Fisheries Theme Team

Great Lakes Fisheries

Introduction

The Great Lakes hold about 20 % of the world supply of freshwater and about 95 % of the supply in the United States. Approximately 30% of the US population lives in the region and the total shoreline, which is longer than the Atlantic, Gulf or Pacific coasts, ranges from highly developed and urbanized to very remote and undeveloped. The lakes themselves are equally diverse ranging from the large, cold and deep (410 meters) Lake Superior to the shallow (65 meters) and warm Lake Erie. Fishery productivity in the Lakes is largely determined by their temperature and nutrient enrichment. Lake Erie, the southernmost and shallowest, is also the warmest with summer temperatures in the Western Basin often reaching 26 degrees Celsius. With the exception of Lake Erie, the watersheds around the Great Lakes are dominated by forest ecosystems. As a result these lakes are deep, cold and clear and support primarily cold water fisheries with a variety of salmonids. The watershed around Lake Erie is primarily agricultural and urban. As a result it receives more nutrients and sediment loading and is biologically the most productive, but with primarily cool water forms dominated by percids and centrarchids.

Management Coordination

Management of the system requires cooperation and coordination between 8 states and the province of Ontario, two countries, and a number of Native American Nations. The Lake Erie commercial fishery is the largest freshwater commercial fishery in the world, but it is primarily on the Canadian side and has fallen off drastically in recent years. In general the commercial fishery in the region is declining or steady at best and is competing with a very large charter fishery (over 2000 licensed captains) and a large sport fishery. On some of the lakes the fishery is maintained only with extensive stocking programs and on other lakes natural reproduction dominates. While each of the states and Ontario set their own regulations and do much of their own stock assessments, coordination of the Great Lakes fishery is done by the Great Lakes Fishery Commission (a bi-national organization) through an individual "Lake Committee" for each Lake. Developing management strategies for sport fishing is just as important as developing management strategies for the commercial fishery but we must recognize the obvious difference--there are millions of sport anglers to manage and deal with.

Ecosystem Models and Ecosystem Management

The development of biological and physical models has been underway for years in the Great Lakes region. In the early 1980s Drs. Keith Bedford (Ohio Sea Grant) and David Shwab (GLERL) began the development of the Lake Erie Forecasting System. This ultra-sophisticated physical model is now up and running on Lakes Erie, Michigan and Ontario, and is very useful to resource managers and the fishing public to identify temperature gradients, water masses, current patterns, etc. in addition to waves and storms. In 1994, under the leadership of the International Joint Commission (IJC), US State Department, a major effort to develop ecosystem models for the Great Lakes was initiated. Ultimately, these were to improve fishery management and lead to ecosystem management within each of the Lakes. The IJC's Council of Great Lakes Research Managers has carried the effort forward with a number of "Modeling Summits" and interest and activity is very high within the region. While these summits have been very successful, there are still significant spatial and temporal hurdles that must be jumped before we can effectively link the biological and physical models that have been developed. Furthermore, while excellent bioenergetics models have been developed, we still have difficulty modeling the base of the food chain and understanding its impact on forage fish compared to the top down impacts of predators.

Better management of each of the Lakes is also the goal of USEPA and Environment Canada in their leadership of the development of Lakewide Management Plans (LaMP) for each of the Lakes. Each Lake has a LaMP Committee and fisheries interests are well represented.

Major Fishery Management Issues

Aquatic Nuisance Species. The Great Lakes are the home to over 140 aquatic nuisance species (ANS), and about 2/3 of these have come in since the St. Lawrence Seaway opened in 1959. The sea lamprey and the zebra mussel are probably the poster children for ANS. While controlling sea lamprey is certainly not solved, it is indeed a real success story. On the other hand, the zebra mussel has drastically altered the ecosystem and reduced the economic value of the Lake Erie fishery by more than 50%. It has also been implicated in the development of harmful algal blooms (Microcystis sp.) in Lake Huron and Lake Erie. Finally, we were unable to reach agreement on a management strategy to prevent the ruffe from escaping from Lake Superior and as a result it is only a mater of time before it is in all of the Lakes. Controlling the current crop of ANS and preventing new ANS from entering the system are very important issues.

Ecosystem Changes. ANS and man's activities have caused very significant changes in the ecosystem of the Lakes. In Lake Erie since the zebra mussel invaded, water clarity has increased 6 fold, phytoplankton and zooplankton densities have been drastically reduced, benthic macroinvertebrate populations are changing rapidly, rooted aquatic vegetation is proliferating, the smelt population has crashed, the walleye population is about half of its previous level, the round goby has invaded and become the most abundant nearshore species, and on and on. As a result, establishing reasonable and safe quotas is much more difficult. In Lake Michigan the yellow perch population has crashed and we are unsure of the cause.

Contaminants. Toxic substances are probably a greater concern in the Great Lakes region than anywhere in the world, and there is some type of fishing advisory regarding edibility of fish on all of the Lakes. The IJC has designated 43 harbors in the region as "Areas of Concern" (AOC) because of severe degradation of beneficial uses of the water and the habitat. Contaminated sediments are the most common problem in each of these AOCs. Each of the AOCs has developed or is in the process of developing a "Remedial Action Plan" (RAP) to address the problem.

From a fisheries standpoint, we must improve our understanding of contaminant transfer across trophic levels and within the system. We must also reduce contaminant levels within fish, human exposure to contaminants from eating fish, and we must gain a better understanding of sublethal impacts of contaminants on fish.

Habitat Degradation and Loss. The impact of habitat alteration and loss on fish has been, and will remain, a very important research area in the Great Lakes. However, we must take this research to the next level to determine how man's activities on land impact the watershed and ultimately fish habitat, and even further to determine how socio-economic policies impact land-use activities.

Sea Grant's Role

Sea Grant's role on all of these issues should be to perform the research or collaborate with the management community on research to address these issues. Sea Grant should also assist in communicating with decision-makers and non-scientists to make these complex scientific issues understandable. Finally, IJC and a number of other organizations have identified a shortage of highly trained limnologists and fishery managers to replace an aging workforce. Clearly, developing these new scientists is an area where Sea Grant can play a leadership role.