structure and supply flows having been defined, we can now research one by one, the most efficient EQUIPMENT the oxygenation, purification, thermoregulation when these can not be obtained from the natural environment.

1. THE REARING VOLUME

1.1. Limit design

The rearing volume is defined by the zootechnical factors and by the organization of purchases and sales. We shall refer ourselves to the modelization of production, especially that of FAURE *.

*  Seminary organized by GEDITS (Groupe d'Etude et Diffusion de l'information Technique on Salmoniculture) on the production of large (Oct. 1986).

For the same annual production, we can thus installate structures of very different sizes.

The SIZE of the structure will be defined by :

-   The maximum stock during the year,

-   The rotation of the stock (time period spent by the fish in the structure)

The study of fishculture thus commences by the management study of the stocks.

-   The MAXIMUM STOCK determining the rearing VOLUME depends on :

• The planning of the fish inputs: the more staggered they are in time the greater the production will be for a same facility,

• The growth variability : the more staggered their arrival at commersize is the better the production will be for a same stock,

• The commercial size of the animals : the bigger they are, the greater the stock for a same production will be (especially when the cycles overlap).

The maximum stock thus depends principally on the Biological factors and on the purchase-sale planning.

-   The ROTATION OF THE STOCK will define the DEPRECIATION of the rearing structure. This rotation depends on the GROWTH SPEED. Which can be controlled by the temperature, the rotation of the stocks also depends on the animals and output sizes in the rearing.

It is with this notion of profitability for the rearing structure, the speed up of the growth rate by means of heating, that brought about the use of of recycled waters in rearing, so as to economize calories. The analysis of the project consists in balancing the costs linked with recycling + heating, with the gain obtained by the greater growth speed.

1.2. Conception of the structures : an exemple -

The possibility to obtain higher densities reduces the investment cost in tanks for a given production.

The different tropisms can be negatively or positively employed to improve the distribution of the animals in the rearing volume: food, oxygen, lighting.

The most spectacular results are obtained with fish which normally stay at the “bottom” such as the brown trout, salmon, eel, silurius, catfish.

Indeed, when a good distribution of the animals in the tank is obtained, it permits limiting competition with regards to the water, oxygen, food, lighting, a more homogenous growth rate and “better” animals (agressivity). We can still improve on the results, in separating certain parts of the tank : food, habitat, etc…

We shall find here under a skeleton diagram furnished by P. MAUREL and employed by an eel rearing specialist.

with eels, it was known that in offering the animals supports (grils, tubes), the density could be greatly increased (up to 150 kg/m₃).

The disadvantage of these supports is that they are priviliged zones for fouling and the development of Algae and fibrous fungui.

Such a structure is only possible if the water is kept completely clear by means of intense water treatment, of the food distribution zone which is separated from the habitat zone and the rapid collection of fresh mud.

The cost of the installation of the tank will be balance with the improvement of the water quality, the reduction in the main purification system and the increase in density.

DIAGRAM OF AN EEL TANK BY P. MAUREL (1)

(1) AQUINOXE, 8 rue d'Ouessant, B.P. 40 - 35760 - St. GREGOIRE - FRANCE

• The habitat zone is installated in accordance with the dominating tropisms of each species : support (eel), light (silurus). It is well oxygenated by the recycled supply flow of water.

• The feeding zone is supplied with water which is not recycled during feeding. The food matter will therefore not contaminate the recycling.

• The decantation zone receives no water renewal, the tropisms for the oxygen and the currents keeps the fish in the habitat zone. The mud extracted is dense (feeble time stay, no mechanical mixing, mud and faeces only, which the animal do not put back into suspension).

• Advantage : The clarified water permits sanitary treatments and rapid water flows over the filter.

• No decantation required

• Disadvantage : Supplementary tank costs.

2. WATER SUPPLY FLOWS

The defining of the rearing volume involves zootechnical and commercial factors which will be seen here below.

The remaining infrastructures for the fish culture are linked with the HYDRAULIC network and WATER TREATMENT systems, oxygenation, heating, purification.

Their definition entails the choice and calculation of:

-   The dimension of each structure (the bigger it is the more expensive it will be) which will depend on the supply flows.

-   The power of each device:
Quantity of oxygen required, quantity of polluants to be eliminated, type of pathogenic germs to be destroyed. These will vary according to the species and category of the animals.

-   The type of machinery to choose : surface aerator or deep well type, gas or fuel heating, etc… for which the choice will depend on their efficiency, and local criteria, for example availability.

2.1 Limit design of the hydraulic network system

It is defined by the supply flow

In reducing the supply flow by means of certain technical devices, we considerably reduce the cost of the facility.

The supply flow can have different functions:

-   Oxygen supply

-   Evacuation of waste matter

-   Supply of calories or negative kilocalories

-   Food supply (bivalve rearing)

The impact of the supply flow on investment being important, it is advisable to study solutions of substitution or cost reductions for the functions which concern the supply:

-   The water flow can be thus reduced with regards to oxygen requirement :

• by staggering, the feeding periods

• by increasing the oxygen tenor input :

Use of pare oxygen : (see example here under)

-   The supply flow can be reduced as to concern the purification needs:

• By organizing the tanks (see below)

• By purifying the water in the tank : BIOMACO system (see report of Mr. PETIT-MEDRAP Session on engineering - TUNIS)

• By use of a highly digestable food.

-   The caloric or negative kilocalorie requirements can be reduced by means of insulation (covered).

AN EXAMPLE OF HOW TO REDUCE IN SIZE THE HYDRAULIC NETWORK SYSTEM WITH REGARDS TO THE OXYGEN

WHERE - Q = the supply flow

- ∆ O₂ = the concentration of oxygen in the water taken away from the threshold tolerated by the species;

- TE = water treatment (oxygenation, purification)

- CO = Oxygenation capacity to be furnished to the tank.

A given oxygen supply, can be obtained by different means. The choice of the supply flow is determinant for the investment, the choice of the O₂ concentration is determinant for the operating costs.

Thus in the example given here below, the required supply permits from 2.25 m³/H à 11.5 m³/H for a same stock.

NUMERIC EXAMPLE

HYPOTHESIS - Oxygenation of the tanks for 100 kg of animals, which means 25 g/H of dissolved oxygen must be furnished.

- 25° C temperature (saturation : 8 mg/l)

- Oxygen threshold in the : 5 mg/l)

- Presence of a biological filter, which requires 20 g/H Of oxygen.

• A supply flow with a aeration system which recovers the water at 90% of saturation

• 

• A supply flow having an aeration system before passing through the filter and a second before passing into the tanks.

• A supply flow with an oxygenator (oxygen paid for) furnishes water at 25 ppm.

2.2 Limit design of the water treatment systems

The supply flow systems consists in:

-   a supply flow of water from the exterior

-   a recycled supply flow.

Both of these supply water flows can represent all or part of the water flowing into the tanks.

• The supply water flow can, when of good quality, ensure all the functions devolving to water in fishculture.

In numerous cases the procurement of a water supply flow from the exterior is rather cheap : gravitional water intake, from a river and by the use of tides

• The recirculation of the water reduces its qualities, which necessitates one of more water treatments.

Recycled flow

To maintain 10 g/m³ of SM at average value in the tanks, a minimum flow is necessary:

Qp × 10 g/m3
	=
Pollution eliminated by the new water		Pollution engendered by the fish
which is Qp = 2.5 m3/H

A new water flow of 2.5 m³/H implies that the water contains so SM at tank inlet level. Thus this is either new water, or water obtained from a filter with a 100% output. Such a filter, if feasible, would be very expensive.

Thus we shall test flows of more than 2.5 m³H and calculate the outputs with the formula stated here above, while employing the value of the example, which is:

W = 25 g/H

Qo = 0.1 m³/H

C = 10 g/m³

The surface of the decanter is given for a sediment coefficient of (2). (See report by J. PETIT/MEDRAP session of Engineering)

We remark that:

-   it is not the smallest flow which permits the greatest economy on the decanter.

When one must recycle water due to a insufficiency in the quality or the quantity of the supply, two types of questions can be asked:

-   How much of the water supply is it necessary to conserve?

-   Which devices are necessary so as to satisfy the requirements in oxygen, heating, etc… of the rearing?

ELIMINATION OF POLLUANTS

The water supplied will carry the waste matter out of the rearing.

The quantity eliminated is the product of the supply flow by the concentration in the tank.

The more exact one is about the quality of the water the greater the supply water flow will be, and if insufficient one should demand filters (elimination of the ammonia, and of the organic matter in suspension).

To study the effect of the choices on the investment that one can make, it is recommended to use the following formula:

-   R is the purification efficiency necessary so as to obtain C concentration in the tank (g/m³) with a new water supply Qo (m³/H),
with a recycled water supply Qp (³/H),
and a polluant discharge W (g/H).

-   The higher R is the more expensive the device with equal discharge flow will be, for a given device (decanter filter, sterilizer), it is easy to follow the evolution of the costs depending on the thresholds and flows chosen.

EXAMPLE

HYPOTHESIS -   100 kg of animals
fed at 2% with a dry pellet food

-   Objective: 10 g/³ max de matter in suspension

-   Load : 50 Kg/m³, and no decantation possible on the tank

-   Feeding at 2% which gives 300 g of SM per Kg of food
(this corresponds to a transformation index of 1.5 – 1.6)

-   0.1 m³/H of new water at disposal.

-   above a certain flow flow there is no more gain in the structures surface area although the admittible output is less.

We can thus study the investment and operation cost engendered by a more or less important input of new water for each problem studied:

-   Elimination of ammonia and SM

-   Elimination of pathogenic germs.

We propose here under an example so as to define the power necessary in relation to water treatment.

This power, whether it be a oxygenator or a filter, will vary with the choice of the minimum or maximum thresholds of the physico-chemical parameters concerned: oxygen, ammonia, SM, etc…

OXYGEN REQUIREMENTS

The calculation of the oxygen requirements can be done with the use of diverse modelizations (LIAO, SPARRE, etc…). An evaluation can be obtained for a trout type food, in considering that the oxygen/food consumed ratio has a value of 250 – 300 g of oxygen per ton of food (280 g/T of food for trout).

The choice of the minimum oxygen thresholds to be maintained will determine the power to furnish so as to dissolve the correct quantity of oxygen necessary for the animals.

EXAMPLE

Hypothesis : -   Water input 2 m³/H at 25° C (8 mg/10₂ max.)

-   100 Kg of fish fed at 2% of their live weight per day, which is 2 Kg/d entailing an oxygen consumption of around 25 g/H.

Basis : - 1 Kg of dissolved oxygen per KwH at Omg/l of oxygen (high speed turbines, hydroprojectors) standard (0ppm - 20° C).

-   Quantity of oxygen dissolved in water at C concentration

Cs, Maximum concentration in oxygen (saturation)

We then remark that the power required can very by a factor of 7.5, when the threshold maintained for the oxygen in the tank passes from 3 to 7 mg/l and this for a same quantity of dissolved oxygen which is available for the fish.

CONCLUSION

The limit design of the different parts of a rearing and thus the cost, is greatly influenced by the choice of certain parameters.

It is possible to obtain significant investment reductions by analyzing the different situations one by one, an optimization between investment and operation costs must then be carried out so as to define the “right choice”.