Biological Characteristics of the Spotcheek Emperor, Lethrinus rubrioperculatus, in the Northern Mariana Islands

Abstract

As a result of commencement of an incipient commercial fishery in the southern islands (SI) of the Commonwealth of the Northern Mariana Islands (CNMI), biological characteristics for the spotcheek emperor, Lethrinus rubrioperculatus, were estimated from the CNMI SI, including seasonality of spawning, sex ratios, length at sexual maturity (LM), length at transition (LT) to male phase, age, and growth. LM and LT estimates corresponded to ages of 1 and 3 – 4 yr, respectively, and are important in managing hermaphroditic species such as the spotcheek emperor by ensuring that fishery size selection does not significantly reduce effective stock reproduction. Age of the oldest fish was 8 yr, with South Southern Islands (SSI) fish mostly 0 – 2 yr old and North Southern Islands ( NSI) fish 1 – 4 yr old. Average size of 0-age fish was 22.2 cm fork length (LF) from the SSI and 18.7 cm LF from the NSI, indicating an initial high growth rate not captured by specimen collection. Growth curves for the NSI and SSI weresignificantly different at the 5% level. Age and growth parameters were estimated using age- and length-based methods, which resulted in similar values for instantaneous growth coefficient (k) and asymptotic length (L∞). Results support further study into life history characteristics of the spotcheek emperor, in particular maximum age and lengths at maturity and transition, in other locations in the CNMI SI as well as in other Indo-Pacific jurisdictions.