Feeding of European cisco (Coregonus albula and C. lucinensis) on the glacial relict crustacean Mysis relicta in Lake Breiter Luzin (Germany)

Abstract

Lake Breiter Luzin, located in north-eastern Germany, is known for the rare occurrence of sympatric populations of European cisco, Coregonus albula and C. lucinensis. Moreover, the lake is inhabited by the glacial relict crustacean Mysis relicta, currently found in only three other lakes in Germany. In the present study, the role of M. relicta in the diet of ciscoes was investigated. Between 2001 and 2002 ciscoes, mysids and zooplankton were caught in Lake Breiter Luzin and stomach contents of ciscoes were analysed. There were seasonal changes in the food items in the stomachs, largely reflecting changes in prey availability. The main food items were copepods (45-81%) and mysids (5-26%). Cladocerans had high amounts in the diet only in summer. Seasonal changes in selectivity were also noted for most prey groups. There were also some consistent patterns of prey preference, with an overall preference for mysids. In general, the prey composition in cisco stomachs did not show significant diet changes, but there were some significant differences between day and night feeding in single prey groups, such as cladocerans. Diet composition of ciscoes varied with the different depth strata in which the fish were caught. With increasing depth, the proportion of mysids in the diet significantly increased, whereas that of copepods significantly decreased. Between C. albula and C. lucinensis, no distinct differences in feeding were evident. Mysids provided an additional and important food resource to ciscoes, and were mainly consumed when the availability of other prey organisms decreased, as in autumn and in the deeper strata of the water column. However, mysids preyed on the same food organisms as ciscoes, indicating a strong competition for food between fish and mysids.

Hydroacoustic estimates of fish densities in comparison with stratified pelagic trawl sampling in two deep, coregonid-dominated lakes

“…This could explain the highly variable catches from deep layers at almost identical hydroacoustic density estimates. Because the coregonids in Lakes Stechlin and Breiter Luzin perform diel vertical migrations and are thus concentrated in the layers just below the thermocline at night (Mehner et al, 2007b;Scharf et al, 2008), the trawl is moved through the layers with highest fish densities during the lifting process from deep layers. This may have caused erroneously high catches, and can be prevented only by applying nets than can be closed already at the sampling depth.…”

Genetic population structure of sympatric and allopatric populations of Baltic ciscoes (Coregonus albula complex, Teleostei, Coregonidae)

“…Such a pattern of physiological segregation but low trophic differentiation presumably exists for the species pair in Lake Breiter Luzin, since both lakes are deep, with steep temperature gradients and overall low productivity [ 27 ]. Recent data suggest C. albula and C. lucinensis in Breiter Luzin have similar diets [ 53 ], as in Lake Stechlin [ 29 ]. However, adaptive divergence may be weaker in Lake Breiter Luzin than in Lake Stechlin.…”

Does the Ice Age legacy end in Central Europe? The shrinking distributions of glacial relict crustaceans

“…In suitable habitats, glacial relict crustaceans can be found in high abundances and play a significant ecological role in pelagic food webs, often comprising most of the diet of commercially valuable inland fish species, such as vendace, whitefish and others (Lasenby, Northcote & Fürst, 1986; Sandlund, Næsje & Jonsson, 1992; Scharf et al, 2008). However, during the 20 th century and especially during the last few decades, glacial relict crustaceans in the southern part of their distribution have faced increasing anthropogenic pressure, with extinctions reported in many locations.…”