Graduation date: 2004
Quantitative assessments of many West coast rockfish stocks of both major and
minor importance to commercial fisheries have shown varying declines in abundances. The population sizes of less-abundant, co-occurring unassessed species may also be
declining. However, determining stock status of the many non-targeted, minor species with high levels of certainty and quantifiable predictability may be prohibitively expensive and/or impractical because of the dearth of available data. Using a system of qualitative indicators may provide a cost-effective method to create preliminary assessments of the relative status of minor rockfish stocks and subsequently prioritize future studies. This project was undertaken to test a system of indicators to characterize the status of West Coast rockfish species including Sebastes aurora, S. babcocki, S. aleutianus, S. zacentrus, S. borealis, S. diploproa, and S. reedi. An array of indicators including catch per unit effort, the proportion of positive hauls, and length composition data were used to detect possible changes in the density, distribution, and size composition of the population. Data were taken from three West Coast bottom trawl surveys conducted by the National Marine Fisheries Service. The
percentage of trends indicating linear decline were summarized and stocks were
subsequently ranked in order of greatest concern over declining populations. S. babcocki was ranked as the stock of greatest concern with 52% of the indices showing negative trends while negative trends for S. diploproa, S. zacentrus, and S. borealis were found in 26%, 23%, and 20% of the indices, respectively. Less than 15% of determined trends were negative for S. aleutianus, S. aurora, and S. reedi. Our interpretation of the health of the population projected by the indicators was compared to the population status based upon formal stock assessments for four species, S. alutus, S. crameri, S. melanostomus, and S. rufus. Indicator-based assessments show potential to preliminarly assess numerous species simultaneously and identify species of greatest concern over declining populations.