Lipid class dynamics during development in early life stages of shortbelly rockfish and their application to condition assessment

Abstract

Lipid class dynamics and the relationship between weight and length were analysed during early life stage (ELS) development in wild populations of shortbelly rockfish Sebastes jordani to investigate their utility in a condition or nutritional status assessment. Analyses from more than 3000 field-captured shortbelly rockfish indicated little variation in weight for a given length and provided limited application in the assessment of condition. The fractionation of total lipids into individual classes revealed trends in lipid metabolism throughout development. These trends were described best using a stage-specific regression model, since Sebastes show defined early life history transitions. Among developmental stages, triacylglycerols (TAG) and polar lipids (PL) were the dominant lipid classes and cholesterol (CHOL), sterol/wax esters, and nonesterified fatty acids were found in lower concentrations. In the preflexion stage, low concentrations and constant levels of TAG along with the combined influence of endogenous and exogenous sources of energy compromised the use of TAG as an index of nutritional status. However, during flexion through juvenile stages, TAG levels increased indicating an accumulation of energy reserves with development, thus providing a valid indicator of nutritional status in later stages. Large fluctuations in PL concentrations during development suggested complex metabolism which may be due to changes in cell volume and cell membrane proliferation with development as well as catabolism. CHOL declined in larval stages, then remained constant with increasing size through the juvenile stage, negating its use as a normalizer for variations of mass in a TAG/CHOL ratio prior to juvenile transformation. This study provides the first documentation of lipid dynamics during early life stages following parturition in a marine viviparous teleost.

Maternal Age as a Determinant of Larval Growth and Survival in a Marine Fish, Sebastes Melanops

“…The importance of measuring a direct index of TAG availability rather than total lipids is evident from the lack of correspondence of the latter with either growth or survival. High variability in oil globule volume at a given larval size is evident in other larval rockfish (Norton et al 2001), suggesting a trait susceptible to selective mortality processes, although the role of maternal age in determining oil volume has not been previously reported. The oil globule is likely the major source of energy sustaining larvae during the difficult transition to exogenous feeding.…”

“…Older black rockfish females provision their larvae with significantly larger oil globules than younger females, and the size of the oil globule appears to strongly affect larval growth and survival. At extrusion, most of the yolk has already been absorbed in rockfish larvae, but endogenous energy is available in the oil globule, which is primarily composed of triacylglycerol (TAG), the lipid fraction providing energy for metabolism and growth (Norton et al 2001). The importance of measuring a direct index of TAG availability rather than total lipids is evident from the lack of correspondence of the latter with either growth or survival.…”

Winter ichthyoplankton biomass as a predictor of early summer prey fields and survival of juvenile salmon in the northern California Current

“…We estimated ichthyoplankton carbon content based on literature values from regression equations that relate body morphology to carbon weight of individuals (Lasker et al 1970, Pepin 1985, Norton et al 2001. We used 22 equations to calculate the carbon content, including multiple equations for some taxa based on their larval size range if values were available.…”

Upwelling and the condition and diet of juvenile rockfish: A study using 14C, 13C, and 15N natural abundances

“…Composite otolith size was then regressed on standard length, and the residual (with sign changed) was used as another index of condition over the life span of the fish (Suthers et al 1992). Total lipid was extracted from selected fish using methods outlined in Norton et al (2001). Specimen total lipid content was also regressed on standard length, and the residual deviation from the mean trend (ϭ lipid anomaly) was determined.…”