Abstract
Each year, over 45 countries export 30 million fish from coral reefs as part of the global marine ornamental aquarium trade. This catch volume is partly influenced by collection methods that cause mortality. Barotrauma in fish resulting from forced ascent from depth can contribute to post-collection mortality. However, implementing decompression stops during ascent can prevent barotrauma. Conversely, venting (puncturing the swim bladder to release expanded internal gas) following ascent can mitigate some signs of barotrauma like positive buoyancy. Here, we evaluate how decompression and venting affect stress and mortality in the Yellow Tang (Zebrasoma flavescens). We examined the effects of three ascent treatments, each with decompression stops of varying frequency and duration, coupled with or without venting, on sublethal effects and mortality using histology and serum cortisol measurements. In fish subjected to ascent without decompression stops or venting, a mean post-collection mortality of 6.2% occurred within 24 h of capture. Common collection methods in the fishery, ascent without decompression stops coupled with venting, or one long decompression stop coupled with venting, resulted in no mortality. Histopathologic examination of heart, liver, head kidney, and swim bladder tissues in fish 0d and 21d post-collection revealed no significant barotrauma- or venting-related lesions in any treatment group. Ascent without decompression stops resulted in significantly higher serum cortisol than ascent with many stops, while venting alone did not affect cortisol. Future work should examine links in the supply chain following collection to determine if further handling and transport stressors affect survivorship and sublethal effects.
Highlights
Each year, over 45 countries remove and export 14–30 million fish from coral reefs as part of the marine ornamental aquarium trade (Bruckner, 2005; Wood, 2001)
Mortality occurred
With the objective of informing management on collection practices in the aquarium trade, our study focused on the short- and long-term mortality of reef fish subjected to decompression and venting as barotrauma prevention and mitigation practices, respectively
Summary
Over 45 countries remove and export 14–30 million fish from coral reefs as part of the marine ornamental aquarium trade (Bruckner, 2005; Wood, 2001). ∼90% of freshwater aquarium fish are successfully cultivated in aquaculture facilities, most tropical marine aquarium fish are wild-caught (Wood, 2001). Collecting live fish for the aquarium trade involves removing reef fish from SCUBA diving depths (∼10–35 m) to the surface. Collection is followed by transporting fish from the collection site to an export facility where they are held for 1–7 days prior to shipment. The fish are packaged in plastic bags with enough water to turn around in and 100% oxygen, placed in boxes, and shipped to an import facility where they may be held for several days. Mortality may occur at any point in this supply chain, impacting each participant in the industry, and negatively affecting coral reefs through increased collection pressure to replace losses (Stevenson, Tissot & Dierking, 2011; Tissot et al, 2010)
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