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

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.

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Stable water isotope variation in a Central Andean watershed dominated by glacier and snowmelt

Hydrology and Earth System Sciences ◽

10.5194/hess-17-1035-2013 ◽

2013 ◽

Vol 17 (3) ◽

pp. 1035-1050 ◽

Cited By ~ 60

Author(s):

N. Ohlanders ◽

M. Rodriguez ◽

J. McPhee

Keyword(s):

Isotopic Composition ◽

Isotope Composition ◽

Seasonal Pattern ◽

Water Source ◽

Close Relation ◽

Related Factors ◽

Central Chile ◽

Ice Melt ◽

Relative Contribution ◽

Glacier Melt

Abstract. Central Chile is an economically important region for which water supply is dependent on snow- and ice melt. Nevertheless, the relative contribution of water supplied by each of those two sources remains largely unknown. This study represents the first attempt to estimate the region's water balance using stable isotopes of water in streamflow and its sources. Isotopic ratios of both H and O were monitored during one year in a high-altitude basin with a moderate glacier cover (11.5%). We found that the steep altitude gradient of the studied catchment caused a corresponding gradient in snowpack isotopic composition and that this spatial variation had a profound effect on the temporal evolution of streamflow isotopic composition during snowmelt. Glacier melt and snowmelt contributions to streamflow in the studied basin were determined using a quantitative analysis of the isotopic composition of streamflow and its sources, resulting in a glacier melt contribution of 50–90% for the unusually dry melt year of 2011/2012. This suggests that in (La Niña) years with little precipitation, glacier melt is an important water source for central Chile. Predicted decreases in glacier melt due to global warming may therefore have a negative long-term impact on water availability in the Central Andes. The pronounced seasonal pattern in streamflow isotope composition and its close relation to the variability in snow cover and discharge presents a potentially powerful tool to relate discharge variability in mountainous, melt-dominated catchments with related factors such as contributions of sources to streamflow and snowmelt transit times.

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Growth Rates of Juvenile Red Drum Sciaenops ocellatus Reared on Commercial Salmon Feed in Fresh and Salt Water

Journal of the World Aquaculture Society ◽

10.1111/j.1749-7345.1993.tb00174.x ◽

1993 ◽

Vol 24 (3) ◽

pp. 422-424 ◽

Cited By ~ 8

Author(s):

William A. Wurts ◽

Robert R. Stickney

Keyword(s):

Growth Rates ◽

Salt Water ◽

Red Drum ◽

Sciaenops Ocellatus

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Application of RNA : DNA Ratios to Evaluate the Condition and Growth of Larval and Juvenile Red Drum (Sciaenops ocellatus).

Marine and Freshwater Research ◽

10.1071/mf9960283 ◽

1996 ◽

Vol 47 (2) ◽

pp. 283 ◽

Cited By ~ 60

Author(s):

JR Rooker ◽

GJ Holt

Keyword(s):

Growth Rates ◽

Standard Length ◽

Red Drum ◽

Sciaenops Ocellatus ◽

Starvation Period ◽

Diel Periodicity ◽

Diel Variations ◽

Study Support ◽

Natural Temperature ◽

Biochemical Condition

RNA:DNA ratios in individual red drum (Sciaenops ocellatus) were measured in laboratory-reared larvae and juveniles (6-20 mm standard length; age 16-40 days) to assess the effects of growth, starvation, and diel periodicity on biochemical condition. RNA: DNA ratios were correlated positively with both absolute (mm day-1) and instantaneous (% day-1) growth rates. The effect of starvation was evaluated daily over 5 day periods at three ontogenetic stages (20, 30, and 40 days). Significant differences in RNA:DNA ratios of fed and starved larvae were observed and changes in biochemical condition were detected statistically within 1 to 2 days of food deprivation. RNA:DNA ratios decreased continuously over the entire 5 day starvation period, with relative reductions in RNA : DNA ratios decreasing with increasing age. Diel variations in RNA : DNA ratios were investigated in controlled (constant) and natural (cyclical) temperature environments over a 48 h period. RNA: DNA ratios were highest during daytime periods (0800, 1200, 1600, 2000 hours) and markedly reduced at night (0000, 0400 hours). Since RNA: DNA ratios from controlled and natural temperature treatments did not differ significantly, cyclical variations in temperature did not appear responsible for diel variations in biochemical condition. Findings from this study support the use of nucleic acids as reliable indices of growth and condition and suggest that RNA: DNA ratios are potentially suitable measures to assess the condition of wild-caught S. ocellatus.

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Variation in the isotopic composition of striped weakfish Cynoscion guatucupa of the Southwest Atlantic Ocean in response to dietary shifts

Brazilian Journal of Biology ◽

10.1590/1519-6984.01416 ◽

2017 ◽

Vol 78 (2) ◽

pp. 202-210 ◽

Cited By ~ 1

Author(s):

M. N. Paso Viola ◽

L. Riccialdelli ◽

A. Jaureguizar ◽

H. O. Panarello ◽

H. L. Cappozzo

Keyword(s):

Atlantic Ocean ◽

Isotopic Composition ◽

Isotope Composition ◽

Trophic Levels ◽

Sampling Location ◽

Southwest Atlantic ◽

Δ13c And Δ15n ◽

Size Classes ◽

Cynoscion Guatucupa ◽

Dietary Shifts

Abstract The aim of this study was to analyze the isotopic composition in muscle of striped weakfish Cynoscion guatucupa from Southwest Atlantic Ocean in order to evaluate a possible variation in δ13C and δ15N in response to dietary shifts that occur as animals grow. We also explored for isotopic evidence of differences between sample locations. The results showed an agreement between isotope analysis and previous conventional studies. Differences in the isotope composition between sampling location were not observed. A positive relation exists between isotope values and total body length of the animals. The Cluster analysis defined three groups of size classes, validated by the MDS. Differences in the relative consumption of prey species in each size class were also observed performing isotope mixing models (SIAR). Variation in δ15N among size classes would be associated with the consumption of a different type of prey as animals grow. Small striped weakfish feed on small crustaceans and progressively increase their consumption of fish (anchovy, Engraulis anchoita), increasing by this way their isotope values. On the other hand, differences in δ13C values seemed to be related to age-class specific spatial distribution patterns. Therefore, large and small striped weakfish remain specialized but feeding on different prey at different trophic levels. These results contribute to the study of the diet of striped weakfish, improve the isotopic ecology models and highlight on the importance of accounting for variation in the isotopic composition in response to dietary shifts with the size of one of the most important fishery resources in the region.

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