California Sea Grant College Program
Characterization of developmental changes during the establishment and progression of pregnancy in viviparous nearshore rockfish (Sebastes spp.) and the determination of patterns of post-natal growth
- Author(s): Chaillé, Peter M.
- et al.
The rockfish (Sebastes spp) is a long-lived viviparous marine teleost found around the world. The diversity of the genus and the wide range of habitats in which is found make it essential that more is known about the effects various changes in the environment have on its reproduction, development and growth.
Ovarian cyclicity proceeded under controlled conditions and recurrent seasonality was observed in fish that had previously spawned in culture. Delayed fertilization indicates that pregnancy is not a prerequisite for broodstock selection. Characterization of development from first cleavage to parturition established convenient indices to identify changes in development associated with different environmental conditions. Experiments performed to further characterize the ontogeny of osmoregulatory development established protocols for in vitro incubation of embryos and revealed that a reduced salinity conferred significant survival and growth advantages as compared to embryos developing within the mother. These results indicate some maternal physiological inhibition of development may occur.
Growth patterns of grass (S. rastrelliger) and brown (S. auriculatus) rockfish reared in the laboratory were characterized as was growth of two groups of brown rockfish collected during their first and second year of development. Changes in both weight and length followed a sigmoid curve comprising an early phase of exponential growth transitioning to a phase of exponential decay. The constituent phases of this curve and the combined data over a period of 1083 culture-days were precisely described by the Gompertz equation. This equation also described the growth of young-of - the-year copper rockfish (S. caurinus) with similar accuracy. Validation of the Gompertz equation was achieved by reference to sizes of rockfish raised from birth. The mathematical model precisely depicted growth from birth to sexual maturity. These data may find application in the development of rockfish culture programs and assist fisheries managers in assessing size and age relationships.
Overall the findings can be applied to the existing knowledge of the endocrine control of osmoregulation and to the existing body of data on the endocrine control of pregnancy in the rockfish. The protocols developed will facilitate further examination of the effects of changes in environmental conditions on viviparous reproduction.