Trophic position and individual feeding histories of fish from Lake Okeechobee, Florida

Fry, Brian; Mumford, Patricia L.; Tam, Franklin; Fox, Don D.; Warren, G. L.; Havens, Karl E.; Steinman, Alan D.

doi:10.1139/cjfas-56-4-590

Cited by 39 publications

(53 citation statements)

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“…A similar pattern has been recorded from several other fishes (Kline et al 1998;Doucett et al 1999a;Fry et al 1999;Overman and Parrish 2001;Grey et al 2002) and is generally considered as evidence that larger consumers feed at a higher trophic level (but see Overman and Parrish 2001 who demonstrate a more significant effect of age). Interestingly, there was no such relationship with length or age in eels from Lough Ahalia, suggesting that in eels, weight may be a better indicator of predatory scope than length.…”

Section: Discussionsupporting

confidence: 80%

Stable isotope analyses provide new insights into ecological plasticity in a mixohaline population of European eel

et al. 2005

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Recent studies have shown that anguillid eel populations in habitats spanning the marine-freshwater ecotone can display extreme plasticity in the range of catadromy expressed by individual fishes. Carbon and nitrogen stable isotope analysis was used to differentiate between European eels (Anguilla anguilla) collected along a short (2 km) salinity gradient ranging from <1 per thousand to approximately 30 per thousand in Lough Ahalia, a tidal Atlantic lake system. Significant differences were recorded in mean delta13C, delta15N and C:N values from eels collected from fresh, brackish and marine-dominated basins. A discriminant analysis using these predictor variables correctly classified ca. 85% of eels to salinity zone, allowing eels to be classified as freshwater (FW), brackish (BW) or marine (MW) residents. The results of the discriminant analysis also suggested that a significant proportion of eels moved between habitats (especially between FW and BW). Comparisons of several key population parameters showed significant variation between eels resident in different salinity zones. Mean condition and estimated age was significantly lower in MW eels, whilst observed length at age (a correlate of growth) was significantly higher in MW eels, intermediate in BW and lowest in FW eels. This study has demonstrated that the ecology of eels found along a short salinity gradient can be extremely plastic and that stable isotope analysis has considerable utility in demonstrating intra-population variation in diadromous fishes.

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Section: Discussionsupporting

confidence: 80%

Stable isotope analyses provide new insights into ecological plasticity in a mixohaline population of European eel

et al. 2005

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“…In most studies of aquatic food webs, N is likely to be of least use in separating the contribution of different producers. The usefulness of N lies in its relatively large degree of fractionation across trophic levels, which can help to elucidate trophic levels of consumers (Fry et al 1999;Pinnegar and Polunin 2000).…”

Section: Separation Of Isotopic Signatures Of Producersmentioning

confidence: 99%

Sulfur stable isotopes separate producers in marine food-web analysis

et al. 2004

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Ecological applications of stable isotope analysis rely on different producers having distinct isotopic ratios to trace energy and nutrient transfer to consumers. Carbon (C) and nitrogen (N) are the usual elements analysed. We tested the hypothesis that producers unable to be separated using C and N would be separated by sulphur (S), by reviewing estuarine and marine food web studies using all three elements (total of 836 pairwise comparisons between producers). S had a wider range of values across all producers than C and N (S: 34.4, C: 23.3, N: 18.7 per thousand ), and a higher mean difference among producers (S: 9.3, C: 6.5, N: 3.3 per thousand ). We varied from 1 to 10 per thousand the distance producers must be apart to be considered separate. For each of these gap distances, S-separated producers tied on C and N in 40% or more of cases. Comparing the three elements individually, S had fewer tied pairs of producers for any gap distance than C or N. However, S also has higher within-producer variability. Statistical tests on simulated data showed that this higher variability caused S to be less effective than C for analysing differences among mean producer values, yet mixing models showed that S had the smallest confidence intervals around mean estimates of source contributions to consumers. We also examined the spatial and temporal scales over which S isotope signatures of the saltmarsh plant Spartina alterniflora varied. Differences between samples taken within tens of metres were smallest, but between samples hundreds of metres apart were as different as samples thousands of kilometres apart. The time between samples being taken did not influence S signatures. Overall, the use of S is recommended because it has a high probability of distinguishing the contribution of different producers to aquatic food webs. When two elements are employed, the combination of S and C separates more producers than any other combination.

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“…Post (2003) confirmed the shift to piscivory by concurrently analyzing gut contents and otolith microstructures. In a recent review of individual specialization, Bolnick et al (2003) suggested that the large isotopic variance found in several different consumer populations (Fry et al 1978;Angerbjorn et al 1994;Gu et al 1997;Ben David et al 1997;Beaudoin et al 1999;Fry et al 1999) could provide evidence of individual specialization. However, none of these studies considered how the isotopic variability among food sources could affect intrapopulation isotopic variability of consumers.…”

Section: Introductionmentioning

confidence: 99%

A critical evaluation of intrapopulation variation of δ13C and isotopic evidence of individual specialization

2004

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Individual variation in the diet of consumers is common in many ecological systems and has important implications for the study of population dynamics, animal behavior, and evolutionary or ecological interactions. Ecologists frequently quantify the niche of a population by intensive analyses of gut contents and feeding behaviors of consumers. Inter-individual differences in delta13C signature can indicate long term differences in feeding behavior, often unattainable by a single snapshot analysis of gut contents. If a consumer's food sources have unique delta13C signatures, then the intrapopulation variation in delta13C may be useful for quantifying diet variation and detecting isotopic evidence of individual specialization. However, intrapopulation variation in delta13C can underestimate or overestimate dietary variation, and therefore is not directly equivalent to a dietary based niche. In this paper we show that intrapopulation variability of delta13C in consumers critically depends on the isotopic range and distribution of food sources. Our analyses fundamentally challenge how we interpret the intrapopulation isotopic variance of delta13C, and how we evaluate isotopic evidence of individual specialization.

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Trophic position and individual feeding histories of fish from Lake Okeechobee, Florida

Cited by 39 publications

References 0 publications

Stable isotope analyses provide new insights into ecological plasticity in a mixohaline population of European eel

Stable isotope analyses provide new insights into ecological plasticity in a mixohaline population of European eel

Sulfur stable isotopes separate producers in marine food-web analysis

A critical evaluation of intrapopulation variation of δ13C and isotopic evidence of individual specialization

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