Abstract

Globally, dolphinfish Coryphaena hippurus is highly sought after by recreational and commercial fisheries. Discards in the recreational fishery have increased due to regulations and ethical angling. In order to determine the fate (live or die) of these discards, it is important to characterize the injuries from different hook locations. This study examined the extent of damage inflicted on dolphinfish hooked in the roof of the mouth using computed tomography (CT) and gross necropsy evaluations. We hypothesized that damage resulting from hooking in the roof of the mouth would be no more severe than from hooking in the jaw of most teleosts. Forty-two dolphinfish carcasses were collected and frozen: 16 were hooked in the roof of the mouth, 12 hooked in the eye via the upper jaw or roof of mouth, and 14 were hooked in the jaw, and served as controls. The heads were removed from all 42 fish and CT scanned, and 33 of these were evaluated using gross necropsy. Damage to the roof of the mouth was greater than expected, and in some individuals, we observed nondisplaced to comminuted fractures of the bones of the suspensorium, hematomas in and laceration of the extraocular muscles, and damage to the optic nerve. These injuries have the potential to compromise vision and therefore decrease post-release survival rates of an obligate sight-feeding species. We evaluated the effectiveness of CT scanning to diagnose injury, and found that the scan images could accurately identify fractures and some soft tissue damage, but the gross necropsies proved more telling of the mechanism of the injury. We conclude that roof-of-mouth hooked dolphinfish likely have moderate discard mortality. This will be valuable information when estimating an overall discard mortality for use in future dolphinfish stock assessments and management.

Acknowledgements

Funding for this work was provided by NOAA Saltonstall-Kennedy grant NA15NMF4270346 and a North Carolina State University CMAST summer fellowship. We thank Jeffery Merrell, Claire Pelletier, Kelsey Moore for assistance with dolphinfish sampling, and Kate Archibald for assistance with gross necropsy.

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+ Student presenter