Does unreported catch lead to overfishing? / by Francisco Blaha

Is not the most know fact that the key element of IUU fishing in our region is not the Illegal fishing (as vessels without a license) but is Unreported (which is either; under-reporting – declaring less from what the caught, and/or miss - reporting declaring different species from what was caught). Besides the economic impact of unreporting, there are downstream consequences since you will never take the right management decisions with the wrong data.

 verifying reporting the hard way... one by one in the Solomons

verifying reporting the hard way... one by one in the Solomons

One area that I always assumed that would be immediately benefit for totally accurate reporting is stock assessment and modelling, since it would immediately impact the outcomes of the assessment, yet this recent "Fish and Fisheries" paper by Merrill B Rudd & Trevor A Branch somehow challenges that concept, to refocus it on the trends more than the actual figures. While I think in principle this paper was a response to the recent drive into catch reconstructions, I like the concept of the trend focus. It makes me think… and I like thinking.

Below is the abstract, but as always read the original!

Catches are commonly misreported in many fisheries worldwide, resulting in inaccurate data that hinder our ability to assess population status and manage fisheries sustainably.
Under-reported catch is generally perceived to lead to overfishing, and hence, catch reconstructions are increasingly used to account for sectors that may be unreliably reported, including illegal harvest, recreational and subsistence fisheries, and discards.
However, improved monitoring and/or catch reconstructions only aid in the first step of a fisheries management plan: collecting data to make inferences on stock status. Misreported catch impacts estimates of population parameters, which in turn influences management decisions, but the pattern and degree of these impacts are not necessarily intuitive.
We conducted a simulation study to test the effect of different patterns of catch misreporting on estimated fishery status and recommended catches. If, for example, 50% of all fishery catches are consistently unreported, estimates of population size and sustainable yield will be 50% lower, but estimates of current exploitation rate and fishery status will be unbiased. As a result, constant under- or overreporting of catches results in recommended catches that are sustainable.
However, when there are trends in catch reporting over time, the estimates of important parameters are inaccurate, generally leading to underutilization when reporting rates improve, and overfishing when reporting rates degrade. Thus, while quantifying total catch is necessary for understanding the impact of fisheries on businesses, communities and ecosystems, detecting trends in reporting rates is more important for estimating fishery status and setting sustainable catches into the future.