Aeromonas hydrophila causes symptoms of hemorrhagic septicemia in acute cases and can cause death in freshwater fish, whereas Saprolegnia parasitica is the cause of ulcers complicated by fungal mycelia located on skin that has lost its scales for various reasons. Both pathogens co-infect recirculating aquaculture systems at the İzmir Katip Çelebi University Fisheries Research and Training Center. Clinical, bacteriological, parasitological, and mycological studies were carried out on 25 fish samples during the infestation. Sabouraud glucose agar and malt extract agar were used to isolate the fungus, and the bacterial isolates were streaked on tryptic soy agar (Oxoid) with 5% defibrinated sheep blood. Gray-white cotton-like patches, erosions on the skin, and hemorrhaging were detected on the infected fish samples. The analytical profile index test and molecular identification showed that the bacterial agent was A. hydrophila and a fungal examination and amplification by polymerase chain reaction confirmed that the mycotic agent was S. parasitica.

The hereby study investigated gibel carp (Carassius gibelio) in a mesotrophic lake (Lake Beyşehir, Turkey) from April 2013 to March 2014, in order to outline population structure and some growth properties of the species. Two water quality variables (Chlorophyll-a, Trophic State Index (TSI)) were detected seasonally to define trophic status of the lake. Length and weight distributions, length -weight relationship, sex ratio, gonadosomatic index (GSI), condition factor (CF) and von Bertalanffy equation were calculated for C. gibelio sampled monthly. Trophic status of the lake was defined as mesotrophic. Total length and weight of C. gibelio samples was determined in the range of 8.5 and 28.4 cm and 15 and 408 g, respectively. Mean total length and weight of individuals were calculated as 17.5 ± 2.37 cm and 88.6 ± 39.02 g, respectively. There was a negative allometry between length and weight for C. gibelio. The fish samples were composed of 52% females and 48% males, between II and VII years old. Spawning period of the species occurred between April and June after GSI values reached their maximum in March. The CF values were validated between 1.5-1.7 besides the mean rate of females and males were 1.6 and 1.5, respectively. The parameters of von Bertalanffy equation were calculated as L ∞ : 19.8 cm, W ∞ : 652.9 gr, k: 0.934. In conclusion, C. gibelio has almost lost the economic value since the individuals are smaller than market size (≥ 250 g), probably due to lack of nutrients/mesotrophic situation of Lake Beyşehir.

Turkey produces most of the European sea bassin Europe and bacterial diseases are the main cause of economic loss during the production cycle. This research presents the first extended study of the Aeromonas veronii infection in sea bass on the Turkish coast of the Aegean Sea. An outbreak was observed in three different sea bass farms and diseased fish with clinical symptoms were sampled. Abdominal distention, hemorrhages on the body and anus, enlarged spleen and liver, and hemorrhages in the internal organs were detected from clinical and pathological examinations. Biochemical and molecular identification confirmed the pathogen to be A.veronii.The histopathological observations demonstrated that the pathogen caused bacterial colonies in the fibrous connective tissue, granuloma, and vacuolar degeneration.The primary causes of the disease were proved through an infection experiment. 80% and 90% mortality were calculated in 0.85 x 108 CFU ml-1 and 1.28 x 108 CFU ml-1 experimentally infected groups with clinical and pathological signs of the disease respectively. Recently, the pathological symptoms of the disease had been confused with pasteurellosis infection in cage farms but the presence of A.veronii has been confirmed in the current study. A detailed study is needed to investigate the overall status of the disease in the Aegean Sea in order to design an appropriate preventive strategy.

Yersinia ruckeri is the etiological agent of yersiniosis or enteric redmouth disease (ERM) which is a Gram-negative enteric bacterium (Davies, 1989;Raida & Buchmann, 2008). It is best known as a pathogen of salmonids and causes major losses in fish farms (Bastardo et al., 2012). Yersinia ruckeri was first isolated from a rainbow trout (Oncorhynchus mykiss

Vibriosis caused by Listonella anguillarum was reported in several fish species from both fresh and saltwater conditions. This pathogen causes disease in rainbow trout, sea bass, and sea bream in Turkey, however, it has not been reported from meagre (Argyrosomus regius) before. Great loss of meagre was observed in the Recirculated Aquaculture System at the Faculty of Fisheries of Izmir Katip Celebi University, which had been transferred from a commercial hatchery for a nutrition experiment. Clinical signs of vibriosis were observed in infected fish, i.e. haemorrhage in the anal area and pectoral fins, mostly as tail ulcers. Petechial haemorrhages in the muscle, liver, peritoneal membranes and pyloric caeca were determined by necropsy. A Gram-negative, rod-shaped, motile bacterium was isolated, showing a positive reaction to oxidase, catalase and gelatin tests, and being sensitive to O/129. Biochemical identification tests and PCR amplifications identified the bacterium as Listonella anguillarum. In slide agglutination test with anti L. anguillarum O1 (ATCC43305) serum, all isolates were positive. The isolated bacteria was resistant to oxytetracycline, sensitive to enrofloxacin, flumequine, phosphomycin, furozulidone, kanamycin and oxolinic acid. In this study, the isolated bacteria from meagre were determined as Listonella anguillarum O1 with biochemical, moleculer identification and agglutination tests.

Saprolegniosis is a serious fungal disease that mostly affects freshwater fish species and eggs. It has a cotton wool-like appearance on the body of amphibians, crustaceans and several fish species. Infected gilthead seabream (Sparus aurata) were subjected to clinical, microbiological, parasitological and pathological investigation. On the infected skin samples, grey-white cotton-like patches, erosion of the skin and scale affusion were detected. Lesions covered the whole body of S. aurata in the advanced stages. Bacterial growth and parasitic symptoms were not observed in microbiological examination. Microscopic examination showed hyphaes carrying cysts that were long and branched. In scanning electron microscopy overviews fungal zoospores were observed. In histopathological observations of sections of skin, erosive-ulcerative dermatitis and mycelium of Saprolegnia parasitica were seen in the muscle tissue. Gene sequence-based identification found Saprolegnia parasitica. S. parasitica has not until now been detected in S.aurata. The low salinity of the brackish water is believed to be the predisposing factor of Saprolegniosis in sea bream in this case.

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Dwarf suckermouth catfish are preferred especially for small aquariums. They are usually referred to as tank cleaners and commonly traded in the ornamental fish sector. Since these fish are nocturnal, it is difficult to observe their reproductive behavior and larval development. This study was carried out to determine the reproductive variables of bushymouth catfish (Ancistrus dolichopterus) under aquarium conditions. Three broodstocks bushymouth catfish with an average initial weight and a total length of 10.5±0.3 g and 9.5±0.2 cm were stocked in three 240-L aquariums with the ratio of 1:2 (male: female). The observations were made in triplicate tanks for six months. Females laid an average of 39.78±0.41 eggs and fertilization and hatching rates were 75.05% and 62.94%, respectively. It was found that the transition time from egg to apparently larval stage was 105.28 h, and bushymouth catfish showed an indistinguishable development from the hatching to juvenile stage without a real larval transition stage. The results of the study provide basic information on the reproductive performance and early development of bushymouth catfish.