Sm. Parkyn et al., EFFECTS OF CRAYFISH (PARANEPHROPS PLANIFRONS, PARASTACIDAE) ON IN-STREAM PROCESSES AND BENTHIC FAUNAS - A DENSITY MANIPULATION EXPERIMENT, New Zealand Journal of Marine and Freshwater Research, 31(5), 1997, pp. 685-692
The effects of New Zealand freshwater crayfish or koura (Paranephrops
planifrons: Parastacidae) on organic matter processing, sediment accum
ulation, and benthic invertebrate communities were investigated using
four replicate treatments of 0 (control), 4-5 (medium), and 8-11 (high
) similar-sized koura in 0.5 m(2) artificial stream channels colonised
by benthic invertebrates from a pasture stream, Waikato, New Zealand.
Wineberry (Aristotelia serrata) leafpacks were placed in each channel
and after 7 weeks the leaf matter remaining was significantly lower i
n both medium and high koura channels than in controls. The amount of
sediment (surficial cover by fines and weight of suspendable sediment)
was also significantly reduced in high koura density channels. Densit
ies of invertebrates other than crayfish were not significantly differ
ent among treatments; however, taxa richness and invertebrate biomass
were significantly lower in high koura channels than in controls. Our
results suggest that freshwater koura may play a keystone role in stru
cturing benthic invertebrate communities either directly through preda
tion, or indirectly by sediment bioturbation and increasing organic ma
tter processing rates.