|The significance of the crayfish Paranephrops zealandicus as shredders in a New Zealand headwater stream|
Usio, N.; Townsend, C.R. (2001). The significance of the crayfish Paranephrops zealandicus as shredders in a New Zealand headwater stream. J. Crust. Biol. 21(2): 354-359
In: Journal of Crustacean Biology. Crustacean Society: Washington. ISSN 0278-0372, more
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Despite their prevalence in headwater streams, crayfish are largely ignored in most leaf de-composition studies. We conducted a field survey in 30 pools along a headwater stream to document the biomass of various shredder invertebrate species and subsequently compared their leaf processing and particulate organic matter (POM) production rates in a laboratory experiment. The crayfish Paranephrops zealandicus dominated the shredder functional feeding group, comprising 99% on average of the total biomass of shredder invertebrates. This was followed by the stonefly Austroperla cyrene, which made up only 0.62%. A laboratory experiment, using stoneflies and two size classes of crayfish, showed that processing rates of large crayfish (normalised by body weight) were lower than those of small crayfish and stoneflies. However, large crayfish had the greatest impact on leaf decomposition and POM production. It is their large body size and dominance of invertebrate biomass that determines the significance of crayfish as shredders. Given their widespread distribution in New Zealand and elsewhere, crayfish may play key roles as shredders in many headwater streams, especially where shredder insect diversity/abundance is low.