Accounting for the fish condition in assessing the reproductivity of a marine eel to achieve fishery sustainability

Abstract

Spawning potential ratio (SPR) is a commonly used biological reference point to inform management decisions; however, the fish reproductivity may vary substantially with different body conditions, and the variability has not been well understood. Here, we examined the maturity, fecundity, and SPR of a marine eel Conger myriaster. The results showed that total fecundity increased with length and hepatosomatic indices (HSI), whereas relative fecundity (total fecundity/body weight) decreased with body weight, suggesting length- and condition-driven reproductive strategies. A length-structured per-recruit model was used to estimate SPR and examine the influence of HSI in resultant management decisions. Our results suggested that this stock was subject to a high risk of recruitment overfishing. Fish condition greatly influences the estimates of SPR-related reference points. For example, when HSI increased from 0.6% to 1.8%, F40% increased by 91%. In addition, using spawning stock biomass to calculate F40% could produce a bias of 23%. We highlight the need for monitoring the changes in fish fecundity and conditions in fisheries assessment, which may contribute to the robust management of data-poor fisheries.

Keywords

• SPR
• Fecundity
• Body condition
• Harvest restriction
• Conger myriaster