In our study, we estimated fishery selectivities for the commercial bottom trawl fishery using a new approach that complements estimates from stock assessment models.
Our results show clear differences in commercial fishery selectivities among species, areas, and over time.
Averaging depth distributions was reasonable because effects of survey bottom trawl selectivities (that may have differed because of area or year) were removed.
Vulnerabilities, like selectivities, were scaled to a maximum of one.
Given vulnerabilities at length for commercial bottom trawls, an expression for commercial fishery selectivities at length can be derived because p(d\L) [N.
Our best estimates of commercial bottom trawl fishery selectivities for each subarea, year, and species were based on subarea-specific fishing effort data (Tables 1-2) and our best estimates of depth distributions for the whole coast and sexes combined.
Selectivities for species with strong ontogenetic migration (sablefish, shortspine thornyheads and Dover sole) changed most over time.
Higher proportions of total commercial bottom trawl effort in deep water (where large fish are most common) during the early years caused relatively high selectivities for large fish in the southern subarea.
Commercial bottom trawl selectivities for smaller fish on the left-hand side of the selectivity curves resemble the underlying vulnerability curves.
Commercial bottom trawl selectivities for large long-spine thornyhead may have increased slightly over time as the fishery moved into deeper water (Fig.