The consultant was called upon to make a number of visits to advise on technical aspects of existing and planned projects. The most important aspects of these visits are discussed in this section.
Prokopos is situated approximately 35 km south west of Patras in the Peloponnese. It is a brackish lagoon with a surface area fluctuating between 100 and 400 ha in summer and winter respectively, and is connected with the sea by a 2.4 km canal. It has an average declared production of 25 t/year (50% eels, 45% mullet, 5% bass), thought in practice to be up to 30% greater than this. The lagoon is owned by the state, administered by the Patras fisheries office, and managed by an 18-member cooperative.
The principal interest of this lagoon lies in its having a number of particular features and problems, one or more of which probably affect most lagoons in Greece. These are:
The presence of a popular tourist development at Kalogria Beach; the development extends some way up the supply canal, and activity in the summertime in and around the canal mouth is said to discourage the entry of fry.
The wetlands surrounding the lagoon are the habitat of a rare species of Mediterranean pine, and as such the area may be designated as a National Park.
The fishing rights of the area flooded in winter are disputed, and widespread “poaching” is said to take place; this problem leads the cooperative to carry out an unusual fishing practice known as “girovolia” (“circular fishing”) in an attempt to remove as many fish from the lagoon as possible before the winter rise in water level; this technique not only causes routine mortality of small fish, but occasionally mass mortalities of several tonnes due to reduced water quality and stress.
The cooperative and the party controlling the water flow in the large irrigation scheme upstream of the lagoon are in dispute, reputedly due to the latter's failure to achieve cooperative membership; consequently the water level in the lagoon tends to rise at the most inconvenient times, e.g., when fishing is taking place.
The substantial flow of fresh water through the lagoon, heavily laden with suspended solids and nutrients from farming activities upstream, causes particular water quality problems and also the slow silting up of the whole lagoon; the productive summer area 30 years ago was 220 ha - now that area is halved and many parts of the lagoon are covered in reeds due to the shallower water.
The majority of the problems described above are due to the inability to control the inflowing fresh water. Unless this flow is brought under control, any other improvements made will in the long term be largely worthless due to continued siltation.
The basic steps in the improvement of the lagoon should be:
Construct a canal to divert the fresh water directly to the sea, probably at a point further upstream.
Calculate the water exchange required in the lagoon.
Ensure that the size of the supply canal is sufficient to allow this exchange to take place.
Alter the orientation of the seaward mouth of the canal to prevent siltation.
Install sluice(s) close to the fisheries station to control levels and exchange.
Dredge out deeper overwintering areas in the lagoon.
Install a collecting basin at the lagoon exit.
Install new screens and traps.
Consider subdivision of lagoon with net fences to allow better stock management.
Construct (semi-) intensive ponds with pumping system in the swampy area on the lagoon periphery near the station.
The costs of any improvements made must be carefully assessed to ensure that they are proportionate to the likely resulting increase in production. This lagoon is already quite productive compared with most Greek lagoons - probably close to 300 kg ha-1 - and further increases in productivity may be difficult to achieve.
The lagoon is probably unique in possessing such a wide ranging variety of physical, social and legal problems, and as such may provide an interesting subject for a model development.
The Messolonghi fisheries office is promoting a trial using enclosures to demonstrate to local fishery managers the potential for keeping small fish alive for ongrowing. The present policy of removing even the smallest fish from the traps is widespread - one summer fish down to 40 or 50 g average weight are kept for sale, anything less returned to the water usually dead. This practice is highly wasteful and totally needless, and any efforts to promote change must be applauded and supported.
Two enclosures, each of 1 500 m2, have been strongly and adequately constructed using the usual lagoon materials of wooden stakes and black plastic 10 mm netting; they are located in a side channel opening into the main Messolonghi navigation channel, relatively close to the open sea, where there is said to be good water exchange; the maximum and minimum water depths are 0.5 and 0.3 m respectively. It is proposed to stock the enclosures to reach a final stocking density of 1 kg/m2, or 1 500 kg/enclosure (bass and bream). In order to supply the oxygen requirements of such a stock, there would have to be a continual movement of water through the enclosures and a replacement rate of at least 4 times a day. Detailed measurement of water levels and quality parameters over a continuous period of time is essential before high stocking densities are attempted, and a provisional maximum stocking density should be set at 250 kg/enclosure. A further danger of enclosures, particularly in shallow water such as in this case, is the accumulation of waste food and faeces causing deterioration of water quality within the enclosure; feeding practices should be carefully controlled to prevent such accumulations.
Kokala is situated 3 km south of Preveza on the southern and seaward side of the mouth of Amvrakikos Gulf. It is a shallow (average 0.3 m) unproductive lagoon of 30 ha, belonging to the Nomarchia of Aitolias-Akamanias; administration is the responsibility of the Messolonghi fisheries office.
A number of ‘improvements’ have been made to the lagoon and funded by the Nomarchia. The works carried out were:
dredging of a 100 m × 5 m × 2 m deep channel along the western edge of the lagoon
dredging of previously silted up 300 m long sea water connecting canal to 2 m depth
construction of a heavy rock pier at the canal mouth to prevent siltation and blockage.
Unfortunately these works may not be effective for the following reasons (as recounted by the local fishery manager):
the deepened area within the lagoon is necessary, but on its own will not encourage very much better water circulation as it is connected directly to the outlet canal
the deepening of the supply canal has led to such a reduction in water velocities that they are unlikely to be great enough to encourage fry to enter the lagoon
the new orientation of the rock pier at the canal mouth is such that it is likely to act as a perfect trap for ‘sea grass’ which is washed up in large quantities on the shore.
This is a distressing situation, bearing in mind the commitment of the Nomarchia to improve the lagoon. It is a prime illustration of how well-intended funds can be largely wasted owing to a failure or breakdown in communication between the funder, the improver and the intended beneficiary.
The commitment of substantial funds to small, potentially unproductive lagoons such as Kokala must be debatable, even if they are well directed. The potential annual income of Kokala if producing 6 t/year (200 kg/ha) would be in the region of Dr 4.2 × 106 (average price of Dr 800/kg). Any improvements made should therefore be in proportion to this income; if it is assumed that the fishery can tolerate an annual depreciation sum of 10% of income and that the life of works carried out is 20 years, then the maximum that can be afforded for improvements is approximately Dr 9.6 × 106. For lagoons already in production, the costs must be balanced against any potential increase in production which is likely to be much smaller than the new production achieved in a previously unused lagoon.
The first site visited at Palio Varka is privately owned. The site is exposed to the prevailing north wind with a fetch of about 10 km. The first cages installed were constructed from discarded 200-litre steel oil drums supporting steel spars and walkways, an often first attempted method of cage construction; these were found inadequate for a number of reasons and have been discarded. The cages presently in use, and supporting a recently imported population of sea bass, are of an articulated, raised walkway design, the principal materials being wood and polystyrene. They were designed by a local naval architect and have been well made; the principal problem lies with the method of attachment of the polystyrene blocks to the walkways - presently steel bands are used, which tend to work loose. However, these cages are not suitable for the exposed nature of the site. The operators are aware of this and are intending to replace them with an imported design.
The second site visited was at Bogonitsa Bay, on the north side of the Gulf, and belonging to the Preveza fisheries office. The cages installed were also constructed by a local naval architect, but following the proven “Kames cage” design. The principal fault in these cages was the underspecification of the corner brackets - although stainless steel, the thickness of the plate used was only 2 mm; it should be at least 6 mm. Another more immediate problem was the means of attachment of the cages to the central mooring chain, the deficiency of which was causing significant abrasion to the wooden cage members. The usual “lug and pin” method of attachment used for this type of cage was omitted and a system of chains, shackles and tyres used instead. It was strongly recommended that all these deficiencies be made good.
The newly created Institute of Marine Biology at the University of Crete is instigating an imaginative and well-planned development programme for aquaculture and is fortunate in possessing an experienced and motivated team of people. Their proposals are for an experimental hatchery and pregrowth unit in Herakleion and for production in cages in Elunda Bay.
The following comments can be made regarding the suitability of Elunda for cages:
The bay is very sheltered, being 5 km long and averaging 1 km wide. High mountains to the north provide shelter to some extent from the prevailing winds; two bays on the east side provide further sheltered sub-sites.
The depth at the narrowest part and entrance to the bay is 4 m, that in the deepest part in the central basin 8 m; for cages, the greater the depth under the cages the better, up to a maximum practical depth of 50 m. Greater depth aids dispersal of wastes and distances the fish from the “pool” of decaying wastes which inevitably builds up on the seabed underneath an intensively fed cage unit, and acts as a potential contaminator and source of disease. The depth in Elunda Bay, therefore, gives some cause for concern bearing in mind the limited water exchange.
A canal passing through the isthmus closing the bay to the south allows a certain amount of water exchange (said on average to be around 1 × 106 m3/day), the general direction of flow being north to south; this flow is a useful benefit, but the inability to deepen or even maintain the canal due to archaeological remains nearby is a constraint.
The carrying capacity calculations that have been carried out present realistic development targets (40 t as a pilot stage, 400 t as a maximum initial production target); however, as production exceeds 200 t and approaches the maximum, some deterioration in water quality must be expected; if eutrophication caused by fish production is balanced by an appropriate level of mussel culture, as is practised at Cenmar in Yugoslavia, then the situation may to some extent be controlled. If the environmental impact of farming is continuously monitored from prestart-up through different stages of development, as is proposed, then expansion can be controlled when water quality starts to deteriorate.
The model proposed for the development of cage farming in the bay, e.g., the allocation of concessions 70% to inexperienced local operators, 20% to experienced outside operators, and 10% to the University should, if successfully applied, provide the most rapid transfer of technology to the local operators, who learn by the example provided by the experienced operators; the University research activity acts as a stimulus to new methods and ideas.
A bay in many ways ideally suitable for cages is located 1 km to the east of Elunda on the opposite side of the peninsula; it is sheltered, deep (17–25 m) and would appear from the chart at least to offer good water exchange; it is also separated physically and visually from Elunda which is a very popular tourist resort. This site was not, however, visited.
The programme of the University should be properly supported, offering as it does to investigate many of the potential problems and constraints of intensive mariculture in Greece.
The consultant was asked for advice by the Hellenic Agency for Local Development (ETA) concerning three sites owned either by local communities or municipalities.
One of the functions of ETA is to carry out feasibility studies for local communities and municipalities, and lagoon improvement and aquaculture is one area of their activity. The three sites in question were Lefkas lagoons, Mati Tyrnavou (a spring-fed fresh water lake) and Mavrotopos (potential for marine pond farm). Advice was provided on the first two sites but only the latter could be visited.
The municipality of Alexandroupolis owns 600 ha of low-lying, predominantly sandy land adjacent to the sea, 7 km east of the town. Various proposals have been put forward for aquaculture development on this site, mostly integrated systems with intensive and semi-intensive components. The site has two major constraints:
the shore is open to the south and the depth of water shallow (<2 m) to a distance of more than 500 m from the shore, presenting problems for a water intake
the land is predominantly sandy, presenting problems for sealing of ponds.
One solution proposed for the seawater intake consisted of:
A 50–100 m channel excavated in parallel with the shoreline and 20–30 m from it.
This channel connected to the sea at each end by two further channels.
The entrances to these channels to be protected by rock arms.
The pumps to withdraw water from channel (a).
The size of the various components would depend on the volume of water extracted.
Before deciding on strategies for pond development, a detailed soil survey of the site is required, being properly carried out along preset transects and examining the soil profile to a depth of 2 m. Although the site is predominantly sandy, there are areas of silty clay present, notably along the course of the old river bed; the extent and depth of such areas must be evaluated.
This site, being developed by SPEKA in conjunction with a local cooperative as a demonstration centre for a variety of aquaculture systems, has been discussed in detail by a number of other consultants visiting the site. This consultant would add the following comments:
The southern bay proposed for cage culture is sheltered and has a depth of about 10 m, and as such is physically suitable. However, doubts must be raised concerning potential water quality problems due to the closed nature of the bay and the likely eutrophication as a result of intensive cage culture. The same comments made concerning Elunda Bay apply here too. More basic data are required regarding water exchange (tide and current measurements), water quality (especially existing eutrophication and oxygen levels), and bathymetry. Calculations may then be made to estimate carrying capacity.
The water intake to the hatchery is of fundamental importance. In this case not enough consideration has been given to the correct positioning of intake and outlet points; not only is the intake threatened by the potential environmental impact of the proposed cage units, but also by its proximity to the outlet (about 80 m). Shortage of project funds was given as one reason why the inlet/outlet points could not have been located more satisfactorily; this is a pity given the otherwise apparently comprehensive treatment of the other hatchery components. One relatively cheap solution to the input problem could be to use an existing but old pier structure extending 70 m out into the bay; this pier was formerly used for loading iron ore and is still in reasonable repair. The intake point could thus be located at any depth down to 10 m depending on the relative quality of water at different levels. The cost of approximately 80 m of extra delivery pipe plus the means of supporting the pipe from the pier would have to be assessed against that of the previously proposed concrete structure on the shore.
The elevation of the hatchery above sea level appears to be unnecessary, but due to the low cost of electricity for agricultural enterprises in Greece (about Dr 3/kWh) the impact on production costs will not be significant (less than Dr 1/fry if production is 250 000).
Closure of the 300 m wide mouth in the northern lagoon with a rock/earth barrier and installation of sluices has been suggested as a means of controlling the environment. This would appear to be costly and possibly counterproductive. It is recommended that as a first stage the lagoon mouth is closed using a system of simple net fences and traps as are presently used in Messolonghi. This would not significantly hamper water exchange, which is presently good, and would allow some assessment of the present productivity of the system. Simple adaptations could be made to the traps to prevent the unnecessary loss of small fish, which presently happens in Messolonghi.
The lagoons at Kavala (notably Keramoti, Agiasma, Eratino and Vasova) have been the subject of extensive improvement in recent years. The reason for this is the good relationship existing between the cooperative members and the local fisheries office, and the honest declaration of catches by the members.
The consultant was asked to advise on the siting of a pregrowth unit for growing hatchery reared fry of 1–2 g up to 30–50 g prior to stocking in lagoons or ongrowing more intensively. All four sites were visited. The most favourable location for a unit appeared to be at the main mouth of Eratino lagoon. Water quality here appeared to be excellent and an intake could be inexpensively located in the area enclosed by the newly constructed traps and screens. The unit could be located close by and discharge into the deep over-wintering pond on the opposite side of the fishery station. Electricity is not presently available, but a supply is shortly to be installed.