The production of an endogenous supply of fish feed for all Greek aquaculture projects will be possible in the near future. The country has two modern animal feed mills which will be able to produce both marine and fresh water fish diets. At present the pelleting equipment at the mills is so new that pilot batches of fish feed will have to be produced before suitable pellets for all farmed fish are formulated able to compete both in price and quality with the present imported feeds (some trout pellets using a steam pelleter have been produced for several years).
The technical staff at these feed mills are collaborating with the nutrition group of the NCMR in Athens, in order to produce satisfactory pellets. As already mentioned, the installation of a post-pelleting fat sprayer to be used in conjunction with the steam pelleting mill at Ioannina would complement the fat sprayer that exists on the “extruder” line at Plati.
No carotenoids are being incorporated into most trout diets produced in Greece. It is suggested that “pink” coloration might improve the image of trout in the Greek market. This would reflect the situation in northern Europe where farmed trout consumption did not “take off” until a pink fleshed product was introduced.
There does not seem to be much possibility of introducing novel cheap (plant) materials into the diets of fish farmed in Greece; an exception may be the use of carob seed germ meal, tomato seed meal or linseed meal. The development of good pelleted food produced in Greece should concentrate on the utilization of conventional animal feed materials that can be produced there at a lower price than elsewhere in Europe.
There is the opinion among some farmers in Greece that home produced pelleted feed is inferior to imported feed. This may have been so in the past but there is no reason to believe that this will be so in the future. It does mean, however, that ELVIZ may have to mount a strenuous marketing campaign in order to obtain a dominant sales position.
The possible development of the use of fish silage has been fully discussed and an investigation into this source of fish food should be carried out. Conversations with marine fish farmers in Greece have indicated a wish to collaborate in the study of the use of ensilaged fish.
There are few reports relating to the intensive feeding and culture of mullet. From the natural feeding habit of these fish it would seem that mullet are not ideal for intensive culture. They are, however, cage cultured in Greece (Pilos) and consideration should be given to intensive feeding. Mullet have a market price approximately twice that of trout and a comparable FCR and specific growth rate. Thus, it would seem reasonable to develop a mullet feed that could be used intensively, particularly as previously mentioned for Mugil capito which has a diet requirement of approximately 24% compared with that of 40% required by trout.
Moreover, Mugil cephalus is tolerant of freshwater and the development of improved feeding procedures (supplementary feeding or via pond fertilization) should be studied to enable the farming of mullet in fresh/brackish waters to be practised. Attempts have been made in the lagoons of Vasova, Eratino, Agiasma and Keramoti in the Kavalla region to feed a supplement to mullet either of fish meal or maize meal. Fish kept in wintering canals were fed from April until June. There was no evidence that this supplementary feeding resulted in increased growth. Growth in freshwater is somewhat slower than in brackish but this might be offset to some extent by possible higher freshwater temperatures.
Many artificial foodstuffs have been used in the rearing of mullet for breeding purposes, e.g., fish meal, rice bran and peanuts; fish meal and soymeal; soy and maize plus vitamins and groundnut cake; any mixtures of rice bran and fish meal. All this and many other experimental findings indicate a catholic food utilization by mullet. Also it has been reported that mullet, unlike many other fish, are capable of assimilating nitrogen in the form of urea as well as in the form of protein. As urea may be considered as an economic source of nitrogen its use in mullet feeds should be re-investigated.
The intensive rearing of mullet to produce a “mid-price” fish of 250–500 g should, from the nutritional point of view, be feasible in Greece. This will, however, require the development of inexpensive prepared feeds for the different stages of mullet growth. This development in Greece should parallel development in the successful propagation of juveniles from hatcheries.
With the development of a fish feed industry in Greece attention must be given to the quality control of (a) raw materials, and (b) pelleted food. Also attention must be given to what must be regarded as a form of quality control, namely (c) the feeding aspects of fish husbandry.
(a) Raw material analysis and control
The quality of a feed is dependent on the quality of its ingredients. Quality control of raw materials is already practised as standard procedure for other animal feed production. However, analysis systems should be developed which are more specific to the needs of producing a satisfactory fish pellet; for example, the development of assays for toxins known to inhibit fish growth and the screening of fish meal for the presence of urea which, although a nitrogen source, cannot be utilized by most fish.
(b) Pelleted feeds
Pelleted fish feeds have many advantages; less waste, higher feed intake, improved feed efficiency, lower handling costs, easier storage, and less bacterial contamination. However, compared to other livestock feeds, fish feeds are unique in that the particle size of the feed is critical. Also the food is subject to water during feeding and the feeds are not chewed by fish as in the case of other animals.
The fineness or coarseness of grind of the feed ingredients can exert a significant effect both on the physical properties and the nutritive value of the finished feed product. Fine grind of ingredients often improves pellet quality which reduces pellet breakage and the production of fines. ELVIZ should consider finer grinding for their fish pellets.
Quality control methods should be developed as new fish diets are formulated in Greece. Standards for “hardness”, “solubility”, and “fines” should be established together with routine proximate analysis of the pellets. As fish feed production is developed at ELVIZ this will undoubtedly occur.
(c) Feeding of fish
The maintenance of accurate feeding and nutrition records appeared to vary in the Greek farms visited. Much effort should go into demonstrating to farmers the need for records on feed fed, age of feed, food conversion ratios, adjustments of feed according to body weight and frequency of feeding. It is particularly important that an understanding of possible deterioration of fish food in storage, especially during the summer months when temperature exceeds 30°C, be understood by farmers.
Explanations should be given for the reasons for keeping records; this is essential for the success of aquaculture in Greece.
Finally, with the development of increased aquaculture and the more intensive farming of more fish in Greece will come the inevitable consequence of water pollution. No feed has yet been developed that does not result in excretory products from the fish contaminating the ambient water. However, just as other countries in Europe are engaged in feed research in order to reduce the polluting effect of intensive feeding of fish, so might Greece consider this possibility.
Fig. 1 Commercial catches in relation to total fish catches
GULF OF CORINTH