KOMODO - Estimation of cormorant-induced mortality in western Baltic cod

The cod stock in the western Baltic Sea is in a historically poor state. The stock shows no signs of recovery, although fishing pressure has been low for years. The majority of juvenile cod produced by the few remaining parents do not seem to make it to adulthood. Cormorants are once again widespread along the coasts and also eat cod, especially smaller specimens. How much cod do the cormorants eat and what role do cormorants play in non-recovery of the cod stock in the western Baltic Sea?

What kind of fishing experience do you want?

Fishing for salmon in the Baltic Sea is not only a popular recreational activity, but also an important industry. By improving the protection of weak salmon populations in the Baltic Sea, it was decided in 2022 to limit the harvest of salmon to fish without adipose fin (stocked fish). At the same time, a bag limit of one salmon per day per angler was introduced. But what do anglers think of these new regulations and which fishing experience would they prefer?

Acoustic telemetry on cod and flatfish in the Bay of Lübeck

How exactly do cod and flatfish live and survive in the brackish water environment of the Baltic Sea? We equip fish with transmitters so that they can tell us about their lives - and we better understand how they behave under changing environmental conditions.

Processing of German fisheries data for use in stock assessment of commercially used stocks in the Baltic Sea

Stock assessment involves fisheries data from all countries around the Baltic Sea. To ensure that the different national fisheries data can be smoothly merged into one single data set, sophisticated preliminary work from each fishery research institute is required – also from us.

Coordination of data collection from commerical fisheries in the Baltic Sea

The Thünen institute of Baltic Sea Fisheries does not only data about fish stocks in the Baltic Sea, but is also involved in international cooperation, e.g. with the EU and other Baltic Sea countries.

From a fish sample to stock assessment

Population models want to be fed with numbers of fish caught. However, at the landing site the fisher only report the landed weight, not the numbers of landed fish. Our expertise is to convert landing weights of the fisheries into numbers of herring or cod to provide the stock assessment models with the appropriate data feed.

Age validation studies on wild fish: basis for accurate age determination

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 interpret the ring structures in their ear stones (otoliths). To verify the relationship between the lighter and darker rings in the otoliths of fish and the true fish age, we carry out age validation experiments on wild fish.

What is the catch of gillnet fishermen?

The gillnet fishery is a central pillar of the German fisheries in the Baltic Sea. We regularly sample the catches and by-catches on board of gillnetters.

Fisheries research surveys: Monitoring of fish communities

Eine Seefahrt, die ist lustig… A research vessel cruise is mainly hard work onboard at sea, according to a fixed station grid and a tight schedule, under almost any weather condition. Specialized knowledge, routine and perseverance are required here.

Improved calculations with fish data

A fish species forms different populations in its distribution area. These populations are called "stocks" in fisheries biology. The fish stocks of a species differ considerably in part because they are adapted to the particular environmental conditions of the marine area in which they live. We have more information for one stock and less for another, and stocks can have different levels of productivity. To account for these differences, we try to adapt population models to individual stocks in order to improve catch predictions.

Fishes of the Baltic Sea - counted once yearly

What is the status of a commercially used fish stock in the Baltic Sea – and how does it develop? Given that most stocks are “shared stocks”, this question is raised annually and can only be answered in cooperation with other Baltic Sea countries. The answer is highly important for both fishing industry and anglers, and conservationist.

Science onboard of German fishing vessels: Catch sampling in the Baltic Sea

Sampling the commercial fisheries of the Baltic Sea is one of our main tasks. For this purpose, our scientific observers regularly go to sea with fishermen to measure the catch on board. On land, we process unsorted catch samples from the fisheries to collect biological parameters like maturity and age.

Baltic Sea Fisheries: A bank for our data

During our surveys and other investigations we collect a variety of data. To save these data so that we can find and work with them, we need a database, which is not available in a shop. Therefore the Institute of Baltic Sea Fisheries, in collaboration with the two other Fisheries Institutes in the Thünen Institute, develops a database that fits our needs.

Recreational fishing in Germany

German marine angling program

Next to the commercial fishery the recreational fishery plays an important role concerning the removal of biomass from fish stocks. For certain species recreational fishery catches can have a significant share of the total landings. In addition to its importance for the scientific stock assessment recreational fishery has particular commercial relevance.

Agent-based modelling of angler behaviour

The project contributes to a better understanding of the behaviour of recreational anglers and their responses to management decisions as precondition for sustainable recreational fisheries management.

Population structure of cod and plaice in the Baltic Sea

In the Baltic Sea, the stocks of only two demersal fish species - cod and plaice - have so far been regulated by catch quotas. The catch quotas determine the exploitation intensity of individual fish stocks. The goal is to achieve maximum sustainable yield from a stock. If stock allocation is unclear, there is a risk of under- or over-exploitation of neighboring stocks.

Otoliths make the difference

Where do you come from? What is your stock? If the fish had an identification card with information on the place of birth, this could be easily answered. Unfortunately, we have to apply significant effort to draw this secret from the fish – using their ear stones.

Tagging Baltic Sea cod (TABACOD)

How old is a fish, and how fast does it grow? These simple questions are almost impossible to answer for eastern Baltic cod, with massive consequences for fisheries management. A large-scale international tagging project may be the key to solving this problem.

Catch and release mortality of eel

European eel is an important target species for european anglers. Catch restictions and minimum landing sizes lead to high releases of recreational caught eel.

Mortality of cod released by anglers in the Baltic Sea

Previous investigations showed that a significant number of cod caught by anglers has not reached the minimum landing size of 38 centimeters and have to be released. About 45 to 70 % of all individuals caught from boats and charter vessels are undersized.