Changes in life-history traits in relation to climate change: bluefish (Pomatomus saltatrix) in the northwestern Mediterranean

This study shows the strong relationship between the increasing surface temperature in the NW Mediterranean and the expansion northwards of the bluefish distribution range with the species reproducing in the new distribution areas. Two shifts in temperature were detected: the first one in the early 1980s and the second around 1997. This last shift, explained by warmer springs ( April- June), when the species migrates for spawning, led to the observed changes in bluefish. In the western Mediterranean basin, a significant increase in bluefish landings was observed by the mid nineties, whereas in the Catalan coast, the northern edge of the species distribution, a northward expansion was observed from 2000. At present, spawning takes place all along the Catalan coast ( June to September), including the new distribution areas, being 21 degrees C the threshold for the presence of larvae in the plankton. This temperature was not attained in June two decades ago. The highest concentrations of larvae were located near the mouth of the Ebro River and their distribution to the north did not extend beyond the thermal front. Bluefish has taken the advantage of the changing environmental conditions and is established in new northernmost distribution areas.