Bruinvis Phocoena phocoena op zijn retour in de Zuidelijke Noordzee

Following the rapid ‘return’ of Harbour Porpoises Phocoena phocoena in Dutch nearshore waters, reflected in systematic sightings (seawatching data), ‘accidental reports’ of sightings by the general public as well as in strandings data (national database aturalis), a decline in general abundance has been reported. This decline is possibly a retreat from nearshore waters rather than a reduction in the population as a whole in the southern orth Sea, but it is possible that Harbour Porpoises do indeed move back to their recently more traditional areas in the northern half of the orth Sea. The peak in abundance was in 2006, when many thousands were seen and over 500 washed ashore in The etherlands. A small resident population became established in the Delta area (Zeeland), the only part of the country where Harbour Porpoises can be seen throughout the year. The initial increase in nearshore waters was probably caused by a shift in wintering distribution, in particular of smaller (young), mostly male Harbour Porpoises. The sexratio flipped from predominantly females to predominantly males around the year 2000. It would be interesting to see if the reverse would happen if porpoises continue to decline in years to come.