The use of endogenous and exogenous resources during the early development of Atlantic redfish (Sebastes spp.)

Laurel, Benjamin Jeffrey (1998) The use of endogenous and exogenous resources during the early development of Atlantic redfish (Sebastes spp.). Masters thesis, Memorial University of Newfoundland.

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Abstract

Atlantic redfish (Sebastes spp.) are a commercially exploited groundfish in the NW Atlantic, yet little is known about the early life history of these species. Their ovoviviparous reproductive strategy and restriction to deep benthic environments during spawning makes studying embryogenic and larval stages difficult. Proper management of exploited fish species, however, depends upon a comprehensive understanding of early development as it is during the egg and larval stages that recruitment variability is considered to be largely determined. I conducted two separate investigations describing the use of endogenous and exogenous resources in larval red fish in an attempt to both provide insight into recruitment processes as well as understand the evolutionary success of these species. -- The first study examined changes in lipid and fatty acid profiles in developing pre-extruded larvae. During development within the female there was nearly a 50% reduction in total lipid, suggesting that lipids are an important source of energy and that metabolism of these resources occurs prior to parturition. Triacylglycerol was preferentially catabolised over polar lipids unlike other Atlantic groundfish during embryogenesis such as cod (Gadus morhua) and halibut (Hippoglossus hippoglossus). High variability in these lipid reserves suggests that sensitivity to mismatches in prey after parturition likely varies between broods, assuming increased endogenous resources reduces risk of starvation. -- The second study investigated behaviour, growth and survival of larval redfish reared under prey densities of 0. 500. 1500 and 4500 prey L⁻¹ in laboratory conditions. Some larvae lived to day 18 in the 0 prey L⁻¹ treatment despite possible handling stress from collection and transporting. Growth, survival and condition of larvae varied with prey concentration but were highest in the 1500 prey L⁻¹ treatment. The significantly lower prey bite:orient ratios in the 4500 prey L⁻¹ treatment suggest that larvae may have become confused at higher prey densities. A possible confusion effect may have explained the significant reduction in growth and survival of larvae reared in the highest prey treatment. Although the prey densities used in this experiment are higher than those reported in the field, comparisons with other rearing experiments suggest that prey availability may not be as limiting to redfish as for other commercially important species such as Atlantic cod.

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