The White Sea threespine stickleback population:spawning habitats, mortality, and abundance

Hypothesis: Stickleback abundance in the White Sea is limited by availability of spawning habitats. Organisms: Threespine stickleback, Gasterosteus aculeatus; eelgrass, Zostera marina. Times and places: June (spawning period of stickleback) 2009-2011 and 2014; 60 locations along the White Sea coast. Methods: We sampled with a beach seine (length 7.5 m, height 1.5 m, mesh size 5 mm in wings and 1 mm in purse) in coastal zones within 30 m of the shore. Results: Around 60% of the entire stickleback population occurs in the northwestern part of the White Sea (Kandalaksha Bay). This region has favourable spawning habitats, i.e. protected inlets with a high density of eelgrass and other macrophytes. Other parts of the White Sea are more exposed to waves and have less vegetation. We estimated that the White Sea currently supports about 740 million stickleback at the beginning of the spawning season, with a total biomass of about 1600 metric tonnes.