Distribution and structure of coastal ichthyoplankton communities of the Bay of Fundy in southern New Brunswick, Canada

Ichthyoplankton communities from Saint John Harbour and Passamaquoddy Bay on the New Brunswick shore of the Bay of Fundy, Canada, were sampled seasonally between 2011 and 2014. Saint John Harbour is an industrialised port whereas Passamaquoddy Bay is less developed, with a focus on aquaculture. In total, 32 species of fish eggs and larvae were recorded: 26 species in Saint John Harbour and 25 in Passamaquoddy Bay. Nineteen species were common to both areas. The dominant species in Passamaquoddy Bay were Enchelyopus cimbrius, Urophycis sp., Scophthalmus aquosus, and Tautogolabrus adspersus. In Saint John Harbour, E. cimbrius, Urophycis sp., Clupea harengus, and Pseudopleuronectes americanus were most abundant. The communities of the two areas were significantly different. This was most pronounced in summer when Saint John Harbour had a much higher proportion of C. harengus and much lower overall abundances, relative to Passamaquoddy Bay. Saint John Harbour demonstrated higher taxonomic diversity than Passamaquoddy Bay, attributable to the wider variety of salinity regimes present within the harbour. In both areas, the ichthyoplankton communities were strongly seasonal with the highest abundance and diversity in summer. Surface temperature was the best predictor of community composition. Given its industrialisation, Saint John Harbour had a surprisingly diverse ichthyoplankton community, comparable to the less impacted Passamaquoddy Bay. The strong flushing in the harbour by high riverine output and tidal exchange may diminish industrial impact. We strongly recommend incorporating ichthyoplankton into the long-term monitoring of Saint John Harbour and provide guidance to this end.