Histochemical localization of non-specific esterase, alkaline and acid phosphatase in the intestine of free-living goldline (Sarpa salpa L. 1758) was investigated. Fish were caught in the vicinity of the town of Zadar (Adriatic Sea, Croatia), and samples of three parts of the intestine proper (anterior, middle and posterior) as well as the rectum were used for presentation of non-specific esterases, alkaline phosphatase and acid phosphatase. Non-specific esterase activity was found in the cytoplasm and brush border of enterocytes in all investigated intestinal segments and the rectum. The activity was stronger in the middle and posterior part of the intestine but weaker in the anterior segment of the intestine as well as in the rectum. Intestinal alkaline phosphatase was detected in the brush border and supranuclear cytoplasm of enterocytes of all investigated intestinal segments. Enzymatic activity gradually decreased in a posterior direction. Acid phosphatase activity was observed as a fine granular reaction product in the supranuclear region of enterocytes and was almost equal in all investigated intestinal segments as well as in the rectum. The possible role of enzymes in intracellular digestion and transport is discussed.

This paper reports the results of a diet analysis from the digestive tracts of 203 great cormorants shot at the Donji Miholjac fishponds in eastern Croatia, in the period 2000-2002. Eight fish species were determined. The dominant species was common carp (Cyprinus carpio) with a relative frequency of 73.4%, followed by grass carp (Ctenopharingodon idella) (11.6%), bighead carp (Aristichthys nobilis) (7.2%), pikeperch (Sander lucioperca) (2.0%), wels catfish (Silurus glanis) (1.7%), pike (Esox lucius) (1.5%), topmouth gudgeon (Pseudorasbora parva) (1.5%) and Prussian carp (Carassius auratus gibelio) (1.1%). The diet spectrum of the great cormorants from the Donji Miholjac fishponds was in accordance with the structure of the fish population in the fishponds. The average stomach weight per bird was 244 g. When birds shot with an empty stomach were excluded, the average stomach weight increased to 286 g. The length of consumed fish ranged from 40-335 mm, with 47% of the fish belonging to the length category 100-149 mm. The study revealed no significant relationship between the weight of the consumed fish and the body weight of male and female cormorants.

The risk of wild ducks exposure to heavy metals in the environment was assessed by analyzing 20 wild ducks shot in the hunting area at the fish farm in Donji Miholjac, Eastern Croatia. Liver samples obtained from 10 Mallards and 10 Common Pochards were examined for heavy metals (Cd, Pb, As, Hg) by using flame atomic absorption spectrophotometry (AAS). Significant difference in heavy metal content between analyzed species was confirmed only for Cd (P≤0.01), and no differences were found between genders within species. The results obtained suggest the importance of wild ducks as bioindicators of heavy metal pollution, especially Common Pochard for Cd, and Mallard for Pb accumulation

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