Lucie Všetičková

The food of roach, Rutilus rutilus (Actinopterygii: Cypriniformes: Cyprinidae), in a biomanipulated water supply reservoir

Roach, Rutilus rutilus (Linnaeus, 1758); bream, Abramis brama (Linnaeus, 1758); and European perch, Perca fluviatilis Linnaeus, 1758 typically dominate fish stocks in water supply reservoirs (drinking water reservoir) of the Czech Republic (Pivnicka 1992). Roach are feeding generalists, usually utilising the most available food resource (Hellawell 1972, Prejs and Jackowska 1978, Prejs 1984, Horppila and Nurminen 2009). Such dietary plasticity allows it to find food in habitats offering less than ideal conditions for other species, whose feeding demands may be greater (Barus and Oliva 1995). Planktonic crustacean such as Cladocera and Copepoda tend to dominate in the food of younger age classes; Tarvainen et al. (2002), for example, found 0+ roach (71–90 mm) to be exclusively zooplanktivorous (Bosmina, Chydorus), while Hammer (1985) observed the same cladoceran species dominating roach fry diet in Lake Lankau (Germany). Similarly, Vasek et al. (2006) as well as Peterka and Matěna (2009) have both described ACTA ICHTHYOLOGICA ET PISCATORIA (2014) 44 (1): 15–22 DOI: 10.3750/AIP2014.44.1.03

Consumption of plant material by perch (Perca fluviatilis)

Abstract. While removing fish during reservoir biomanipulation, it was noted that the diet of normally piscivorous 5+ to 7+ perch was dominated by macrophyte fragments, with fish eggs sub-dominant. To the best of our knowledge, macrophytes have not previously been reported as a food item in perch. Here, we briefly discuss this finding and its significance for perch diet studies.

Assessment of possible diel and sex-related differences in round goby (Neogobius melanostomus) diet

Abstract. Several aspects of invasive round goby (Neogobius melanostomus) biology are based on sporadic observations or anecdotal reports only, e.g. they are night feeders, they prey on eggs and larvae of native fish and male feeding ceases or is highly restricted during breeding due to nest-guarding. To test the general validity of such hypotheses, we assessed diel and inter-sex differences in diet and feeding intensity of 232 gobies (144 female [54 day:90 night] and 88 male [39 day:49 night]) caught during the breeding season. Gobies took primarily aquatic insect larvae and did not predate on eggs, larvae or juveniles of native fish. Unlike previous studies, we observed no diel difference in feeding intensity or diet composition; hence no universal diel pattern can be implied for round goby feeding. On the other hand, we observed significant inter-sex differences in both feeding intensity and diet composition, with males consuming less food than females, presumably due to restricted feeding activity during nest-guarding. Inter-sex shifts in both diet composition and amount of food were less than expected, however, suggesting that, under most conditions, there is no reason to expect a fatal decrease in male energy intake, as suggested by some earlier studies.