Diet composition affects the rate and N: P ratio of fish excretion

Eric K. Moody, Jessica R. Corman, James J. Elser, John L. Sabo

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


Nutrient recycling by fish can be an important part of nutrient cycles in both freshwater and marine ecosystems. As a result, understanding the mechanisms that influence excretion elemental ratios of fish is of great importance to a complete understanding of aquatic nutrient cycles. As fish consume a wide range of diets that differ in elemental composition, stoichiometric theory can inform predictions about dietary effects on excretion ratios. We conducted a meta-analysis to test the effects of diet elemental composition on consumption and nutrient excretion by fish. We examined the relationship between consumption rate and diet N : P across all laboratory studies and calculated effect sizes for each excretion metric to test for significant effects. Consumption rate of N, but not P, was significantly negatively affected by diet N : P. Effect sizes of diet elemental composition on consumption-specific excretion N, P and N : P in laboratory studies were all significantly different from 0, but effect size for raw excretion N : P was not significantly different from zero in laboratory or field surveys. Our results highlight the importance of having a mechanistic understanding of the drivers of consumer excretion rates and ratios. We suggest that more research is needed on how consumption and assimilation efficiency vary with N : P and in natural ecosystems in order to further understand mechanistic processes in consumer-driven nutrient recycling.

Original languageEnglish (US)
Pages (from-to)456-465
Number of pages10
JournalFreshwater Biology
Issue number3
StatePublished - Mar 1 2015
Externally publishedYes


  • Assimilation efficiency
  • Diet manipulation
  • Ecological stoichiometry
  • Food quality
  • Nutrient recycling

ASJC Scopus subject areas

  • Aquatic Science


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