Seasonal variation in diel activity and microhabitat use of an endemic New Zealand stream-dwelling galaxiid fish

Summary 1. Seasonal variation in microhabitat use and activity of 14 giant kokopu Galaxias argenteus, a drift‐feeding galaxiid fish, was compared using radiotelemetry. 2. During winter giant kokopu predominantly used low velocities and intermediate depths by night and day. Activity recorded during 2...

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Bibliographic Details
Published in:Freshwater biology 2003-10, Vol.48 (10), p.1765-1781
Main Authors: David, Bruno O., Closs, Gerard P.
Format: Article
Language:English
Subjects:
activity
Agnatha. Pisces
Animal and plant ecology
Animal, plant and microbial ecology
Animals
Annelida and closely related phyla: sipuncula. Echiura. Nemertinea
Autoecology
Biological and medical sciences
Freshwater
Fundamental and applied biological sciences. Psychology
Galaxias argenteus
giant kokopu
Invertebrates
microhabitat
radiotelemetry
salmoniformes
Vertebrata
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Summary:Summary 1. Seasonal variation in microhabitat use and activity of 14 giant kokopu Galaxias argenteus, a drift‐feeding galaxiid fish, was compared using radiotelemetry. 2. During winter giant kokopu predominantly used low velocities and intermediate depths by night and day. Activity recorded during 24 and 72 h periods indicated that fish were consistently active at night and inactive during the day. Activity data corresponded with point‐in‐time habitat use data, both of which indicated that fish were concealed amongst cover during the day and used open water habitats at night. 3. During summer, giant kokopu used higher water velocities, shallower depths and coarser substrata, particularly at night but also occasionally during the day relative to winter. Giant kokopu were active by both day and night in summer, although periods of activity were less defined and less predictable than during winter. 4. Adults used predictable home reaches at base‐flow, with most individuals repeatedly using of one or two cover locations within their ‘home’ reach. Reaches used by fish were relatively short (rarely exceeding 26 m) irrespective of season and always included a single pool‐riffle sequence. 5. Diel and seasonal behaviour of giant kokopu was generally comparable with that exhibited by other drift feeding fish species in small temperate streams. However, the nocturnal activity of giant kokopu contrasts with activity patterns in various salmonids, indicating that the impact of predation by different drift feeding fish may vary considerably.
ISSN:0046-5070
1365-2427
DOI:10.1046/j.1365-2427.2003.01127.x