Porpoises and fishing nets

Porpoises in the wild have been observed from the Fynshoved peninsula to study how they react to a fishing net. Direct observations of how porpoise behaviour is affected by fishing implements have never been made before. The study seems to indicate that porpoises react to fishing implements at far greater distances than those assumed up until now. The study may be of great significance to how we think the secondary catch problem should be tackled.

The number of porpoise observations in an area with (circles) and without (triangles) a fishing implement, as a function of the number of metres from the fishing implement, observed from the Fyns Hoved peninsula. The reason the number of porpoise observations declines proportionate with the distance to the un-deployed net is that the net distance is correlated with the distance from the observer (from a 20-metre-high slope). Once the net is put into the water, the dispersion of porpoises changes strikingly, so that very few porpoises are found near the fishing implement. Surprisingly, the effect continues all the way out to a distance of more than 80 metres. From: Nielsen (2009), Thesis Report, University of Copenhagen.

Field work at the Fyns Hoved peninsula.