Movements of shortfinned eels, Anguilla australis, in Lake Ellesmere, New Zealand: Results from mark‐recapture studies and sonic tracking

Abstract

Movements of non‐migratory and migratory shortfinned eels in Lake Ellesmere, New Zealand, were studied from recaptures of streamer‐tagged eels and tracking of eels tagged with sonic transmitters. Of the 9956 streamer‐tagged eels, 1982 were recaptured by commercial fishers over 5 years, some as many as 7 times. Most non‐migratory eels were recaptured at, or adjacent to, their original capture site, although some eels had moved to 11 of 12 regions in the lake within 3 weeks of tagging. Transplanted non‐migratory eels showed a tendency to home to their original capture site. Although most eels do not appear to move more than a few kilometres they are capable of periodic extensive movements; we conclude that there is a single population in the lake. The mobile portion of the population will be important in repopulating areas where eel numbers have been reduced by commercial fishing. Migrating eels always congregated at Taumutu, the area where the lake is artificially opened to the sea. There was some evidence that extensive movement of sonic‐tagged eels resulted from handling during tagging, and movement of eels effectively ceased at water temperatures < 12°C when eels remained in deeper parts of the lake, probably to over‐winter.

Keywords:

• shortfinned eel
• Anguilla australis
• movements
• mark‐recapture
• tags
• sonic tags
• localised movement