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Feeding habits of co-existing populations of the freshwater eels, Anguilla australis Richardson (shortfinned eel), and A. dieffenbachii Gray (longfinned 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.

The distributions of shortfinned eels (Anguilla australis) and longfinned eels (A. dieffenbachii) of all sizes in three New Zealand coastal streams were investigated during summer by sampling stratified, randomly chosen pool, run, and riffle sites from tidal to upper reaches. In all streams, both species were widespread, although a greater proportion of the total population of shortfinned eels was present in the lower reaches and small eels (<300 mm total length (TL)) had advanced further up stream than longfins in two of the streams. The biomass (g m -2 ) of longfinned eels <300 mm TL was greatest in riffles, whereas that of comparable-sized shortfinned eels was evenly distributed across habitat types in all streams; in contrast, eels 300 mm TL of both species showed no consistent pattern of habitat use between streams. Multiple regression analysis of species biomass (g m -2 ) for four size groups (<100; 100-199; 200-299; 300 mm TL) against 16 habitat variables, indicated that the distribution of shortfinned eels <300 mm TL was most closely associated with distance from the ocean, Received 12 September 1997; accepted 24 December 1997 whereas that of longfinned eels of the same size group was most closely associated with water velocity and substrate. Medium-large eels ( 300 mm TL) of both species were strongly associated with cover, with longfinned eels using a greater variety (macrophytes, banks, in-stream debris, shade) than shortfinned eels (primarily riparian cover). Overall, our findings suggest that the longfinned eel is a more generalist species, living in a broad range of habitats, whereas the shortfinned eel is more specialised, as is reflected in differences in their distributions and habitat associations. M97051

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Otolith microstructure and microchemistry were examined in the glass eels of 5 species of Anguilla to compare the early life histories among the New Zealand temperate eels A. dieffenbachii and A. australis, and 3 species of tropical eels (A. bicolor pacifica, A. marmorata and A. celebesensis) collected in Indonesia and the Philippines. The ontogenetic patterns of fluctuation in increment widths and changes in otolith Sr:Ca ratios were similar in all species examined. They all showed an abrupt increase in increment width and a sharp drop in Sr:Ca ratio, suggesting the onset of metamorphosis from leptocephalus to glass eel. However, age at metamorphosis was different among the 5 species, as was age at recruitment to estuary (average ± SD), which was 297 ± 25.3 d in A. dieffenbachii, 268 ± 31.3 d in A. australis, 195 ± 25.8 d in A. bicolor pacifica, 170 ± 15.9 d in A. marmorata and 116 ± 17.7 d in A. celebesensis. Ages at metamorphosis and recruitment showed a linear relationship in all 5 species, and both of these ages were greater for the New Zealand temperate species than for the tropical eels. A. dieffenbachii recruited to freshwater habitats at the largest size and after the longest larval duration of any species of Anguilla ever reported. This suggests that in New Zealand A. dieffenbachii spawns at a location where their leptocephali take longer to reach their freshwater habitat than A. australis. This is in contradiction to speculation that A. dieffenbachii spawns closer to New Zealand than A. australis, based on the more advanced stage of gonadal maturation that has been observed in the silver eels of the former species.KEY WORDS: Eel · Anguilla · Early life history · Otolith · Growth increments · Sr:Ca ratios · Metamorphosis · Inshore migration Resale or republication not permitted without written consent of the publisher