Life‐history constraints, short adult life span and reproductive strategies in coral reef gobies of the genus Trimma

Body size influences many life‐history traits, with small‐bodied animals tending to have short life spans, high mortality and greater reproductive effort early in life. In this study, the authors investigated the life‐history traits and reproductive strategies of three small‐bodied coral reef gobies of the genus Trimma: Trimma benjamini, Trimma capostriatum and Trimma yanoi. The authors found all Trimma species studied attained a small body size of <25 mm, had a short life span of <140 days and experienced high estimated daily mortality of 3.0%–6.7%. Furthermore, the pelagic larval phase accounted for 25.3%–28.5% of the maximum life span, and maturation occurred between 74.1 and 82.1 days at 15.2–15.8 mm, leaving only 35%–43% of the total life span as a reproductively viable adult. All mature individuals had gonad structures consistent with bidirectional sex change, with bisexual gonads including both ovarian and testicular portions separated by a thin wall of connective tissue. In the female and male phases, only ovaries or testes were mature, whereas gonadal tissue of the non‐active sex remained. One T. benjamini individual and one T. yanoi individual had ovarian and testicular tissue active simultaneously. The results of this study highlight the life‐history challenges small CRFs face on their path to reproduction and reproductive strategies that could be beneficial in fishes with high and unpredictable mortality and short reproductive life spans.