Genetics, dispersal, and the rescue effect; a case study in coastal Skagerrak cod
Late Lunch Talk by Ingrid Spies
Low levels of migration can result in observable levels of genetic
differentiation among marine fish stocks. Higher levels of migration
(≥10%) may be sufficient to counteract the effects of depletion due to
overfishing (i.e. a rescue effect). However, intermediate levels of
dispersal may be insufficient for a rescue effect, but may result in
undetectable levels of genetic differentiation. Such a situation may
be problematic for fisheries managers because genetic results can be
interpreted as panmixia, when in reality there are distinct ecological
stocks. A simulation framework is employed to answer questions about
dispersal rates and demographic rescue when significant genetic
differentiation is not detected. Simulations are based on inner and
outer coast Skagerrak and North Sea Atlantic cod (Gadus morhua).
Preliminary results suggest that dispersal between the North Sea and
the outer Skagerrak coast may be sufficient for a rescue effect.
However, migration from the North Sea to the inner coast is much
smaller, and the inner fjords appear to represent distinct
populations. Further work will investigate how different levels of
fishing pressure would affect the level of connectivity between the
North Sea and the outer Skagerrak coast.