Australian Barotrauma Study: Fish in a Sock

An experiment conducted by Australian researchers showed there was no difference in survival between unvented fish, vented fish, and those repressurized using drop weights. Experimenal fish were held in a large, vertical enclosure (dubbed the "sock") to document survival rates of treated fish. The photograph shows the sock aboard the DPI&F research vessel Tom Marshall near Double Island Point, Australia.

Ian Brown and colleagues completed, in 2008, a study of barotrauma in several species of Australian reef fishes. This study is commendable both for its scope- it is unquestionably one of the most thorough studies of barotrauma- and for the novelty of the methods used

Among the six species of fish studied, Ian and colleagues found no difference in survival between vented and unvented individuals.

They also provide the first assessment of the potential use of shot, or drop, weights as a means of repressurizing fish. Again, they found no difference between control fish and those released using shot weights.

A brief description of their results has been presented in video form. The video notes that Ian and colleagues found that barotrauma treatment increased survival of one species (saddletail snapper). Presumably, this resulted from comparing control (untreated) fish against all of those that were treated (vented + shot weight), regardless of treatment type. No treatment affect was observed among the five remaining species.

I was present for some of the initial discussions of this project. There was spirited debate about what constituted a proper control. The concept for, what they now call the "sock" came up in that meeting. To their credit, they developed and used the sock, to good effect, rather than deciding that it would be difficult to employ: a decision far too many researchers on this side of the Pacific would have reached.

Ian et al., G'donya.

The results of this study are available in report form (see below) and are being published in the fishery literature.

Brown, I. W., W. D. Sumpton, M. McLennan, D. J. Welch, J. Kirkwood, A. Butcher, A. Mapleston, D. Mayer, G. Begg, M. Campbell, I. Halliday, and W. Sawynok. 2008. National strategy for the survival of released line-caught fish: tropical reef species. Project Report PR07-3313, Queensland Department of Primary Industries and Fisheries, Brisbane, Australia.