The science of sustainable seafood, explained

Fishery management is composed of small, concrete actions—which ones are best?

Fishery management is a catch-all concept encompassing a collection of smaller, defined fishing regulations. As a whole, it is continuously evaluated: e.g. FAO produces a biennial report on the status of world fisheries; NOAA produces an annual status of stocks for congress and the American people. Missing, however, has been an evaluation of the smaller regulations within fishery management. There are many levers that managers can pull to alter fishing pressure—which ones are most effective? What tool should managers reach for in the fishery management toolbox? A new paper, Melnychuk et al. 2021, evaluates those specific regulations to determine which are best at contributing to effective fishery management systems.

What are examples of fishery management regulations?

In simple terms, fishery management regulates the amount of fishing pressure on a population of fish. The goal is to maintain fish stock biomass within a sustainable range or rebuild depleted populations back to healthy levels.

In the paper, the authors break fishery management down into two basic types: stock-level regulations and national or international policies. Stock-level regulations target specific fish populations and include basics like evaluating and monitoring the stock’s biomass, but also complex ones like implementing a quota-based catch system. National or international regulations are large-scale, beyond individual stocks, like claiming an exclusive economic zone (EEZ) or having a national policy to govern fisheries. For example, the Magnuson-Stevens Act governs fisheries in the U.S., while the Common Fisheries Policy does so in the EU.

Fishery management over the past 50 years

Researchers traced the regulatory and population history of 288 fish stocks (representing 30% of reported catch) to determine how regulatory actions interacted with stock status changes. The scientists built an index of stock-level regulations and national-level regulations to trace the management “intensity” of both over time. The figure below shows how both stock-level and national/international management intensity has increased over the last 50 years.

Researchers found that, by far, the most impactful stock-level management action was implementation of a rebuilding plan—a formalized and dramatic reduction of fishing pressure aimed to allow an overfished stock to recover quickly. Rebuilding plans were chronicled as a separate measure throughout the paper because they are turned on or off as needed each year, whereas the other measures are usually permanent once put in place.

Figure 1 from Melnychuk et al. 2021.
This is Figure 1 from Melnychuk et al. 2021. Purple represents rebuilding plans, blue is stock-level management measures, and orange is national/international-level management levels. On the top right, the different dashed blue lines that compose the solid blue stock-level management intensity index and the dashed orange lines that compose the solid orange national/international-level management index. The top-left graph represents the proportion of the 288 stocks that have had the measures implemented over time. A timeline of the intensity deepening over time is represented in the lower graphic. From Melnychuk et al. 2021.

The above figure shows how fishery management has changed over the last 50+ years. It has generally gotten more intense (i.e. better) over time, but the increasing need for rebuilding plans shows it has not been good enough (until recently). The figure follows the simplified trend of global stock status: Fisheries developed in the 1960s-1970s, matured and were often overfished in the 1980s-1990s, then management intensified from the 1990s-present day and fish stocks have been steadily recovering. The management history from this paper pairs well with Hilborn et al. 2020, a paper that traced the biomass of these same fish stocks and found most to be healthy or recovering, indicating that overfishing of those populations has been curbed.

Rebuilding plans are highly effective, but not the goal

In the absence of regulation, society incentivizes the overexploitation of shared, common-pool resources, like carbon emissions exploiting our shared atmosphere. Fisheries developed in a similar way, where little to no regulation led to overfishing. However, rebuilding plans have been an effective management tool for ending overfishing and improving population levels. Mike Melnychuk, the lead author on the paper explains, “when fish stocks are depleted as a result of overfishing, an emergency measure entailing stricter regulations can be implemented. When these rebuilding plans are implemented, they tend to immediately decrease fishing pressure and allow stock abundance to recover.”

Figure 4 from Melnychuk et al. 2021
This is Figure 4 from Melnychuk et al. 2021. The top panel shows how fishing pressure (U/UREF) varies over time before and after management measures are implemented. You can see how effective a rebuilding plan is for quickly reducing fishing pressure. The bottom panel shows how fish stock biomass (B/BREF) changes before and after management measures are implemented. You can see how a much faster a rebuilding plan improves biomass. The ratio of both fishing pressure and biomass is considered sustainable between 0.8-1.2 by FAO.

Rebuilding plans are the most effective way to rebuild a depleted stock, but the goal should be not to need one, Melnychuk says, “If fisheries management systems are strong enough, then overfishing can be avoided and large sustainable catches can be harvested annually, rendering emergency measures like rebuilding plans unnecessary.”

However, non-emergency management is complex. It’s hard to measure which specific management actions are most impactful, but evidence points to a cumulative effect—the more management actions, the better. “As fisheries management measures are implemented, fishing pressure is usually reduced toward sustainable levels and stock abundance usually increases toward management targets” said Melnychuk. He compares fishery management to the “swiss-cheese” model of preventing the spread of disease—each measure has holes in it, but layered together adds up to comprehensive protection.   

The capacity caveat

When reporting on any global fish stock dataset, the caveat is that data availability is often limited by management capacity—the fish stocks with limited information about their biological status tend to be the same stocks with weaker management and enforcement. This paper included 288 stocks—an impressive undertaking (and certainly progress), but representing just under a third of all reported catch (to say nothing of unreported catch).

Scientific capacity allowed for this data to be collected, enforcement capacity allows the regulations to do their jobs. Without these kinds of management capacity, fisheries are left to develop on their own, leading to overfishing.

The good news is that we know how effective rebuilding plans and layering regulations will be to usher those stocks toward sustainability once capacity is developed.

Max Mossler

Max Mossler

Max studied environmental perception & policy in grad school. He thinks a lot about how other people think about the planet. He is the managing editor at Sustainable Fisheries UW.

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