Research project Investigation of homing behaviour in locally spawning herring aggregations on the Swedish east coast

Population structure in marine commercial fish stocks is of vital interest for the fisheries management. Herring abundance on the Swedish east coast is in decline and concerns have been raised  whether local subpopulations are going to be eradicated. In this project, we study herring population structure and homing behaviour by analysing the chemical signature of the otolith core. The question whether temperate marine fishes typically consist of self-sustaining populations or “open” populations still remains unresolved.

At the heart of this population connectivity problem lays the nature of the stock separation mechanisms. Fish populations could be segregated either by environmental forcing, accompanied with opportunistic recruitment of juveniles to spawning areas, or by philopatric behaviours (i.e., inclination of an individual to return to or remain in its natal area). Here we study natal dependence on the choice of spawning site was tested by measuring the contents of various traceelements in the otolith core of recaptured tagged fish. Quantification of the trace elements: will be  obtained using scanning micro PIXE in combination with a genetical survey. These results will indicate whether natal origin can be differentiated between spawning sites, or if the herring stock has a strong connectivity between spawning aggregations.