Long-term changes in population dynamics and life history contribute to explain the resilience of a stock of Micropogonias furnieri (Sciaenidae, Teleostei) in the SW Atlantic

Abstract

We analysed the long-term changes in the population dynamics and life history of whitemouth croaker (Micropogonias furnieri) off Southern Brazil, to understand how four decades of heavy fishing (1976–2017) has affected its population dynamics. In the first three decades, size and age structure were eroded with the loss of the larger (> 60 cm total length) and older (>20 yrs. old) individuals. Individual growth increased sharply until the early 2000s and stabilized thereafter. The age at first maturity decreased by one year for females, the total mortality (Z) increased three-fold, and the stock size decreased approximately 90 %. Despite changes in the population structure due to intense fishing and high exploitation rates, the landings remained high until the late 2000s and in the last decade decreased less than expected by a former stock assessment. The resilience of the stock can be explained by its life history traits: (i) high fecundity, (ii) multiple spawning events during a protracted reproductive season in coastal waters, (iii) large estuarine nursery grounds unaffected by industrial fishing and (iv) faster growth and earlier sexual maturation due to the reduction in food competition and possibly evolution via gear selectivity. However, the stabilization of individual growth rates, the high rate of exploitation and the low spawning potential warn of the risk of further population decline and fishery collapse if intense fishing pressure continues.