Biology of four sympatric sticklebacks in Cobscook Bay, Maine, a boreal, macrotidal bay

Four species of sticklebacks were collected during May, June, August, and September 2011–2013 in a survey of fishes of Cobscook Bay, a macrotidal bay in eastern Maine, U.S.A. Threespine ( Gasterosteus aculeatus ) and ninespine ( Pungitius pungitius ) sticklebacks have circumpolar distributions; blackspotted ( Gasterosteus wheatlandi ) and fourspine ( Apeltes quadracus ) sticklebacks are limited to northeastern North America. Sticklebacks were collected in the intertidal zone with beach seines and in the pelagic zone with trawls. Up to 30 individuals of each species from each sample were measured and weighed. Individuals were identified as gravid or not in 2012 and 2013. Catch-per-unit-efforts of the most abundant threespine (18,878 individuals) and second most abundant blackspotted sticklebacks (2433) were greatest in the innermost part of the bay, on mudflats, in 2012, and in August. Fewer than 100 fourspine and fewer than 50 ninespine sticklebacks were caught over the three years, mostly in the inner bay. Length-frequency distributions suggested age classes of 0+, 1+, 2+ and a few 3+ for threespine sticklebacks and 0+ and 1+ for blackspotted sticklebacks. Most gravid individuals of those two species were present in May and June. Spawning occurred earlier in 2012, an unusually warm year, than in 2013. Changes in presence, timing, and abundance of other species in the fish survey corroborated the influence of the record warm conditions in 2012 in the Gulf of Maine on the fish community of Cobscook Bay. Blackspotted and ninespine sticklebacks are vulnerable to population decline from warming in the Gulf of Maine because they are near the southern limits of distribution.