Changes in the population structure and life history associated with long-term intense fishing of the Argentinian croaker Umbrina canosai in southern Brazil

Abstract

Identifying changes in the population structure and dynamics for fish stocks is important to support its management. Data obtained from 1976 to 2019 allowed to follow up long more than four decades the changes in the population structure and life-history of Umbrina canosai, an intensely exploited demersal sciaenid fish in southern Brazil. Intense fishing caused the truncation of the length/age structure with the loss of most of the bigger/older fishes and the sex ratio change, with increasing frequencies of males. A considerable increase in individual growth was observed and attributed to the lower competition for food due to the reduction in the density of the overall coastal benthic-feeding fish community caused by intense fishing. The large increase in the mortality and the exploitation rate resulted in a drastic decrease in the reproductive potential despite some anticipation in the sexual maturation. Despite the adaptative response to intense fishing, the high exploitation rates and the drastic reduction of the spawning potential ratio in recent years, are clear evidences that U. canosai could be reaching its adaptive capacity for resilience. Therefore, an urgent necessity for a drastic reduction of the fishing mortality to avoid the economic collapse of the fishery is required.

Keywords

• fishery collapse
• growth
• life history
• mortality
• reproduction
• spawning potential ratio