External Organisations

  • Lund University, Sweden
  • Municipality of Viborg, Denmark

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This project supports the research area fish migration. In many shallow lakes cyprinid fishes like roach (Rutilus rutilus) and bream (Abramis brama) aggregate in inlet- and outlet streams during winter. Up to 85 % the bream and roach may leave the lake and individuals may stay out of the lake for periods up to 7 months during winter. However there is interannual variation in the part of the population that participates in this so called partial migration. Since 2005 DTU Aqua has investigated patterns of seasonal migrations of cyprinids in three Danish lakes and thereby, in combination with international collaborators, furthered our knowledge on the behavior of some of the most common fish species in Denmark. This has resulted in numerous publications/reviews about partial migration. By expanding the investigation period to include 2011-2016 we have increases the length of the time series leading to a better understanding of the annual variation in migration patterns. In addition we included the effects of seasonal prey migration on top predator fitness in the study. Top predators such as pike (E. lucius) are important species in recreational fisheries, and in order to optimize fisheries management its crucial to understand the biology of these predators, Since the migrating cyprinids are important prey for the pike and since previous results have shown that pike do not follow the prey into the stream, the migration of cyprinids are likely to affect seasonal patterns of predator fitness. Overall, this project increases our knowledge on fish behavior and fish population dynamics in lakes and thereby expands our tool box for management of lacustrine fishes. 

During the project period focus has been on three areas (the last two as part of a PhD project with deadline in 2017):

Mechanisms behind partial migration
The risk of predation from birds and fish as well as the distribution of feeding resources are two very likely explanatory components in spatial ecology of fish in general and  partial migration in specific. DTU Aqua have published several studies and reviews focusing on these as well as other mechanisms involved in partial migration such as body morphology, sex, individual variations in boldness and temperature 

The influence of cyprinid partial migration on top-predator pike feeding dynamics
Pike feeding patterns and prey availability in a number of open and closed lakes are monitored from early fall to late spring. This could reveal that pike in open lakes where prey abundance fluctuate during season require more management attention i.e. due to restricted growth and/or increased cannibalism in periods with low prey abundance. 

Migration between neighboring lakes
Two of the three focal lakes in which we are monitoring seasonal migrations are situated only 3 km apart and connected by a small stream. So far it has become obvious that from time to time large amounts of fish move from one lake to another. By continuing to pit tag and monitor fish migration we are likely to observe more of these mass migration events, which in turn facilitate a better understanding of why and when these mass migrations occur. Clearly, the level of fish exchange between neighboring lakes is an important factor to consider when it comes to management of lakes. 

The project is coordinated by DTU Aqua.



  • Research area: Freshwater Fisheries and Ecology
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ID: 2286875