Rapid morphological divergence of cultured cod of the northwest Atlantic from their source population

IA Fleming,BF Wringe,CF Purchase

doi:10.3354/aei00145

Abstract

The performance of aquaculture escapees in the wild depends in part on how their morphology differs from that of wild fish. We compared farmed Atlantic cod Gadus morhua morphology to that of wild cod from the same ancestral population. Traditional and geometric morphometrics showed that farmed cod had relatively smaller fins, heads, eyes, and jaws than wild cod for a given size. Conversely, drumming muscle size and metrics of body and liver condition were greater in farmed fish. As the observed differences are likely due to phenotypic plasticity, their fitness consequences for escaped farmed fish may be transient.

Highlights

Fish exposed to culture develop phenotypes that differ from those of their wild counterparts (Fleming & Gross 1994, Araki et al 2008, Bailey et al 2010, Chittenden et al 2010)
Through programmes that sought to diversify the Canadian aquaculture industry, experimental Atlantic cod Gadus morhua broodstocks were created from wild-caught fish, and their offspring were stocked to commercial cage aquaculture farms
These first-generation farmed cod afforded us the unique opportunity to study the morphological effects of exposure to the aquaculture environment on fish that had not experienced the intensive selection regimes common in more established species (e.g. Atlantic salmon Salmo salar)

Summary

Introduction

Fish exposed to culture develop phenotypes that differ from those of their wild counterparts (Fleming & Gross 1994, Araki et al 2008, Bailey et al 2010, Chittenden et al 2010) The phenotypes they develop may be beneficial under culture but may reduce the fitness of an individual when exposed to another environment (e.g. the wild environment following escape). Through programmes that sought to diversify the Canadian aquaculture industry, experimental Atlantic cod Gadus morhua broodstocks were created from wild-caught fish, and their offspring were stocked to commercial cage aquaculture farms. These first-generation farmed cod afforded us the unique opportunity to study the morphological effects of exposure to the aquaculture environment on fish that had not experienced the intensive selection regimes common in more established species (e.g. Atlantic salmon Salmo salar). We discuss the differences in morphology in terms of potential fitness effects on escapees in the wild

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Conclusion