Natural mortality of marine pelagic fish eggs and larvae: role of spatial patchiness

Abstract

Daily instantaneous natural mortality rates of marine pelagic fish eggs and larvae are higher than expected from the trend of mortality rate with dry weight in the sea. The difference between observed mortality rates and those predicted from the trend of mortality with dry weight is directly and positively correlated with the patchiness of their spatial distribution, which suggests that it is caused by the feeding of predators on patches of eggs and larvae. The product of weight-dependent mortality, 5.26 X 10-3 , and 1 + Lloyd's patchiness index predicts mortality rates close to those that have been measured from the field by other workers. Mechanisms that control the spatial patchiness of eggs and larvae may control early life history survival and thereby influence relative year-class strength of adult fish stocks.