A new method for back-estimating fish catches shows a misreporting that can have severe consequences for marine ecosystems. Photo: I. Pettersson/Azote

Baltic Sea fisheries

One fish or two fish?

Consistent misreporting of fish catches in the Baltic Sea has severe consequences for marine ecosystems

Story highlights

  • Back-estimating fish catches, and comparing these figures with those actually reported by the fishermen, reveals consistent misreporting
  • Misreporting of catches can lead to fisheries policies that are poorly matched to the reality of the fish stocks
  • This in turn can have severe consequences for an already strained Baltic Sea ecosystem

A new study done by centre PhD-student Jonas Hentati-Sundberg and researcher Henrik Österblom reveals that misreporting of fish catches in the Baltic Sea is and leads to wrong estimates for fishing quotas. This in turn can have severe consequences for an already strained Baltic Sea ecosystem.

Counting backwards
The results of the study, which was recently published in ICES Journal of Marine Science, is based on a new method for back-estimating fish catches, and comparing these figures with those actually reported by the fishermen.

"Swedish fishers are required to report data about both catch and effort daily. We have looked at the records of these reports from 1996 to 2009 and compared them to data from our own model," explains Hentati-Sundberg.

The model shows how fishing effort and fishing capacity affects the estimation of fishing quotas. Even with conservative figures to make sure the estimates are not exaggerated, the authors found that there was a significant difference over certain years and that the catches fishers report were often different from the estimates from the model.

Request publication

Red fish or blue fish?
The study shows that misreporting has occurred both with regards to fish catch quantities and to the composition of the catch in terms of species.

"Over the study-period we see first a strong over-reporting of herring catches, followed by an under-reporting instead. This pattern corresponds to an imbalance that we see in the fishing quotas that were set at the time"

Jonas Hentati-Sundberg, author

Small pelagic fish, such as herring and sprat, are important parts of the food web in the Baltic Sea. Making sure their stocks are maintained at sustainable levels is therefore crucial for the resilience of the whole system.

Consequences of misreporting
Hentati-Sundberg consequently warns that misreporting in fisheries can cause poorly adjusted fishing quotas to be set.

"Fishing quotas are set in relation to an estimate of the total fish stock, and fish stock in turn is calculated partly based on the catches that fishers report," Hentati-Sundberg explains.

"Misreporting of catches can therefore lead to fisheries policies that are poorly matched to the reality of the fish stocks."

The study demonstrates how misreporting in fisheries affects our view of the ecosystem and skews our knowledge of it. The consequences of this are yet unknown, and Hentati-Sundberg suggests that a re-assessment of the trends in fish stocks, based on their model, could help shed some light on this.

Closing the gap
Hentati-Sundberg's research describes a fisheries system whose dynamics is largely driven by top-down management regulations.

"The transformation from an unregulated to a highly regulated and un-flexible social-ecological system can be tracked with historical data," says Hentati-Sundberg, who will continue developing methods and using long-term data to bridge this important knowledge gap.

Request publication

Related info

Citation

Hentati-Sundberg J., Hjelm J., Österblom H. 2014. Does fisheries management incentivize non-compliance? Estimated misreporting in the Swedish Baltic Sea pelagic fishery based on commercial fishing effort. ICES Journal of Marine Science. doi:10.1093/icesjms/fsu036

Jonas Hentati-Sundberg's research focuses mainly on fisheries in the Baltic Sea. He uses statistical methods to understand social-ecological interactions and long-term development of fishing fleets and fishing strategies.