Although no hard data are available to quantify this, an enhacement programme for Turkish Black Sea seatrout is justified by the belief that the stock has been reduced drastically in recent years by a combination of overfishing and damage to breeding areas, and will be further threatened by continuing engineering and agricultural developments in the spawning rivers.
The enhancement programme should not be delayed pending further years of scientific investigation aimed at establishing accurate baseline data, partly because the “baseline” itself is continually being moved (usually to the detriment of the stock) and partly because to be successful a breeding programme must begin while sufficient wild broodfish are still available. Scientific studies should instead be incorporated as one part of an integrated enhancement and protection programme, with the following major components:
Hatchery building, followed by production and release of smolts
Scientific and economic quantification of the results of releases by mark and recapture, assessment of stock numbers, and collection of basic biological data on the Black Sea seatrout
Implementation of a rational protection and management programme for Black Sea seatrout.
(a) Hatchery building and operation
It is recommended that one site should be selected from those described above, and a single prototype hatchery be constructed. The following assumptions and calculations were made to determine the size of facility required:
Target production. The hatchery will produce 250 000 seatrout smolts of average weight 50 g annually. It is assumed the majority of fish smolt at 1 + (i.e., in spring one year after hatching).
Requirement for broodstock and broodstock tank space. Allowing a 60% mortality of eggs, fry and fingerlings between fertilization and smoltification, the hatchery requires 625 000 eggs annually to meet the target production.
Assuming an average egg yield of 1 500 eggs/kg of ripe female, and an average weight of female broodfish of 3 kg, 139 females will produce 625 000 eggs. The total requirement of productive brooders (males + females) is therefore about 200, i.e., 600 kg at an average weight of 3 kg. To allow for unproductive fish and a margin for safety, space is planned for holding 1 000 kg of broodfish.
If circular fibreglass tanks of 8 m diameter and holding 1 m depth of water are used for broodfish, each tank will contain about 50 m3 of water. At a maximum stocking density of 10 kg/m3, 1 000 kg of broodfish therefore require 2 tanks. (Imported equipment required is listed in Appendix 1.)
Incubators. Eggs are incubated in fibreglass and aluminium trays or boxes held in fibreglass troughs (“California” system). Assuming 3.5 m long troughs each housing 7 boxes are purchased, and eggs stocked at a water requirement of 1.5 l per box, a total of 12 troughs will be required to incubate 600 000 eggs. Incubators must be housed indoors. They require a total floor space of 60 m2.
Fry tanks. Fry will be grown from first-feeding up to an average size of 2.5 g in 2 × 2 × 1 m deep fibreglass tanks. Assuming the survival of 400 000 fry, maximum total biomass to be held in these tanks is 1 000 kg. At a maximum stocking density of 10 kg/m3, these require 100 m3 of tank space, i.e., 25 tanks. Allowing spare tanks for grading, etc., 30 tanks should be purchased. Fry tanks should be accommodated indoors, and require a total floor area (allowing for access, etc.) of about 200 m2.
Smolt tanks. Fish are grown from 2.5 g until smoltification at an average weight of 50 g in 8 m diameter circular tanks, the same as those used for broodstock.
The target output of 250 000 × 50 g smolts has a total biomass of 12 500 kg. At a maximum stocking density of 20 kg/m3, these require 625 m3 of tank space, i.e., 13 tanks. Allowing one spare tank for grading, the total requirement for 8 m diameter tanks is therefore: 13 (smolts) + 2 (broodstock) + 1 (grading) = 16. Allowing for access, etc., these require an area of about 2 500 m2, but can be sited outdoors.
Water requirement. Allowing 1 l/min/kg of fish, the maximum water requirement for smolts and broodfish is 13 500 l/min (225 l/sec). Eggs and early fry need a maximum of only 1 500 l/min (25 1/sec). The total water requirement therefore totals around 0.25 m3/sec. However, it is recommended that supply pipes, drains, etc., should be designed to carry at least twice this amount (0.5 m3/sec) to allow for expansion and unforeseen contingencies.
Costs. The approximate costs of imported tanks and equipment are given in Appendix 1. In addition, site preparation, provision of services, and erection of buildings would require expenditure in local currency. Many of these items are site-dependent. They can be minimized if the recommendation to expand the existing rainbow trout farm on the Çağlayan River is accepted.
Operational aspects of the enhancement programme
Marking. Smolts should be marked before release, probably by a freeze-branding technique using liquid nitrogen, but in any case in such a way that year-classes can be differentiated when the same fish are recaptured as adults two or more years later. Different marks might also be used within a year-class to allow subsequent evaluation of varying recapture rates following releases at different sites or time-periods.
Fish trap. To facilitate recapture of returning adult fish to allow evaluation of success of the “ranching” programme, and to collect broodstock for stripping in the hatchery, it is recommended that a permanent fish trap be built downstream of the hatchery. This should be designed to catch upstream migrants.
Broodstock. It is believed that the Black Sea seatrout stock can be justifiably differentiated as a unique sub-species, Salmo trutta labrax, which also has a landlocked form in the same area. Morphological differentiation is largely on the basis of the number of gill-rakers on the first branchial arch, but it is presumed that the sub-species also possesses physiological peculiarities adapting it for life in the Black Sea region. Whilst it is known that “foreign”, Atlantic forms of seatrout have been introduced into the western Black Sea, it is thought that the stock inhabiting the eastern rivers of Turkey remains “pure”. Therefore, any enhancement programme undertaken in this region should first attempt to build up stocks of this “native” sub-species. Only if the numbers of fish remaining prove to be so low that insufficient broodstock can be built up should consideration be given to importing other strains.
Broodstock captured in the fish trap during their upstream migration would be transported to holding tanks in the hatchery and kept until ready for stripping. If necessary during the years before the first returns, their numbers could be supplemented with broodstock captured by movable traps in other nearby rivers. This would result in mixing of populations between rivers, but still preserve the sub-species intact. If sufficient broodstock are caught to supply the hatchery's needs each year, fish can be released after stripping. However, if numbers available are too low, it will be necessary to build up a captive broodstock by retaining parent fish in the hatchery from one year to the next, and perhaps also by growing-on-hatchery-reared fish to maturity.
At all times some broodfish should be permitted to pass the fish trap to utilize natural spawning beds upstream.
Importation of eggs. A hatchery specializing in production of juvenile Black Sea seatrout is known to be in operation in the Soviet Republic of Georgia, which borders eastern Turkey. The Black River seatrout hatchery, near the town of Suchumi, produces fish for restocking Soviet rivers in the eastern Black Sea catchment, and its seatrout stocks are thought to be closely related to those of the nearby Turkish rivers. If insufficient eggs can be obtained from broodstock captured in Turkish water, therefore, a good second option would be to purchase eggs from this Soviet unit to supply the proposed new hatchery. FAO and/or Government should make early contact with the authorities of the USSR to explore this possibility. Only if this second option fails should consideration be given to importing eggs from outside the Black Sea basin. In this case the first choice might be Caspian stocks form Iran or the USSR, followed by Atlantic stocks from Scotland or Norway.
(b) Scientific and economic evaluation of results
Marking of all smolts released from the hatchery and trapping of migrating adults will allow the market value of returning hatchery-reared fish to be compared with their cost of production, indicating whether “ranching” of Black Sea seatrout is economically viable. If it is, plans might be made for construction of more hatcheries and recapture facilities on other rivers. Private investors might wish to participate in this. Evaluation of the true rate of fish survival, however, depends on firm control over the illegal fishing activity which is currently rampant both in the sea and rivers (see below).
Marking and recapture will also permit collection of basic scientific data on the fish stock which are currently scarce (i.e., age and size at first maturation, and growth rate of fish in the sea), as well as estimation of the total population size (hatchery reared and wild-spawned fish). Information on growth rate and age of down-stream migrating smolts, and of juvenile fish, can be obtained by sampling in rivers using electro-fishing apparatus (see also below). However, in the case of parr it is thought impossible to differentiate individuals belonging to the landlocked stocks of brown seatrout in the same rivers from those which will eventually smolt and migrate to the sea.
(c) Protection and management programme
Environmental protection. Government should consider protecting at least some of the remaining spawning areas for Black Sea seatrout by postponing plans for further hydro-electric or other engineering developments in selected river catchments. The consultant recommends that this protection be given initially to the most easterly rivers: Kapistre, Çağlayan and Findikli. Proposed DSI developments on these rivers are relatively small, and could be shelved pending evaluation of the results of an enhancement programme without significantly damaging the region's electricity production potential, since there are many other planned projects which can be implemented first. Agricultural development which involves stripping of native bush from steel hillsides, resulting in serious erosion, land-slips, and consequent deterioration of water quality, should also be discouraged in these catchments.
Fishery protection. Overfishing is believed to be a major factor in the decline of Black Sea seatrout (and sturgeon) stocks. Though the landing of these species is forbidden by law, they continue to be taken both as a by-catch and deliberately by commercial and sport fishermen.
The financial incentive to catch the fish is strong: seatrout have a first sale price of about LT 20 000/kg ($US 10/kg) (and caviar ca. LT 500 000/kg = $US 250/kg). For example, one parttime fisherman told the consultant that a catch of only two average-sized seatrout will earn him the equivalent of a month's salary in his full-time job at a tea factory. Whilst it is therefore not surprising that some people will break the law, the attitude of illegal fishermen to this law is unusual. All the fishermen questioned well understood the necessity for stock protection. Many of them expressed the wish that Government would act strongly to “save” these endangered species before it was too late. But all spoke freely about their activities, giving their names and details of their catches in front of government officials with no fear of the consequences. The law is clearly not only not respected, but absolutely discounted by the fishermen, who say that enforcement is non-existent. All branch offices of the Ministry of Agriculture in the major towns have personnel whose duties include fisheries law enforcement, but even the staff themselves admit they are not attempting to do the job. Reasons given include lack of necessary equipment and insufficient staff. The former may have some justification. For example, one fisherman said that he had, very occasionally, seen a fisheries inspector in his area. “But the inspector came in a car during office hours; we fish in a boat at night!” However, the excuse of insufficient staff would be more convincing if all the personnel currently employed were busy, which they are obviously not.
One pre-requisite for a successful enhancement programme would, therefore, be the firm enforcement of laws designed to protect the stocks from excessive and illegal exploitation. In the case of seatrout this is necessary not only to allow stocks to recover unmolested, but also to provide a basis for policing a legal fishery for the species in the future. Under the current system, the sole beneficiaries of any enhancement programme will be illegal fishermen. This state of affairs would presumably not be acceptable either to Government or to any external funding agency. A vital part of any proposal for hatchery building and fish releases, is a clearly formulated policy for stopping illegal fishing, and licensing and controlling a legal fishery in the future. The legal fishery might be placed in the hands of cooperatives and/or companies, who would pay for fishing rights over designated areas, thus funding the production of smolts for release.
