Big Fishery, Big Data, and Little Crabs: Using Genomic Methods to Examine the Seasonal Recruitment Patterns of Early Life Stage Dungeness Crab (Cancer magister) in the California Current Ecosystem

Elizabeth M J Lee,Kathleen G O’Malley

doi:10.3389/fmars.2019.00836

Elizabeth M J Lee, Kathleen G O’Malley

Open Access

https://doi.org/10.3389/fmars.2019.00836

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Abstract

The California Current Ecosystem (CCE) is a dynamic marine ecosystem from which many socioeconomically-important fisheries species are harvested. Here, a genotyping-by-sequencing (GBS) approach was used to examine genomic variation in an early life stage (megalopae) of the Dungeness crab (Cancer magister), which constitutes the most valuable single-species commercial fishery in the CCE. Variation in abundance and timing of megalopae recruitment has been extensively studied for over two decades in Coos Bay, Oregon, USA. Within the CCE, documented timing of Dungeness crab life history events indicates that coastal megalopae recruitment is expected to occur April through July; however, long-term studies in Coos Bay have observed late-season recruitment from August to October. Based on variation at 1,913 presumably neutral loci, evidence was found for weak, yet significant differentiation (FST estimate = 0.0011) between the 2014 expected-season recruits (n=47) and late-season recruits (n=47) collected in Coos Bay. However, two putatively adaptive loci with a high FST estimate (0.2036) between expected-season and late-season recruits were identified. These findings support the hypothesis that expected-season and late-season megalopae recruiting to Coos Bay within the same year may have originated from different locations or from different breeding groups. Understanding marine species connectivity between ecosystems is important when considering how future changes in ocean conditions may impact fishery harvests.

Highlights

The California Current Ecosystem (CCE) is a dynamic marine ecosystem that spans from Vancouver Island, British Columbia, Canada to Baja California, Mexico (Fautin et al, 2010)
The largest peak in abundance was observed in May during expected-season and the second largest peak in abundance was observed in September during the late-season
We found evidence for weak genetic differentiation, based on variation at 1,913 presumably neutral loci, between the 2014 expected-season (May) and late-season (September) Dungeness crab megalopae recruits in Coos Bay, Oregon, an estuary within the CCE

Summary

Introduction

The California Current Ecosystem (CCE) is a dynamic marine ecosystem that spans from Vancouver Island, British Columbia, Canada to Baja California, Mexico (Fautin et al, 2010) This large marine ecosystem exhibits spatial and temporal variations in ocean conditions, such as sea surface temperature, sea surface height, timing of spring transition, alongshore winds, and Genomics and Dungeness Crab Recruitment upwelling events (Guisan and Thuiller, 2005). Under the current management strategy, it is estimated that greater than 90% of all age four male crabs are harvested annually; indicating that the coastwide CCE Dungeness crab commercial fishery landings (Washington, Oregon, and California, United States) are a reasonable proxy for the size of the age 4 year class (Hackett et al, 2003). The CCE harvest variability has often been attributed to larval success of each year class, when the Dungeness crab are most vulnerable to ocean conditions (reviewed in Botsford et al, 1989; reviewed in Botsford and Lawrence, 2002; reviewed in Rasmuson, 2013)

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