Conventional methods of monitoring fish populations and aquatic ecosystems often are too "coarse" or broad-based and fail to identify variables that can affect the accuracy of sampling results.

This incorrect or incomplete survey information, generally collected by government agencies for use in regulatory policy making, can lead to misperceptions about the actual changes occurring in the aquatic environment and fisheries.

To address this problem in the North Sea, the German Fisheries Institute conducts an annual survey at fine spatial scale with the participation of an interdisciplinary team of scientists, technicians and university students. Sara Adlerstein, a research scientist at the School of Natural Resources and Environment, co-authored "20 Years of the German Small-Scale Bottom Trawl Survey (GSBTS): A Review," a paper summarizing the survey results. She participated in the data collection for a number of years prior to joining the University.

The German Small-Scale Bottom Trawl Survey, as it is called, uses the same protocols as an ongoing annual large-scale survey, but focuses on high-intensity sampling in selected areas. Analysis of data obtained during the surveys demonstrates how a more finely tuned sampling can yield new and complementary information, which in turn enables more accurate estimates of fish populations and leads to better-informed fisheries-management decisions.

Adlerstein says the findings suggest similar small-scale surveys could be used effectively in the Great Lakes to improve the assessment of fish distribution and abundance, which provide the basis for setting state and federal regulatory guidelines.

"Conducting complementary small-scale surveys would produce knowledge to improve the quality of collected data, as well as lead to possible cost savings by helping to optimize the survey design of annual assessments," says Adlerstein, who is currently collaborating with the Great Lakes Science Center-U.S. Geological Survey and the Michigan Department of Natural Resources on Great Lakes fisheries research and analysis.

The German survey was initiated in 1987 to provide additional and complementary information to the larger International Bottom Trawl Survey, which is used to monitor the condition of commercially important fish stocks in the North Sea and to make recommendations for fisheries management. Siegfried Ehrich of the Institute for Sea Fisheries in Hamburg, Germany, is the lead scientist and co-author of the recently published paper.

The German survey research team initially started with four survey areas, each 10 nautical miles by 10 nautical miles square. Over the course of 20 years, the spatial extent was increased to 12 areas strategically distributed over the North Sea.

Using intensive surveying methods, the German survey scientists investigated small-scale patterns and ecological processes. Their sampling efforts yielded information on the effects of spatial scales and the interactions of bottom fish with the physical environment, as well as on the biological interactions of other aquatic organisms and within the fish community.

In the course of their survey work, they identified many variables, such as the time of day, weather conditions, trawling speed and direction of water currents, which affected the size and composition of the fish samplings.

These insights provided a framework for improving the large-scale International survey in ways that would yield more accurate assessments of fish populations and the North Sea ecosystem structure.

Adlerstein conducted research in connection with the German survey for approximately five years while she was a faculty member at the University of Hamburg. She argues that fisheries research suffers from a disconnect between the biologists conducting routine assessment surveys and the modelers using the generated data for research.

Furthermore, she says, monitoring, which should be an important research effort, is too often considered a second-class activity. "Surveys are being conducted all around the world, often at great expense, but they produce limited data because they are not well-informed by ecology and statistical design," Adlerstein explains.

"At the same time, fishery science suffers from poor information. There are many impediments that keep universities and government agencies from working together collaboratively."

In the German Small-Scale Bottom Trawl Survey, the government agency for fisheries partners successfully with university faculty and students. "It is a good example of how an agency benefits from the expertise and creativity of people in academia, and how a university can carry out research at a scale not affordable for an academic institution," Adlerstein concludes.

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By Claudia Capos

For more information, contact Mary Vingerelli at vingerel@umich.edu or call 734-763-6605.