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Figure 4

 


   



Perry Jeffries, Professor Emeritus
Graduate School of Oceanography

Perry Jeffries earned BS and MS degrees at URI, and a PhD degree at Rutgers University. He came to the Narragansett Marine Laboratory as an Assistant Professor of Oceanography. His research interests include coastal ecosystems (structure and patterns of change), zooplankton distribution and abundance, and fatty acid and amino acid pools in relation to environmental conditions.


It was a cold and stormy night—January 6, 1959— when the Narragansett Marine Laboratory, predecessor to the Graduate School of Oceanography (GSO), burned to the ground. Everything was lost, including irreplaceable records and a manuscript that Marie P. Fish had left on her desk for a final check. Her husband, Charles J. Fish, founder and director of the lab, moved his staff to the old Washington County Jail in Kingston and started anew.
      As the ashes cooled, a research program on the bottom fishes and invertebrates in Narragansett Bay and Rhode Island Sound emerged. Marie Fish needed information about seasonal migrations to correlate with recordings of underwater sound, a matter of critical interest to the U.S. Navy. Charles Fish, whose classic dissertation on the plankton of the Woods Hole Region set the bar for seasonal studies, realized an extra benefit. Long-term changes in a complex of interacting populations inhabiting coastal waters could be measured rather than left to anecdotal accounts. When Charles Fish retired in 1966, he gave me his data, and I have worked to maintain a program designed to perpetuate his ideas.
      Every week since January 1959, a trawler has left Wickford Harbor and made a 30-minute otter tow in mid-Narragansett Bay and in Rhode Island Sound. The net collects animals (three inches and larger) living on and just above the bottom. We measure water temperature and count and weigh each species. Winter flounder are given special attention: individuals are measured and sex is noted.
      Because we do the same thing week after week, we can observe gradual and long-term changes. No record comparable to this 42-year-old data set exists for any coastal area; thus the data become more valuable every year.
      Annual abundance is the total of average monthly catches for a species. Thus, for a year-round species, up to 52 samples reduce to a single estimate of abundance. Sampling was less frequent during the early days but now, thanks to Captain Tom Puckett's dedication aboard the trawler Cap'n Bert and several generations of outstanding graduate assistants, we rarely miss a week. The record is available for management purposes and, since 1999, all have had access to it.
      The local scientific community requests specimens from the trawl, and surprising uses have been found for our temperature data. I could hear a sigh of relief when I gave bottom water temperatures to the engineers of the Jamestown Verrazano Bridge who needed to take temperature into consideration before mixing and pouring concrete in the middle of winter.
      The winter flounder confounds me as I attempt to explain the changes that occur among the 24 species that make up 99 percent of the year-round catch. Winter flounder once made up 50 percent of the inshore fisherman's income, but the population is now a mere vestige of its former glory. Intuition tells me that an 80 percent decline from the first to the fourth decade of our program is not entirely due to overfishing and pollution—two common explanations for problems in coastal waters.
      After the flounder population reached a low point in 1976, I published a paper with Bill Johnson, a GSO graduate student in 1980 who assisted with the trawl, reporting a correlation between warmer winters and the flounder's 86 percent decline from a peak in 1968. But correlation does not prove causation, and warming from 1971 through 1975 amounted to about 2°C, which seemed insufficient to produce a major biological effect (see Figs. 1 and 2). Besides, there was little ancillary information for corroboration, and back then no one was talking about climatic warming in coastal waters.
      I learned from Candace Oviatt, director of the Marine Ecosystem Research Laboratory, that sand shrimp raised havoc in outdoor aquaria by eating anything they could get their claws on. Was this inch-long terror, previously capable of feeding only during warmer months, now able to feed in winter? If so, the flounder's reproductive efforts would be disrupted.
      After the flounder population recovered briefly (1978–1983), I proposed a theory in a paper with Mark Terceiro, a GSO doctoral student in 1985, who used part of the trawl record for his dissertation. We combined warming and predation to explain the flounder's behavior. Winter flounder have an unusual ability to repopulate in estuaries at extremely low temperatures, a time when predators are either offshore or inactive. Shrimp have adapted, and since 1970, following warmer winters have invaded the flounder's refuge, devouring its eggs and larvae. Extrapolating Sandra Whitehouse's 1994 GSO dissertation results on shrimp feeding rates, I calculated that predation might well destroy all the young flounder produced during a single winter in Narragansett Bay.
      To strengthen our theory, we needed evidence that shrimp thrived during winter. Soon thousands of shrimp appeared, entangled in the trawl's manila ropes. Our skeptics would not be stilled until measurements were made of shrimp feeding rates at low temperatures. Some biologists insist that fishing pressure is the controlling factor. This cannot be true because the flounder population recovered in the late 1970s, only to collapse again as the warming trend recurred (compare Figs. 1 and 2).
      Studies on plaice in the North Sea bolstered the shrimp theory. Plaice belong to the same genus as winter flounder, and they prosper following cold winters. North Sea shrimp belong to the same genus as sand shrimp, and they fare well during warm winters, feeding on plaice eggs and larvae. The predator-prey genera are the same, only the species differ. I call it a congeneric correspondence: Similar species interact in the same way on both sides of the North Atlantic.
      From the early 1980s on, when the flounder population collapsed a second time, unusual events took place among the Bay's crabs: Sand crabs appeared in January and commenced to shed. Previously, this species and the related Jonah crab, along with other invertebrates, waited until spring to begin their migration from the ocean.
      The flounder population entered the new millennium at less than 10 percent of the total catch. Against a background of warmer winters, the winter flounder's future is not promising.
      It follows that the myriad bottom foods in Narragansett Bay once supporting winter flounder have become available for others, which may explain increases of migratory lobsters, crabs, squid, butterfish, and scup. Outsiders, chiefly warm water visitors to the Bay, have taken over bottom habitats. Note how scup filled in the gaps left by winter flounder (see Fig. 2). In 1995, it looked as if invertebrates would overrun both the Bay and Rhode Island Sound. Recently, however, their numbers have fallen off. Body size is small and the species are less desirable, so commercial value is less than it was during the flounder's halcyon days (see Fig. 3).
      One exception is lobster, which defies all explanation. How long can that population endure? Several years ago, I saw three offshore trawlers at the mouth of the Bay, dragging the bottom with their huge nets; a fourth was leaving. What were they after? Not fish. The catch would not have been enough to cover fuel costs. It must have been lobsters, whose numbers had reached an all-time high in 1992 (see Fig. 4). Then came an oil spill that killed millions of lobsters.
      I wonder when outdated fishery economics, ineffective management, and perhaps even greed will catch up with our splendid crustacean. The population is unstable; its numbers in the Bay dropped one-half in a single year (1998–99), and it remained there through 2000. Perhaps its limit has been reached (see Fig. 4).
      A major conclusion emerges: The winter flounder's rise and fall are part of a bigger whole that changes continuously. Prior to 1970, the controlling dynamics were Bay-centered. The balance shifted to Rhode Island Sound in the early 1970s, went back to the Bay after two cold winters, and finally returned to R.I. Sound in the early 1980s, where it has remained ever since. Reflecting this dynamic balance, the 24 major species fall into five groups for the 1959–1998 period:
Group 1. Progressive increases: butterfish, lobster, squid, Atlantic herring, little skate, striped sea robin, fourspot flounder;
Group 2. Multimodal (several) increases: cancer crabs, conch, spider crab, Mantis shrimp, scup;
Group 3. Indeterminate: horseshoe crab, starfish, fluke, ocean pout, red hake;
Group 4. Multimodal declines: winter flounder, windowpane flounder, silver hake;
Group 5. Progressive decreases: cunner, tautog, northern sea robin, longhorn sculpin.
      The Bay's winter flounder population established a pattern that others seemed to follow. Flounder thrived twice following cold winters, but each time, winters soon warmed, and the populations waned. During the flounder's first collapse, scup, a warm-water species, migrated more strongly into the Bay to take its place. Invertebrates and butterfish, another warm-water migrant, characterized the aftermath of the flounder's second collapse.
      For migrating bird populations, the eminent ecologist Robert MacArthur would have called this Bay-Sound relation an expression of his Principle of Equal Opportunity—go to the habitat where the getting is good. We now know that that principle applies to fish and bottom invertebrates as well as to birds. You might say that the Bay has less control of its destiny as warm water visitors take over.
      Group 5 has the big losers in the numbers game. Cunner and tautog are related, though the former is a pest for recreational fishermen and the latter is a commercially valuable species. Longhorn sculpin reproduce during winter, so their eggs and larvae may also fall prey to shrimp. The demise of the cunner and northern sea robin is a mystery.
      Deciphering the information presented by the trawl data provides me with more than statistics and ecological theory. Its patterns unveil the whole that every oceanographer knows is the proper way to study an issue. This was Charles Fish's credo. He rebuilt a laboratory to support a graduate program that embodies this ideal, making certain that the message is clear for generations to come. Credit also goes to the administration of the Graduate School of Oceanography and to the state of Rhode Island for supporting this study.