Exploiting sensory ecology to reduce seabird by-catch
In a previous study, we reported that deploying small amounts of biogenic oil derived from the livers of school sharks (Galeorhinus galeus) was effective in reducing the numbers of seabirds attending fishing vessels and seabird diving activity in the Hauraki Gulf, New Zealand. This seabird assemblage was numerically dominated by Flesh-footed Shearwaters (Puffinus carneipes) and the globally vulnerable Black Petrel (Procellaria parkinsoni). The results suggested that the oil deterrent operated via an olfactory or chemesthetic mechanism. Here we compare the deterrent effects of shark-liver oil with three other fish oils, in the Flesh-footed Shearwater–Black Petrel assemblage. We also report on trials assessing the deterrent efficacy of shark-liver oil and one other fish oil in an assemblage including four species of albatrosses (Diomedea spp., Thalasarcche spp.), Southern and Northern Giant-Petrels (Macronectes giganteus and M. halli), and Cape Petrels (Daption capense). Shark-liver oil was the most effective deterrent of the four fish oils tested in the Flesh-footed Shearwater–Black Petrel assemblage, but it did not deter albatrosses, giant-petrels or Cape Petrels from attending vessels. Thus, the deterrent was effective only on burrow-nesting seabird species. These results may provide further support for our speculation that the deterrent operates via an olfactory mechanism, while corroborating other work linking life-history characteristics of seabirds to their sensory ecology. We recommend research to investigate the mechanism and active ingredients by which shark-liver oil deters some species of seabirds. We also suggest testing fish oils on White-chinned (Procellaria aequinoctialis) and Grey (Procellaria cinerea) Petrels, and Sooty Shearwaters (Puffinus griseus), as well as in other areas occupied by Flesh-footed Shearwaters, to assess further potential for this natural oil or its ingredients to reduce by-catch of seabird species globally.