Jellyman--Diet of eels in Lake Pounui

New Zealand Journal of Marine and Freshwater Research abstracts

Diet of two species of freshwater eel (Anguilla spp.) in Lake Pounui, New Zealand

DONALD J. JELLYMAN

Freshwater Fisheries Centre Ministry of Agriculture and Fisheries P.O. Box 8324, Riccarton Christchurch, New Zealand

Abstract Feeding habits of co-existing populations of the freshwater eels, Anguilla australis Richardson (shortfinned eel), and A. dieffenbachii Gray (long-finned eel) were studied in Lake Pounui, Wairarapa. A combination of sampling equipment gave a sample of 682 shortfinned eels and 310 longfinned eels ranging in length from 13 to 135 cm. Both species probably feed intermittently and are opportunistic feeders, consuming a wide range of food items, although feeding of individual eels was normally selective for a single prey species. Diet of each species changed with size. Smallest eels of both species ate mainly amphiphods and insect larvae; the snail Potamopyrgus antipodarum was the dominant food organism for shortfinned eels of 30-69 cm but was unimportant to longfinned eels. Longfinned eels > 40 cm were principally piscivorous but fish did not become an important part of shortfinned eel diet until eels were > 70 cm. At similar sizes, the two species had different diets. Eels of the same species but from different habitats generally had similar diets, but diets in both species varied between the two sampling periods. The feeding of both species of eel changed markedly during a period of high lake levels, when they fed almost exclusively on earthworms and grass-grub (Porina) larvae.

Keywords Anguilla australis; Anguilla dieffenbachii; diet; feeding behaviour; lakes; stomach content; benthic invertebrates; terrestrial invertebrates; fish; diet overlaps; floods

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