Pathology of Ocular Lesions Associated with Gas Supersaturation in White Seabass

Abstract

Cultured juvenile white seabass Atractoscion nobilis (WSB) can suffer from intraocular emphysemas and exophthalmia in the hatchery environment. To identify the cause, two size-groups of WSB were exposed to five gas saturation levels, ranging from 98% to 122% total gas pressure (TGP), over a 96-h exposure period in 18°C and 23°C seawater. Histological examination revealed that the gross and subgross lesions associated with gas supersaturation included corneal and orbital emphysema, along with subretinal, optic nerve, and iridial hemorrhage. Corneal emphysema was the most prominent gross lesion, with the severity and prevalence increasing between size-groups and water temperatures as TGP increased. Following the same pattern was orbital emphysema, which affected more than 93% of the fish examined and caused hemorrhage in the subretinal space, around the optic nerve, in the iris, or a combination thereof. Iridial hemorrhage occurred in 91% of the fish examined and decreased significantly with fish size. The prevalence and severity of hemorrhage in the subretinal space increased significantly with TGP and fish size but not with temperature. Optic nerve hemorrhage was absent in small fish exposed at 18°C but increased significantly with temperature and fish size. The reverse was true for the large fish.

Received January 28, 2011; accepted October 16, 2011

ACKNOWLEDGMENTS

This work was funded by the Ocean Resources Enhancement and Hatchery Program, which is administered by the California Department of Fish and Game. We thank the entire hatchery staff for culture efforts of the fish, and we extend our gratitude to P. Yochem who provided advice on animal veterinary care and K. Gruenthal for her time spent reviewing this manuscript. All experimental procedures were also reviewed and approved by the HSWRI's Animal Care and Use Committee.