Are spatial and temporal patterns in Lynn Canal overwintering Pacific herring related to top predator activity?

• Main Authors: Boswell, Kevin M, Rieucau, Guillaume, Vollenweider, Johanna J, Moran, John R, Heintz, Ron A, Blackburn, Jason K, Csepp, David J
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: NRC Research Press (a division of Canadian Science Publishing) 2016
• Subjects: Pacific; Humpback Whale; Alaska
• Online Access: http://hdl.handle.net/1807/72359; http://www.nrcresearchpress.com/doi/abs/10.1139/cjfas-2015-0192

In Southeast Alaska, overwintering Pacific herring (Clupea pallasii) form large conspicuous schools which are preyed upon by an abundance of mammalian and avian predators, thus leading to the question of why herring adopt a strategy that appears counter productive to predator avoidance during these periods. We examined the spatial and temporal dynamics of overwintering Pacific herring and associations with predators through monthly hydroacoustic surveys during two consecutive winters. Large variation was observed through the winter season in herring distribution, school morphology and density. Herring school characteristics and biomass estimates were negatively correlated with humpback whale abundance patterns during both winters and as whales departed towards the end of winter, herring distributions shifted from dispersed schools in the water column toward deep, dense schools. We postulate that the schooling patterns observed in Lynn Canal overwintering herring are likely to be mediated by predation threat rather than energetics or feeding activities. An additional consequence of humpback whales dispersing herring in the water column may be an increased threat of predation by other surface-oriented predators. The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author.