Towards length-optimized fishing in the Baltic Sea

The cod population in the southern Baltic Sea is beginning to approach levels found in the 1980s, partly due to successful breeding, reductions in illegal fishing and better management. However, the individual size of the Baltic cod is relatively small. The Swedish Cod Fishermen’s Producers’ Organisation (STPO) is working with researchers from the Institute of Marine Research at the Swedish University of Agricultural Sciences to develop sustainable cod fishing practices in the Baltic Sea, with the aim of improving the cod’s average size.

Large, well-developed cod are valuable to the fishing industry and to the Baltic’s ecosystem. Increasing the average size of the cod could probably be done in a variety of ways, but a small increase in the caught size would be a more effective use of the population. This is called length-optimised fishing and is based on making the most of the cod’s growth potential. This could lead to the cod population’s size structure becoming more as it originally was, improving the internal dynamics of the ecosystem and, by extension, also benefitting the fishing industry, both through increased catches and the catch having a higher value.

Purpose and aim
This project will develop fishing practices that allow the cod to grow to a larger size and demonstrate that these methods are practically applicable to normal activities. Together, fishermen and researchers will find ways of developing cod fishing in the Baltic Sea, thus achieving good continuing development of the population. The aim is that this cooperation can function as a model for future partnerships between fishermen and researchers.

The project is expected to lead to a strategy for how the Baltic fishing industry can change its fishing methods. In addition, the project will provide increased understanding of factors that influence the growth of cod in the Baltic Sea. If the project is successful it may also be launched for other fisheries in the Baltic Sea.

The project has two phases. The first one will investigate the conditions that may influence the size of the cod. Studies include:

  • Biological conditions relating to growth and why cod often have a low bodyweight. The Institute of Marine Research will analyse data on food availability and other environmental factors.
  • Conditions for changing the size structure of cod catches, while retaining profitability.
  • An analysis of current management and fishing regulations to see the extent to which they counteract changes to fishery methods.

The results from phase 1
The first phase ended with a seminar between fishermen and researchers on December 13, 2013. Read more about the seminar here.

The results of phase 1 are quite unexpected and means that the project is likely to come up with different conclusions than first expected. It turned out that the theoretical work that was supposed to be the basis for the project * was incorrect and the project has now published a correction **.

*(Froese et al., (2008) "Size matters: How single-species management can contribute to ecosystem-based fisheries management" Fisheries Research, 92(2–3): 231–241.)
** (Svedäng H. 2014. Comments to Froese et al. (2008): Size matters: Ne quid nimis, Fisheries Research, 149:74–75).



Project status

Start: 2013-03-01
End: 2014-03-31

Project manager

Staffan Larsson, Sveriges Torskfiskares Producentorganisation (STPO)