1 - INTRODUCTION TO THE WORKSHOP
1.1 Objectives
MEDRAP II Project organized a workshop on Lagoon Management in Nador, Morocco, from September 30th to October 5th, 1991, in the framework of aquaculture development in the Mediterranean and in view of the recommendations agreed upon in the last Steering Committee held in Tunis on April 26th,1991.
Three objectives were fixed :
1.2. Opening Session
The opening session was held in MAROST premises in Nador, on the lagoon borders bearing the same name.
Were present at this session, his Excellency the Governor of Nador, the Representative of the Ministry of Marine Fisheries and Merchant Marine, the MEDRAP II Project Coordinator, the General Director of MAROST Company, the Director of «Institut Scientifique des Pêches Maritimes» and several personalities in Marine Sector.
Were present also more than 20 participants of the following countries : Algeria, Albania, Egypt, Spain, France, Libya, Morocco, Tunisia and Turkey (see participants list in annex).
Mr.Abderrahmane Abouhala, Director General of MAROST, welcommed the participants on behalf of the President of ONA Group. He thanked all personalities who honored the workshop, particularly the Governor of Nador, and pointed out the effort made by MEDRAP Project to promote aquaculture in the Mediterranean Basin. Special thanks were addressed to MEDRAP II Project Coordinator for his great efforts to develop aquaculture at regional scale, within the Mediterranean.
Mr. Abouhala reminded the valuable contribution of FAO and MEDRAP II Project in establishment and launching the MAROST Project.
Mr.Rochdi, Deputy Director of Marine Fisheries and Aquaculture, representing the Ministery of the Marine Fisheries and Merchant Marine, expressed his satisfaction as to the holding of the workshop in Nador. He mentioned that the choice of Nador lagoon to promote the aquaculture activities is mostly appropriate. Mr.Rochdi emphasized the crucial role of aquaculture in the nutrition and protein production, which comes in harmony with fishing activities, he mentionned the support in fiscal matter provided to aquaculture sector and it's priority in the development plans. Mr.Hassen Akrout, the Project Coordinator, called upon to thank the Moroccan authorities and MAROST Company for holding the workshop in Nador. He presented a brief overview of the objectives as well as the MEDRAP II Project activity since its launching in early 1991.
Mr.Akrout reminded that MEDRAP II Project priorities, were to establish three networks through the member countries: Training, Research and Production. He expressed his wish to see the rapid expansion of these Networks.
As to the workshop theme, he noted that the use of modelling essentially in hydrodynamic, biologic and bio-economic components appears to be the best tool, for lagoon management.
His Excellency the Governor was satisfied as to the holding of the workshop in his country and wished all participants a nice stay and urged them to closely cooperate in order to preserve the lagoons from actual damage raising from urbanisation, industrial and agricultural pollution. He concluded with in an optimistic note that the workshop would contribute to a better management of the lagoons.
1.3 Adoption of the agenda, and Designation of the Officials
The Agenda included as Annex I was unanimously adopted.
Mr. Abderrahman ABOUHALA, General Director of MAROST and Mr. Arian PALLUQI, Albania Representative, were unanimously designated respectively Chairman and Vice Chairman.
Mr. A.BERRAHO, Moroccan Delegate and MR.BELKHIR, MEDRAP II Expert were apointed Reporters of the Workshop.
1.4 Constitution of ad hoc Committee
Talking into consideration the main objectives of the workshop, consisting in the initiation of the modeling concept, three major components in the mechanisms of lagoon ecosystem management were envisaged. It was decided to establish three working Sub-groups as follows :
| • | Working Sub-group 1 | : | on lagoon hydrodynamic modelling |
| • | Working Sub-group 2 | : | on lagoon biological modelling |
| • | Working Sub-group 3 | : | on lagoon economical modelling. |
2- MINUTES OF THE WORKSHOP
2.1. CUPIMAR Experiment in Lagoon Management for Aquaculture Purposes
By Lazaro Rosa
CUPIMAR is a marine fish farming company, situated in Cadiz - Spain.
CUPIMAR succeeded in the management of salt pen belonging to the lagoon system of the Cadiz
bay, actually supporting a large aquaculture activity. Thus, from the beginning to now, culture system
has evolved from extensive and non profitable system to a semi-intensive and benefit ones. The
biomass too progressed from 200 kg/ha with 70% made up by mussels (in extensive culture) to
1,000 kg/ha with 70% composed of sea bream and sea bass. The income was 300.000 US$/ha. In
parallel way, to rearing development, CUPIMAR was successful in the artificial reproduction of
clams, shrimps and particularly with sea bream.
The actual production is as follows:several millions of sea bream fingerling. 700 tons of finfish made up by sea bream (450tons), sea bass(150 tons), clams(50 tons), oyster(25 tons) and shrimp (25 tons).
The forecasted production, during 1992, is fixed to 800 – 900 tons for all species. The new strategy, undertaken in the assessment and management of the salt pen allowed CUPIMAR to increase its income from 100.000 US $ at the starting of marine culture to 13 million US $, actually.
According to the improved layout, beneficial impact was recorded at both social and environmental levels. Regarding the social level, the number of employees increased from 50 at the starting of the project to 500 actually, as the salt pen were becoming productive, the environment also improved and grass and beautiful plants are now seen along the rearing basins from the esthetic point of view.
Through that communication, care should be given when realizing such management after environment studies have been conducted on the site. It is also recommended to reduce risks by diversifying the production and making an optimal use of natural resources.
2.2. MEDRAP II member countries experiments in lagoon management and assessment
(present situation, needs and constraints)
2.2.1. Egypt experiment in lagoon management
By Magd Morsi El Bawab
Bardaweel lagoon is cited as a case study to show the Egyptian experience in lagoon management, it mainly concerns the fishery as it is considered as an extensive aquaculture activity. The present communication summarizes the description of Bardaweel lagoon regarding its structure, functions and ecological system, and the important role that Bardaweel lagoon is playing on both level, the social and the economical ones.
Indeed, the lagoon is offering work opportunity to more than 3000 workmen and insuring 15 to 20 % source of income for Egyptian population. The production of Bardaweel lagoon is exceeding 0,8 % of the total Egyptian production. The high productivity of Bardaweel lagoon, is due to the particular ecological conditions of the system, which is receiving alternative inlets of fresh and marine water, respectively from neighbouring land and sea. Such water inlets, are very profitable to the trophic chain. On the other hand, as Bardaweel lagoon is unpolluted, care has to be taken to avoid problems caused by the interaction between fishery and fishing technics. Egyptian authorities, pointed out the importance in preserving the lagoon environment which could be severely affected by inappropriate fishery management.
2.2.2. ALBANIA experiment in lagoon management
By Arian Palluqi
Along its marine coasts, Albania shows several lagoons covering a total area of 12.000 ha and having the common following characteristie: the depth is varying from 0,3 to 1,5 m while the temperature and salinity are respectively ranging from 15 to 60% and 5 to 35°C. The large amplitude of both salinity and temperature implies a large variation of dissolved oxygen which is ranging from 2 to 8 mg/liter and the renewing water within these lagoons seems to be very low according to tide extend (30 to 38 cm) which is very weak and insufficient.
During last years, the minimum average yield was 60 kg/ha/year and the maximum one was 80 kg/ha/year of fish 60% of that quantity consisted on valuable fish.
From time to time, fish yield is affected and interrupted because of sand barrier formation within the communication between the sea and lagoons, also because of lacking of fresh water inlet.
Furthermore, the Butvinti lagoon shows some peculiarity regarding the evolution of its components. In spite of relatively great depth o 20 m, all the lower water layers below 7 m depth are rather anoxic and salinity ranges from 18 to 30 % while the temperature ranges from 10 to 27°C.
The main fish barrier in the lagoon is the fishing gear, trammel and gillnets for finfish and traps for eel.
With regards to mussels in this lagoon, there are fifty two structures for its culture and the rate of mussel production attains, very often, an average of 4.000 tons.
Authorities in Albania are convinced that management is of great interest in lagoon exploitation. To further improve the yield it is envisaged to develop a strategy on modern technology.
To realize the transition from traditional lagoon management to valliculture, Albanian authorities bring out the following items:
correcting the lagoon management with special regard to the hydraulic aspect;
using selective and modern fishing gears,
solving the seed problem by building hatcheries.
2.2.3. TURKEY experiment in lagoon management
By Kamil Dilek
According to earlier records, there was 33 lagoons in Turkey covering 66.000 ha, this number has been in constant decrease sue, in particular to structural modifications.
Actually, in Turkey, there are only 10 lagoons with 32.000 ha in size and mainly considered as benefit for fishery activities. In spite of having a large coastline, the production is still being low when compared to other countries production. The average yield within Turkish lagoons varies from 36,4 kg/ha/year to 60 kg/ha/year.
In order to increase the lagoon productivity there are big needs to manage Turkish lagoons by acting on their structure, improving the extensive aquaculture and enhancing the semi intensive and the intensive ones. On the other hand, the type of fishing harrier must be changed, and parallely, training of fisherman should be reviewed as well. Modern type of fishing barrier, when introduced in lagoon is important and will, doubtless, lead to increase the lagoon efficiency.
2.2.4. ALGERIA experiment in lagoon management
By Zaier Abdel Nasser
Lake Mellah is the most important Algerian coastal lagoon covering a surface area of 860 ha and communicating with sea through a long channel (900 m) which shows a sandy mud sedimentology. The exchanging water between the lake Mellah and the sea is restricted and largely influenced by wind directions and velocity. Because of its geographical and topographical situation, the lagoon receives an inlet of freshwater from neighbouring rivers in winter time which is of great benefit to marine resources.
During the last decade, lake Mellah knew several activities leading to its management and its structures modifications such as :
the settlement of capetchades consisting in two systems activated alternatively over the year. The main species aimed are sea bass, sea bream, grey mullet and eels;
introduction of mussel culture using fixed tables;
enhancing natural and extensive clam;
implementing of a sea bass hatchery of 200.000 fingerlings yield capacity.
Furthermore, Algerian authorities conceived, for the near future, a pilot programme to develop new and rational aquaculture technics within the lake Mellah. The main guidelines of that strategy are the following :
reorganizing existing aquaculture activities;
constructing a hatchery to facilitate artificial reproduction of both oyster and clam;
introducing the sea bass intensive rearing, using cages within the lake Mellah.
The above described management will take into consideration the impact on the hydrodynamic aspect within the lagoon with special regards to the ecological and biological evolutions.
2.2.5. LIBYAN experiment in lagoon management
By Salem Zagouzi
The Libyan coast exhibits four big lagoons and many other small ones. The main important lagoons are namely the following:
Farwa lagoon: it is located about 150 km west of Tripoli and has a surface area of 310 ha. The lagoon's basin Bukammash sound is separated from the sea by a narrow bar of about 11 km length known as Farwa island. That lagoon is communicating with the sea through two openings. The western one is relatively wide (3.5 km width at high tide) and the eastern one is about 10 m width. The depth varies from 0.5 to 2.5 m and water characteristics are indicated by a salinity of 41 % and temperature ranging from 11 °C (in winter) to 29°C in summer, while the pH mean value is 7.5, dissolved oxygen is about 6 ppm and transparency of between 1 to 1.5 m.
Aïn El Ghazalah lagoon : is situated about 60 km cast of Derna and has a surface area of about 150 ha. The depth is ranging from 0.5 to 2.0 m with an average recorded of 1.5 m. One solid hill block protects the lagoon from the north and the north east. The lagoon receives, in spring, an inlet freshwater of about 0.5 m3/sec with a salinity of about 8% while the temperature is 23°C and p117.8.
The water characteristics of the lagoon indicate in summer a salinity of 40 – 42 %, a temperature of 22°C and PH of 8 while the transparency is often 1 m.
Since two years, the authorities in Libya started growing and fattening two marine species the sea bass and sea bream in Aïn El Ghazala, using local made floating cages, the yield, in 1990 was ten tons sold in the local market. Fingerlings were collected from the wild and such activities should not lead to big scale fish farming which could be of big risks because of unabundent fingerling in natural coastal water, on the other hand attention should be given to the exchanging of the water between sea and lagoon and which is very limited due to sand bars formation in front of the openings of that lagoon.
Furthermore, some management concerning the rational exploitation and use of lagoon is on going and will consist in special housing construction for aquaculture activities.
2.2.6. MOROCCO experiment in lagoon management
By Abdellatif Berraho
In Morocco, there are two aquaculture centers: the center of Oualidia, known for its ostreiculture carried out in a very skilled manner at five oyster beds, is produces about 150 tons of Japanese oysters per year for local market needs. The center of Nador, being recently in progress development, is including a complex and integrated farming of valued and commercial shellfish and crustacea. Fry and shell broods, are mainly produced in specialized hatcheries. The center of Nador, is exporting valued marine species towards Europe.
Furthermore and regarding the sites of big potentialities to be used for aquaculture purposes, there are two main types:
low and estuary zone, often including salt pen, such as the estuary of Moulouya on the Mediterranean coast, salt pen of Asilah and the estuary of Loukkos, on the Atlantic. These zones are not yet exploited because they need more investment, more technical knowledge and more civil engineering works as well;
marine lagoons: there is an urgent needs to take into consideration the several constraints, that these lagoon are presenting against their exploitation for aquaculture purposes. Thus, a strategy should be conceived for aquaculture development. These lagoons are the one of Nador (Mediterranean coast) and lagoons of Moulay Bousselham, Sidi Moussa, Oualidia and Khnifiss, on the Atlantic.
Research should be initiated to determine the main objectives for establishing the aquaculture national development plan. Thus, fundamental and accurate studies, should concern the sites of great interest for aquaculture, such as the hydrodynamism, sedimentology, ecology, biology and socio-economy. While these lagoons present good opportunities to improve production through aquaculture activities, the lagoon of Nador remains the only one with the best potentialities for aquaculture, it has the largest surface area and depth, and shows good hydrobiological conditions, a large advantage for marine culture.
2.3. Lagoon production potentialities :
role and impact of aquaculture activities on environment
By Olivier Guelorget
All along the Mediterranean coasts, there are a number of lagoons, different from each other, but presenting almost the same organization from the point view of sedimentology and biology. Within each lagoon, there is a fundamental parameter which is managing the qualitative as well as the quantitative organization. That parameter, is called the confinement which can be defined as the renewing time of inlet marine water at a given point within the system.
The system zonal organization is mainly based on the study of benthic settlement distribution, which is characterizing the environment and can survive for such a short or a long term, to its valuable conditions.
Six zones have been defined, enumerated from I to VI (see figure), which are described and distributed from the point of communication between the lagoon and the sea to the land edges. Several studies conducted in different types of lagoons, showed that zonation has been seen as well as in lagoons heavily affected by fresh water inlet than in the hypersaline ones.
The determination of macroflora and macrofauna benthic species, is needed to indicate to which zone is belonging the sampling point.
The variation of phytoplankton, in term of chlorophylle biomass (mg/m3 m Chla), can show according to the above cited zonation, maximum within zone IV/V while the benthic macrofauna biomass has the greatest rate in zone III, which is characterized by filtering molluscs with mainly, the Veneridae Ruditapes decussatus.
The lagoon system biological organization study allows an evaluation of biological potentialities and
permits to locate the importance of trophic compartments within the system.
On and after the zonal organization schema, which is linked to the confinement, there has been proposed
a zonal management for aquaculture purposes. Thus, the above described methodology takes
into consideration, the sedimentology organization and allows to evaluate and predict the impact of
any aquaculture activity that could be realized within the lagoon system.
2.4. Modelisation : problem set in lagoon management for aquaculture purposes
By Mohieddine Belkhir
The major importance is granted to ecological studies when establishing a management plan and taking decisions. Thus management raises many problems linked to social, cultural, economical and ecological aspects. Regarding the complexity of such interdependence of the different components of the system, the modelisation should be considered as and approaching tool and should contribute to understand the mechanisms of the system by describing, analyzing ad simulating it, this will surely help, at the conception level, to determine the best type of management to be introduced within a given lagoon system. But, it has to be noted that there is no typical and common model that could be applied to all lagoons as these lagoons are different in functions and structures. However, in specific cases, such ash hydrodynamism, the modelling is a useful tool that allows to predict management impact on the lagoon structures and functions.
Thus, this communication is basicaly dealing with various difficulties when modelling applied to lagoon management for aquaculture purposes and intending to show the usefulness of the modelisation, its complexity and limits of its application as well.
2.5. Hydrodynamic modelisation : case study use of commercial model
By Abdellatif Orbi
The general bibliographic review introduced is related to different kinds of models and mathematical equations usually used in both the Atlantic and the Mediterranean.
Channel islands, situated in «Golfe Normand - Breton» have been a subject of modelisation, it is listed as a case study to illustrate the two dimentional mathematical model used to investigate tidal currents; on the other hand, by this example, the lecturer tries to show the usefulness of such numerical model in describing the current circulation and helping in the conception of lagoon management. Furthermore, attention is focused on in situ measurements which improve the knowledge and help understanding of current circulation within the system… The quality of in situ measurements is of a great importance and allow to have better calibration and validation of the model. Thus actually, the Marine Fishery and Scientific Institute realized several investigations within Dakhla bay, in Morocco, and gathered a lot of datas which will be used to define the conceptual model and permit, in a second step to establish the mathematical model.
2.6. Hydrodynamic and biological lagoon modelling: case study of the lake of Tunis
By Mahmoud Moussa
Since ten years, modelisation is considered as a leading technology for scientists, managers and decision makers and thus, it constitutes in the field of lagoon management, the tool that allows both to understand of aquatic ecosystem functionning and to predict aquaculture activities impact on the environment. Lake of Tunis, taken as an example to illustrate such modelling application before undertaking any management, was the subject of several year of studies related to the hydrobiology and sedimentology aspects. Indeed, a lot of datas collected in situ, were used to calibrate the water circulation model within the lagoon and the water exchanges between that lagoon and the sea, the biological model is dealing with the simulation of the biological parameters evolution, in time and apace.
The final model applied to lake. Tunis reminds the one of LEHMANN, using the kinetic laws completed by in situ measurements. That final model realized in 1984 and validated according to in situ measurements in 1988–89 after the lake of Tunis management, is supposed to be able to draw up a schema of water quality evolution during the coming five years.
2.7. Development of extensive clam culture (Ruditapes decussatus)
in Atlantic coastal lagoons of Morocco
By M.S. Shaffee
Extensive culture operation of clams (Ruditapes decussatus) were undertaken in three different lagoons in Morocco. These lagoons namely Oualidia, Sidi Moussa and Moulay Bousselham are situated along the Atlantic coast. When compared to non protected, the protected culture using a nylon mesh covers, gave better growth and better survival rates. Maximum yields can be obtained at densities varying from 100 to 500 individual/m2, for large size animals (more than 30 mm); spats will take three years to attain commercial size of 40 mm, while the medium size clam and the large one will need respectively two and one year.
Furthermore, the natural stocks of clams, in Morocco, are being destroyed as a result of overfishing in Moroccan coastal water and an ever increasing demand from European markets regarding that species.
One way of safeguarding the natural stocks and enhancing the conditions of fishermen, will be the implementing of extensive culture programmes within Moroccan coastal lagoons.
2.8. Global approach of a aquaculture influence on marine ecosystem
By Cédric Bacher
Modelling experiment applied to aquaculture field allows to bring out some thoughts on modelling usefulness on aquaculture-environement interactions and on the way to follow prior to starting the lagoon system functionning study.
The basin of Marennes-Oléron is taken as a case study being presented in the economical, historical and ecological context, to explain the effort caried out and analytical modelling.
This site of great ostreicol production was studied and modelisation was applied with the view to establish a management strategy of yielding and environment with special regard to respectively the medium trophic capacity and interactions with neighbouring ecosystems. The final model contains two sub-models: the carrying and the biological ones, and should help in simulating the coupling between the horizontal carrying process, the primary production and the oyster growth (Crassostrea gigas). Using this model, several sets od data were analyzed, interesting conclusions were made, such as evaluation of the nitrate impact supplied by the side basin and the influences of reared oyster biomass over the yielding and over different components of the trophic chain.
This analytical approach linked to all running phenomenons will lead in a progress way, to the introduction of new compartments and sedimentology processes as well as to the coupling of the regional models related to the oceanic circulation and the side basin functionning. Thus, one thought is committed regarding firstly, the scale processes in space and time and which modelling is to be taken into consideration and, secondly, the development and the adjustment of modelling tools.
That global approach consisting in the organization of the processes into hierarchy, and in the analyzing of the system functionning is applied to the Thau lagoon. Pluridisciplinary research team engaged in the Thau study allows to show the complexity of the system and the needs of leading, such survey linked to the physical, chemical and biological aspects within the several components of the system.
The following steps in modelisation are definite according to the above cited knowledge and have
to provide answers to such accurate problems. The modelling experiment in the Marennes-Oléron
bay and the existing datas gathered on the Thau lagoon are of interest and should help in formulating
some recommendations on lagoon management for aquaculture purposes. For instance, it is
necessary to control the evolution of the system and to define the different conceptual models (ecological,
analytical and empirical ones).
Parallely, it is obvious to undertake laboratory experimental studies which are of big importance to
evaluate matter fluxes and processes.
Furthermore, to improve knowledge and to go further in lagoon modelling, cooperation should be
enhanced between specialized institutions to establish survey and monitoring network; there will be
great common benefit when technical and scientific know-how brought together as well as the existing
data base.
2.9 Actual and future management within the Nador lagoon
By Abderrahmen Abouhala
A detailed description of physical hydrodynamical characteristics of Nador lagoon, indicates that it can offer high potentialities, regarding its surface area which is covering 11,500 ha, and its relatively deep water which is varying from 5 to 6 meters. As the lagoon is communication with the sea through a long channel, it would be well to note that the renewing water is too weak and there is confinement raised within the exterior zones beside: this phenomenon, some constraints are set and attention should be given to resolve them:
land covering with sand of the channel:
induced pollution by Nador sewage outlet;
effluents from oued Salouane.
Recently, MAROST has produced 450 tons/year of marine species of which 300 tons are sea bass and sea bream. Actually, MAROST is producing 2 millions fry of sea bass, 3 millions post larvae of shrimps, 10 millions of oysters and 20 millions of shell brood. The Staff is composed of 250 persons and investment reached 150 millions MDh.
The futur production expected for 1994, will be 3.000 to 4.000 tons of fish and slower progression of yielding for others (the oysters and clams), while shrimp rearing, will be done using intensive system. Local shell brood production, will be realized in the near future and will satisfy the Oualidia center's need. Lastly, Nador lagoon channel will be studied with the aim to it's stabilization while a pond basins will be constructed to increase the treatment capacity of sewage treatment station.
2.10. Bio-economic aspects on lagoon management
By Carlos Martinez
Let us consider the great place that lagoons are occupying at both economical and social point of view, but also for touristic, industrial and fishing purpose. In order to protect lagoons structures and their biological resources from unforecasted pollution and overfishing, aquaculturists should have to convince judges and bargain with other firms about property rights.
An important part of the job in the aquaculture firms is to be made at the law courts around the negociation tables.
Furthermore, the cost inherent to any transaction of negociation process may block the way to any agreement. On the other hand, these firms have frequently to confort long established interests where the social and individual efficiency will play a convincing and conclusive role.
Although the law is to be considered the basic one while the vital framework within aquaculture business has to be conducted and the behavior of competitors could make necessary to consider the convenience of certain uncontrolled activities. Some law and economic models could be useful to understand this kind of problems. The question is that could it be necessary under some circumstances, to harvest over the legal quotas.
2.11. Working Sub-groups reports
2.11.1 Lagoon hydrodynamic modelling
1. Lagoon environmental study
Multidisplinary approach
There is a need to collect in situ data measurements over a minimum of one year period in
order to describe the ecosystem functionning such as:
- hydrodynamic parameters survey;
- sedimentology and geology monitoring;
- inlets evaluation.
- meteorological study.
Hydrodynamic model
The knowledge of physical circulation and the simulation of the dynamism of the water
column is of great interest to help in conceiving the lagoon management.
Interrelation between hydrodynamic and biological models
Interrelation study will allow to forecast the impact of aquaculture on a given lagoon system.
Thus, to improve the yield and preserving the biological resources.
2. Recommendations
- Hydrodynamic models should proceed any applications of management schemes including the aquaculture in lagoons.
- MEDRAP member countries authorities should protect the ecosystem of lagoons accordingly with hydrodynamic models.
- MEDRAP Coordination center should help in elaborating software applicable to the study of the hydrodynamic of lagoons.
2.11.2. Lagoon biological modelling
1. Originality and biological interest of the lagoon systems in aquaculture
Due to its interface sea-land positions, lagoon systems are subject to marine and continental double influence. These environments are very productive (12% of the biosphere production are issued from the lagoons).
Lagoons are managed by confinement, a fundamental parameter responsible for the qualitative and quantitative biological organization.
While comparing to open coastal marine systems, we notice an amplified exchange between the different trophic levels in lagoon environment. It is therefore a wide field of observations, experimentations and productions particularly interesting.
The geologic and trophic lagoons role is obviously essential notably towards the bordering marine field.
The lagoon observation access and their easy functionning description are due to their apparent ecological structure. This is equally important to evaluate their tropic capacity.
2. MAIN PROBLEMS ENCOUNTERED IN LAGOONS
The opening to the sea is essential to maintain the lagoon system. The continental contributions issued from the basin side (land inlets) enriched the lagoon ecosystem and participate to its functionning but may disturb the development of aquaculture activity and other trophic chain (example of Thau).
Coastal management (several activities) would have an obvious impact on lagoon ecosystem. Aquaculture and fishing activities may have a negative impact on the lagoon system stability and perennity.
3. Biological modelling of lagoon system
A thourough knowledge of the lagoon organization and its functioning is required for it's exploitation. The analysis of its process, in time and space, should lead to understanding the ecosystem and should establish its modelisation such as ecological, analytical and empirical modelisation.
4. Recommendations
- polyculture introduction;
- progressive introduction of aquaculture allowing an ecosystem adaptation to that activity;
- management and assessment of rearing considering the exploited areas holding the activities;
- establishment of protected areas within the lagoon ecosystem.
- assessment of the ecosystem carrying capacity;
- technological adaptation to the rearing areas;
- personnel qualification;
- establishment of monitoring and control surveys according to the management required;
- interrelation between researchers and producers who should partially finance the aquaculture research activities;
- feasibility studies should be conducted and submitted to the agreement of an assessment committee who will authorize further developments.
Establishment of data base on the existing lagoon system.
Pilot project
The study of one or several appropriate sites (lagoon) should be undertaken at a pilot project
in order to develop an integrated research leading to modelisation.
2.11.3. Lagoon bio-economic modelling
Introduction
From the bio-economical and socio-economical point of view, the aquaculture activity should consider
the external world (the lagoon itself, other human activities on the lagoon and the global socio-economic
structure) and the internal-technical and economical world.
1. External considerations
Hydrobiologic aspects of the lagoon
Before building any aquaculture project, the hydrobiological model must be studied.
Indeed, it is necessary to get a complete knowledge about physical and biological ecosystem
before exploitation.
Interconnection with other activities in the lagoon
a) Traditional fisheries
They offer complex social problems. It is necessary to ascertain that the traditional fisherman
will be able to develop their activity or be integrated in the aquaculture projects. The
experience on this subject is that traditional fisheries will get a great benefit through the
management of the lagoon and that the new technics will be efficient enough to offer well
paid jobs and to increase the number of workers on the lagoon.
b) Urbanization, tourism, other industries.
Aquaculture activity generally do not disturb these industries. But we must consider the
possibility that other human activities could be more efficient. On the other hand, uncontrolled
activities (pollution and so on) can prevent the aquaculture industry to develop.
Interconnection with national, regional and international situation.
The legal, economical and commercial aspects at these levels must be studied.
2. International considerations.
Feasibility study in accordance with hydrobiological requirements.
Feasibility study in accordance with economic requirements:
- financial: aquaculture firms require a strong starting investment and use to require some
years to get it return. So the financial costs must be carefully evaluated;
- technical: modern aquaculture needs high level technicians and special structures;
- marketing: the aquaculture products are to be sold in a market, so that the laws of offer
and demand must be considered.
3. Recommendation
The aquaculture projects in lagoons should be integrated in its environmental context at the local, national and international levels.
The particularity of aquaculture project in lagoon requires to take into account the economic risks.
Legal support is necessary to insure the project viability.
- Forbidding antisocial uses of the lagoon.
- Protection from unloyal competition.
- Possibility of temporal and conditional monopoly.
Training and technical support.
3- WORKSHOP GENERAL RECOMMENDATIONS
Regarding the benefit and the high economical value that lagoons offer respectively to scientists and producers, considering that lagoon systems are of complexity and diversity characteristics, and that they can be affected by a non appropriate management.
The participants of the workshop on lagoon management held in Nador, Morocco, from 30 September to 5 October 1991, brought out the following recommendations:
MEDRAP member countries should work on the preservation of the ecological equilibrium of the lagoon systems in accordance with hydraulic management to improve the renewing water within the lagoon and with respect to the biological and socio-economic aspects.
Biological, hydrodynamical and socio-economical modelling should be developped to lagoon management with special regards to hydrodynamic model, which must preceed any application of specific management schemes within lagoon.
The authorities of MEDRAP II member countries, should bring out a well organized aquaculture activity in lagoon:
by insuring integrated planning of lagoon management and aquaculture;
by insuring connection between research survey and production;
by providing good level of technicians adapted to sophisticated technology;
by taking a lagoon as a pilot project to measure the training of appropriate technicians.
Regarding the particularity of the aquaculture activities within lagoon, authorities of MEDRAP countries should also:
evaluate the carrying capacity and adjustment of the production;
take into account the economic risks which may be harmful;
provide legal support to insure the Project viability:
- by forbidding antisocial uses of the lagoon;
- by protecting the producers from unloyal competition;
- by the adoption, if necessary, of temporal and conditional monopoly.
by conceiving a methodology approach to be used as guideline in lagoon management for aquaculture purposes using the modelisation as a tool in the matter;
by initiating technicians in modelisation and to enhance their scientific level, regarding the lagoon management within specialized institutions;
in elaborating software applicable to the hydrodynamic lagoon study and realizing a data base in the matter as well.
