A new study by Jonas Hentati-Sundberg and Henrik Österblom at the Stockholm Resilience Center together with Joakim Hjelm from the Swedish University of Agricultural Sciences reveals that misreporting of fish catches in the Baltic Sea is and leads to wrong estimates for fishing quotas. Which could have severe consequences for an already strained Baltic Sea ecosystem.
The results of the study is based on a new method for back-estimating fish catches, and comparing these figures with those actually reported by the fishermen. The study is based on daily catch and effort reports made by Swedish fishermen from 1996 to 2009.
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.
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. The researchers found, for example, a strong over-reporting of herring catches at the first part of the study period followed by under reporting in the second part. A pattern corresponding to the imbalances in fishing quotas set during this time.
As 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. Continued misreporting can cause poorly adjusted fishing quotas to be set and thus 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.