Conservation translocations of marine species: A global review
Translocation, the intentional movement and free-release of living organisms, is a conservation tool that is used around the world. As industrialization, climate change, and habitat loss accelerate, conservation biologists increasingly undertake translocations to mitigate the damage incurred to wild populations and ecosystems. We observed that terrestrial species comprise the majority of highly published conservation translocations and suspected that marine species may be overlooked in the review literature. To elucidate the prevalence of, motivations for, and potential barriers to conservation translocations in marine environments, we conducted a systematic search for marine translocation papers in ISI Web of Knowledge and Academic Search Complete between 1883 and June 2013. Our search terms were designed to be inclusive, maximizing sensitivity at the expense of specificity so as to avoid missing relevant publications. We manually screened search results to determine which papers actually dealt with marine conservation translocations. We then summarized the habitat type and conservation status of translocated species, the motivations and geographic locations of translocation projects, and the organizations undertaking the translocation.
Our inclusive search of two major research databases yielded 12,505 unique references. Of these, 587 describe the translocation of marine species for commercial, aesthetic, research, or rehabilitation purposes, and 412 document the translocation of marine species for conservation benefit. The majority (56%) of conservation translocation papers involved the release of individuals into an existing population of conspecifics (reinforcement), while 41% described the release of individuals into areas from which they had been extirpated (reintroduction). Taxonomic biases differed between the two types of translocations: reintroduction papers largely concerned fish (27%) and bird (22%) species – a trend also reported in reintroduction reviews with a terrestrial focus. Conversely, marine reinforcement papers primarily involved invertebrates (40%) and plants (35%). This suggests that taxonomic bias not only influences which species are translocated for conservation purposes, but also where (relative to current range) and when (pre- or post- extirpation) they are translocated. Despite being conservation-motivated, only 24% of reinforcement projects and 24% of reintroduction projects involved species considered at risk by the IUCN Red List of Threatened Species. To our knowledge, this study provides the first summary of worldwide conservation translocations of marine species, and may help elucidate reasons (ecological or otherwise) for the biases observed.