Effects of seal-related liver worm on Baltic cod growth and mortality (39411)

The number of grey seals has increased markedly in the Baltic Sea within recent years. Grey seal is final host for the liver worm Contraceum osculatum, where cod is one of several transport hosts. Concurrent with the rise in number of grey seal, the prevalence (number of infected cod) and intensity of infection (number of liver worms per infected cod) with liver worm has increased, and up to 340 worms can now be found in single cod livers. 
Field studies have shown that intensity of infection correlates negatively with the condition of the fish, indicating that liver worm may have a negative effect on the health status of the fish. Yet, from field investigations it is difficult to separate potentially negative effects of liver worms from that of reduced food availability or poor oxygen conditions. 
In the present study we will perform controlled laboratory experiments to 1. determine the potential costs of housing liver worm.2. estimate the effects of liver worm on cod growth and mortality.3. use data generated in i) and ii) in bioenergetic modeling to calculate the effect of liver worm on the maximal food consumption and growth of individual cod. This will subsequently be scaled to the level of the population. 

Partners
DTU Aqua, National Institute of Aquatic Resources (coordinator)
University of Copenhagen, Denmark (coordinator)
Danish Fishermen PO, Denmark

Funding
The projects is funded by the European Maritime and Fisheries Fund (EMFF) and the Danish Fisheries Agency.

Research area: Fish Biology
Research area: Aquaculture
Research area: Marine Populations and Ecosystem Dynamics