摘要:

Physico‐chemical conditions and macroinvertebrate faunas of 20 South Island lake outlets were investigated in summer‐early autumn of 1990–94. Four outlet types were recognised: unregulated alpine, unregulated mid/low elevation, regulated hypolimnetic and regulated epilimnetic outlets. Alpine outlet waters had significantly lower (P <0.05) alkalinities and conductivities (6–12mg l‐1CaCO3and 13–45 μS cm‐1) than all other outlets (11–36mg l‐1CaCO3and 36–93 μS cm‐1), whereas pH values were similar among outlet types. Substrate size was significantly greater in modified epilimnetic than natural mid/low elevation outlets (P <0.01). Total number of taxa and invertebrate densities were significantly lower in alpine and hypolimnetic outlets than natural mid/low elevation outlets (P< 0.05, andP <0.01 respectively), and distinct differences were observed in the relative abundances of major taxonomic groups. Alpine streams were dominated by the mayfliesDeleatidium(Leptophlebiidae), andNesameletus(Siphlonuridae), the gripopterygid stoneflyZelandoperla decorataand predatory hydrobiosid caddisflies; molluscs were absent, and filter‐feeding hydropsychid caddisflies rare. In contrast, the hypolimnetic outlets were dominated by filter‐feeding hydropsychids (87–93% of the fauna), and no stoneflies were found. Epilimnetic and unregulated mid/low elevation outlets had similar communities, however invertebrate densities were significantly lower in regulated surface release outlets. Altitude, outlet width, velocity, conductivity, and percentage of the catchment in forest, were all implicated as factors explaining differences in community composition.

ISSN:0028-8330    

DOI:10.1080/00288330.1994.9516632

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The diets and feeding periodicities of six small fish species were investigated in a New Zealand coastal stream over the diel period of 4 to 5 March 1993. Aquatic insect larvae dominated the diets of all fish except common bully,Gobiomorphus cotidianus, and longfinned eel,Anguilla diejfenbachii, which had a large proportion of ostracods in their diets. Dietary overlap was greatest between species pairs which were associated in the same microhabitats:A. dieffenbachiiand bluegilled bully,G. hubbsi;torrentfish,Cheimarrichthys fosteri, andG. hubbsi;andG. cotidianusand upland bully,G. breviceps. Similar patterns in feeding periodicities existed for some of the species with associated diets;A.diejfenbachiiandC. fosteriwere nocturnal feeders, whereasG. hubbsifed during daylight. BothG. cotidianusandG. brevicepswere also diurnal feeders. In part, the results supported the hypothesis that species with temporal segregation of feeding are likely to have more similar dietary compositions, whereas those feeding at the same time are likely to show a greater degree of prey selectivity.

ISSN:0028-8330    

DOI:10.1080/00288330.1994.9516633

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor