Life history characteristics and stock status of the thumbprint emperor (Lethrinus harak) in Saipan Lagoon

Abstract

Analysis of the life history of the thumbprint emperor (Lethrinus harak) sampled from Saipan Lagoon during 2005-2006 revealed sex-specific differences in von Bertalanffy age and growth parameters. Length at 50% reproductive maturity was estimated as 19.6 cm fork length (FL) for females and as 18.7 cm FL for males for the corresponding ages of 2.6 and 2.4 years. Available data from several sources for this data-poor coral reef fish were analyzed to assess its population status in Saipan Lagoon, Northern Marianna islands. Estimates of total mortality (Z) within the period 2005-2011 were derived by using length-converted catch-curve analysis and the Chapman-Robson estimator. Natural mortality (M) was estimated from 3 models based on applicable observations and parameter estimates derived from data for thumbprint emperor in Saipan Lagoon. Exploitation ratios (E) derived with combinations of Z and M estimators within the period 2005-2011 showed a wide disparity, although no estimate of average annual E exceeded 0.5 (an E over that threshold would have indicated overexploitation). Location-specific life history studies should be pursued to support local research and management goals. Standardized methods for the estimation of life history parameters would allow empirical comparisons between regions.