Use of in‐stream cover types by adult banded kokopu (Galaxias fasciatus) in first‐order North Island, New Zealand, streams

Abstract

The relative importance of wood material in providing in-stream cover for adult banded kokopu (Galaxias fasciatus) was determined in firstorder, North Island, New Zealand, streams. Three groups of streams, each differing in the relative amount of three types of in-stream cover (i.e., wood, boulders, undercut banks) were selected and banded kokopu were sampled in their pools using electric fishing. Banded kokopu occurred beneath boulders, undercut banks, and wood material in all pools except those lacking any in-stream cover, or those where large (total length >400 mm) eels were present. Their presence in pools was therefore highly dependent on in-stream cover, provided large eels were absent. In streams where the cover provided by boulders was lacking, banded kokopu selected mainly undercut banks and wood. However, in streams containing large amounts of bank and boulder cover, wood was under-utilised, indicating that it was least preferred. In pools providing a choice of cover types, bank cover was more frequently used than other types, indicating that it is preferred. The mean size of banded kokopu in pools was positively related to their relative abundance, and their abundance was in turn related to habitat quality as defined by in-stream cover. Streams with the least amount of bank cover had the lowest number of pools occupied by banded kokopu, fewer banded kokopu per pool, fewer pools containing two or more banded kokopu, and the smallest banded kokopu. Collectively, these data indicate that bank cover in pools provides optimal habitat for banded kokopu, and that wood material was important only where other types of more permanent cover were lacking. Logs and wood slash from logging operations could therefore be important for increasing banded kokopu habitat in logged streams where bank and boulder cover are scarce.

Habitat use by banded kokopu(Galaxias fasciatus)and giant kokopu(G. argenteus)co‐occurring in streams draining the Hakarimata Range, New Zealand

“…he association of both giant and banded kokopu with slow-flowing waters (pools and backwaters) that contain some form of in-stream cover is well documented (Jowett et al 1998;Chadderton & llibone 2000;Whitehead et al 2002;rowe & Smith 2003). However, previous studies have shown that the presence of in-stream cover is more important than its composition, as giant kokopu have been associated with boulders, undercut banks, logs, debris dams, and aquatic vegetation david & Closs 2003).…”

“…In first-order streams, it is not unusual for only one banded kokopu to occupy an entire pool (rowe & Smith 2003). However, studies of giant kokopu in higher order South island streams found many pools contained a hierarchical group of fish David & Closs 2003).…”

“…Some separation of banded and giant kokopu habitats based on pool size was expected, as giant kokopu are known to prefer deep (>0.5m) waters (Chadderton & allibone 2000; and occur in a variety of habitats including large coastal water bodies such as estuaries and swamps (mcdowall 1990). although banded kokopu also occur in deep waters of larger streams (Chadderton & allibone 2000), they are most common within small first-and second-order streams (mcdowall 1990;Jowett et al 1998;rowe & Smith 2003).…”

“…For banded and giant kokopu, in-stream cover appears to be an essential feature of microhabitat selection; however, cover preferences can vary depending upon availability. rowe & Smith (2003) found within Coromandel/ north island streams, banded kokopu would use either boulders, woody debris or undercut banks depending upon which cover type was available. However, when a choice of in-stream cover existed, banded kokopu selected undercut banks more often than any other cover type.…”

“…2002). Both species are known to have an affinity for pool habitat that contains some sort of in-stream cover (Jowett et al 1998;Chadderton & Allibone 2000;Whitehead et al 2002;Rowe & Smith 2003), and both species can be associated with tannin-stained or acidic waters (Taylor & Main 1987;McDowall 1990;. However, differences in habitat selection by banded and giant kokopu have also been documented; banded kokopu are rarely found in streams lacking a forest canopy (McDowall 1990;Jowett & Richardson 2003), whereas giant kokopu can occur in various forested and pastoral habitats including estuaries, swamps, drains, and ponds (McDowall 1990;.…”