The dependencies between the abundance of Chironomus f. l. plumosus and bream (Abramis brama) net catches in a lowland reservoir (Zegrzyński Reservoir, central Poland)

Abstract

Chironomus f. l. plumosus larvae, a valuable food of bream (Abramis brama (L.)), dominate in the benthos of the extra-littoral zone of the shallow, lowland, eutrophic Zegrzyński Reservoir. Bream is the dominant fish species in this reservoir, making up to 80% of total net catches. During eight years of studies, very regular Chironomus population dynamics were noted in the lotic part of the central, broad basin of the reservoir. There were usually two peaks of the abundance: the higher one in spring, and the much lower one in late summer. reservoir in particular years. The total bream catch per year in the reservoir studied also correlated positively with the average yearly abundance of Chironomus. The correlation between Chironomus abundance and bream occurrence (measured by commercial net catches) in the reservoir studied suggests that this environment is used by bream mainly as a feeding ground. In the years with a low spring Chironomus peak of abundance, the bream leave the reservoir, searching for food in its inflows -two large, lowland rivers. This corresponds to much lower catches noted in the reservoir in the years of low Chironomus abundance.

Water residence time in the Włocławek dam reservoir (the Vistula river, Poland) affects its macrozoobenthos structure

“…Chironomus sp. also dominated in the Zegrzyński Reservoir (Prus, 2009) and was one of the dominant taxa in the Ribeirao das Anhumas Reservoir in Brazil, where its densities in different zones were comparable (Corbi and Trivinho-Strixino, 2002). On the other hand, a significantly higher density of Chironomus sp.…”

Long-term changes in the fish community structure revealed by gillnet monitoring in a shallow, lowland reservoir

“…Among the commonly occurring fish species in Sulejów Reservoir, only roach was able to crush a wide range of Dreissena mussels and effectively utilize this new food resource (Prejs et al 1990, van den Berg 1993, Nagelkerke and Sibbing 1996, Molloy et al 1997, Kobak et al 2010, so interspecific food competition could primarily be limited to the smaller specimens (<15 cm). At this stage, roach mostly competes for zooplankton and chironomids with common and white bream (van den Berg 1993, Nagelkerke and Sibbing 1996, Kakareko 2001, Prus 2009). Roach specimens can switch to feed on zebra mussel much faster (>160 mm TL) and more effectively than bream (>370 mm TL), and it is also able to consume much larger mussels (typically 6-18 mm long and a maximum of 19 mm) than common bream (typically 6-8 mm long and a maximum 13 mm).…”

“…In turn, bream are theoretically more efficient at utilizing different food sources, such as benthos or zooplankton, and their high-backed bodies deter predation. Furthermore, as a multiple spawner, the species can better overcome short-term, unfavourable environmental conditions (Pivnička and Švátora 1977, van den Berg 1993, Mann 1996, Nagelkerke and Sibbing 1996, Kakareko 2001, Prus 2009, Targońska et al 2014. As a result, short-term fluctuations in the populations of these two species should be expected.…”