Stock–Yield Model for a Fish with Variable Annual Recruitment

Many fish populations have variable annual recruitment, which challenges both population model development and conventional management strategies. Here, we develop a stock– yield model to assess the sustainability of the commercial catch of goldeye Hiodon alosoides from western Lake Athabasca of northeastern Alberta, Canada. Goldeyes have highly irregular annual recruitment; many year-classes are poor and dominant year-classes appear an average of only 1.7 times per decade. In the late 1990s, the mean annual commercial catch from this population was about 11,500 goldeyes—primarily fish from the 1982 and 1989 year-classes. A best-fit stock–yield model developed for this population incorporated (1) the restrictions of the catch from a historic fishery that depleted this population during the 1950s and early 1960s; (2) the restrictions of the known total stock size in the early 1970s, obtained from mark–recapture studies; (3) long-term annual estimates and patterns for stock recruitment (1972–2008); (4) a natural annual mortality rate of 20%; and (5) stock estimates for 1994 obtained from the catchability coefficient (catch per unit effort divided by the magnitude of commercial stock estimated from mark–recapture data for 1972 and 1973). The model suggested that an annual commercial catch of 10,000 goldeyes was sustainable over all years and conditions (1947–2004). This small modeled catch, about 2% of the long-term mean stock number of 540,000 goldeyes, ensured that at least a few thousand mature goldeyes would survive to spawn through periods of poor stock recruitment lasting more than a decade. These results suggest that fish populations with irregular annual recruitment can sustain only a low exploitation rate to prevent stock extinction during long periods of low recruitment.