Brown bullhead catfish (ameiurus nebulosus) in Lake Taupo

Abstract

Brown bullhead catfish (Ameiurus nebulosus) were first discovered in Lake Taupo during the early 1980s and are believed to have originated from an illegal liberation into the southern end of the lake. A native of the southern and eastern states of America, these catfish have been in New Zealand since 1878 and are now widespread throughout the Waikato region. In 1995 the population structure, abundance, age, growth rate and diet of catfish in the littoral zone (<5 m deep) of Lake Taupo were examined by setting fyke nets overnight in three different habitat types. A total of 6247 catfish was caught from 269 fyke-net sets (mean CPUE 23 fish net–1 night–1). Catfish abundance was greatest in shallow, sheltered, macrophyte-dominated bays, where the population was skewed towards small catfish (<150 mm FL). Adjacent rocky headlands and escarpments supported populations of large fish (>150 mm FL) and small fish. Low numbers of catfish across all size classes were caught from exposed sandy sites. The diet of catfish was size and habitat dependent. Small catfish (<150 mm FL) fed predominantly on chironomids, Cladocera, gastropods, caddisfly larvae, plant material and detritus. Larger catfish were found to prey to a greater extent on koura (Paranephrops planifrons), fish and terrestrial invertebrates.