New Zealand stream crayfish: Functional omnivores but trophic predators?

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dc.contributor.authorParkyn, Stephanie M.
dc.contributor.authorCollier, Kevin J.
dc.contributor.authorHicks, Brendan J.
dc.date.accessioned2009-07-07T04:49:49Z
dc.date.available2009-07-07T04:49:49Z
dc.date.issued2001
dc.description.abstract1. The feeding ecology of the crayfish Paranephrops planifrons in streams draining catchments in native forest and pastoral land was investigated using analyses of both stomach contents and stable isotopes of carbon and nitrogen. We aimed to (1) identify the energy sources of crayfish, (2) determine whether these were affected by ontogeny or land use change, and (3) assess the functional and trophic roles of crayfish in New Zealand hill-country streams. 2. In native forest streams, crayfish stomach contents were dominated volumetrically by leaf detritus (>60%), but in pasture streams aquatic invertebrates constituted more than 40% of stomach volumes and leaf detritus <30%. Stable isotope analyses revealed that crayfish from both native forest and pasture streams incorporated energy from aquatic invertebrates into their body tissue but did not appear to utilize detritus for growth. Therefore, deforestation had little impact on crayfish energy sources. 3. In native forest streams, adult crayfish (≥20 mm orbit-carapace length (OCL)) consumed greater amounts of leaf detritus than juvenile crayfish, but a corresponding change in stable isotope signatures was not detected. Ontogenetic shifts in diet were not consistent between land use suggesting that change in local habitat and food resources, as a result of land use change, affect crayfish food choice more than factors related solely to age or size. 4. Crayfish appear to occupy the trophic position of a predator, but by functioning as omnivores, they have dual roles as both predators and processors of organic matter. The use of gut content analysis in conjunction with stable isotope analyses revealed that the functional and trophic roles of P. planifrons differed, with implications for the interpretation of diet studies and understanding of the role of omnivores in food webs.en
dc.identifier.citationParkyn, S.M., Collier, K.J. & Hicks, B.J. (2001). New Zealand stream crayfish: Functional omnivores but trophic predators? Freshwater Biology 46(5):641-652.en
dc.identifier.doi10.1046/j.1365-2427.2001.00702.xen
dc.identifier.urihttps://hdl.handle.net/10289/2212
dc.language.isoen
dc.publisherWiley-Blackwellen_NZ
dc.relation.isPartOfFreshwater Biologyen_NZ
dc.rightsFull text of this article may be requested by emailing AProf Brendan J. Hicks: hicksbj@waikato.ac.nzen
dc.subjectenergy sourcesen
dc.subjectfunctional roleen
dc.subjectland useen
dc.subjectomnivoryen
dc.subjectontogeneticen
dc.subjectstable isotopesen
dc.subjecttrophic roleen
dc.titleNew Zealand stream crayfish: Functional omnivores but trophic predators?en
dc.typeJournal Articleen
pubs.begin-page641en_NZ
pubs.elements-id42211
pubs.end-page652en_NZ
pubs.issue5en_NZ
pubs.volume46en_NZ
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