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The purpose of this study was the identification and quantification of biochemical parameters over a 1-year cycle and to provide a detailed picture of seasonal changes in plasma metabolites and enzymes. Using the novel methods of machine learning techniques, the authors created and generated for the first time comprehensible classification models for exploring the importance of blood chemistry parameters, strength, mutual interactions or dependencies, and reliability of particular parameters within the seasonal groups.

The available data concerning rapid identification of fish bacteria via commercial phenotypic tests demonstrate that there is no agreement regarding the choice of selection of the tests. However, API 20E, an identification system for Enterobacteriaceae and other non-fastidious Gram-negative rods developed for clinical specimens, seems to be increasingly used for the identification of fish pathogens. In this work, adaptation of API 20E for fish bacterial isolates and its distinctiveness for fish bacteria was assessed. For some bacterial fish isolates, their identification must be regarded as only presumptive. Some strains are wrongly identified because they are not included in the database of API 20E system. For comparable results, API 20E has to be adapted for bacterial fish isolates, and there should be a consensus among the fish health professionals regarding the incubation temperature and the duration of the incubation time before performing readings. API 20E reactions should be compared with the diagnostic schemes based on reactions in conventional phenotypic tests. Due to their significance for fish health and impact on the aquaculture, and because of the need for their rapid identification, some important fish bacteria should be included in the API 20E system, such as Yersinia ruckeri, Edwardsiella ictaluri, Vibrio anguillarum.

The aim of the study was to observe the influence of different ploidy levels in fish on micronucleus occurence. Twenty minutes after fertilization, one group of rainbow trout eggs was exposed to water temperatures of 26C in duration of 20 minutes to induce triploidy. Second group was kept in water temperature of 10C, which is optimal for development of rainbow trout. The frequency of micronucleated erythrocytes was determined in the peripheral circulation of rainbow trout 67 days (following absorption of the yolk - swim-up stage) and 128 days (fry stage) post fertilization. There was a significant difference (P

Aeromonas hydrophila was recovered from fish living in lake Vrana on the Croatian island of Cres. The occurence of the bacterium in the fish was assessed and related to gross signs of disease and findings at necropsy as a potential health hazard for fish. Isolated bacteria were subjected to morphological, physiological, biochemical and antibiotic susceptibility tests. A total of 26 A. hydrophila isolates were obtained. There was a clear seasonality, as no isolates were recovered in the summer months. Most of the isolates were sensitive to all the antimicrobials used in the study except novobiocin and penicilling G. Affected fish manifested haemorrhages over the skin, in the liver, kidney and swim bladder, spleen infarcts, fatty liver, ascitic fluid and swollen haemopoietic tissues. A. hydrophila does not appear to pose a major threat for the fish in the lake at present but under unfavourable and stressful conditions it could seriously compromise fish health.

Investigations of the adaptability of two growth groups of coho salmon fry (1+ and 0+) while being transferred from freshwater (FW) into seawater (SW) were performed in the season autumn/winter on four locations (three locations in the Adriatic Sea and one in the FW fish farm, Luknja). Average weight of the 1+ group was 116 g, and average weight of the 0+ group was 86 g. Changes in body composition and condition factor were examined immediately prior to SW transfer, during the early stages of smoltification and for a period of 30 days post-SW transfer. Fish samples (n=10/time point) were taken in FW, during the transport, and after the transfer into the sea (22.5, 45 and 90 min ; 3, 6 and 12 hours, and also 1, 2, 4, 8 and 30 days following the transfer). Results from the experiments demonstrate some differences in the adaptive fitness between the two age groups examined, with inferior adaptation being expressed by the 0+ group. Over the period of investigation an increase in body moisture and decreases in body lipid and protein were observed, when compared against FW controls regardless of smolt age. This might be interpreted as indicating malnourishment due to aphagia, since appetite loss has been described in this, and other oncorhynchids during SW transfer.

Virtually no comprehensive work has been published on tuna plasma chemistry parameters and its correlation with tissue histological status. This work will be useful for establishing plasma biochemistry reference values for bluefin tuna. Heparinized blood samples were collected from bluefin tuna. Plasma biochemical analyses were performed using standard techniques. Organ tissues were processed histologically and stained with haematoxylin/eosin. Mean, median, standard deviation, standard error of mean, 25th percentile, 75th percentile and range difference of minimum and maximum values were calculated for each variable measured. Obtained values represent preliminary results. All blood biochemistry parameters, except ALT, passed a Kolmogorov-Smirnov normality test. In a number of hepatocytes, different degrees of fatty changes were visible. Normal ranges of plasma activity vary between species and normal values must be produced from a representative population of each species. This work will be followed up by other studies on blood chemistry values of bluefin in the Adriatic Sea involving more individuals from several locations that could provide a base for reference levels