Sampling the Bay Over the Long Term
David L. Taylor, GSO Doctoral Candidate
Jeremy S. Collie, Professor, Graduate School of Oceanography
David Taylor earned a BA in biology from Bucknell University and an MS in marine science from North Carolina State University. His major professor is Jeremy Collie and his primary research interest is the effect of temperature on predation of juvenile winter flounder by sand shrimp in Narragansett Bay.
Jeremy Collie earned a B.Sci. in biology from the University of York in England and a PhD in biological oceanography from the MIT/WHOI Joint Program. His research focuses on quantitative ecology with an emphasis on benthic habitat and fish population dynamics.
Marine fish and inver tebrate populations typically
exhibit wide annual variation in abundance. Fisheries scientists have the intriguing
yet difficult task of identifying the factors that cause this year-to-year variability.
What proportion of observed fluctuation in species can be attributed to human
activity, such as over-fishing and pollution, and what proportion is due to
natural variations in the marine environment? This question is especially relevant
to Rhode Island, the Ocean State, whose citizens depend on the surrounding waters
for livelihood and recreation. For researchers to make informed decisions about
the status of fish and invertebrate populations, they need species abundance
data spanning a sufficiently long period of time so they can distinguish between
natural variation in populations and fluctuations that are caused by human practices.
The University of Rhode Island Graduate School of Oceanography (GSO) Bottom-Trawl Survey is the longest continuous record of fish and invertebrate abundance in Rhode Island. The survey was initiated in 1959 by Charles J. Fish, founder and director of the Narragansett Marine Laboratory, the precursor to GSO. With the trawl survey it was possible to quantify the seasonal occurrences of migratory fish populations; previously scientists had relied on anecdotal accounts. Realizing its value as a documented record of long-term fluctuations in fish and invertebrate abundance, Fish continued the trawl survey until he retired in 1966. The trawl was then passed to H. Perry Jeffries, GSO professor emeritus, who maintained the survey for more than 30 years until he handed it over to Jeremy Collie's lab in 1998. The parameters measured on the trawl have been increased over time and now include abundance and biomass for each species, surface and bottom water temperatures, and sex and length for winter flounder, Pseudopleuronectes americanus.
In a Maritimes article (Spring 1994) about the role of warming climate on declining fish populations in Narragansett Bay, Jeffries eloquently described the purpose of the Bottom-Trawl Survey. "If the public saw undersea plants and animals as clearly as, say oak and pine trees, calamities similar to those in the Bay would produce outcries silenced only by promises for further explanation," he wrote. "Society can't control all natural phenomena, but we do have the responsibility to record environmental change and advance hypotheses for important mechanisms when they lie right at our doorstep. This has been our mission..."
The Bottom-Trawl Survey is more than 40 years old and is widely recognized as one of the most significant long-term field surveys in the world. The foresight of Fish and Jeffries in persisting with the trawl has proven invaluable. The following is a brief account of how the trawl and the survey data have become a Rhode Island institution.
The Bottom-Trawl Survey is the benchmark of the status of living resources in Narragansett Bay. It tracks the seasonal and longer-term abundance patterns in fish and invertebrates. Analysis of the data reveals important shifts in the species that constitute the Bay's ecosystem. Many resident fish species have declined precipitously in abundance; these include the commercially valuable winter flounder, silver hake, cunner, and tautog. Coincident with this decrease, populations of many invertebrates, such as rock crabs and squid, and seasonal migratory fish, most noticeably butterfish and scup, are increasing.
Fisheries scientists and resource managers have monitored the abundance trends of benthic invertebrates that may be significant predators on bivalve populations. The recent increases in the number of invertebrate predators may explain recently observed declines in clam landings and must therefore be taken into account when shellfish are transplanted and sites are chosen for aquaculture leases.
The information generated by the trawl has also been widely used as reference data to assist the ongoing biological and hydrological monitoring programs conducted by Michael Scherer of Marine Research, Inc., an environmental consulting firm, for the Brayton Point Power Plant Station in Mount Hope Bay and surrounding waters. Finfish populations in Mount Hope Bay have been monitored since 1971 to determine whether persistent population declines or shifts in community structure have occurred and whether or not they might be attributable to operations at Brayton Point Station. Scherer routinely uses the trawl data to compare the abundance trends of dominant fish species in Narragansett Bay with survey data collected in Mount Hope Bay. In addition, Henry Rines, Applied Science Associates, has used the long-term temperature data as a baseline for comparison of water temperatures in Mount Hope Bay that have been elevated as a result of thermal effluent from Brayton Point Station.
The Bottom-Trawl data are used for formal assessment and management of commercially important fish and invertebrate species. The data generated by the trawl survey corroborates results from surveys that the Rhode Island Department of Environmental Management conducts each spring and fall, thus providing a long-term perspective on abundance of key species in Narragansett Bay. Fish and Wildlife Division staff, for example, routinely use the trawl data to assess winter flounder abundance in the bay.
A Rhode Island Intergovernmental Fisheries Task Force is evaluating the status of commercial fisheries management in Rhode Island. The immediate goal of this project is to restructure commercial fishing licenses; the ultimate goal is to undertake a comprehensive review of all aspects of fisheries management in Rhode Island. The trawl survey has been extremely valuable to the Task Force by providing long-term abundance information on the status of the commercially important stocks.
Finally, the trawl is an excellent source of living marine specimens for experiments and community outreach programs. Save the Bay has exhibited marine animals collected from the trawl in their outreach programs on the different species found in Narragansett Bay. Narragansett Bay creatures have appeared at the Rhode Island flower show and in classrooms in Rhode Island and Massachusetts. The Atlantic Ecology Division of the U.S. Environmental Protection Agency has used animals and algae collected from the trawl for marine life touch tanks that have been exhibited at Rhode Island Earth Day and the Rivers Day Celebration sponsored by the Pawcatuck, Salt Ponds, Saugatucket, and Narrow River Watersheds Coalition. Marine animals from the trawl have also been incorporated into public displays in Rhode Island at Beavertail State Park in Jamestown and the New England Aquarium in Newport, and in Connecticut at the Mystic Marinelife Aquarium. These displays allow the public to observe and to appreciate the denizens of Narragansett Bay.
In conclusion, this long-term fish trawl is an important record of marine life in Narragansett Bay. Its value increases each year as new data are collected and the record grows longer. These data are the history of the Bay community in decades past and, therefore, provide a tool for managers intent upon sustaining our resources for future generations.
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