Seabirds as guides for fisheries management: European shag Phalacrocorax aristotelis diet as indicator of saithe Pollachius virens recruitment

Sh Lorentsen,T Anker-Nilssen,Ke Erikstad

doi:10.3354/meps12440

Abstract

Seabirds as guides for fisheries management: European shag Phalacrocorax aristotelis diet as indicator of saithe Pollachius virens recruitment

Highlights

During the last few decades, fisheries management has experienced a shifting focus, from managing targeted species to a much wider focus on ecosystems and the impact of fisheries on these ecosystems, so called ecosystem-based fisheries management (EBFM) (e.g. Link 2002, Pikitch et al 2004, Smith et al 2007)
We found large inter-annual variation in both the IMR/ICES abundance estimates of recruitment of 3 yr old saithe and the biomass of 0 and 1 yr old saithe in the shag diet (ANOVA, F7,1163 = 9.00, p < 0.001, and F7,1163 = 20.67, p < 0.001 for 0 and 1 yr old saithe, respectively; Fig. 1)
Studies on captive shags show that otoliths from e.g. gadoid fishes are recovered in much higher frequencies that otoliths from many other fish species in seabird diets, including sandeels (Ammodytes spp.), sprat Sprattus sprattus and herring Clupea harengus (Johnstone et al 1990)

Summary

Introduction

During the last few decades, fisheries management has experienced a shifting focus, from managing targeted species to a much wider focus on ecosystems and the impact of fisheries on these ecosystems, so called ecosystem-based fisheries management (EBFM) (e.g. Link 2002, Pikitch et al 2004, Smith et al 2007). In fisheries management, monitoring pelagic fish populations is performed using research vessels and scientific trawl surveys. While such monitoring is needed to assess the recruitment and adult stock size of the commercially targeted species, it is often time consuming and expensive to carry out. For fish species that spend most of their immature life in shallow waters, trawl surveys are limited by the inaccessibility of these areas to large vessels. Even though these fish species may be an important target for commercial fisheries, they cannot be surveyed properly until the young re-enter the open seas. When the nursery grounds of fish are inaccessible to research vessels, seabirds might be used as a complementary tool to assess the strength of young cohorts long before they recruit to the population targeted by the fisheries

Methods

Results

Conclusion