Conservation Status Assessment of Demersal Elasmobranchs in the Balearic Islands (Western Mediterranean) over the Last Two Decades

Abstract

[eng] More than half of the Mediterranean sharks and rays are threatened by fishing exploitation.However, population assessments are limited by the scarcity of specific data on fishing catches. In thisstudy, we assessed temporal trends of the indicators developed within the European Marine StrategyFramework Directive over the last two decades in order to assess the conservation status of demersalsharks and batoids in the Balearic Islands, which represent an important fraction of the bycatchof bottom trawling in this area. On the basis of a georeferenced, fishery-independent dataset of19 species of elasmobranchs, we analyzed 20 year time series (2002–2021) of nine indicators regardingarea distribution, population size, population status, and community structure. Between 30% and50% of the elasmobranch species and functional groups showed increasing trends in distributionarea and population size. This was especially true for batoids, whereas the distribution area andpopulation size of most sharks remained stable over the study period. The remaining indicatorsshowed stability or, in some cases, variable trends. Only in one case did we find a negative trendsustained all along the time series (i.e., the proportion of R. radula large individuals in relation tothe reference period). Overall, our results suggest that the populations of elasmobranchs from theBalearic Islands show stable or recovery trends, mainly in terms of distribution area and density.However, it remains elusive whether this community can recover to the levels of more than half acentury ago, before the development of the bottom trawl fishery, or whether this apparent currentsteady state should be interpreted as a new equilibrium.