title: Population size, growth and movements of Anguilla australis in a small lake.
abstract: To study growth rates, movements and estimate population size of shortfin eels Anguilla australis in a small lake (2·5 ha) near Christchurch, New Zealand, 617 A. australis were tagged with PIT tags. Tag retention was high (95%) and over the seven recapture events spread over 2 years, 55% of tagged A. australis were recaptured. Growth of recaptured A. australis averaged 13·1 mm year(-1) and declined slightly with increasing total length. Distance moved from original capture site increased with increasing time at large. Population estimates of A. australis > 400 mm (susceptible to capture by fyke net) from recaptures of individuals averaged 1451 A. australis, with a biomass of 170 kg ha(-1) . An average of 6·6% of the estimated total population matured as male silver A. australis each year. Results from radio-tracking of four A. australis gave an average nightly foraging area of 2780 m(2) , and there was no apparent preference for inshore movement (within 5-6 m of the shoreline) or offshore movement. Fyke-net efficiency (total catch relative to the estimated total population available to each net) measured over four consecutive nights fishing was 88%. The lack of precision of the shoreline triangulation system used, ±10 m, meant that the positional data were considered too coarse to be used in a proposed novel population estimation technique based on determining population size within foraging areas.
authors.affiliation: National Institute of Water and Atmospheric Research Limited, P. O. Box 8602, Riccarton, Christchurch, New Zealand.
authors.forename: D J
authors.initials: DJ
authors.lastname: Jellyman
authors.affiliation: National Institute of Water and Atmospheric Research Limited, P. O. Box 8602, Riccarton, Christchurch, New Zealand.
authors.forename: S K
authors.initials: SK
authors.lastname: Crow
mesh_terms: D000811:Anguilla / Q000254:growth & development / Q000502:physiology*; D063147:Animal Distribution; D000818:Animals; D001522:Behavior, Animal; D018533:Biomass; D060106:Lakes; D008297:Male; D009520:New Zealand; D011156:Population Density
keywords: New Zealand; PIT tags; foraging area; freshwater eels; mark-recapture; population estimates