DCF (Data Collection Framework): Age validation studies on Baltic round- and flatfishes
We would like to know the age of a fish as precisely and accurately as possible. Since fish do not swim around with an identification card, we have to use the partly imprecise interpretation of ring structures in their ear stones (otoliths). To verify the relationship between structures in ring formation and true fish age, we carry out age validation experiments on wild fish.
Age validation is a central pillar for the understanding of the biology of fish stocks. Presently, the age determination of many fish stocks is subject to significant levels of uncertainty despite numerous efforts in the past. Accordingly, the predictions of the stock assessment are uncertain.
Therefore, we initiated catch-release experiments. Thereby we want to validate the age of abundant Baltic roundfish species like cod and whiting as well as flatfishes such as plaice, flounder or turbot. We analyse the ring structures the fish has produced between release and recapture. Thus, in the future we can improve the age determination for these fish species and the quality of input data to populations models and of ecological studies.
In a pilot study we identified tetracycline as the most appropriate chemical to mark the otoliths for an age validation study. We are catching live fish to mark them internally (with tetracycline as a time tag inside the otoliths) and externally (with a numbered so-called spaghetti tag for the detection by fishers and anglers upon recapture). Then we hope and wait that the marked fish are recaptured and returned as whole fish for further analysis. A reward is paid for each recaptured fish when the whole individual fish is returned.
9.2013 - 12.2027
Project status: ongoing