Timing, frequency and environmental conditions associated with mainstem-tributary movement by a lowland river fish, golden perch (Macquaria ambigua).

Wayne M Koster,Damien J O’Mahony,David R Dawson,David A Crook,Paul D Moloney,Howard I Browman

doi:10.1371/journal.pone.0096044

Wayne M Koster, Damien J O’Mahony + Show 4 more

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https://doi.org/10.1371/journal.pone.0096044

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Abstract

Tributary and mainstem connections represent important links for the movement of fish and other biota throughout river networks. We investigated the timing, frequency and environmental conditions associated with movements by adult golden perch (Macquaria ambigua) between the mainstem of the mid-Murray River and a tributary, the Goulburn River, in south-eastern Australia, using acoustic telemetry over four years (2007–2011). Fish were tagged and released in autumn 2007–2009 in the mid-Murray (n = 42) and lower Goulburn (n = 37) rivers within 3–6 km of the mid-Murray-lower Goulburn junction. 38% of tagged fish undertook mainstem–tributary movements, characterised mostly by temporary occupation followed by return of fish to the original capture river. Approximately 10% of tagged fish exhibited longer-term shifts between the mainstem and tributary. Movement of fish from the tributary into the mainstem occurred primarily during the spawning season and in some years coincided with the presence of golden perch eggs/larvae in drift samples in the mainstem. Many of the tributary-to-mainstem movements occurred during or soon after changes in flow. The movements of fish from the mainstem into the tributary were irregular and did not appear to be associated with spawning. The findings show that golden perch moved freely across the mainstem–tributary interface. This demonstrates the need to consider the spatial, behavioural and demographic interdependencies of aquatic fauna across geographic management units such as rivers.

Highlights

In lotic ecosystems, connections between tributaries and the mainstem function as conduits for the flow of organic material and energy, and are critical for supporting riverine biodiversity and maintaining habitat heterogeneity [1,2,3]
Of the 79 golden perch tagged during the study, 68 were detected by the listening stations and three were reported by anglers as caught in the Goulburn River and retained (Table 1, Fig. 2)
About one quarter (11 out of 42) of fish tagged in the Murray River moved into the Goulburn River

Summary

Introduction

Connections between tributaries and the mainstem function as conduits for the flow of organic material and energy, and are critical for supporting riverine biodiversity and maintaining habitat heterogeneity [1,2,3]. While many previous studies of fish movement in rivers have focused on the ecological importance of longitudinal (i.e. along a river channel) and lateral (i.e. river–floodplain) movements [5,6,7,8], there is growing evidence that mainstem–tributary movements are important for maintaining fish populations in river networks [9,10]. Hydrological regimes are a major driver of river ecosystems and provide cues for a range of important behaviours in fishes, including movement and spawning [13,14,15,16]. Hydrological regimes are often modified to the extent that these golden perch tend to congregate at mainstem–tributary junctions during the spawning season in late spring and early summer [22]

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