Swim for it: effects of simulated fisheries capture on the post-release behaviour of four Great Barrier Reef fishes

Published source details Raby G.D., Messmer V., Tobin A.J., Hoey A.S., Jutfelt F., Sundin J., Cooke S.J. & Clark T.D. (2018) Swim for it: effects of simulated fisheries capture on the post-release behaviour of four Great Barrier Reef fishes. Fisheries Research, 206, 129-137.
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This study is summarised as evidence for the following.

	Action	Category
	Establish handling and release protocols in non-recreational fisheries Action Link
	Reduce the duration of exposure to air of captured fish before release Action Link

Establish handling and release protocols in non-recreational fisheries

A study in 2014 in an area of coral reef on the Great Barrier Reef, South Pacific Ocean, Australia (Raby et al. 2018) found that the ability of fish to return to the reef or seabed after handling and release was affected by handling technique and air exposure. Average time spent immobile following release was higher after “high stress” handling (1 min forced exercise, 5 min air exposure) than “low stress” handling (no forced exercise or air exposure) for coral trout Plectropomus leopardus (4 vs 9 s), emperor Lethrinus spp. (0 vs 1 s) and snapper Lutjanus carponotatus (0 vs 9 s). Time to reach the nearest reef was also higher after high stress handling than low stress handling (trout: 13 vs 19, emperor: 10 vs 19, snapper: 18 vs 33 s), although the time taken to find shelter was similar (coral trout: 20 vs 24, emperor: 20 vs 135, snapper: 108 vs 130 s). In addition, fish subject to high stress handling (all species) took longer to reach the ocean floor and exhibited lower tailbeat and ventilation rates. The proportion of time immobile was similar between treatments for all species except snapper, which spent more time immobile after high stress handling. Sixty-two fish caught by hook and line from reefs at depths of 5–20 m were transferred to a 30,000 l tank where they were fed every 2–3 days. After 1–5 days, fish were transported by boat to a release site 8–12 m from the nearest reef. Fish were released after high or low stress handling to simulate angling practice.

(Summarised by: Leo Clarke)
Reduce the duration of exposure to air of captured fish before release

A study in 2014 in an area of coral reef on the Great Barrier Reef, Coral Sea, Australia (Raby et al. 2018) found that the overall behaviour of reef fish released after minimal air exposure was improved compared to longer air exposure. Average time spent immobile under the boat following release was lower after “low stress” handling with no air exposure than “high stress” handling that included air exposure for coral trout Plectropomus leopardus (low: 4 s, high: 9 s), emperor fish Lethrinus spp. (low: 0 s, high: 1 s) and Spanish flag snapper Lutjanus carponotatus (low: 0 s, high: 9 s). Time to reach the nearest reef was also lower (trout, low: 13 s, high: 19 s; emperor, low: 10 s, high: 19 s; snapper, low: 18 s, high: 33 s). Time taken to enter shelter was not affected by handling conditions, but varied with species (trout, low: 20 s, high: 24 s; emperor, low: 20 s, high: 135 s; snapper, low: 108 s, high: 130 s). In addition, fish subject to lower air exposure (all species) took less time to reach the ocean floor and exhibited higher tailbeat and ventilation rates (see original paper for data). In August-September 2014, a total of 62 fish were caught by hook and line from reefs 5–20 m deep and transferred to a 30,000 l tank. After 1–5 days, fish were transported by boat to a release site 8–12 m from the nearest reef. Fish were released after “low stress” handling (no forced exercise or air exposure) or “high stress” handling (1 min forced exercise, 5 min air exposure) to simulate capture by hook and line.

(Summarised by: Leo Clarke)