Changes in isotopic composition of red drum (Sciaenops ocellatus) larvae in response to dietary shifts: potential applications to settlement studies

Abstract

The stable isotope composition of larval fish tissues may serve as a chemical tracer of recent settlement due to food web differences among planktonic and demersal habitats. We present the background for the utilization of δ13C and δ15N to trace settlement of red drum (Sciaenops ocellatus), an estuarine-dependent species. The effect of ontogeny and temperature on the relative contribution of growth and metabolic turnover to changes in isotopic composition was examined by simulating dietary shifts in the laboratory. Fractionation was examined as a function of size and the effect of food deprivation was evaluated. Published growth rates were used to estimate the time period within which the isotopic composition of a new food source should be reflected in larval tissues. In response to dietary shifts, larvae exhibited quick changes in δ13C and δ15N in a pattern closely resembling predictions based on growth alone. Fractionation values were about +1‰ for δ13C and +1.6‰ for δ15N. There was no effect of 4 days of food deprivation on δ13C and δ15N. Given the fast growth rates reported for newly settled red drum, their isotopic composition should exhibit a shift within 1-2 days and stabilize about 10 days following settlement.

Differential δ13C and δ15N signatures among scallop tissues: implications for ecology and physiology

“…All values become progressively closer later in the summer and fall as metabolite stores in the muscle are utilised by the gonad. Herzka et al (2000), postulated that for poïkilotherms such as fishes and crustaceans, the contribution of metabolic turn-over to isotopic changes is poor, whereas in endotherms as mammals and birds, it is high due to their higher basal metabolism (Tieszen et al, 1983;Hobson & Clark, 1992). However, in P. maximus, it seems that the metabolism is important enough to produce such changes in isotopic composition of the various tissues.…”

Turnover rates of nitrogen stable isotopes in the salt marsh mummichog, Fundulus heteroclitus, following a laboratory diet switch

“…Most laboratory diet-switch experiments (Hesslein et al 1993;Herzka and Holt 2000;MacAvoy et al 2001;Bosley et al 2002;Tominaga et al 2003) and field studies (Vander Zanden et al 1998;Maruyama et al 2001) show that growth is the primary factor causing stable isotopic change in fish following a diet shift. One field study of larval red drum has found significant metabolic turnover, and the authors suggest that differences between larval energetic requirements in the laboratory and in the field may account for variation between lab and field results (Herzka et al 2001).…”

“…Stable isotopes have been used to determine the placement of mummichogs in food webs (Deegan and Garritt 1997) and estimate habitat use (Currin et al 2003). Knowledge of species-specific and tissuespecific turnover and nitrogen discrimination is important for accurate interpretation of isotopic data because past studies have demonstrated variation between species (Hesslein et al 1993;Herzka and Holt 2000;MacAvoy et al 2001;Bosley et al 2002) and also between tissues of the same species (Tieszen et al 1983;Hobson and Clark 1992).…”

Comparison of isotopic turnover dynamics in two different muscles of a coral reef fish during the settlement phase

“…McCormick andMakey 1997, Lecchini 2005). This major event in the life history of reef fishes is generally called metamorphosis (McCormick and Makey 1997) and may correspond to rapid variations in internal stable isotope compositions (Herzka and Holt 2000). Thus, comparing carbon and nitrogen isotopic compositions during that phase might provide information about physiology and tissue turnover.…”