University Of Tasmania
142892 - Quantifying prey availability using the foraging plasticity of a marine predator.pdf (1.58 MB)
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Quantifying prey availability using the foraging plasticity of a marine predator, the little penguin

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journal contribution
posted on 2023-05-20, 21:09 authored by Cavallo, C, Chiaradia, A, Deagle, BE, Hays, GC, Jarman, S, Julie McInnesJulie McInnes, Ropert-Coudert, Y, Sanchez, S, Reina, RD

  1. Detecting changes in marine food webs is challenging, but top predators can provide information on lower trophic levels. However, many commonly measured predator responses can be decoupled from prey availability by plasticity in predator foraging effort. This can be overcome by directly measuring foraging effort and success and integrating these into a measure of foraging efficiency analogous to the catch per unit effort (CPUE) index employed by fisheries.
  2. We extended existing CPUE methods so that they would be applicable to the study of generalist foragers, which introduce another layer of complexity through dietary plasticity. Using this method, we inferred species‐specific patterns in prey availability and estimated taxon‐specific biomass consumption.
  3. We recorded foraging trip duration and body mass change of breeding little penguins Eudyptula minor and combined these with diet composition identified via non‐invasive faecal DNA metabarcoding to derive CPUE indices for individual prey taxa.
  4. We captured weekly patterns of availability of key fish prey in the penguins’ diet and identified a major prey shift from sardine Sardinops sagax to red cod Pseudophycis bachus between years. In each year, predation on a dominant fish species (~150 g/day) was replaced by greater diversity of fish in the diet as the breeding season progressed. We estimated that the colony extracted ~1,300 tonnes of biomass from their coastal ecosystem over two breeding seasons, including 219 tonnes of the commercially important sardine and 215 tonnes of red cod.
  5. This enhanced pCPUE is applicable to most central‐placed foragers and offers a valuable alternative to existing metrics. Informed prey‐species biomass estimates extracted by apex and meso predators will be a useful input for mass‐balance ecosystem models and for informing ecosystem‐based management.

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Publication title

Functional Ecology










Institute for Marine and Antarctic Studies


Blackwell Publishing Ltd

Place of publication

9600 Garsington Rd, Oxford, England, Oxon, Ox4 2Dg

Rights statement

© 2020 The Authors. Functional Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society. This is an open access article under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0 License) (, which permits use, distribution and reproduction in any medium, provided the original work is properly cited

Repository Status

  • Open

Socio-economic Objectives

Assessment and management of pelagic marine ecosystems; Marine biodiversity