Common coral trout, Plectropomus leopardus Lacepe`de, crimson snapper, Lutjanus erythropterus Bloch, saddletail snapper, Lutjanus malabaricus (Bloch & Schneider), red emperor, Lutjanus sebae (Cuvier), redthroat emperor, Lethrinus miniatus (Schneider) and grass emperor, Lethrinus laticaudis Alleyne & Macleay, were tagged to determine the effects of barotrauma relief procedures (weighted shot-line release and venting using a hollow needle) and other factors on survival. Release condition was the most significant factor affecting the subsequent recapture rate of all species. Capture depth was significant in all species apart from L. malabaricus and L. miniatus, the general trend being reduced recapture probability with increasing capture depth. Recapture rates of fish hooked in either the lip or mouth were generally significantly higher than for those hooked in the throat or gut. Statistically significant benefit from treating fish for barotrauma was found in only L. malabaricus, but the Correspondence: Wayne Sumpton,

Promotion of better procedures for releasing undersize fish, advocacy of catch-and-release angling, and changing minimum legal sizes are increasingly being used as tools for sustainable management of fish stocks. However without knowing the proportion of released fish that survive, the conservation value of any of these measures is uncertain. We developed a floating vertical enclosure to estimate short-term survival of released line-caught tropical and subtropical reef-associated species, and used it to compare the effectiveness of two barotrauma-relief procedures (venting and shotline releasing) on red emperor (Lutjanus sebae). Barotrauma signs varied with capture depth, but not with the size of the fish. Fish from the greatest depths (40-52 m) exhibited extreme signs less frequently than did those from intermediate depths (30-40 m), possibly as a result of swim bladder gas being vented externally through a rupture in the body wall. All but two fish survived the experiment, and as neither release technique significantly improved short-term survival of the red emperor over non-treatment we see little benefit in promoting either venting or shotline releasing for this comparatively resilient species. Floating vertical enclosures can improve short-term post-release mortality estimates as they overcome many problems encountered when constraining fish in submerged cages.

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A new technique to ameliorate the effects of barotrauma was tested based on observations of pink snapper, Pagrus auratus (Forster), inadvertently piercing their everted stomach with their teeth and releasing trapped swim bladder gases. This technique was termed buccal venting and involved piercing the everted stomach protruding into the buccal cavity or out of the mouth with a 16-gauge hypodermic needle (a practice previously not encouraged). Short-term (~3 days) survival of buccal-vented fish was not significantly different from laterally vented fish nor untreated controls. Both buccal and lateral venting techniques were shown to cause no harm and allowed fish to return to depth. The short-term (1-3 days) post-release survival of line caught snapper was 88% with no significant difference in survival across three depth ranges tested (37-50, 51-100 and 101-180 m). Survival of sublegal pink snapper (<35 cm TL) was not significantly different (P > 0.05) from that of legal-sized fish (≥35 cm TL). Healing of the swim bladder was observed in 27% of pink snapper dissected after ≤3 days in captivity, and healing of stomachs was observed in 64% of pink snapper that had been buccal vented. Relatively high post-release survival rates of line caught pink snapper may offer some protection for snapper stocks where high fishing pressure and legal size restrictions result in the majority of the catch having to be released. K E Y W O R D S :angling, buccal, discard mortality, stomach, swim bladder, venting.