Natural mortality estimates throughout the life history of the sea cucumber <i>Isostichopus Badionotus</i> (Holothuroidea: Aspidochirotida).

Abstract

The Natural Mortality coefficient (<i>M</i>) is a key parameter for stock assessments. The need to establish age-specific natural mortality coefficients is widely recognized because <i>M</i> decreases rapidly over the early stages of the life cycle until it reaches a stable <i>M</i> value around the age-at-maturity. The aim of this study was to estimate <i>M</i> during the life cycle of the sea cucumber <i>Isostichopus badionotus</i>, a species under heavy fishing exploitation in the Caribbean Sea and the Gulf of Mexico. Coefficients <i>M</i> at age were estimated using two models: The Gnomonic Interval Model (GIM) and the Chen & Watanabe model. Two different scenarios were simulated considering early and late age-at-maturity. Estimated <i>M</i> values using the GIM model for the early maturity scenario were 2.15 to 2.35 year^-1 (interquartile range) for the juvenile stage and 0.39 to 0.43 year^-1 for the adult stage; for the late maturity scenario were 0.65 to 0.71 year^-1 for the juvenile stage and 0.68 to 0.74 year^-1 for the adult stage. The Chen & Watanabe model <i>M</i> estimates for juvenile stage were between 0.85 and 2.23 year^-1 and 0.39 and 2.23 year^-1 for the early and late maturity scenarios respectively; for adult stage were between 0.97 and 0.21 year^-1 and 0.62 and 0.43 year^-1 respectively. The GIM estimated high natural mortality rates during larval stages. These estimates provided a higher level of certainty for the population models to more effectively manage a fishery and improve stock assessments.