Estimation of Catches of Non-Target Species Using Observer Data

Distribution of longline hooks set and hooks observed in the WCPFC Statistical Area, 1992–2007

Delta Lognormal Models With Splines where F1, the logistic part, is the probability that the catch rate in a stratum is positive and F2, the lognormal part, is the catch rate in a stratum if the catch rate is positive Logistic Model Lognormal Model

Statistics on DLN Models of CPUE for Key Shark Species and groups

Oceanic Whitetip Shark Blue Shark Thresher Sharks Mako Sharks Oceanic Whitetip Shark Silky Shark “CPUE Heat Maps” Effect of latitude and longitude on longline catch rates of key shark species determined from observer data

Oceanic Whitetip Shark Mako Sharks Blue Shark Effect of year_month on longline catch rates of key shark species determined from observer data Oceanic Whitetip Shark Silky Shark

What does the “year-month” effect tell us about the populations of non-target species? Probably less than we might expect. There are errors in species identification early in the time series, e.g., no silky shark. Operation changes are the known problem (Clarke et al. 2010): Japan LL fishing in AFZ ceased in 1997. A trip limit for sharks was imposed in Australia in 2000. Shark finning was banned in Hawaii in 2000. Shallow sets were banned in Hawaii from 2001 to 2004. The use of wire traces generally has declined since 2004. Wire traces were banned in Australia in 2005. The extent of shark targeting is the unknown problem: Did Japan LL increasingly target blue sharks in Australia prior to 1997? What about the high blue shark catch rates in the temperate North Pacific?

Estimates of Catches of Key Shark Species in the WCPO East of 130E Longline Effort