Mean temperature of the catch increases quickly in the Mediterranean Sea

The mean temperature of the catch (MTC) is an indicator that has been recently proposed in order to assess the effect of global warming on the exploited marine communities. In this study, we applied the MTC to the catches from the western, central, and eastern Mediterranean Sea for the period 1970 to 2010. We found that the MTC of Mediterranean subareas has been increasing at higher rates compared to those previously reported and its increase is strongly related to sea warming. The rate of MTC increase varied among subareas (0.56, 1.05, and 0.29 degrees C per decade for western, central and eastern Mediterranean subareas, respectively) and could have been higher had Lessepsian species, i.e. species of Indo-Pacific origin migrating through the Suez Canal, been included in the analysis (their catches are not yet officially recorded). The MTC rates we detected are higher than those previously reported for the Mediterranean as a whole. Our results indicate that, in the Mediterranean, the ratio of thermophilous to psychrophilous marine species has been changing in favour of the former, indicating either an increase in their relative proportion in the catches or a decrease in the relative proportion of the psychrophilous species. Both conditions indicate that global warming has a strong effect on marine exploited communities.