The diet of roach, Rutilus rutilus (L.), and bleak, Alburnus alburnus (L.) larvae and fry in the shallow littoral zone of a heated lake

Abstract

This paper presents the results of analyses of the dietary composition of 0+ roach, Rutilus rutilus (L.), and bleak, Alburnus alburnus (L.) inhabiting Lake Gosławskie. The following hypotheses were verified: (i) the dietary composition of fish changes over time; (ii) fish somatic growth causes variation in the spectrum of dietary components. Species richness in the diets of roach and bleak larvae and fry was high. In comparison with other dietary components studied, cladocerans were dominant. The tendencies for change in the indicators of feed variety during the study cycle in both fish species were very similar. In the initial period, the diets of roach and bleak larvae and fry were not varied. After the age of two months, the feed composition of the diets widened progressively, and reached its maximum in August. The variety of the dietary composition of early developmental stages of roach and bleak was strictly correlated to body length. The diet of roach fry (16-30 mm) was significantly more varied than that of larvae (6-15 mm) and the largest fish (>30 mm). With bleak, the dietary variety indicator increased proportionally to body length until they reached a length of 30 mm.

CORRESPONDING AUTHOR:

Elżbieta Bogacka-Kapusta, Instytut Rybactwa Śródlądowego, Zakład Ichtiologii, ul. Oczapowskiego 10, 10-719 Olsztyn, Tel./Fax: +48 89 5241039, +48 89 5240505: e-mail: ela@infish.com.pl