Long-term trends in yield and catch rates of the coral reef fishery at Apo Island, central Philippines

Abstract

Fish yields and catch rates recorded in the 1980s were compared with daily roving creel surveys carried out in 1997/98, 2000 and 2001 at Apo Island. Total annual fish yields were measured six times over the period 1980–2001. Total fish yield was 19–25 t km^–2 year^–1, with reef and reef-associated fish accounting for 15–20 t km^–2 year^–1, for five measurements. A sixth measurement, made in 1986, estimated 36.7 t km^–2 year^–1. Annual yield remained stable over the study period. Carangidae and Acanthuridae accounted for 26–47% and 16–27% of the catch, respectively. Non-reef catches declined over time, from 6.21 t year^–1 in 1980/81 to 1–2 t year^–1 in 2000 and 2001. Estimates of annual hook and line catch per unit effort (CPUE) increased from 0.13–0.17 kg man^–1 h^–1 in 1980/81, to 1–2 kg man^–1 h^–1 in 1997–2001. For target families, hook and line CPUE was consistently higher in 1997–2001 than in 1980–86. However, hook and line CPUE for Carangidae and Acanthuridae declined significantly between 1997 and 2001. Possible reasons for the long-term patterns of fish yields and catch rates are discussed. Differences in methods used in estimates, and changes in gears and fishing effort over the years, make comparisons difficult.