Data requests may be made to Scott Olszewski, RIDEM Marine Fisheries Section, scott.olszewski @dem.ri.gov or can be found on the URI Graduate School of Oceanography Fish Trawl Survey website.
Due to the long history of RIDEM’s coastal trawl surveys, these records are an excellent source of data to track long-term trends in fish populations. One valuable observation has been a shift from demersal to pelagic species over time, most likely due to warming water temperatures along with an increased presence of species that are typically found in more southern waters, which is possibly evidence of a changing ecosystem.
Trends in Coastal Fisheries
As the long-running coastal trawl surveys have shown, Rhode Island’s coastal fisheries have shifted dramatically in the last 40 years from demersal (bottom-feeding) to pelagic (open water) fish species. There are a number of theories on what is causing this change including shifts in the species of fish that fishermen are targeting, changes in the predator-prey complex, and climate change. This shift may cause unpredictable future changes in marine ecosystems in Rhode Island. For example, the shift from demersal to pelagic fish species may have future impacts to species diversity and prey availability. The demersal species that are decreasing in Rhode Island waters tend to specialize in eating mollusks and crustaceans, while the pelagic species that are increasing tend to be more opportunistic in their feeding habits and do not limit their diet to mollusks and crustaceans. So the shift in fish species could lead to a change in the populations of demersal prey items, which could ultimately impact other fish populations. The long-term effects are not known, making monitoring essential.
There has also been a shift from traditional species found in Rhode Island, which are considered to be northern species, to higher abundances of more southern species. This shift is likely tied to changes in ocean temperature caused by climate change. It is unclear how this may ultimately affect the Rhode Island fisheries, as some valuable species may decline (e.g., American lobster, Atlantic cod, and silver hake), but other commercial fish stocks may enter the area (e.g., Atlantic croaker, black sea bass, butterfish, scup, and summer flounder). Even outside of long-term impacts, shifting fishing behavior and changing requirements in fishing gear may cause short-term challenges for fishermen, especially in terms of capital investment and catch limits that may be better tailored to previous distributions of fish species.
The relationship between human activities, interspecies interactions among fish, and climate are complex, and the trajectory of fish populations cannot be predicted with 100% certainty. One species might be negatively impacted by warming waters, but positively impacted by a greater abundance of its prey species. There will likely be winners and losers in this battle for ecosystem balance which makes maintaining a long-term monitoring effort invaluable to our ability to track fish population trends, and will continue to play a critical role in determining how these changes might play out in the future.