September 27th, 2016 — Each day in fishing communities around the world, not every fish is counted. This happens in part because of illegal fishing, poor or incomplete surveys and discarded fish from commercial operations.
Recording how many fish are caught is one important requirement to measure the well-being of a fish stock — if scientists know the number of fish taken from the ocean, they can adjust management of that fishery to keep it from being overfished. Missing catch data, however, are rampant, causing concern that fisheries around the world are overfished.
A new study by University of Washington scientists finds that in many cases, this isn’t true. Specifically, misreporting caught fish doesn’t always translate to overfishing. The study was published online this month in the journal Fish and Fisheries.
“While quantifying total catch is important for understanding how much is removed from the system, it is possible to manage sustainably even if we don’t know those numbers,” said lead author Merrill Rudd, a UW doctoral student in aquatic and fishery sciences. “This paper shows there are some situations where, just because there is unreported catch, it doesn’t mean we are overfishing.”
The researchers modeled five different misreporting scenarios on a simulated fishery: complete reporting of catch numbers, constant over-reporting, constant under-reporting, increasing reporting rate over time and decreasing reporting rate over time. They found that in cases where misreporting was constant, the fish population could still be managed sustainably over the years because misreporting was proportional each year.
But in cases where misreporting increased or decreased year to year, those fisheries were found to be over- or under-fished.
In other words, the catch reporting trends — not the specific numbers of fish caught — are the most critical elements to consider when trying to understand a fishery’s overall status, the authors said.