The Nutrition of Fish in the Curonian Lagoon and the Coastal Zone of the Baltic Sea

Abstract

We investigated the nutrition of 13 fish species inhabiting the Curonian Lagoon. The research material was obtained in the areas of Ventė Cape, Dreverna and Kiaulės Nugara in the spring, summer and autumn of 1996, 1998 and 1999. Altogether, the intestinal tracts of 539 fishes were investigated. In the coastal zone of the Baltic Sea, the nutrition of 11 fish species was investigated. The research was carried out at the Klaipėda Strait and in the sea sections of Klaipėda-Giruliai and Klaipėda-Nida in April-August. The total number of 345 specimens was investigated. It was established that the main food components of roach and silver bream in the middle and northern parts of the Curonian Lagoon are molluscs (Dreissena), Chironomidae larvae, zooplankton and plants. The nature of nutrition of bream, vimba, pike-perch and perch depends on the biotope and various environmental conditions. In the Curonian Lagoon, the main food components of bream are molluscs, zooplankton and detritus. The main food components for bream dwelling in the Baltic Sea are sea molluscs, worms (Polychaeta) and amphipods. In the Curonian Lagoon, the food spectrum of vimba, a migratory fish, consists of Chironomidae larvae, zooplankton, land insects and detritus. The food spectrum of vimba dwelling in the Baltic Sea is narrower and consists of worms (Polychaeta), amphipods, molluscs and detritus. The ration of grown-up large perch mostly consists of ruff and juveniles of perch and Cyprinidae fishes. The main food components of perch juveniles are amphipods, Mysidae, Chironomidae larvae and molluscs. The acclimatised Crustaceans also play an important role in the ration of perch of the Curonian Lagoon. In the sea, smelt juveniles and goby predominate over other food components of perch. The food composition of pike-perch of the Curonian Lagoon mostly consists of ruff, roach, perch and smelt. Pike-perch juveniles mostly feed on Mysidae. In the sea, pike-perch feed not only on other fish species but on large benthic crustaceans as well, such as sea lice (Mesidotea entomon) and shrimps. The ration of juveniles mostly consists of Mysidae. The food composition of non-commercial fish, such as ruff, gudgeon and three-spined stickleback is very similar to that of commercial fish species. The main food component of bleak, dace and cod is flying insects. The main food components of fish inhabiting the coastal zone of the Baltic Sea are molluscs, worms (Polychaeta), Gammaridae, zooplankton and various fish species. The food composition of flounder and turbot largely depends upon their biotopes. The main food objects of these fish are molluscs (Mytilus edulis), worms (Polychaeta), amphipods and Mysidae. In the sea stretch between Klaipėda and Nida, where Mytilus edulis are rare, turbot feed on goby, Baltic herring and sand-eel. In the intestinal tracts of whitefish caught in the water area between Klaipėda-Nida, Gammaridae, shrimps and goby are found. The intestinal tracts of planktophagous fish, Baltic sprat and smelt, are filled exceptionally with zooplanktonic crustaceans, i.e. Crustacea Copepoda. In addition to Crustacea Copepoda, the diet of herring also consisted of worms (Polychaeta), Gammaridae and insects.