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.