Seasonal cycles in whole-body proximate composition and energy content of forage fish vary with water depth - PubMed (original) (raw)

Seasonal cycles in whole-body proximate composition and energy content of forage fish vary with water depth

Johanna J Vollenweider et al. Mar Biol. 2011.

Abstract

Quantifying the nutritional quality of forage fish is integral for understanding upper trophic levels as forage fish are the dominant prey for top predator fish, marine mammals, and sea birds. Many existing reports documenting body composition of forage species are not comparable due to confounding effects. This study systematically assessed the variability in proximate composition and energy content of 16 forage species in southeastern Alaska (57.2626 N/133.7394 W) between 2001 and 2004. Variation in energy and lipid contents was related to habitat, epipelagic planktivores varying most, mesopelagics intermediate, and demersal species relatively invariable. Season was the greatest source of variation as a result of short growing seasons at high latitude and energy allocation strategies for reproduction and growth. Among species that varied seasonally, energy and lipid increased over summer and declined during winter. Annual differences in body composition occurred during periods of peak energy content. Sampling recommendations and guidance for bioenergetics models are provided.

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Figures

Fig. 1

Fig. 1

Map of the two study sites in southeastern Alaska, Lynn Canal and Frederick Sound

Fig. 2

Fig. 2

Boxplots depicting the variation in the body composition of forage species pooled over all collections, including energy density (kJ g−1), % lipid, % protein, and % moisture

Fig. 3

Fig. 3

Seasonal cycles in the body composition of Pacific herring (Clupea pallasi) (±SE) is presented as an example of the seasonal cycles observed in other forage fish

Fig. 4

Fig. 4

Frequency of seasonal variation in body composition of forage species by depth group expressed as the percentage of comparisons of adjacent seasons that are statistically different (±SE). Like symbols indicate statistically similar groups determined by ANOVA (P < 0.05)

Fig. 5

Fig. 5

Magnitude of seasonal variation in body composition of forage species depicted as the mean coefficient of variation (CV) of the annual means of body composition (energy density, lipid, protein, and moisture contents) by depth group (±SE). Like symbols indicate statistically similar groups determined by ANOVA (P < 0.05)

Fig. 6

Fig. 6

Maximum discrepancies (±SE) in the body composition (energy density, lipid, protein, and moisture contents) between comparisons of (1) annual and seasonal mean body compositions, and (2) maximum and minimum seasonal mean body compositions. Species are grouped by depths they inhabit

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