Oil sardine (Sardinella longiceps) off the Malabar Coast: density dependence and environmental effects

Marine fish stocks are known for extensive variation in landings, with temporal fluctuations attributable to density-dependent as well as environmental effects. In this paper we analysed a 44-yr time-series of oil sardine Sardinella longiceps landings from the Arabian Sea off the Malabar Coast of India. Density dependence was detected in the landings of oil sardine, reinforcing the potential for sustainable yields. Significant environmental factors (precipitation and sea level reflecting the strength of upwelling) during the monsoon period (June-August) are hypothesized to affect the dynamics of landings by influencing spawning and recruitment success. Together, density dependence and environmental variability during the monsoon explained 80% of the among-years variance in landings. Our results have important consequences for understanding catch variability and are potentially useful for facilitating management of this commercially important fishery.