Scientists Study Climate’s Role on the Impact of the Long Island Sound Fishery

For over a decade scientists and resource managers at the Connecticut Department of Energy and Environmental Protection have noticed a trend in its annual Long Island Sound Trawl Survey: species of fish that favor warmer water temperatures are increasing, while fish that favor cooler temperatures are decreasing (see LISS climate change indicators). In addition, temperature trends recorded in the

Summer flounder, or fluke, at top, is faring well in Long Island Sound, while the population of winter flounder, below, is declining (see story below).

Summer flounder, or fluke, at top, is faring well in Long Island Sound, while the population of winter flounder, below, is declining (see story below).

CT DEEP Water Quality Survey since 1991 and continuous temperature records taken at the Millstone Power Station intakes since 1976 show that water temperatures in the Sound have increased significantly.  In 2016, a Long Island Sound Study-New York and Connecticut Sea Grant research project was  completed that puts together all available physical and biological data to build a model of the Sound’s climate from the 1970s to the present with the goal of better documenting these past changes and as a tool to predict what may be coming in the future.

The strength of this model is that it was built using a methodology called ‘hindcasting’ – judging the ‘skill’ of the model output in matching known physical and chemical measurements from past events. Once the model could predict the past,

it was then used to forecast the most probable future conditions if climate change continues. First, the researchers identified significant correlations between increases in temperature and the observed shift in fish populations. They also identified the principal driver of changes to the Sound’s physical environment as atmospheric forces in the Pacific and over Alaska that control the path of the jet stream.  An index of these Pacific events explained 80 percent of the change in the abundance of warm tolerant fish species in the Sound over the past decades. The model was then used as a forecasting tool to simulate the effects of climate on the Sound’s physical environment and marine resources if carbon dioxide levels increase at current rates (one percent per year) for 20 years.

Among the findings were:

  • Since the 1970s, the surface and bottom temperature range in the Sound has risen 0.3-0.4 degrees Celsius (~0.5-0.7 degrees Fahrenheit) per decade, for a total of about 1.6 degrees C (2.8 degrees F). The most dramatic increases have occurred in the spring. This change in temperature is leading to a longer optimal growing season for warm-water species and a shorter season for cold-water species.
  • The volume of freshwater flowing into the Sound from its rivers is increasing, resulting in a drop in salinity. All the reasons for these changes are unclear but increased precipitation in the form of large storms instead of mild rain within the large Connecticut River watershed may be a principal cause, as well as land use changes that lead to increased stormwater runoff.
  • Future projections indicate a calendar shift in temperature of several weeks to a month which will result in warm-water species migrating into the Sound earlier in spring and staying later in fall, which will greatly increase competition between them and historically abundant cold-tolerant species.

The research team included Nickitas Georgas of Stevens Institute of Technology, Penny Howell of CT DEEP, Marine Fisheries Division, Vincent Saba of the National Oceanic and Atmospheric Administration and Alan Blumberg and Philip Orton of Stevens Institute of Technology. The full report for the study, Analyzing History to Project and Manage the Future: Simulating the Effects of Climate on Long Island Sound’s Physical Environment and Living Marine Resources, is on the LISS website in the research grant section.

A Tale of Two Flounders: One Species Prefers Warm Water; the other Cooler

Two species of flounder reveal how climate can shift abundance of fish in Long Island Sound. Summer Flounder and winter flounder are flatfishes, types of fish which lie on their side rather than on their belly and have both eyes on one side of their head. While they share similarities. their numbers have gone in different directions in recent years. Summer flounder are increasing in response to fishery management quotas that began in 1993. They also prefer the warmer temperatures that have occurred in the Sound in recent years. But winter flounder, severely overfished in the 1980s, have not responded to efforts to restore their numbers.  While winter flounder showed signs of recovery in the 1990s, continued overfishing in moderate amounts combined with their preference for cooler temperatures and subsequent lower numbers being produced, have led to record low numbers. Summer flounder feed on fish and squid. Winter flounder remain mostly on the sea bottom feeding on worms, clams, and shrimp.


Source: CT DEEP Long Island Sound Fish Trawl Survey. See the Game Fish indicator page for survey data on six fish, including winter and summer flounder, that are popular with recreational anglers in Long Island Sound.

Teachers’  Webinar

View recording, PowerPoint, and key concepts from  Penny Howell’s webinar to Long Island Sound teachers (Jan. 18, 2017).

Webinar recording (at LIS YouTube page)
key concepts

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