Climate and weather factors affecting winter sheltering by shoreline Copper Rockfish Sebastes caurinus in Howe Sound, British Columbia

J B Marliave,L A Borden

doi:10.1038/s41598-020-71284-4

Abstract

We monitored winter sheltering behavior of Copper Rockfish (Sebastes caurinus) in layered boulders at a shoreline in British Columbia and identified possible links to climate change and evolutionary adaptation. During late autumn and winter, these fish were inside the interstices of the boulder pile (termed “winter sheltering”); these fish were actively swimming above the boulders during spring through early fall. Sheltering duration did not vary between normal and most El Niño years (154–177 days). Sheltering longer than 6 months occurred during strong La Niña winters (197–241 days). Additionally, the proximate stimulus for entry into sheltering was intense Arctic outflow windstorms. Emergence from sheltering appears linked to water temperatures, occasionally related more to spring river flooding (snowmelt). The winter sheltering behavior we describe may be unique to shoreline populations in inland seas. Sheltering may confer a fitness advantage by conserving energy or reducing mortality from predation, thus increasing longevity and chances for successful reproduction. Our observations suggest that an ONI threshold of 0.8 °C or greater would be better suited than the current 0.5 °C threshold used to define ONI events.

Highlights

Behavior can be an adaptive trait in terms of response to climate trends
The present survey illustrates the use of interstices among boulders for sheltering during winter by Copper Rockfish
Tagging surveys in Puget Sound showed that copper rockfish on high relief habitats have small home ranges (< 5 m2) compared to those found on low relief h abitats[9], suggesting that it is reasonable to consider minimal off-reef movement for the population in the present study

Summary

Introduction

Behavior can be an adaptive trait in terms of response to climate trends. Rockfishes are long-lived, have infrequent year-class success, and adults of inshore species tend to remain resident at home s ites[1,2,3], making their life history amenable to protection of broodstock by means of area closures. Earlier research in Howe Sound found that, during winter, Copper Rockfish increase their use of interstices created by multilayered boulder piles, where they become relatively inactive[6]. This winter sheltering behavior was documented in Puget S ound[7]. We used diver surveys of in-versus-out with respect to sheltering in boulders to determine the seasonal duration of sheltering over a period of 13 years With this long-term observational, field-based data set we examined the link between local weather patterns, large scale climate indices and rockfish sheltering behaviour to demonstrate how biological data can better inform our understanding of climate patterns. Howe Sound are used together with survey observations to assess size demography and residency of copper rockfish at this shallow shoreline site

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Results

Conclusion