Selective fishing and shifting production in multispecies fisheries

Abstract

A limited ability to target or avoid individual stocks complicates successful output management in multispecies fisheries. For vessels in these fisheries, reducing harvest of one species often requires simultaneous reductions in harvest of other stocks. The extent to which multispecies allocation targets can be met may depend critically on harvesters’ ability to substitute production across species. We introduce a measure of compositional control that captures the level of forgone production resulting from imperfect selectivity. This metric is then applied to data from the New England multispecies groundfish fishery and used to test for evidence of limited selectivity in the composition of individual vessel daily landings. Results indicate that increases in landings of one species generally require simultaneous increases in landings of other species — a finding that suggests difficulty in substituting production across groundfish species. Our measure is seen to vary widely through time as well as across vessels and species and may be affected by both environmental conditions and incentives created through management. The model developed here should hold value for managers and researchers seeking to assess interstock economic trade-offs in multispecies fisheries.