Natural and Anthropogenic Influences on the Mount Hope Bay Ecosystem 2006 Northeastern Naturalist 13(Special Issue 4):27–30 Fisheries in Mount Hope Bay: Notes on a Special Symposium from a Session Moderator Giancarlo Cicchetti (Symposium Session Moderator)* Abstract - This contribution represents a summary of talks presented during the afternoon session of the Mount Hope Bay Symposium, focused directly on issues surrounding observed winter flounder populations, as prepared by the session moderator. Introduction A special symposium, “Fisheries of Mount Hope Bay,” convened in May 2003 at the joint meeting of the Southern New England Chapter of the American Fisheries Society and the New England Estuarine Research Society. Eight well-attended and interesting talks were presented, all with a focus on the status of economically important winter flounder (Pseudopleuronectes americanus Walbaum) and other fish in Mount Hope Bay. These talks and the subsequent afternoon discussion session addressed two key questions. First, have there been declines in winter flounder populations (or in other fish populations) in Mount Hope Bay? And second, if so, to what extent (if any) does the Brayton Point Station power plant contribute to these declines, in the context of other influencing factors? As the talks and discussions progressed, it became evident that the scientists involved were divided into two groups. On one side were those who believed that Mount Hope Bay does not have a fisheries problem relative to Narragansett Bay (i.e., fisheries declines), or that (if there were a problem) the effects of the power plant would account for an insignificant contribution to that problem. On the other side were those who believed that Mount Hope Bay does have a problem with declining fisheries, and also believed that thermal heating and larval entrainment from the power plant contribute to that problem. The intent in writing this article is to summarize and organize the conclusions presented at the talks in the Symposium in a factual and impartial manner. Not all of the eight talks presented in the Special “Fisheries” Symposium are also published in this volume; contact information for authors, and abstracts of talks not published here can be obtained from printed conference materials and from other sources (see Appendix in Roundtree and MacDonald, the issue). *US Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Atlantic Ecology Division, 27 Tarzwell Drive, Narragansett, RI 02882; cicchetti.giancarlo@epa.gov. 28 Northeastern Naturalist Vol. 13, Special Issue 4 Does Mount Hope Bay Have a Winter Flounder or Fisheries Problem? Most of the presentations and discussion at the symposium focused on winter flounder. Scientists generally agreed on data that indicate winter flounder abundances in Mount Hope Bay (a subestuary of Narragansett Bay) have declined since the mid-1980s. However, a vigorous discussion ensued around whether winter flounder in Mount Hope Bay have declined relative to winter flounder in Narragansett Bay. J. DeAlteris (University of Rhode Island [URI]) and coauthors (Lawler, Matusky, and Skelly Engineers) analyzed long-term data sets for many species, finding no differences between Mount Hope Bay and Narragansett Bay for most data sets. One data set did show that winter flounder abundance trends in upper Mount Hope Bay exhibited greater declines than in Narragansett Bay. The authors attributed this trend to differences in gear efficiency following dredging, and following replacement of a sampling net with a new net. Further, R. Rountree (School for Marine Science and Technology [SMAST] at UMass Dartmouth) and D. Witting (NOAA) presented evidence (also from long term data sets) that declines in winter flounder in Mount Hope Bay were intermediate to declines in other areas within Narragansett Bay. A. DeLong and J. Collie (URI) similarly analyzed long-term data sets, but, in contrast to the above studies, concluded that winter flounder abundance in the upper portion of Mount Hope Bay has declined more severely than in Narragansett Bay as a whole. M. Gibson (Rhode Island Department of Environmental Management [RI DEM]) used a biomass dynamic population model to suggest that Mount Hope Bay winter flounder populations have experienced greater declines relative to their rebuilding capacities than have winter flounder populations in Narragansett Bay. Debate did not resolve the issue of whether Mount Hope Bay has a fish problem relative to Narragansett Bay, with scientists on both sides of the issue remaining committed to their original positions. In the open discussion session, it was suggested that comparisons between Mount Hope Bay and Narragansett Bay might not be appropriate. The argument was made that Mount Hope Bay and Narragansett Bay suffer from different sets of problems and are not really comparable estuarine systems. By this logic, if flounder populations in Narragansett Bay and Mount Hope Bay are subject to totally different suites of stressors, then trying to tease out any power plant-related stressor via comparisons between the two systems would be inappropriate. Following this thinking, we should tackle the important issues affecting populations in each system, without necessarily trying to compare fish abundances in the two systems. Does the Power Plant Contribute to a Fisheries Problem? The second key question of the session was: if Mount Hope Bay does have a winter flounder or fisheries problem, to what extent, if any, does the 2006 G. Cicchetti 29 Brayton Point Station power plant contribute to that problem in the context of other factors? The factors that may contribute to fisheries declines include overfishing, power plant mortality, predation, and eutrophication. Overfishing There was general agreement that overfishing has affected populations of winter flounder and other fishes, but less agreement on the relative importance of overfishing compared to other factors. T. Englert and J. Burnett (Lawler, Matusky, and Skelly Engineers) used a RAMAS population model to suggest that overfishing dominates as a cause of winter flounder declines in Mount Hope Bay. Using a biomass dynamic model, M. Gibson agreed that overfishing was a larger source of mortality for winter flounder than was power plant mortality, but this model also showed that population recovery would require decreases in both fishing mortality and in power plant mortality. Power plant mortality Again, the RAMAS model of T. Englert and J. Burnett showed that power plant mortality was minimal, while M. Gibson used a statistical modeling approach to show that power plant operation was correlated to winter flounder mortality, and to show that winter flounder stocks cannot be rebuilt without decreases in both power plant-related mortality and fishingrelated mortality. A. Delong and J. Collie undertook a two-stage analysis in which they first compared abundance and mortality of 7 life-history stages to conclude that egg/larval stages and some later juvenile stages best represented total juvenile mortality. Next, these authors statistically examined a large number of environmental variables (including fishing mortality, cormorant abundance, etc.), and found that power plant coolant water flow and temperature were primary correlates to declines in egg/larval life-history stages in upper Mount Hope Bay. Predation D. Taylor of URI combined gut-content analyses and other data to show that Crangon septemspinosa Say (sevenspine bay shrimp) are capable of consuming large numbers of winter flounder eggs, and also showed that this consumption increases with locally higher temperatures. In discussion, the idea was brought up that power plant heat may lead to local higher temperatures, and consequently winter flounder would suffer greater mortality due to increased predation by sand shrimp. Other predators may also influence winter flounder population dynamics. D. French-McKay and J.J. Rowe (Applied Science Associates) described a trophic model suggesting that cormorants are capable of consuming many winter flounder in Mount Hope Bay. P. Webb (Roger Williams University) showed data that a fair number of seals inhabit Mount Hope Bay, but trophic analyses indicated that these seals probably do not eat enough winter flounder to significantly impact populations. 30 Northeastern Naturalist Vol. 13, Special Issue 4 Eutrophication Several scientists gave presentations in previous sessions of the Mount Hope Bay Symposium on eutrophication-related dissolved oxygen regimes of Mount Hope Bay. In this “Fisheries” session of the symposium, R. Rountree and D. Witting presented long-term data sets suggesting that general shifts in fish communities from benthic dominance to pelagic dominance may be related to eutrophication, and that declines in benthic fish abundance may thus be related to regional-scale processes. Conclusion Discussion on these issues throughout the symposium was divided into the two schools of thinking that were evident in the talks. One group believed that Mount Hope Bay does not have a winter flounder/fisheries problem relative to Narragansett Bay, and that the Brayton Point Station power plant is not a major contributor to fisheries declines in Mount Hope Bay. The other group believed that Mount Hope Bay does have a winter flounder problem, and that the Brayton Point Station power plant does contribute to this problem. Acknowledgments This is contribution number 03-095 of the Atlantic Ecology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, United States Environmental Protection Agency. However, the views and information in this paper have not been subjected to Agency-level review and therefore do not necessarily reflect the views and policies of the US Environmental Protection Agency.