Metabolic costs of viviparity in yellowtail rockfish,Sebastes flavidus

Abstract

We estimated the energy utilized by developing embryos and larvae of yellowtail rockfish,Sebastes flavidus, by determining the routine metabolic rate of adult females throughout gestation and subtracting the mean metabolic rate of non-gestating fish. The pattern of maternal oxygen consumption during gestation was such that metabolic demands did not become significantly elevated until intra-ovarian embryos had hatched and larvae were being incubated (i.e. 24–28 d post-fertilization). Metabolic rates of females in this latter stage of gestation were 82% higher than spent females and 101% higher than those of non-reproductive males. We determined that 0.08996 cal embryo-1 was consumed during gestation as compared to the change in energy content of embryos from fertilization to birth which was 0.08690 cal embryo-1. The difference between the energy consumed and the energy lost during the 29 d gestation period indicated that extra embryonic sources contributed only 3.4% or 0.00306 cal embryo-1 of the energy utilized after fertilization. Our observations agree with previous work which determined that embryos and larvae ofS. flavidus are primarily lecithotrophic and that the relatively high fecundity ofS. flavidus coupled with a small egg size, rapid embryogenesis and brief gestation period characterize this species as a relative r-strategist within a genus whose species range broadly over the ‘K end’ of the r-K continuum.