New England Fisheries, Science
Innies-And-Outies: New Science Reveals Closed Area Effectiveness for Atlantic Cod
With NOAA poised to review the New England Fishery Management Council’s Omnibus Habitat Amendment – and in the face of some fishermen who claim that marine protected areas within the cold waters off New England show no benefit, and others that claim the new sector quota system eliminates the need for closed areas all together – a timely paper was recently released by two New England-based marine scientists, Dr. Graham Sherwood and Dr. Jonathan Grabowski. As the proposed habitat amendment proposes some major reductions to existing protected cod habitat, we hope NOAA is paying attention.
“Couch potato cod” and other closed-area benefits
The paper, with the lengthy (yet informative) title: “A comparison of cod life-history parameters inside and outside of four year-round groundfish closed areas in New England, USA” (ICES Journal of Marine Science) concludes that New England fishery closed areas have indeed had net positive results on cod biology.
Cod caught in three out of the four studied closed areas – the Cashes Ledge Closed Area and the two large closed areas on Georges Bank (Closed Area I and II) – were consistently older, lengthier, and exhibited stronger growth characteristics than cod caught outside the areas. The cod also tended to have heavier bodies, leading some to refer to these fish as “couch potato cod.”
More older cod bodes well for the future of the population and future fisheries
All four areas not only consistently produced older fish than the fish caught outside, but the median-age cod caught in the Cashes Ledge and Jeffreys Ledge closures and in Closed Area I were 50 percent older than those caught outside. Furthermore, the two areas farthest from shore—Closed Area II and the Cashes Ledge Closed Area – had cod populations with the most complete age structures, important for productivity of the fish.
The paper also references the scientifically-documented benefits of the presence of older fish in a population – specifically old, large female cod – for improving the resiliency and productivity of the overall cod population. Yet, as the authors note, there are “no [management] measures in place explicitly to ensure the survival of old/large females.” They point to area management approaches, including closed areas, as perhaps the only effective management solution for providing protection for these larger, more mature cod that are so critical to cod’s future.
These positive results are particularly remarkable for the Cashes Ledge Closed Area, given that after centuries of fishing effort, the area had only been closed to year-round commercial cod fishing for 5-7 years when the study’s cod sampling was done. In addition to the obvious refuge benefits that a large closed area provides to the depleted cod populations, the authors point to literature on the ecological improvements that have been observed in many of these closed areas that may also “translate into advantages for cod” such as protecting benthic biodiversity.
This is good news, but should not be considered an argument to reopen the closed areas: one paper referenced by the authors concluded that closed area benefits to predatory fish like cod might take as long as 40 years to reveal themselves.
The paper’s authors properly caution about the need for further research on the subject, but even so, this important paper led me to four conclusions:
First, MPAs in colder waters like those in New England do appear to benefit fish, particularly one of our most iconic and overfished species – Atlantic cod.
Second, proposals to open up most of the closed areas on Georges Bank, as currently proposed in the New England Fishing Council’s Omnibus Habitat Amendment – at a time when Atlantic cod in New England seem to be at their lowest estimated levels in the region’s history – are irresponsibly short-sighted.
Third, if a recreational fishery for cod is going to be allowed in these closed areas, there should be a requirement that fishermen release the largest fish so these critically important animals can continue to support productivity in the stock.
Fourth, quotas alone are not enough and never were. Fish live in a broader marine ecosystem, and until managers start protecting the functionality of that whole system – with effective area-based and ecology-based management actions like large marine closures – New England will be destined to continue to chase one stock crisis after another.