Interdepence of perch and pikeperch (KB-14-012-053)

The project could not be completed due to capacity problems.

Many fish stocks in lake Ijssel and Marker are suffering from depletion, including perch and pikeperch. Stock management is single stock oriented, but there is strong interdepence between key commercial stocks. Is the recovery of the separate stocks influenced by the dynamics of the other stocks? Should management first focus on the recovery of a subselection of the stocks?

Healthy fish stocks are a requirement under GES and similar fresh water legislation. Understanding how to achieve a healthy stock levels is crucial. One aspect of this is understanding the interactions between the stocks of interest. If two important stocks will negatively influence each other’s recovery, management needs to be adapted accordingly.

In this project a theoretical model for pikeperch and perch that takes their intraguild predation (IGP), cannibalism and their shared food source smelt into account will be developed. We will investigate how the population dynamics are interdependent, and how visibility conditions (via the attack rates) influence the IGP interactions. Results will be compared to biological data for the two lakes (which have different histories in visibility development) will be published in a peer reviewed journal.