engleski

Diet and growth of spirlin, Alburnoides bipunctatus in the barbel zone of the Sava River

No spirlin have been registered in the barbel zone of the Sava River, Croatia in the late seventies of the last century. Since then, due to improved water quality the presence of spirlin gradually increased in number (23.3%) and in biomass (4.7%). The most dominant item in the diet of spirlin were Bacillariophyceae and Chlorophyceae during every monthly investigation. The diet consisted also of invertebrates which can be considered as a secondary or an accidental prey. The size related analyse of the consumed food showed Bacillariophyceae to be preferred food by fish of all sizes. The back calculated growth in the total length could be expressed by the following formula: Lt = 12.0 (1-e-0.59 (t+0.14)). The phi-prime of spirlin from the Sava river is &#966; &#8217; =4.44. The length-weight relationship, covering the fish from the entire growing period, showed an isometric growth with a b-value of 3.025 (p&#8250; 0.05), except of September when it was significantly allometric. That was confirmed by the non-significant relationship between condition factor and total length (r = 0.014 ; p > 0.05). However, CF in June, September and October (0.86 &#177; ; ; 0.07 ; 0.85 &#177; ; ; 0.09 and 0.87 &#177; ; ; 0.10, respectively) was significantly lower (p<0.05) than in May and July (1.00&#177; ; ; 0.21 and 1.00&#177; ; ; 0.12, respectively). The improved water quality during the last fifteen years enabled spirlin to migrate and enlarge its population downstream, resulting in a slightly decreased condition factor.

cyprinid; Croatia; condition; feeding; threat

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