In-stream behaviour of threatened fishes and their food organisms based on remote video monitoring
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Can remote underwater video be used to investigate the in-stream behaviour of small fishes and decapods? Diel activity of two threatened freshwater fishes (Macquaria australasica and Gadopsis bispinosus), a palaemonid prawn and an atyid shrimp, was established from remote underwater video in a pool of an upland stream in the current study. Decapods and large fishes (>5 cm TL) were nocturnal, whereas, small fishes (<5 cm TL) were diurnal. The suitability of using underwater video to quantify short-term (seconds) behavioural interaction among individuals was also demonstrated, with early-juvenile-phase Gadopsis bispinosus exhibiting interference competition on 35% of occasions when two or more individuals were observed. This study demonstrates that remote underwater video is useful for observing the in-stream behaviour of threatened freshwater fauna where other techniques are not viable, and presents sub-sampling of video as a means of reducing video processing time in assessing fish diel activity patterns.