2.1.1 Protozoan
Examination of fish for external and internal parasites was done with dissecting and compound microscopes. No internal parasites were found in trout, but Ichthyophthirus multifiliis, or “Ich” was found on trout sampled in almost all of the fish hatcheries in the Ioannina. This ciliated protozoan parasite can infect all freshwater fish world-wide. Some losses of small rainbow trout have taken place in Greek hatcheries when this parasite is present. “Ich” was also found on dromitsa (Rutilus sp), carp, and kleni (Leuciscus sp) fish which came from the lake in Ioannina. Small dromitsa are in turn fed raw to trout in all the hatcheries near Ioannina and expose the trout to reinfection. Several trout culturists also complained that many of the fingerling fish purchased from the Tsalis private hatchery near Louros died. Again “Ich” was diagnosed at the Tsalis hatchery and the owner does feed raw dromitsa fish to his trout. No “Ich” was found on trout in the Edessa area even though wild river fish are occasionally used for fish feed.
There was no indication that trout in Greece have ever been exposed to Whirling Disease (Myxosoma cerebralis).
2.1.2 Bacterial
Examination of trout for bacterial diseases was more difficult to accomplish in the field because of technical problems. Cultures and stained slides were made when possible, especially from larger fish. All of the stained slides were negative and only one or two bacterial colonies were noted on two cultures. These colonies were probably caused by contamination.
Two bacteriological cultures taken from fish in Greece were sent to the U.S.A. for further laboratory study. Both produced one bacterial colony each which were found negative for the known bacterial pathogens for trout. It is believed that these colonies were caused as the result of external contamination as the cultures were inoculated from the fish.
In any event, all of the fish from which cultures and stained slides were made appeared to be healthy and in good condition, and it is difficult to obtain pathogenic bacteria from fish like this. There were no ulcers, boils or haemorrhagic areas, etc. indicating bacterial infection caused by furunculosis (Aeromonas salmonicida), general septicaemia (motile forms of Aeromonas or Pseudomonas) or others. The fisheries experts, managers and veterinarians also have never observed in Greece symptoms which would indicate a bacterial infection.
2.1.3 Abnormalities
An occasional abnormal-appearing fish may be observed in trout hatcheries but this condition is not usually serious. Occasionally also one may find fish in most hatcheries which swim on their sides or have curvature of the spine. These conditions are probably generic in nature and not much of a problem. At other times an occasional fish may be blue in colour and again it is nothing serious. On the other hand, there may be many fish which have turned black in colour. In the examination of fish samples in these cases exophthalmia or “pop-eye” has taken place and this causes loss of the eyes or blindness, which in turn causes nerve damage and darkening of the skin. The cause of this condition is usually a super saturation of nitrogen in a spring water supply.
Mechanical agitation of the water to liberate the gas in helpful in preventing the re-occurrence of this problem. If only a few fish turn black in any given raceway then the cause is probably due to mechanical injuries of the eye.
2.1.4 Fungal and Fin Erosion
Fungus (Saprolegnia) on fish and fin erosion were noted in many hatcheries. This condition is not a serious fish problem and can be corrected. The fish do not look good to the public. Fin erosion was a common problem in many hatcheries.
2.1.5 Viral
A survey of trout for virus diseases was limited to Infectious Pancreatic Necrosis (IPN) which is almost world-wide in distribution. This is the only known fish virus which retains its infectivity in 50 percent glycerine, so samples of fish and fish organs were collected in the field. IPN diagnosis for these samples will be conducted in cell culture. As this requires specialized equipment, supplies, and expertise, prepared samples were sent to the U.S.A. for examination.
The presence of IPN was confirmed from glycerine-preserved samples obtained from the Tsalis hatchery near Louros, two hatcheries near Ioannina, and a hatchery in the Preveza area. Similar samples taken from the government hatchery in Louros, and the private hatcheries near Tripotamos and Aghios Nickolaos in the Edessa area, were found to be negative for IPN.
As for the European virus disease of rainbow trout, Viral Hemorrhagic Septicaemia (VHS), INUL, or Egtved as it is called in Denmark, all that could be done in this survey in the field was to rely on symptoms and swimming behaviour. Suspect VHS-diseased fish or organs would have to be airmailed, chilled on ice, to laboratories in Greece, the U.S.A. or Europe for positive identification using cell culture techniques. Formalin-preserved internal organs such as liver, spleen and kidney may also be useful in the identification of VHS when examined by a qualified fish histopathologist.
It is just possible that VHS was present at the State hatchery in Edessa. Trout from 9 to 13 cm were observed swimming in a jerky motion, spiralled along a horizontal axis and quickly reversed direction. Moribund fish came to the surface and were listless. The behaviour pattern is suggestive of fish infected by VHS. These fish did not show any external or internal symptoms of VHS - the skin was not dark, no exophthalmic condition existed, gills were not pale or white, liver was not pale or ruptured, etc. However, fish have been known to die of VHS without showing any of the external or internal symptoms. At this point, we can only suspect that VHS exists or existed at Edessa, especially since the eggs in this group of fish which are dying came from Denmark. Also, there were no bacteria or parasites that could be found on these fish which would cause this type of swimming behaviour.
Formalin-preserved internal organs from fish samples were forwarded to the Eastern Fish Disease Laboratory, Leetown, West Virginia, U.S.A. for analysis. Preserved gill, liver, kidney, spleen and pancreatic material from moribund fish sampled at Edessa government hatchery were examined by the histopathologist of the laboratory. The ichthyophonus cyst he reported is a fungus that historically has been transferred to the hatchery-reared trout by feeding diseased marine and occasionally freshwater trash fish. When trout become heavily infected with this disease they become grotesque in appearance with lordosis and scoliosis (curvature of the spine) and deformed heads. No chemotherapy is known. Prophylaxis consists of sanitation and not feeding raw fish.
There was no histological evidence to indicate that these fish were infected with VHS.
2.1.6 Nutrition
Possibly the most critical problem area in trout culture in Greece today involves diet and quality of the fish feed. Trout require a higher quality and amount of animal and vegetable protein feed than that employed in feeds for other types of fish culture.
2.1.7 Eels and Elvers
As far as the eel or elver situation is concerned, this is thought to be an engineering problem.
