April 6, 2023 — The following was released by the Science Center for Marine Fisheries:
Researchers with the Science Center for Marine Fisheries (SCEMFIS) are continuing their efforts to provide the latest and most up-to-date research on Atlantic surfclams, and to support the sustainable management of the surfclam fishery. A recently published study looks at how current surfclam management deals with uncertainty, and whether this uncertainty affects future sustainability.
The surfclam fishery is sustainably managed; it’s not overfished and overfishing is not occurring, nor have either of these issues arisen since the first fisheries management plan was adopted. The Mid-Atlantic Fishery Management Council (MAFMC) in collaboration with the surfclam fishery has implemented a conservative catch limit on the fishery, but significant uncertainty remains over some key estimates, such as the natural mortality rate and the spawning stock biomass, which measures the reproductive capacity of the surfclam population. Both are key indicators of the health of the stock. The study evaluates the likelihood that this conservative management strategy still could lead to unsustainable fishing.
The study, published in the Journal of Shellfish Research, uses a series of statistical simulations to model how uncertainty about the stock affects the risk that the stock may be overfished with current quotas in place; whether the current risk policy is appropriate; and the extent to which the future economic viability of the surfclam fishery is affected.
To do this, the study used the stock assessment models from the MAFMC’s surfclam assessment, and ran simulations with different values for natural mortality and the steepness of the stock-recruitment relationship, which measures how the rate of recruitment in a fished population reacts when the spawning stock is reduced. The study then examined whether any of the range of values used, when run through the assessment model, would lead to overfishing of the stock. This analysis also examined how harvest levels would affect surfclam density, a critical factor in maintaining a viable surfclam fishery.
Through these simulations, the study finds that the existing surfclam population is “robust to overfishing across a variety of management strategies,” and that “the surfclam stock is unlikely to become overfished or experience overfishing from currently implemented management strategies”.
Economically, the study found that “the fishery is not constrained by the current quota and unlikely to pursue fishing at such volumes that would decrease profit margins,” and the conservative quota cap adopted by the industry “has likely contributed to the sustainability of the Atlantic surfclam stock.”
While making these conclusions, the study also raised concerns about the effects of climate change on these estimates, and that the rapidly warming northwestern Atlantic may have a future impact on surfclam population dynamics. Because surfclams are highly sensitive to rising temperatures, this is a factor that may influence uncertainty in future assessments.