Sammendrag
Crown jellyfish (Periphylla periphylla) has become an increasing biological and economic problem for the fishermen in many Norwegian fjords. It is known to prey on a variety of planktonic species including small crustaceans like krill and calanus as well as fish eggs and larvae. Thus, this jellyfish is both a predator and a food competitor to gadoid fish species. Recent studies suggest that an increasing abundance of jellyfish may have contributed to a decline in the cod stock size and productivity in some Norwegian fjords. Abundant local jellyfish populations may cause substantial economic loss for fishermen, particularly in small-scale fisheries, due to the reduction in annual fish catches and extra effort required for cleaning and fixing fishing nets. This, in turn, has led to changes in the fishing behavior and well-being of the local fishermen. This paper explores the potential ecological and economic consequences of an ongoing periphylla bloom on the cod fishery in the Trondheimsfjord, Norway. A bioeconomic model of cod fishery is developed which incorporates these impacts. The model is tested by simulations based on data collected from commercial fishermen surveys and milieu-related monitoring series. The study provides valuable insights into the impact of a newly established but permanent jellyfish population on the ecologically and commercially important cod species, and how fishermen might adopt such a continued high local jellyfish presence in their prospects for a future as fishermen, and also help policy makers on how to incorporate the experience from this emerging issue into future management and policy process.
Vis fullstendig beskrivelse
