Habitat preferences of shortfinned eels(Anguilla australis), in two New Zealand lowland lakes

Abstract

The habitats used by shortfinned eels (Anguilla australis (Richardson)) in Lakes Ellesmere (Canterbury) and Waahi (Waikato), New Zealand, were determined using a variety of capture techniques during the summers of 1994/95-1997/98. The most successful technique used to catch juvenile eels (<300 mm total length (TL)) in Lake Ellesmere was a 2-m wide beam trawl; larger eels were captured mainly by fine-meshed fyke nets. Trawl catches during the night exceeded catches during the day by a factor of 2.4. In Lake Ellesmere, juvenile eels were mainly caught in the depth range 0.6-1.2 m, on a gravel and/or mud substrate, and within 1 km of the shore. In contrast, larger eels (>300 mm) preferred sandy substrates, but showed no marked preference for particular depths or distances offshore. The spatial distribution of both size groups was non-random. Although water temperature did not influence catch rates (CPUE, catch-per-unit-effort) of either size group, catches of the smaller eels were greater during the new moon phase than during the other phases-catches of larger eels were unaffected by lunar phase. Length-frequency distributions of eels from Lake Ellesmere were strongly bimodal, with eels 200-300 mm poorly represented-this probably M98068 Received 22 September 1998; accepted 15 December 1998 reflects poor recruitment for several years, either because lake opening times did not coincide with the availability of glass eels, or because overall numbers of glass eels were low. Juvenile eels in Lake Waahi, caught in fine-meshed fyke nets and in special brush collectors, were also inshore residents; unlike Lake Ellesmere, juvenile eels could be caught at the lake margins, probably because Lake Waahi is not subject to the same wind-induced water level fluctuations as Lake Ellesmere. Recruitment into Lake Waahi commenced in mid December, but there was evidence of low recruitment in past years for this lake also. An important outcome of this research is that estimates of the number of juvenile eels to be transplanted during stocking programmes should be made using the area of the shallow littoral rather than the area of the whole lake.

Summer spatial patterns of the fish community in a large, shallow, turbid coastal lake

“…The soft mud/clay bottom with an abundance of raupo in the Harts Creek area had the highest biomass of eels recorded in our study. Eels tend to avoid firm sand (Jellyman & Chisnall 1999), and this is consistent with the low abundance of eels in such areas in Lake Ellesmere (e.g., Greenpark Sands, large bays on western side, and localised patches along Kaitorete Spit). The moderately high eel biomass on firm sand within the vicinity of the lake outlet was most likely due to the presence of migrant males congregating there.…”

“…Soft sediments are known to be preferred by eels (Jellyman & Chisnall 1999) and flounders (McDowall 1990). The soft mud/clay bottom with an abundance of raupo in the Harts Creek area had the highest biomass of eels recorded in our study.…”

Evidence of different habitat use by New Zealand freshwater eels Anguilla australis and A. dieffenbachii, as revealed by otolith microchemistry

“…The dominant substrates with the lake are soft mud and sand. Recruitment of eels occurs when lake openings coincide with the arrival of glass eels during spring (Jellyman & Chisnall 1999) and the lake supports a substantial commercial fishery using fyke nets that primarily catch Anguilla australis (Jellyman & Todd 1998 (Table 1) and were identified to species, sex and life history stage as described by Lokman et al (1998). This time period coincides with the typical spawning migration season (Cairns 1941, Todd 1981, and the eels were caught primarily near the outlet area of the lake, with 39 being caught at the 4 sites near the outlet and 1 (Individual LF121) being caught in the Selwyn River (Fig.…”

“…For example, in Lake Ellesmere the smaller juvenile eels of Anguilla australis (< 300 mm) appeared to be more abundant closer to shore, but the larger eels were more evenly distributed and may be able to use a wider range of substrate types in the lake (Jellyman & Chisnall 1999). Similarly, in a shallow lake on the North Island of New Zealand (Lake Waahi, 3.5 m max.…”

A spatial assessment model for European eel (Anguilla anguilla) in a delta, The Netherlands

“…Winter and communication with fishermen), and almost all sampling took place near the shores of lakes or banks of rivers, streams or canals. The electric dipping net data was therefore taken as representative for eel densities near the shores or banks, whereas eel densities further from shores or banks were assumed to be lower (Jellyman and Chisnall, 1999;Schulze et al, 2004;Stevens et al, 2009b). However, no quantification of this is available and therefore the offshore density was estimated to be 50% of the inshore density.…”