On change of stickleback role in fish diet in the 20th century

Abstract

The role of the threespine stickleback Gasterosteus aculeatus (adults, juveniles, and eggs) in the diet of common predatory fish species of the White Sea (Atlantic cod Gadus morhua, navaga Eleginus nawaga, European sculpin Myoxocephalus scorpius) was studied. Samples were collected in the Kandalaksha Bay from June to August 2011–2014. The stickleback was caught with a beach seine, predatory fish – with gill nets. The analysis of the stomach contents of predatory fish (determination to the level of the species, counting, weighing), as well as a review of the scientific literature on the diets of predatory fish of the White Sea over the last century in connection with fluctuations in stickleback numbers. According to the results obtained, in the spawning grounds of stickleback (Zostera seagrass beds), it makes up 60% of the summer diet of the sculpin (this species eats only adult sticklebacks), 52% of the diet of cod (adults, juveniles and stickleback roe) and 15% of the diet of navaga (juveniles sticklebacks). These results are consistent with observations made during the period of high numbers of sticklebacks in the White Sea (1930–1950s). During the period of low abundance (1960s – early 2000s), stickleback was absent in the stomachs of predatory fish.

Keywords: Atlantic cod, Eleginus nawaga, European sculpin, Gadus morhua, Gasterosteus aculeatus, long-term changes, Myoxocephalus scorpius, predation, saffron cod, threespine stickleback, White Sea.