Natural mortality estimates throughout the life history of the sea cucumber Isostichopus Badionotus (Holothuroidea: Aspidochirotida)

Abstract

The Natural Mortality coefficient (M) is a key parameter for stock assessments. The need to establish age-specific natural mortality coefficients is widely recognized because M decreases rapidly over the early stages of the life cycle until it reaches a stable M value around the age-at-maturity. The aim of this study was to estimate M during the life cycle of the sea cucumber Isostichopus badionotus, a species under heavy fishing exploitation in the Caribbean Sea and the Gulf of Mexico. Coefficients M 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 M 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 M 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.

Keywords

• Gnomonic intervals
• Natural mortality-at-age
• Isostichopus badionotus
• Sea cucumber
• Stock assessment
• Fishery