HR: 15:30h
AN: NB14C-01    [Abstracts]
TI: Where have all the caddis gone? The role of culverts, and spiders
AU: * Harding, J S
EM: jon.harding@canterbury.ac.nz
AF: School of Biological Sciences, University of Canterbury, Private Bag 4800 , Chriistchurch, New Zealand
AU: Neumegen, R E
EM:
AF: School of Biological Sciences, University of Canterbury, Private Bag 4800 , Chriistchurch, New Zealand
AU: van den Braak, I L
EM:
AF: School of Biological Sciences, University of Canterbury, Private Bag 4800 , Chriistchurch, New Zealand
AB: Restoration of a 1.5 km urban stream over the past five years has led to surprisingly slow improvement in benthic communities. Analysis of benthic invertebrates at six sites longitudinally showed a marked decline in caddisfly diversity and abundance upstream. This decline could not be adequately explained by changes in water quality, or in-stream physical conditions. Extensive adult trapping on multiple sites on three urban streams has shown that main roads with culverts act as barriers to the upstream flight of adult caddisflies. When adult caddis encounter a road culvert, some are distracted by the surrounding urban conditions (e.g. street lights), and only 30-50% enter the culvert. Of these, about 10-30% do not reach the upstream exit falling prey to spiders or distracted by confounding flight cues. Experimental removal of spiders and webs from three culverts showed an increase in the proportion of caddis exiting upstream. Other confounding effects on caddisflies within the culvert might include light, humidity and temperature gradients. Our results indicate that barriers to adult dispersal and colonisation, such as road culverts and confusing urban habitats, may markedly limit the recovery of urban stream communities.
DE: 9810 New fields (not classifiable under other headings)
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly