Diet composition of herring (Clupea harengus L.) and cod (Gadus morhua L.) in the southern Baltic Sea in 2007 and 2008

Abstract

Diet composition of two commercial fish species, herring and cod, were studied in some regions (mainly Gdańsk and Bornholm Basins, and the Polish coast) of the southern Baltic Sea in 2007 and 2008. Herring is the dominant zooplanktivorous species in the ecosystem of the Baltic Sea, but apart from mesoplanktonic organisms it also eats macroplanktonic and benthic species in considerable amount. The diet of cod consists of fish and crustaceans from pelagic, hyperbenthic and benthic habitats. The feeding preferences of fish indirectly reflect changes in the whole food chain in the Baltic Sea. This research focuses specifically on these invertebrate species, which are eliminated from the environment by most of the ichthyofauna of this region. The aim of this research is to examine the role of invertebrate organisms belonging to Crustacea in the diet of herring and adult cod to supply updated results about feeding of these fish as little data have been collected since the 1990s. The present study is a preliminary survey and results can not be considered conclusive. The restricted numbers of analyzed stomachs of fish and selected seasons of the year addressed in this paper are a starting point for further studies with a larger scope. In this study, 20 to 90% of herring had empty stomachs. Mesozooplankton dominated the diets of small and large herring.

Distribution of organic and inorganic mercury in the tissues and organs of fish from the southern Baltic Sea

“…Cod are predators that feed mainly on fish from the families Clupeidae , cod fry, and benthic crustaceans, and they are even cannibalistic. Herring feed on phytoplankton and zooplankton, small crustaceans and larval fish, while sprat feed on phytoplankton (Casini et al 2004 ; Dziaduch 2011 ; Beldowska et al 2015 ). The highest concentrations of mercury were confirmed in eel and cod tissues and organs, and CH 3 Hg + dominated in the muscle and liver, but it also occurred at high levels in other internal organs (Table 1 ).…”

Forage fish quality: seasonal lipid dynamics of herring (Clupea harengus L.) and sprat (Sprattus sprattus L.) in the Baltic Sea

“…In spring, both Baltic sprat and herring prey mainly on copepods (Möllmann et al, 2004). In summer and autumn, sprat additionally feed on cladocerans while larger herring in autumn and winter favour mysids, amphipods, and polychaetes (Casini et al, 2004), although herring have also been observed to prey on cladocerans during autumn (Dziaduch, 2011). The main copepod species in the Baltic Sea are the calanoid copepods; Pseudocalanus sp., Temora longicornis, and Acartia spp.…”

The forgotten feeding ground: patterns in seasonal and depth‐specific food intake of adult cod Gadus morhua in the western Baltic Sea

“…Unlike the North Sea, in the Baltic Sea stomach sampling has been conducted on a relatively regular basis, at least with regard to the commercially most important demersal fish species, Atlantic cod Gadus morhua (e.g., Arntz, 1974Arntz, , 1977Casini et al, 2016;Dziaduch, 2011;Hüssy et al, 1997;Pachur & Horbowy, 2013;Schulz, 1987Schulz, , 1988Schulz, , 1989aSchulz, , 1989bWeber & Damm, 1991;Zarkeschwari, 1977). Cod is considered the apex predator in the Baltic Sea, and major efforts were invested to improve the understanding of its trophic role.…”

“…The main distributional areas of the two cod stocks differ remarkably in oceanographic conditions and also in prey availability and composition. In the past decades the diet studies mainly focused on the role of EBC in the eastern Baltic food web (e.g., Casini et al, 2016;Dziaduch, 2011;Hüssy et al, 1997;Kulatska et al, 2019;Pachur & Horbowy, 2013). These studies revealed that currently EBC relies strongly on Clupeid prey species such as herring Clupea harengus and sprat Sprattus sprattus,…”