Peter Kuriyama1
1SAFS
October 11, 2016 9:00 (PST): FSH 203
Resolving issues of hook saturation, hook competition, and fixed-site design in the Southern California hook-and-line survey
The Southern California hook-and-line survey has been conducted by the Northwest Fisheries Science Center since 2004 to monitor the untrawlable habitat of the Southern California Bight. Data from the survey have been used in stock assessments and supporting research for a number of shelf rockfish species, such as bocaccio (Sebastes pauicispinis) and vermilion rockfish (S. miniatus). However, an index of abundance estimated from hook-and-line data may be biased due to the fixed-site design of the survey and issues with hook saturation and hook competition. Here, I will present empirical results from the hook-and-line data and results of a simulation study exploring the biases associated with aspects of the survey. Bocaccio are the most sampled species in the survey, and sites with low catch rates of bocaccio have high catch rates of vermilion rockfish. Preliminary results from the simulations indicate that hook saturation causes estimates of abundance to be negatively biased at large population sizes. Additionally, hook competition leads to positively biased indices of abundance, and weighting catch rates by site leads to the least biased index of abundance. These results identify methods of incorporating hook-and-line data from untrawlable habitat into stock assessments and identify biases that are applicable to general hook-and-line survey methods.