Variation in the isotopic composition of striped weakfish Cynoscion guatucupa of the Southwest Atlantic Ocean in response to 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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Stable isotopes reveal post-release trophodynamic and ontogenetic changes in a released finfish, mulloway (Argyrosomus japonicus)

Marine and Freshwater Research ◽

10.1071/mf09014 ◽

2010 ◽

Vol 61 (3) ◽

pp. 302 ◽

Cited By ~ 12

Author(s):

Matthew D. Taylor ◽

Debashish Mazumder

Keyword(s):

Stable Isotopes ◽

Isotopic Composition ◽

Turnover Rate ◽

Isotope Composition ◽

Wild Fish ◽

Ontogenetic Changes ◽

Nitrogen Stable Isotope ◽

Δ13c And Δ15n ◽

Carbon And Nitrogen ◽

Nitrogen Isotopic Composition

Carbon and nitrogen stable isotope ratios were analysed for hatchery-reared, recaptured and wild mulloway, Argyrosomus japonicus, to investigate temporal and growth-related changes in isotopic composition for stocked fish after release, and to evaluate changes in isotopic composition in terms of ontogenetic dietary switches. δ13C and δ15N values decreased and increased, respectively, after release. The isotope composition of released fish was distinct from wild fish until 200 days after release, but after 200 days post-release fish did not differ significantly from wild fish of similar or greater sizes. Abrupt dietary transitions from crustaceans to teleost fish (>50 cm total length (TL)) were evident in a rapid δ13C and δ15N change in wild mulloway, and δ15N was significantly greater in wild fish >65 cm TL compared with wild fish <50 cm TL. Multivariate carbon and nitrogen isotopic data were suitable for separating stocked and wild fish for up to 200 days after release, but did not separate wild fish grouped according to dietary composition. Carbon and nitrogen isotopic composition closely reflected dietary transitions and rapid adaptation by stocked mulloway to wild diets, which was evident in a high tissue turnover rate of up to 0.017 day–1. Stable isotopes are a useful tool for examining the integration of released fish into stocked ecosystems and can be used to describe convergence in the diets of wild and released fish.

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Dietary Shifts and Risks of Artifact Ingestion for Argentine Shortfin Squid Illex argentinus in the Southwest Atlantic

Frontiers in Marine Science ◽

10.3389/fmars.2021.675560 ◽

2021 ◽

Vol 8 ◽

Author(s):

Ssu-Wei Chang ◽

Ruei-Gu Chen ◽

Tsung-Han Liu ◽

Yao-Chang Lee ◽

Chih-Shin Chen ◽

...

Keyword(s):

Marine Pollution ◽

Trophic Levels ◽

Southwest Atlantic ◽

Plastic Materials ◽

Large Populations ◽

Illex Argentinus ◽

Dietary Shifts ◽

Aquatic Food ◽

Taxonomic Groups ◽

Southward Migration

Cephalopods play an important role in both ecology and fisheries. Variations in the dietary compositions of squids with large populations further promote interactions between different trophic levels in marine ecosystems. Moreover, due to marine pollution, squids are also at risks of artifact ingestion, and there is limited understanding about the influence of artifacts on the feeding behavior of squids. We examined 296 stomachs of the Argentine shortfin squid Illex argentinus collected through commercial catches across the Southwest Atlantic from February to April of 2018 and 2019 to establish the monthly dietary compositions and risks of artifact ingestion. The results supported typical observations that the Argentine shortfin squids switched from a diet dominated by crustaceans at small sizes to consuming larger prey, predominantly fishes and/or cephalopods, at large sizes during their growth and southward migration. Significantly higher consumption of fishes was observed in recent years compared with that observed in other studies since 1992. The ingested artifacts examined were composed of plastic and non-plastic materials. Artifacts were observed in 19.9% of the total number of stomachs, with 20.5% of the empty stomachs containing artifact remains. The results indicate that although the main dietary compositions of the Argentine shortfin squid maintain the taxonomic groups of prey compositions, the dietary structure, i.e., composition percentage, is varying. The detection of artifacts suggests that environmental monitoring is needed in this region in order to manage and conserve the squid and safeguard aquatic food safety.

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

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f99-174 ◽

2000 ◽

Vol 57 (1) ◽

pp. 137-147 ◽

Cited By ~ 105

Author(s):

Sharon Z Herzka ◽

G Joan Holt

Keyword(s):

Isotopic Composition ◽

Food Deprivation ◽

Growth Rates ◽

Larval Fish ◽

Isotope Composition ◽

Red Drum ◽

Sciaenops Ocellatus ◽

Relative Contribution ◽

Dietary Shifts ◽

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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Trophic ecology of elasmobranchs caught off Gujarat, India, as inferred from stable isotopes

ICES Journal of Marine Science ◽

10.1093/icesjms/fsq170 ◽

2010 ◽

Vol 68 (3) ◽

pp. 547-554 ◽

Cited By ~ 34

Author(s):

Asunción Borrell ◽

Luis Cardona ◽

Ramanathan P. Kumarran ◽

Alejandro Aguilar

Keyword(s):

Stable Isotopes ◽

Isotopic Composition ◽

Trophic Level ◽

Trophic Ecology ◽

Trophic Levels ◽

The Other ◽

Sphyrna Lewini ◽

Rhincodon Typus ◽

Nursery Habitats ◽

Dietary Shifts

Abstract Borrell, A., Cardona, L., Kumarran, R. P., and Aguilar, A. 2011. Trophic ecology of elasmobranchs caught off Gujarat, India, as inferred from stable isotopes. – ICES Journal of Marine Science, 68: . Habitat use and trophic levels were investigated in 13 species of elasmobranch caught off Gujarat, India, through their isotopic composition. Most of the animals were fished commercially and were immature, suggesting that fisheries operate in nursery habitats. All of the sharks analysed except Rhincodon typus had a higher estimated trophic level (>3.8) than rays and guitarfish (<3.8), suggesting a diet of bony fish and cephalopods. The trophic level of Sphyrna lewini and R. typus increased with total length, indicating ontogenetic dietary shifts, but the other species did not follow this trend. According to their δ13C values, R. typus, Mobula diabolus, and, surprisingly, Rhina ancylostoma appeared to be the most pelagic species. In comparison, Stegostoma fasciatum, Pristis pectinata, Rhinobatos granulatus, and Aetomylaeus maculatus appeared to be the most demersal, inshore species, and their δ13C signatures were significantly different from those of the three aforementioned species.

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