A sudden collapse in distribution of Pacific sardine (Sardinops sagax) off southwestern Australia enables an objective re-assessment of biomass estimates

摘要: Fish. Bull. 102:617-633 (2004). Abstract — Fishery-independent esti- mates of spawning biomass (BSP) the Pacific sardine (Sardinops sagax) on south and lower west coasts Western Australia (WA) were obtained periodically between 1991 1999 by using daily egg production method (DEPM). Ichthyoplankton data collected during these surveys, specifically presence or absence S. sagax eggs, used to investi- gate trends in area within each four regions. The expectation was that BSP positively related. With DEPM model, estimates will change proportionally with if all other variables remain constant. proportion positive stations (PPS), i.e., nonzero counts an objec- tive estimator high for coast regions early 1990s (a period when estimated also high) then decreased after mid-1990s. There a decrease PPS from mid-1990s 1999. particu- larly low followed severe epidemic mass mortality throughout their range across southern Australia. Deviations expected relationship identify uncertainty around BSP. Because estimation is subject less sampling bias than BSP, deviation relation two provides objective basis adjusting some latter. Such approach particularly useful fisheries management purposes problems are suspected be present. analysis undertaken same set samples which estimate derived help provide information stock assessments purse-seine fisheries.