DISTRIBUTION and NUMBERS OF STRIPED DOLPHINS IN THE WESTERN MEDITERRANEAN SEA AFTER THE 1990 EPIZOOTIC OUTBREAK

A survey was conducted in the summer of 1991 in the western Mediterranean to map the distribution and to estimate the number of striped dolphins surviving the 1990 outbreak of the morbillivirus epizootic. The highest densities of striped dolphins were found in the Alboran Sea and the Ligurian Sea. Total numbers were estimated at 117,880 (SE: 38,962; 95% CI: 68,379–214,800). The mortality resulting from the epizootic is unknown but may have been severe because the mean size of dolphin schools observed during the epizootic outbreak was significantly smaller than that before the event. A return to larger school sizes after the 1990 outbreak is not evidence of a recovery but can be viewed as a regrouping of individuals into schools of a preferred size. Calves were observed in 24.6% of the schools. They were not seen in schools of ten or less but were present in about half the schools of 30 or more dolphins, a result which suggests segregation similar to that seen in populations of this species elsewhere in the world.