Unraveling the Mystery of Southern New England’s Cod

The year was 2003. I was out hiking with my dad, and he asked me if I wanted to see a rare fish for the first time. He told me about how he had seen this monster of a fish while bird hunting in southern New England, and he wanted to share this rare opportunity with me. Little did I know that this day would forever change the course of my life.

In the fall of 2012, a large and mysterious rock formation was discovered in the woods of southern New England. The formation, dubbed the Cod Rock, features a tremendous collection of carved rocks, leading the casual observer to believe the rock formation was the site of some sort of ritualistic ceremony. Reporting on the discovery was sparse, and the origins of the rocks was not reported.

Although the plight of Atlantic cod in the Northeast is well known, the rise of fishing in southern New England has puzzled scientists but excited anglers. It is now common knowledge that Atlantic cod is in bad shape, dramatically so. According to the 2019 stock assessments, stocks in the Gulf of Maine and on Georges Bank remain overfished, and the groundfish fishery north of Cape Cod has shifted to haddock and pollock. But if you drive a little further south, a different picture emerges. Over the past decade, cod has gained a foothold in the waters off Block Island. During the winter months, forage and spawning stocks turn into spawning stocks, and anglers come from far and wide to travel in party and charter boats from Point Judith and Montauk in search of the magnificent prey of the whitefish. No, not the 40 and 50 pound mackerel of years past, but healthy, marketable fish with enough 20 pounders to keep things interesting. It’s a pleasant surprise to fishermen, but a mystery to fisheries scientists, especially since the area from New Jersey to Rhode Island is the southernmost distribution area of Atlantic cod. Due to the warming of coastal waters, cod in these southern areas are expected to be particularly vulnerable to the effects of climate change, but this fishery is resilient and even getting stronger. Adding to the confusion is the fact that federal trawl surveys rarely record cod in this area and that, although cod are managed in this area as part of the spawning stock on George’s Bank, the fishery here outperforms other parts of the management unit. New research is helping scientists and managers learn more about the population dynamics of this southern cod and whether it is a distinct and self-sustaining population. New research suggests that southern New England cod, like this well-fed specimen from Kevin Chung, could form their own breeding population. Randomized trials : Larval cod in Narragansett Bay When I was a student at the University of New England in Maine, I found out that the cod in the Gulf of Maine were in very poor condition due to a combination of overfishing and climate change, says Joe Langan, a doctoral student at the University of Rhode Island Graduate School of Oceanography (URIGSO). Imagine his surprise when he learned at the start of his doctoral studies in 2015 that the local cod fishery was booming that winter. The party boat fishermen limited the catch and since all the herring were caught offshore, some even caught cod from shore. The fishermen said it was the best fishing since the 70s, but all I could think about was: You gotta be kidding me! During graduate school, Langan focused his research on winter flounder, but he couldn’t ignore cod. We have been researching larval winter flounder in Narragansett Bay, but we have also continued to catch larval cod as far away as the city limits of Providence. This discovery prompted Langan and colleagues to pause their research on winter flounder and examine historical sighting and fishing data to better understand the life history and abundance of Rhode Island cod. Joe Langan, a doctoral student in the Graduate School of Oceanography at the University of Rhode Island, has found that the number of juvenile cod caught off the coast of Rhode Island in a given year largely predicts commercial and recreational catches two years later. word-image-2704 The team reviewed larval fish catches and trawl surveys conducted by the Rhode Island Department of Environmental Management (RIDEM) and URIGSO. Larval surveys have been conducted sporadically in Narragansett Bay since 2001, but trawl surveys have been conducted in Rhode Island waters since the late 1950s to sample juvenile (less than 8 inches), juvenile (8-15 inches), and adult (greater than 15 inches) cod; these surveys provide a rich collection of data for the research team. The scientists then modeled how environmental conditions such as temperature and precipitation can affect cod stocks. To understand the relationship between the survey results and what anglers see on the water, the research team also looked at recreational and commercial catch data in the region collected by NOAA Fisheries’ Marine Recreational Information Program (MRIP) and NOAA Fisheries’ Vessel Trip Reporting (VTR) program. Facts and Figures Langan and colleagues found that the number of juvenile cod found in trawl fisheries has increased since 2002. In addition, they found that the number of juvenile cod in a given year was a great predictor of commercial and recreational catches two years later, when these fish have reached juvenile size. For example, everyone remembers the 2011 Rhode Island cod bonanza, which was preceded in 2009 by the largest abundance of juvenile cod in the 1979 RIDEM trawl survey. This indicates that the fish caught are juveniles located in the same area and not adults migrating from other locations. In other words: The research team’s findings are consistent with what anglers have observed on the water over the past 20 years. We don’t know exactly why they’re back, but they are back, and all data sources confirm it, Langan says. It wasn’t just being spoiled at a young age that made it possible to tell this story. We observe all stages of Atlantic cod off the coast of Rhode Island: first-hatch larvae, older larvae, juveniles, young fish and adults. That’s strong evidence that these fish in southern New England likely form their own reproductive population, Langan said. He notes that there is evidence that some of the larvae found in the area were imported from the western Gulf of Maine; however, given the presence of newly hatched larvae in Narragansett Bay, the research team is convinced that at least some of the reproduction is local. Although fishermen have enjoyed great cod catches in southern New England in recent years, the future of this fishery is in question as waters continue to warm due to climate change. word-image-2705 Dr. Langan’s findings of a self-sustaining cod stock in southern New England are consistent with the results of a stock structure study conducted by NOAA Fisheries and Fisheries and Oceans Canada, which identified five different spawning stocks, including one in southern New England. The study also complements a growing body of research in morphometrics (analysis of the relative shape of fish), mark-making and genetics, which suggests that southern New England cod may be different from other species. It remains to be seen how these new studies can be reconciled with the current management of the two Atlantic cod stocks (Gulf of Maine and Georges Bank). Climate change Langan’s study found that the situation for cod in southern New England was not good. We found a strong negative correlation between bottom temperature in February and the number of juvenile cod, he says: The higher the temperature, the smaller the number of young cod. And six of the 10 warmest Februarys ever recorded by the URIGSO trawl survey have occurred since 2002, when cod stocks began to increase. As the water warms further, adult cod may find it more difficult due to a combination of unusually warm fall temperatures and an increase in competitors such as black sea bass. For now, however, cod appear to be holding their own in the region, offering a glimmer of hope for this troubled species and giving managers a chance to revisit the assumptions used to try to maintain and restore cod stocks in a warming ocean.