Opportunistic exploitation: an overlooked pathway to extinction

Abstract

How can species be exploited economically to extinction? Past single-species hypotheses examining the economic plausibility of exploiting rare species have argued that the escalating value of rarity allows extinction to be profitable. We describe an alternative pathway toward extinction in multispecies exploitation systems, termed 'opportunistic exploitation'. In this mode, highly valued species that are targeted first by fishing, hunting, and logging become rare, but their populations can decline further through opportunistic exploitation while more common but less desirable species are targeted. Effectively, expanding exploitation to more species subsidizes the eventual extinction of valuable species at low densities. Managers need to recognize conditions that permit opportunistic depletion and pass regulations to protect highly desirable species when exploitation can expand to other species.

The cost of being valuable: predictors of extinction risk in marine invertebrates exploited as luxury seafood

“…High-value species need most stringent regulatory measures for their exploitation [10], because they can still be collected opportunistically after fishers shift to targeting lower value species [24], and conservation must not lose sight of threats to common species [43]. Species-specific bans have been placed on threatened sea cucumbers in a few instances [51] but these regulations do not prevent serial depletion of other species further down the value chain.…”

“…Species-specific bans have been placed on threatened sea cucumbers in a few instances [51] but these regulations do not prevent serial depletion of other species further down the value chain. An alternative is to set a shortlist of allowable species, which excludes threatened species and those important for ecosystem functions [10,24]. This regulatory measure should be accompanied by others, such as capacity and effort limitations (e.g.…”

Soft bodies make estimation hard: correlations among body dimensions and weights of multiple species of sea cucumbers

“…Over this long history of exploitation the fishery has undergone many changes including the species that are harvested, with many commercially less attractive species 'filling the gap' left as higher value species became more scarce, a common feature of many such fisheries (ToralGranda et al 2008;Branch et al 2013). From a research and management perspective this has introduced a sizeable number of little studied species to the fishery as past research focussed on a smaller number of high value species.…”

‘Neo-Europe’ and its ecological consequences: the example of systematic degradation in Australia's inland fisheries

“…Legislation was introduced to regulate inland fishing by the early 1900s. It did not, however, preclude fishing, and it is possible that the decline of highly valued species, such as cod, was exacerbated by opportunistic exploitation during fishing for co-occurring lower-value species [13].…”