3.1.1 Protozoan
“Ich”-infected fish can be treated chemically but this can become expensive and the profit the fish culturists make today is marginal to begin with. Probably the best remedy is to stop feeding freshwater fish and only bring in eggs to private fish hatcheries. If the dromitsa fish must be incorporated into the trout diet then they should be first boiled. This will not only kill “Ich”, but also any other fish parasites present. Mechanical control consists of not having the fish crowded and having plenty of water going through the raceways. The flowing water helps flush out the immature “Ich” parasites befores they can attach to the fish. For chemical control malachite green is recommended. It is already being used today in Greek fish culture as a “cure all”. A 10–30 s dip of fish into 1:15 000 malachite green (66 ppm or 3.3 g / 50 l of water) is not the best treatment but is better than nothing. A 1 to 3 ppm malachite green treatment for 1 h can be tried. Treatments with a combination of malachite green and formalin mixed together should be tried experimentally. The State hatchery at Louros could try, perhaps, 0.1 ppm malachite green and 25 ppm formalin for 1 h or longer with no water added. Variations in concentration and exposure time of this fish to the chemicals also can be tested.
3.1.2 Bacterial
Bacterial disease can be treated with antibiotics, sulfonimids and nitrofurans. Recommendations can be made at a later date if bacterial problems are encountered in trout culture in Greece. If eggs are continued to be imported from Denmark or any other country there is a possibility that some of these bacterial diseases can be transported on or in the eggs to Greece.
3.1.3 Fungal and Fin Erosion
For fungus on fish a 1:15 000 malachite green dip is recommended for 10 to 30 s. The only remedy for fin erosion, especially the lower fins, is to transfer the fish from concrete raceways to earthen raceways to prevent constant abrasion of the fins by the concrete. Feeding the same amount of daily feed more often will help prevent erosion of the dorsal fin. These fish become excited when being fed, especially when they are hungry and then tend to bite each other accidentally as they try to get more food to eat. So if they are fed more often they become less aggressive. Reduced crowding will also help.
3.1.4 Viral
The 10–20 percent survivors from the two raceways of suspect VHS trout at the Louros hatchery should have been destroyed by now, either by burning or burying in quicklime (CaO). Since this lot of eggs from Denmark and, later, the fish have been kept isolated there is hope that if VHS was present it can be contained. There is no chemical or drug treatment available for viral diseases of fish.
It should be emphasized that trout culture in Greece has only been in existence for ten years and only rainbow trout eggs have been imported. No major bacterial problems have been encountered during this survey and Edessa is only suspect for VHS. However, the confirmed presence of IPN in a number of hatcheries in Epirus raises the question of methods in confining and eliminating this disease. Since the transfer of fingerlings and the importation of trout eggs from abroad are being continued, the virus will contaminate previously uninfected hatcheries. Viral diseases, as well as some bacterial diseases, can be transported on or in eggs. Measures must be undertaken to have imports of eggs banned and to encourage large Greek trout hatcheries to produce their own eggs. They can then sell eggs to small hatcheries for propagation. This can be done. If not, it is a certainty that diseases, especially the viral diseases, will be introduced into Greece. This will cause havoc and financial loss to the private trout entrepreneurs. If eggs must be imported then they must be certified disease-free and this is an impossible task for any expert to undertake. Even as late as 1948 VHS was introduced to the U.S.S.R. in an egg shipment of rainbow trout from Denmark (Tesarčik, I., I. Cibulka and I. Kalivoda, 1968 1). Of course, live rainbow trout fingerlings should never be imported and caution should be excercised importing other salmonids like Salmo trutta, Salvelinus fontinalis or other species, because they may be more susceptible to certain fish diseases. The consultant would not even recommend the importation of fast-growing species of carp unless they were certified free of all viral diseases.
There were some problems encountered in fish nutrition. A trout diet of freshwater fish and sardines along with poultry wastes and dry feed is not the best. Freshwater fish can bring in parasites and marine fish could possibly bring in VHS as well as causing nutritional problems. The Greek artificial trout feed is not very good. There are large pieces of soya, extraneous material and dust (fines) in this feed. Also the percent of crude protein is given in percent nitrogen which means little. The other trout feed from Holland which was examined by sight, feel, smell and taste, was of a good quality. The French feed was poorer than the Dutch feed. Hopefully, the feed mill under construction near Ioannina will produce a better quality of feed and will sell for less than DR 22 2 for the Dutch or DR 12 for the French feed.
Since the cost of feed, not only for trout, but also for poultry, hogs, etc., is increasing each day due to increasing costs of soya and fish meal, trout are not the ideal fish to culture for food for the general public. (This does not apply when trout are exported smoked or sold locally for the tourist trade.) Under good conditions trout may produce 1 kg of growth for each 1.5 kg of feed fed. This conversion is not realistic in Greece today. It would be better to put more emphasis on culturing carp or other local fish which do not require this type of high protein feed. The price of carp in Edessa was DR 52/kg compared with cultured trout at DR 39/kg. In Ioannina both carp and trout sold for DR 39/kg. Any experienced fish culturist can produce more kilogrammes of carp than trout for less operational expense. All that is needed is a water supply, ponds which can retain water, feed and fertilizer. The feed expense would be low and chicken manure is a good fertilizer so the cost per kilogramme of fish then will be low.
2 US$ 1.00 = DR 27 as at 19.10.73.
The fellowship provided under this project should be devoted to training in fish pathology especially trout.
In view of the fact that expertise knowledge on viral diseases and their diagnosis in Greece is lacking, it is recommended that suitable candidates receive further training or specialization in this discipline in other countries. These candidates must have a background in veterinary medicine or biology with emphasis on course work in the fields of virology, bacteriology, and protozoology. A high degree of language competence will be required in terms of scientific terminology when communicating with counterparts during the fellowship. Countries which now can offer this type of specialized training include Italy, Germany and the U.S.A. If a veterinarian is chosen for a fellowship there should be an explicit understanding that he would be available to the Fisheries Department for consultancy and diagnostic work.
3.4 SENDING SAMPLES TO FISH DISEASE DIAGNOSTIC LABORATORIES
It is recommended that suspect VHS fish specimens be chilled on ice for shipment since the infectivity of the virus particles for diagnosis in cell culture is easily lost. Detailed and mutually acceptable arrangements for shipping schedules must be made well in advance. IPN fish suspect material, of course, can be air mailed in 50 percent glycerine to the designated laboratory.
The addresses of some laboratories in which diagnosis of fish viral diseases can be made using cell culture and/or histopathology techniques are listed below. Other laboratories in Europe, Asia, and the U.S.A. can also provide this service.
Director of Veterinary Service
of the Ministry of National Economy
2 Acharnon St.
Athens, Greece
Eastern Fish Disease Laboratory
Leetown (P.O. Kearneysville)
West Virginia 25430
U.S.A.
Istituto Zooprofilattico Sperimentale
del Piemonte e della Liguria
Via Bologna 148
10154 Torino, Italy
