Role of temperature-mediated embryo development in the range expansion of cunner into the Bay of Fundy

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University of New Brunswick


Increasing sea-surface temperature has been shown to affect the distribution of coastal fishes. Samples obtained from a monitoring program (2009-2015) of shallow cobble-bottom sites in southwest Bay of Fundy provided the first record (2012) of juvenile cunner Tautogolabrus adspersus in the region. The cunner range extends along the North American Atlantic coast to Newfoundland, but only occasional adults were observed in the Bay of Fundy. To determine whether this recent appearance of cunner was related to increased temperature better supporting embryo development and hatch, lab experiments were conducted to complement field observations of juvenile cunner presence/absence and density. Embryos were held in the lab at constant temperatures at 1oC increments ranging from 11-15°C. Hatch was found to increase with temperature, and was markedly greater at temperatures ≥ 13°C than at lower temperatures. Relationships observed between temperature and hatch in the lab helped explain variation in density of young-of-the-year cunner among study sites and years. This study provides evidence that increasing water temperature is resulting in range expansion of a small coastal fish into the Bay of Fundy, and that this expansion is at least partly related to increased hatching success.