Life-history and reproductive traits of a key coral reef fishery species: the longnose emperor (Lethrinus olivaceus) in Palau
This study presents detailed life-history traits of the longnose emperor (Lethrinus olivaceus) in Palau, including growth, reproduction, and mortality. Findings highlight regional differences and provide critical data to improve stock assessments and management of coral reef fisheries in data-limited contexts.
Subject Tags
- Reefs
- Fisheries
Abstract
Accurate life-history information is essential for conducting data-limited stock assessments of coral reef fishes, yet this information is often lacking in small-scale fisheries. For the commercially important longnose emperor, Lethrinus olivaceus, such information is scarce in Micronesia, limiting the ability to manage this species effectively. To fill this gap, age, growth, and reproductive parameters were estimated for L. olivaceus in Palau using samples collected at fish markets, supermarkets, independent fishers, and targeted sampling in 2017–2019 and 2022–2025 (total n = 528). Information on growth, lifespan, reproduction, and mortality was obtained through analysis of sagittal otoliths and gonad samples. The sex-combined von Bertalanffy growth parameters for this species were estimated to be L∞ = 57.2 cm, K = 0.387 year−1, and t0 = −0.324 years (unconstrained) and L∞ = 56.4 cm, and K = 0.443 year−1 (constrained to t0 = 0). The maximum observed age was 14 years. Longnose emperors were found to spawn in many months of the year including March to June, August, September, November, and December. There was also evidence of functional protogynous hermaphroditism, with several gonad samples containing both female and male reproductive tissues. Furthermore, males were larger (mean length = 53.5 cm) and older (mean age = 7.4 years) than females (mean length = 45.8 cm and mean age = 4.3 years), with no immature males observed. Females were estimated to reach maturity at 43.2 cm and 3.5 years, and sex change to males occurred at 55.1 cm and 7.1 years. Total mortality for both time periods combined was estimated to be 0.438 year−1 and mean natural mortality was estimated to be 0.358 year−1. When compared to other locations at higher latitudes, including Australia, Japan, and French Polynesia, longnose emperors in Palau had faster growth rates, shorter lifespans, and reached smaller sizes. The high diversity of life-history traits among locations highlights the importance of collecting locally-derived information. These findings provide comprehensive life-history estimates for L. olivaceus in Palau, which can be used to improve data-poor assessments and management of this species in the future.
Citation
Muller Karanassos C, Taylor BM, Filous A, Lindfield S, Krueck NC, Wolfe B, Marshell A. 2026. Life-history and reproductive traits of a key coral reef fishery species: the longnose emperor (Lethrinus olivaceus) in Palau. PeerJ 14:e21247 https://doi.org/10.7717/peerj.21247
TNC Authors
-
Alexander Filous
The Nature Conservancy