Evaluating the Potential Effectiveness of Compensatory Mitigation Strategies for Marine Bycatch

Conservationists are continually seeking new strategies to reverse population declines and safeguard against species extinctions. Here we evaluate the potential efficacy of a recently proposed approach to offset a major anthropogenic threat to many marine vertebrates: incidental bycatch in commercial fisheries operations. This new approach, compensatory mitigation for marine bycatch (CMMB), is conceived as a way to replace or reduce mandated restrictions on fishing activities with compensatory activities (e.g., removal of introduced predators from islands) funded by levies placed on fishers. While efforts are underway to bring CMMB into policy discussions, to date there has not been a detailed evaluation of CMMB's potential as a conservation tool, and in particular, a list of necessary and sufficient criteria that CMMB must meet to be an effective conservation strategy. Here we present a list of criteria to assess CMMB that are tied to critical ecological aspects of the species targeted for conservation, the range of possible mitigation activities, and the multi-species impact of fisheries bycatch. We conclude that, overall, CMMB has little potential for benefit and a substantial potential for harm if implemented to solve most fisheries bycatch problems. In particular, CMMB is likely to be effective only when applied to short-lived and highly-fecund species (not the characteristics of most bycatch-impacted species) and to fisheries that take few non-target species, and especially few non-seabird species (not the characteristics of most fisheries). Thus, CMMB appears to have limited application and should only be implemented after rigorous appraisal on a case-specific basis; otherwise it has the potential to accelerate declines of marine species currently threatened by fisheries bycatch

The seed banks of English lowland calcareous grasslands along a restoration chronosequence

We investigated whether the seed banks of ex-arable lowland calcareous grasslands underwent restoration similar to that of the above-ground restoration, andwhether this was influenced by seed-sowing or environmental conditions. We compared 40 sites, where some form of restoration work had been implemented between 2 and 60 years previously, with 40 paired reference sites of good quality calcareous grassland with no history of ploughing or agricultural improvement. We analysed differences between sites and between above- and below-ground vegetation using both a multivariate approach and proportions of selected plant attributes. Seed banks of reference sites were more characteristic of late successional communities, with attributes such as stress tolerance, perenniality and a reliance on fruit as the germinule form more abundant than in restoration sites. In restoration sites, these tended to decrease with restoration site isolation and increase with restoration site age and where soil nutrient conditions were more similar to reference sites (i.e. with relatively low phosphorus and high nitrogen). Seed bank communities of all sites differed considerably from above-ground communities, however, and no overall significant responses to site age, isolation or soil nutrients were detected by multivariate analyses of similarity of species between pairs of sites. Responses to different seeding methods were also barely detectable. While there is some indication from the plant attribute data that the regeneration potential contained in the seed banks of restored sites increasingly resembles that of references sites over time, even seed banks of good quality calcareous grassland are dominated by ruderal species. It is likely, therefore, that permanent seed banks do not facilitate the restoration of ex-arable grasslands