AGE AND GROWTH OF LONGFINNED EELS (ANGUILLA-DIEFFENBACHII) IN PASTORAL AND FORESTED STREAMS IN THE WAIKATO RIVER BASIN, AND IN 2 HYDROELECTRIC LAKES IN THE NORTH-ISLAND, NEW-ZEALAND

Growth rates of New Zealand endemic longfinned eels (Anguilla dieffenb achii) from streams in pasture and indigenous forest, and from two hyd roelectric lakes (Lakes Karapiro and Matahina), were estimated by otol ith examination. Habitat-specific growth was further investigated with measurement of widths of annual bands in otoliths. Longfinned eels 17 0-1095 mm in length ranged between 4 and 60 years old (N = 252). Eels in pastoral streams grew faster (mean annual length increment +/- 95% CL = 24 +/- 3 mm to 36 +/- 7 mm) than eels in streams in indigenous fo rest (annual length increment 12 +/- 2 mm to 15 +/- 3 mm). Eels from t he hydro-electric lakes had growth rates (annual length increments 19 +/- 4 and 19 +/- 7 mm) similar to eels from pastoral streams. Otoliths of most eels showed annual band widths that indicated growth in sever al different habitats, corresponding to growth during upstream migrati on, and limited movement among adult habitats. Estimated age at market able size (220 g) ranged between 7 and 26 years. The particularly slow growth of longfinned eels in streams in indigenous forest has conside rable implications for management. The fast growth rates of eels in hy dro-electric lakes provides evidence for the potential of increased ee l production by stocking. The probable selective production of female eels in these lakes may be nationally important to allow enhancement o f breeding stocks.