Life-history characteristics of coral reef gobies. II. Mortality rate, mating system and timing of maturation

High adult mortality rate is expected to select for early maturation. However, physiological constraints or size-related reproductive benefits might select for delayed maturation, especially in small-bodied species. Additionally, the mating system and the relative intensity of mate competition can modify the timing of maturation. Here, we investigate the influence of mortality rate and mating system on the timing of maturation in 5 species of small coral reef goby that are either polygynous (Asterropteryx semipunctatus and Istigobius goldmanni) or monogamous pair-spawners (Amblygobius bynoensis, Amblygobius phalaena and Valenciennea muralis). All 5 species experienced high annual adult mortality rates with annual survivorship of ≤2.3%. The mean size at maturity, compared to maximum adult size, was smaller than is typical for fishes, indicating selection for early maturity in all of these species. The season of growth had little effect on size at maturity, but had a considerable effect on age at maturity, with summer-growing individuals exhibiting a younger mean age at maturity than winter-growing individuals. As predicted, males of the 3 monogamous pair-spawning species matured earlier and smaller than females (A. bynoensis and A. phalaena) or at the same time as females (V. muralis), but contrary to expectation, males of the 2 polygynous species (A. semipunctatus and I. goldmanni) did not mature later and at a larger size than females. Overall, the timing of maturation in these species is consistent with predictions from general life-history theory, however, the sex-specific timing of maturation may be influenced by body size constraints and the mating system.