Variation in natural mortality: implications for queen conch stock enhancement

摘要

Our long-term investigations of mortality and predation in the large, economically significant gastropod Strombus gigas (queen conch) indicate that instantaeous rtes of natural mortality (M) in nursery grounds in the Bahamas and the Florida Keys are often higher and more variable than recognized earlier. Wide divergence form a simple size- specific curve of natural mortality was caused by seasonal, internannual, and site-specific sources of variation. In the Florida Keys, mortality rates for 200-mm conch were highest in summer and most stable in the fall, but summer values of M varied interannually from <2.0 to 12.0.