Time of hatching affects development, size, yolk volume, and mortality of newly hatched Macrozoarces americanus (Pisces: Zoarcidae)

Abstract

The ocean pout, Macrozoarces americanus, is well developed at hatching and strongly resembles the adult. Developing embryos and newly hatched larvae have teeth, are well ossified and pigmented, and have a complete complement of fin rays. The feeding repertoire is simple and lacks the dramatic behavioural changes that usually occur in less-developed larvae of other species. Length and weight at hatching are positively correlated with time of hatch and differ significantly for early- and late-hatched individuals. Early-hatched individuals have no ossified bones, are smaller, and have higher rates of mortality than late-hatched individuals; however, early-hatched individuals have higher growth rates and larger yolk-sac volumes than late-hatched individuals. The large size at hatching, simple feeding repertoire, short time to first feeding (< 24 h), presence of numerous teeth, rapid yolk absorption, and low mortality are characteristic of newly hatched M. americanus and suggest that the larval stage is of very short duration, if present at all. We suggest that a larval stage is absent and that M. americanus hatch as juveniles.