With the exception of eels, which are the subject of another report by a specialist consultant in this field, the important freshwater fish species cultured in Greece can be divided into two groups: the salmonids and carps.
By far the most important cultured fish in Greece is the rainbow trout (Salmo gairdneri).
Official estimates of total production from Greek rainbow trout farms during 1986 varied from c. 1,800 tonnes (Agricultural Development Bank) to 2,500 tonnes (Ioannina Trout Farming Cooperative), but all authorities were agreed that output is now fairly static from year to year. Similarly, estimates of the total number of trout farms in Greece ranged from 115 (Agricultural Development Bank) to in excess of 200 (PASEGES and the Ministry of Agriculture). Such diversity of figures is inevitable in an industry structured as it is in Greece. Most of the trout farms are very small, and some operate only intermittently. With the exception of a single cooperative at Ioannina to which 16 trout farms producing a total of 300 tonnes per year belong, they are generally selling independently rather than via centralized organizations. This lack of organization and coordination, especially in marketing, is perhaps the biggest problem facing the business.
Almost all Greek trout production is of “portion-sized” fish, but the portion size of 300–350 g in Greece is a little larger than that in most other European countries. Most fish are sold fresh, but some producers hot smoke a proportion of their fish before sale. The owners of many small trout farms also run restaurants, through which fish are sold direct to the consumer at a good price.
Salmonids require large quantities of cold, well oxygenated, and usually running water.
At present, around 70% of Greek trout production comes from the area around Ioannina. There, farms are especially concentrated on the rivers Louros and Voidomadis. On the Louros alone there are 20 trout farms in a distance of 20 km, all reusing the same water. Although no serious pathological problems have yet been experienced, the dangers of such an arrangement are obvious, and those farms furthest downstream live with the worry of periodic deterioration in water quality. Consequently no further licences are being issued for establishment of new trout farms on these rivers.
Elsewhere, however, Greece is blessed with an abundance of water sources suitable for trout farming. In addition to rivers, throughout northern Greece spring supplies are available with constant temperatures of between 13 and 16°C which are ideal for growth of trout. Only a small percentage of these are currently used. Other good sites are available in the region of Karpenissi, Livadia and N. Peloponissos. Western Macedonia contains a number of large, deep lakes which could be suitable for cage culture of salmonids during the colder parts of the year. Crete has several “almiros”, i.e. brackish water springs with salinities ranging between 2 and 7‰ and temperatures of 14–16°C, which are currently unused but would be perfect for trout culture. The largest of these almiros, located a few kilometres west of Heraklion, could alone produce 500 tonnes of trout per year with its minimum flow of 4 m3/sec.
There is thus no shortage of suitable waters for the expansion of trout farming. Further, many existing farms have sufficient water to quickly increase their production substantially if they found it profitable to do so. The limitation on trout output in Greece is therefore not one of sites. The problem is the difficulty of finding remunerative markets into which to sell any increase in output. This will be discussed further below.
The design of hatchery facilities for rearing rainbow trout fry and fingerlings differs between the north-east section of the country (E. Macedonia and Thraki) and the west (Central and W. Macedonia and the Ioannina area). In both cases it is clear that someone has introduced a single design which has subsequently been copied by most of the other producers in the area.
On the eastern side of the country, fry are first-fed in small rectangular concrete tanks or raceways varying in size from 2 × 1 m down to around 1 × 0.3 m, all with 0.2–0.4 m depth. These are fixed structures, typically built to waist or chest height for convenience of working. Water enters at the surface and leaves through an external elbow pipe at the downstream end. For egg incubation and hatching, egg trays comprising perforated plastic bases fixed to wooden frames fit inside the concrete tanks on moulded ledges close to their tops.
Further west, more modern hatching troughs are normally used. Most of these are currently made of painted galvanised steel, but moulded fibreglass is now being adopted. The troughs average c. 2 m × 30 cm × 25 cm deep, and are supported to a convenient height on steel or wooden frames. Water leaves, and its level is set, by plastic elbow pipes at the downstream end. Egg trays are of plastic mesh on wooden frames or of perforated steel or aluminium sheeting. They hang inside the troughs suspended by hooks.
The larger hatcheries in all regions are also equipped with incubation cylinders, usually made of plastics capable of holding 25–40 l of eggs up to the eyed stage of development, at which time they are sold or transferred to incubators as described above for hatching. A few units have adopted even simpler systems for egg hatching, whereby plastic mesh egg baskets are floated on the water surface in fish tanks or rest on the tank bottom in shallow running water.
Egg incubation and early fry rearing are done indoors.
After first-feeding, fry are typically kept on in their hatching troughs until they attain a weight of 2–5 g, before transfer outside to on-growing enclosures.
Most hatcheries receive their water supply via plastic or concrete pipes, but galvanized steel was seen in some units.
Many trout farms retain the capacity to produce their own fry in addition to growing fish to market size. However, the national trend is towards construction of a few large, centralized hatcheries specialising in production of fry/fingerlings for sale to specialist on-growers. Several large state hatcheries either give or plan to give eggs and fry to small farmers free of charge. 9–10 million fry per year (approx. 90% of the country's output) are produced in the Ioannina area.
On-growing to portion-size is normally done in earth ponds or in raceways constructed either completely in concrete or with concrete sides and ends but earth bottoms. As in other countries, ponds and raceways vary in size up to a maximum of c. 80 m long and 10 m wide. Water depth is 0.5–1 m.
Generally, the farms using earth ponds are the older ones, and new construction is entirely of concrete. The standard of both design and construction is variable. Many farms still allow their water to both enter and leave from the top of their raceways, but some have installed improved “monk-type” outlets which draw waste water from the bottom of the tank. Water reaches and leaves the ponds via open concrete channels. In the Ioannina area, where surface water is often used, the farmers have developed an ingenious variety of simple, cheap filters to remove leaves from the supply canals.
Though Greek law requires the construction of sedimentation tanks to remove solids from effluent water, none of the farms visited had these. In the farmers' defence, however, it must be said that the sedimentation ponds used in other countries frequently become useless within a few weeks of commissioning, and are considered by many experts as being of public relations value only.
In a few places, experiments are being conducted with trout production in floating cages moored in lakes. Cages are approx. 5 × 5 × 5 m. Their frameworks are of steel, surmounted by wooden walkways and supported by expanded polystyrene floats. Nets are of nylon. The designs in use are satisfactory. In some areas small, private lakes are stocked with trout fry for subsequent capture by gillnet the following year.
Existing Greek trout farms are generally working satisfactorily, and there is therefore no need to change them merely for the sake of bringing them up to date. However, where a company wishes to renovate an old unit, or where a new construction is planned, it makes sense to incorporate more modern equipment into the design.
Specifically, incubators of the “California” type, such as those produced by the Ewos Company, are thought to give the best conditions of water quality for developing eggs and early fry. Each incubator consists of a fibreglass trough, frequently 3.5 m long, 40 cm wide, and allowing about 20 cm depth of water. A removable vertical standpipe at the downstream end sets water level. Into the trough, 7 special egg trays or boxes fit. Each box is of fibreglass except for its bottom and a screen on the downstream side, which are made of perforated aluminium sheet to allow passage of water. A projecting lip at the downstream edge of the bottom of each box extends to the bottom of the trough and fits tightly against it. Water entering the trough is thus forced upwards through the eggs in the first box, before leaving the box through the downstream screen. The water then passes upwards into the second box, and so on through all seven trays. Thus all water entering the trough is forced to pass in intimate contact with the eggs in every box. For planning purposes, each box holds about 1.5 litres of trout eggs (which number 5–10,000 per litre depending on size). Such troughs require about 12 l/min of water during egg incubation, increasing to 20 l/min after hatch.
Modern hatcheries frequently transfer fry to special tanks either before or shortly after first-feeding. Circular tanks, or square ones with rounded corners, are now favoured because they have no “dead areas” where water flow is poor. Such areas do form in the corners of conventional raceway-type structures (which are currently used in Greece), allowing buildup of waste food and faeces, with resulting deterioration of water quality. Circular tanks can be of any size from about 1 to 15 m diameter. Small ones are normally made of fibreglass, larger ones of concrete or steel on a concrete base. Regardless of size, all work on the same principle. Water entering tangentially at the surface sets up a circulation around the tank. The tank bottom slopes slightly downwards towards a central outlet screen, which fits flush with the tank bottom. Waste materials are automatically swept by the current in towards the outflow screen, underneath which is a sump connected to an outflow pipe. An external standpipe sets water level.
Tanks can be sited in or outdoors, and claims have been made that fish growth is improved when tanks are fitted with lids to reduce disturbance from external sources.
Small fry tanks can be stocked with around 10,000 fry/m2. Larger fish can be kept at densities up to 25 kg/m3. Water flow rates should be about 1 l/min/kg of fish.
Where concrete raceways are to be used, water exchange can be improved by installing “monk-type” outlets, which suck water out from the bottom of tanks.
It is recommended that only plastic pipes be used in hatcheries. Galvanized steel can be dangerous, because dissolved zinc is highly toxic to young fish. Similarly plastic pipes are best for outdoor tanks, but conventional concrete channels are good for raceway supply and drainage.
Many Greek hatcheries do not hold their own broodstock, but instead prefer to buy in eyed eggs each year from specialist suppliers. This makes good economic sense. For small units the cost of broodstock care, added to the income which could be made from alternative uses of broodstock ponds for portion-fish or fingerling production, greatly exceed the market value of the eggs which could be produced.
Eggs from the Ioannina area are sold all over Greece, but some farmers prefer to import supplies from Germany, Italy or Scandinavia, believing that these foreign stocks are of better quality and give superior growth performance.
Eggs are normally stripped or imported between October and March.
Starting with fertilized eggs, Greek trout farms produce portion-size fish in 9–18 months, depending on water temperature, feeding intensity and food quality, and on market demand.
Maturation of rainbow trout in Greece is said to be typically at one-year-old for males and two years for females. This is a full year earlier than is usual in northern Europe, and has important implications for product quality. As trout approach sexual maturation their skin darkens almost to black and their meat quality deteriorates, becoming watery. The body shape of males also changes in an undesirable way. For this reason, trout should always be harvested before the onset of sexual maturation. In Greece, however, a significant proportion of fish, especially males, mature before they are big enough for sale or while they are being kept in ponds at portion-size awaiting a suitable market.
To ensure only top quality fish are offered for sale, this problem must be solved. It is probable that almost all fish fed intensively would reach portion-size before maturation. An end to the practice of holding back growth and storing fish before slaughter would thus in itself probably end the sale of mature fish. However, this solution requires a much more planned and organized approach to marketing.
Technically, the introduction of all-female stocks of trout would greatly help, since females mature a full year later than males. Techniques for this are well established and described in the literature. Further, age at sexual maturation is partly genetically determined. The consultant recommends that different stocks of trout, both from around Greece and overseas, should be systematically compared both for growth performance and age at maturation. These trials could be carried out in N.W. Greece at Louros and in the N.E. at the new State hatchery under construction at Drama. Once the best existing strains have been chosen, a programme of selective breeding has the potential to improve the stocks available to farmers all over the country. In the consultant's opinion, this type of development work would be of more long-term benefit to the industry than the State hatcheries' present stated function, i.e. to give away fry free of charge. If implemented on a lage scale, this give-away policy must undermine the business of private hatcheries in Greece.
Most trout farms use commercially made, dry pelleted feeds, but a few still feed fry on ground liver. The only large producer of fish feed in Greece (ELVIZ - Hellenic Feedstuff Industries) does not enjoy a good reputation amongst the farmers. The basic problem is the absence of local supplies of good quality fish-meal and fish oil. Consequently most trout farmers prefer to use diets imported from Italy (Trouvit or Veronesi), France (Aqualim) or Germany (Alma). Over 75% of on-growing pellets and all fry feeds are imported. Food comprises 60–70% of average farm running costs. A few farms add amphipod crustaceans to the diet of fish destined for smoking, to give a pink colour to the meat.
Feeding is almost always by hand throughout the production cycle. Exceptions are the use of electric vibrator-type feeders on experimental raceways at Louros research farm and a vehicle-mounted blower system to spread pellets to large raceways on Greece's biggest trout farm (Gianetas & Co., Voidomadis River). The latter farm, which has a potential annual production of 350–400 tonnes of trout, also makes its own feeds using Italian machinery with a capacity of about 3 tonnes per hour. One other private farm on the Louros River also has its own pelleting plant.
The introduction of automatic feeders is recommended for use during fry rearing. It has been conclusively demonstrated that small fish grow better when fed their daily ration in many small meals, rather than a few big ones. During and immediately after first-feeding, fish should be offered food very often, preferably every 10 or 15 minutes. All small fish will grow best when fed regularly throughout daylight hours and, where artificial lighting is available, feeding and consequently growth can be maintained for up to 24 hours a day. Such long periods of regular feeding are very difficult to provide using hand feeding alone. There are many designs of auto feeder on the international market. The most usual for fry feeding run on electricity delivered at 24V via a transformer. Food is dispensed by vibrator plates or revolving discs.
Disease has not been a major limiting factor on the development of the Greek rainbow trout farming industry. Occasional problems occur with the usual ectoparasites: Ichthyophthirius, Trichodina, Chilodonella, Dactylogyrus, Lernaea, etc. Bacterial infections are sometimes recorded, but are rarely serious and are considered as secondary infections triggered by some environmental cause, e.g. oxygen deficiency or excess of dissolved CO2. Viral diseases have not been looked for, and therefore not been found.
Marketing is the central challenge facing the Greek rainbow trout industry. As pointed out above, there is plenty of scope for increasing trout production, both by intensification of existing units and by building on new sites. The limitation on such expansion is simply the difficulty of selling the fish at a profitable price. Many units are able to survive only because their owners also run restaurants, through which trout can be sold at a good price but in limited quantity.
Rainbow trout retails in Greece at between 400 and 450 drs/kg fresh. This is lower than e.g. Britain, even though fish prices in Greece are generally higher than in that country. The reason is said to be that Greek people prefer sea fish. Only in the north of the country are freshwater fish widely eaten. In particular, rainbow trout has failed to make a significant impression on the Athens market, and most people in that city have probably never tasted it.
All trout farmers the consultant spoke to said that the Greek government should help them with marketing. By this they meant running advertisements on TV, radio and in newspapers, distributing recipe leaflets, publishing articles and cooking tips through women's magazines, etc., i.e. sales promotion. Though this is necessary, the consultant considers it has one vital prerequisite, i.e. control of product quality by the farmers themselves.
Stories about the “bad trout” are rife. Every producer says he knows of another who feeds his fish low quality food, leading to “off” flavours, or fills them up with food immediately before slaughter to increase their weight. Such practices would sabotage any sales promotion campaign, since each bad fish loses a customer permanently.
The consultant considers the following minimum quality control measures should be applied in Greece:
Additional hygiene regulations, similar to those enforced on other types of meat processing industries, should be applied to premises and equipment for fish processing, e.g. smoking.
Several of the above suggestions concerning icing, transport and display are already incorporated in Greek law. The fact that the law is apparently not enforced raises the question of how these guidelines could be introduced. There are two alternatives:
Many trout farms are too small to finance the purchases of equipment necessary to ensure a high quality of product on their own. Instead, the farmers could voluntarily form themselves into a federation or association, which would both impose quality standards on its members and assist them to meet these standards. A similar system is successful, e.g. in the case of the Scottish Salmon Producers' Association. Members whose fish meet the association's standards are permitted to label their products with a special trademark, which guarantees good prices by assuring the buyer of top quality. The problem with a voluntary system is that some producers will inevitably choose not to join. In Greece, where most of the trout farms are small and their owners independent-minded, this could be especially true. Poor quality trout being sold outside the scheme could ruin the market for everyone.
In these circumstances, government could encourage farmers to join by offering other incentives. It might, for example, subsidise the purchase of refrigerated trucks, ice machines, etc., by the association. The association could then set up depots in the trout farming regions, which could organize physical collection of members' fish and transport to market. At the central depot, quality could be inspected. A levy per tonne of fish sold through the association would provide the balance of funding needed. Given access to regular supplies of good quality fish, the association itself would be in a position to undertake sales promotion (again with government help if available), to begin product development by smoking, vacuum packing, etc., and to make contracts with large buyers, e.g. supermarkets and restaurants or hotel chains.
If, even with these cash incentives, farmers are not willing to “put their own house in order”, the consultant believes the government must impose quality standards on the industry by law, and enforce them by compulsory inspection. This approach has been adopted by the Norwegian government, which has given the Norwegian Salmon Sales Organization a monopoly control over farmed salmon sales. The system works as follows:
To ensure consistent high quality of Greek farmed trout, the consultant believes a firm course of action similar to those described above is necessary.
The formation of an “association” or “organization” and establishment of high product quality should be followed by a (subsidised) sales promotion campaign, aimed primarily at the Athens market and at tourist hotels and restaurants.
The members of the Ipiros Trout Farmers' Cooperative at Ioannina have already proved that increased penetration of the Athens market is possible, given proper organization. Using a 50% grant from the Ministry of Economy, the cooperative was able to buy two 5-ton trucks and 5 mobile shops. The trucks carry the members' fish to Athens, Thessaloniki and other cities, where it is sold through the mobile shops.
However, the consultant believes the cooperative, in common with other traders, is selling its fish too cheap, often at less than 400 drs/kg retail. Wholesale prices at 280–300 drs/kg are very close to production cost for many farmers. Instead of this low cost/low quality/low price approach, trout should be promoted as a new high status fish. Trading on the newly-established top quality (which with farmed fish can be assured much more effectively than with the products of the capture fishery), prices should be pitched at a higher level than hitherto. Low price does not always lead to higher volume of sales. On the contrary, it can lead the buyer to assume the product to be of inferior quality. In the consultant's opinion, the price of fresh trout should be set at least 20% above its current level, bringing it more into line with prices in other West European countries. Increased sales at this level would undoubtedly stimulate further expansion of the industry.
Processing which adds value to trout products should also be encouraged. Smoking is especially promising, and hot-smoked, portion-sized fish is already selling for around 1,000 drs/kg wholesale. Most of it finds markets in the hotel and restaurant sector.
The coho salmon (Oncorhynchus kisutch) is a Pacific Ocean species which has recently been imported into Greece as eggs (from Canada) for experimental culture.
Egg hatching and fry rearing have been done at Louros government hatchery using the same technology as for trout. Some fingerlings are being held on there for further growth trials. Others have been given to Kefalari trout farm in E. Macedonia for culture in conventional raceways, and to ANKO (The Development Company of Kozani) for experiments in floating cages moored in Lake Polyphitos. Results so far indicate that smoltification of a percentage of the fish occurs at 40–100 g during the first summer following importation of eggs in November-January. Subsequent growth has, however, not been good. Kefalari reported that a few fish reached 500 g after a further 8 months, but most individuals were very much smaller than this. Some had hardly grown at all. In the Polyphitos cages, the best specimens increased their weight from approx. 100 to 250 g between November and April, but again most fish did less well than this.
The reason for poor growth is clear. After smoltification, all salmon are physiologically adapted to life in sea water, and cannot be expected to do well if confined to freshwater sites. In neighbouring Yugoslavia, imported coho eggs will also produce smolts of 50–60 g the first summer. When transferred to cages in sea or brackish water, however, these fish grow rapidly to an average size of 1–1.5 kg within 8–9 months. Growth to an even larger size is prevented by the high summer water temperatures in the Adriatic Sea. Coho cannot survive temperatures above the low twenties celsius for long periods, and must consequently be harvested when the water approaches these levels, usually in early June. Cages must then be left empty until the next autumn, in Yugoslavia usually October, when temperatures again fall low enough to stock out the new crop of smolts.
The same technique can be used for rainbow trout, which in Yugoslavia will grow from c. 100 g to an average of 1.5 kg within the coldest 8 months of the year.
Using this technique, not only is fish growth rate greatly superior to that of salmonids held in fresh water, but a new, different product is produced. Salmon and large trout reared in salt water have an attractive, silver skin. Their flesh is firmer, more like that of a marine fish. By feeding a pigmented diet, red-fleshed fish can be produced. Thus this technology may provide the opportunity to introduce a new, high-status sea fish to the Greek market. Salmon already has a reputation in the country. Market traders estimate that fresh 1 kg coho could retail for at least 1,200 drs/kg.
It is highly likely that coastal sites suitable for cage culture of coho salmon and large trout exist in Greece. Requirements for salmon sites are a slight moderation of salinity by freshwater input, preferably down to 35‰ or less, and water temperature of 20°C or less for several months of the year. Rainbow trout have similar temperature requirements but do best at rather lower salinities, preferably below 30‰. Unlike salmon, rainbow trout do not smolt, but they can be acclimatized to salt water when they are over about 50 g in weight. In practice, use of fish over 100 g is recommended. However, when trout are held in the sea the problem of early sexual maturation is especially acute, since mature fish will usually die if not returned to low salinity water.
Sites for both species must of course be suitable for mooring floating cages, i.e. there must be sufficient water exchange to remove wastes and provide fresh well-oxygenated water, depth must be at least sufficient to provide an area of open water underneath the cages equivalent to the depth of the cage itself (and preferably 3–4 times this), and there must be sufficient shelter from the open sea to prevent cages being broken by wind and waves during bad weather.
The consultant recommends that priority be given to the search for such sites, to open the way for trials with this promising new technology, especially with salmon. The most likely areas are considered to be on the west coast between Prevesa and Sagiada, on the east coast in Kolpos Kassandros, and possibly on the north shore of Korinthiakos Kolpos.
Brackish water culture of salmon and trout could also be done on land in the almiros of Crete, where low salinity water is available by gravity flow. Such places could be suitable for construction of versatile hatcheries and on-growing tanks for use with a variety of marine and “freshwater” species.
Where fresh and sea waters mix offshore, but sheltered cage sites are lacking, future salmonid developments could be considered by using on-shore tanks receiving pumped water, or with large, robust, open-sea cages. However, both these methods are more expensive to build and run, and the technology should first be proved in cheaper trials at places where conventional cages can be used.
Common carp (Cyprinus carpio) has been important in Greek freshwater fisheries for many years, but true farming of the species in artificial ponds and hatcheries is a recent development. The species is omnivorous, consuming some plant material but mostly feeding on bottom-dwelling invertebrates. Larvae and early fry, however, eat zooplankton. Carp grow best in warm, static or slow-moving waters. They will reproduce naturally in Greece when water temperatures rise above about 18°C in spring.
Reliable official figures on production of common carp in Greece are difficult to obtain, because most of the country's output comes from small-scale capture fisheries. The best guess for 1986 lies between 2 and 3,000 tonnes. In addition, probably around 500 tonnes per year are imported from Yugoslavia, Bulgaria and Turkey (the highest estimate of imports heard was 3,000 tonnes). Demand is almost entirely in the northern regions of the country. Approx. 100 tonnes per year are exported.
Of the total production, only about 100 tonnes could be said to be farmed, i.e. produced in artificial, managed ponds. However, new farms are now beginning to come on-stream, and this total will certainly increase during the next few years. According to the Agricultural Development Bank, there are already 22 carp farms in Greece, but most of these are very small, and some operate only intermittently.
In Greece, common carp of the “wild” type, i.e. with a low body profile and fully scaled, are preferred. The deep-bodied, “highly-bred” carps grown in much of Central and Eastern Europe are less favoured, especially the scaleless varieties. Consequently carp of wild appearance command the highest prices.
By European standards, Greece has a very favourable climate for carp farming. Many surface waters are warm enough for carp growth to continue for 7–8 months each year. Consequently fish reach a market size of over 1 kg in two summers' growth, compared with the three necessary in Central Europe.
Carp culture can be expanded in three ways: by conventional pond culture to market size, by intensive production in floating cages, or by producing fry in hatcheries for release into natural waters to enhance the fishery.
To be suitable for siting pond farms, both an appropriate water supply (usually from a river) and large areas of unused, marginal land must be available. These criteria can be met in many parts of Greece, but the best potential sites are perhaps to be found in the region of Arta, around Arachthos, between Thessaloniki and Katerini, in the Kavala/Serres area, and in the Peloponissos.
Sites for floating cages, in which the fish will be intensively fed, are in deep lakes. These are to be found in W. Macedonia and further south in the region to the west of Karpenissi.
Waters suitable for stocking with fry to enhance the wild capture fishery exist in many parts of the country, but the best results will probably come from the warm, shallow, eutrophic lakes of E. Macedonia and Thraki.
Using a combination of these methods, Greece has the potential to develop a large carp industry. As with trout, the constraining factor will probably be market demand rather than site limitation.
Before describing the culture systems used for commom carp, mention will be made of three “new” carp species which have recently been introduced to Greece. The technologies for producing these fishes are similar to those for common carp, and they are therefore best considered together.
The introduced species in question are members of a group of fishes known as the Chinese major carps. They originate from the huge rivers of Central and Eastern Asia, but have now been introduced widely throughout the world. The stocks imported to Greece come by way of Eastern Europe. The species are grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix), and bighead (Aristichthys nobilis). The reason for their introduction lies in the fishes' specialised and unusual feeding habits. Grass carp specialise in eating macrophyte plants, both water weeds and plants of terrestrial origin. Silver carp filter phytoplankton from the water, whilst bighead strain out zooplankton. These characteristic feeding habits are adopted once the fish grow to a few centimetres in length. In their larval stages of development all these species, as with common carp, eat zooplankton. The specialised feeding habits of the Chinese carps are very unusual in the fish world. Most fishes are carnivores or omnivores, very few can utilize rooted plants or phytoplankton in quantity. None of the species naturally found in Greece could do so.
The advantages of the new species are therefore easy to appreciate. Any water body, be it a lake, river, or artificial pond, naturally produces both plants and animals. Indeed, it is an inevitable consequence of the structure of the food chain that a much larger quantity of plant material will be produced than animal. Stocking waters with fishes which can directly use plants as food, therefore, gives potential for a very large increase in fish production without any additional inputs of foodstuffs. Stocking with a mixture of species, each of which utilises a different food source, is called polyculture.
Chinese carps generally grow well in the same waters as common carp. However, their breeding habits are adapted to conditions in the large rivers from which they came. They cannot reproduce naturally in short rivers such as those of Greece, or in lakes or farm ponds. There is thus no danger of their population getting “out of control”. However, at temperatures above 24°C eggs can be produced in artificial hatcheries, and the same hatchery technology can be used also for common carp.
At present, the few pond carp farms in Greece are propagating common carp either by natural spawning or by a semi-artificial method in which near-natural conditions are simulated in small ponds. The widely-known Dubits system, or a modification of it, is often employed. Larvae are fed on plankton filtered from natural waters or from large ponds.
Conventional earth ponds of up to 5 ha and 1.5 m depth are used for production of one-summer fish, which average over 50 g. Deeper wintering ponds generally have concrete sides. During the second and final summer, ponds up to 10 ha are employed. Larger enclosures than this may be built in future, but at present the industry is in a very early stage of development. Concrete monks are used as in the rest of Europe.
A problem in pond construction in some areas is the very sandy nature of the soil. To reduce seepage, plastic sheeting is spread on the pond bottoms, then covered with a few centimetres of sand. By the time the plastic sheet disintegrates, the biological activity in the pond will have effectively sealed the soil.
Liming, organic and inorganic fertilization, and supplementary feeding are all done in the same way as in Eastern Europe.
Chinese carps have not yet been much cultured in earth ponds in Greece, but it is planned to do so.
The pond techniques being started in Greece are quite satisfactory, being modelled closely on well-established practices in Bulgaria and Hungary.
The use of floating cages for intensive carp culture is new to Greece. Experiments are being done in Lake Polyphitos at Kozani and in Lake Kremasta near Karpenissi. Cages are the same as those described above for trout. Feeding is with soaked cereal grains and slaughterhouse waste. Technically, the system works well. Common carp produced in cages are of very good quality, but the economics of the method for Greece are not yet proved.
The consultant believes this technique has the best potential for quickly increasing Greek carp production. Like the other methods described above, this one is also a recent innovation in this country. There is currently only one hatchery, at Ioannina, but another larger unit is being built at Arta.
The Ioannina hatchery belongs to a new company set up with the objective of enhancing the fishery in the adjacent Lake Pamvotis. the company is owned by local government, from which much of the capital came. Additional finance was provided by the Ministry of Agriculture. Building was completed in time for fish production to begin in spring 1986, and the project must be self-financing after 1988.
The Ioannina hatchery is well designed and built, and is already exceeding its production targets. Design was by the Hungarian agricultural export company “Agrober”, and the hatchery is closely modelled on the standard successful Hungarian system. Water pumped from the lake into an elevated 200 m3 storage tank falls by gravity through gravel filters in the hatchery roof to fish tanks and incubators on the production floor. There are 4 concrete tanks for broodstock handling. The 40 × 7 l zug jars, 20 × 50 l funnels and 20 × 200 l larval containers are all made of fibreglass. Compressed air is on tap. Outside are 15 × 1,000 m2 earth ponds for nursing, 3 × 300 m2 ponds for temporary broodstock preparation, and 4 × 1.5 ha ponds for long-term care of brooders. The only improvements the consultant could suggest are that the internal pipework would be better in plastic instead of its present steel, zug jars of glass would make observation of eggs easier, and the area of ponds available for nursing is insufficient. Space is available for building more ponds if money permits.
Currently, dry pituitaries are imported from Hungary, but the management is looking for a cheaper supply. Standard Hungarian practice is used to propagate common carp from the end of April or early May until late May, when the Chinese carp propagation season begins. As in Hungary, organophosphorous esters are used at 1 ppm during preparation of nursery ponds to eliminate undesirable plankton, allowing rotifers to bloom as a first food for larvae. Subsequently larger zooplankton (Cladocera) are seeded. Fry are weaned fully onto artificial feed by 20 days of age.
To supplement production from the limited area of nursery ponds, some larvae have been transferred to a 20 ha area of flooded pasture at Bizani. Good results have been obtained there, but larval mortality could be reduced if more proper nursery ponds were built. Given further ponds, it is estimated that the hatchery is capable of producing three times its 1987 output, which was:
|2,000,000 common carp||all of 1–2 months age,|
weighing 0.5–3 g
|700,000 silver carp|
|400,000 grass carp|
Fish are sold for 8–10 drs each.
The first releases of around 2 million fry into the lake at Ioannina were made in summer 1986. They have been so successful that the members of the local fisheries cooperative are now (autumn 1987) catching large quantities of carps averaging over 1 kg. Grass and silver carp have done particularly well. It is possible that grass carp yields in future may fall as most of the rooted weeds are used up, but the clearly-visible dense populations of phytoplankton should sustain high levels of silver carp production for many years.
The consultant recommends that releases of Chinese carps be tried in other eutrophic lakes in Greece. They will not only provide a new extra yield of fish meat, but their removal from the water by fishermen will serve also to reduce nutrient levels in over-enriched waters. This technique is likely to be the cheapest method for increasing carp output in Greece. The existing hatchery and the new one under construction are capable of supplying sufficient fry for the whole country's immediate restocking needs. They will also be able to sell fish for on-growing in ponds or cages.
Since there is a nett import of common carp to Greece, current demand must exceed supply, though probably by only a few hundred tonnes per year. Thus there is room for a modest expansion in production without any increase in overall size of the market.
Imported carps are cheap, fetching 250–280 drs/kg wholesale alive. Prices are low because the imported fish are of the deep-bodied, frequently scaleless type not popular in Greece. Local wild-type carp can be sold for 400–500 drs/kg wholesale. Thus carp culturists should aim to produce only fish of this preferred shape. The difficulty is that wild fish generally grow more slowly than the highly-selected “improved” farmed fish of Eastern Europe. The problem can be solved by holding inbred lines of both types of fishes as broodstock, routinely crossing them to produce F1 hybrids for production. The hybrids normally have the low-profile shape and are fully scaled, but their growth rates are good enough to yield fish averaging 1 kg after two years. The consultant has also observed that such crosses have meat which is less fatty and contains less intramuscular bones than “conventional” farmed carps.
Even on the Athens market, where freshwater fish are not popular, common carp retails for around 500 drs/kg fresh iced. This is a considerably higher price than trout, although in most countries the latter fish commands a much higher status and price than carp. (This again reinforces the belief that trout is being sold too cheaply.) If prices for carp can only be maintained close to current levels, commercial culture of this species should be very profitable.
Marketing problems must, however, be expected with Chinese carps. These are new products, previously unknown to the Greek consumer. At Ioannina, some retail outlets are being found for grass and silver carp at prices around 300–350 drs/kg. However production this year (the first year such fish have been on sale) has been so high that the local market cannot absorb all of it. Consequently there are reports of silver carp being sold at 20–30 drs/kg to trout farmers for use as fish food. Members of the local fisheries cooperative are, however, not worried by such initial problems. They recall similar market resistance after common carp were first introduced to their lake in 1922. Now local demand for this species exceeds supply. The fishermen eat the new Chinese carps themselves, find them of excellent quality, and confidently expect that time will teach other consumers the same.
Chinese carps meat could also be used in processed fish products, e.g. fish cakes, pates and pies. Greek consumption of such convenience foods is predicted to rise during the next few years.
In addition to salmonids and carps, two small freshwater fish farms in Greece are producing tilapias. Generally, these tropical fish will die when water temperatures fall below about 12°C, limiting the areas of the country in which they can be grown. Where their culture is possible, however, they are worth trying because several species resemble sea bream in appearance. For this reason they may be able to command good prices. Some tilapias can also be grown in salt water.
European catfish (Silurus glanis) and a related species known as Greek Silurus (Silurus aristotelis) could be grown as predators in carp ponds (at no more than 1% stocking). They currently appear in wild catches, but their price is lower than in most other European countries. In Athens 0.5 kg specimens retail for about 500 drs/kg.