Trawl Design Training Workshop to be conducted in early December in Ann Arbor Michigan
Great Lakes fisheries managers rely on trawl surveys in their fisheries assessment programs.
A Trawl Design Training Workshop is scheduled for December 4-5, 2013 at the Great Lakes Environmental Research Laboratory in Ann Arbor, Michigan. The workshop is being sponsored by the Great Lakes Sea Grant Network, U.S. Geological Survey, Memorial University, and the Great Lakes Environmental Research Laboratory.
The workshop will be a follow-up workshop from the highly successful Trawl Design Workshop organized by New York Sea Grant. The workshop is developed for fisheries assessment staff from the Upper Great Lakes and will focus on fundamentals of trawl performance, fish behavior, and fish catchability. The workshop will feature trawl simulations of a generic Yankee type trawl design using the Lake Ontario model developed from the previous workshop. The December workshop will expand on the topics of comparability of Great Lake’s trawling programs, factors influencing trawl performance, fish catchability and designing studies to measure fish catchability and comparative gear efficiency.
Bottom trawls are one of the most important fishing gears used in fish stock assessments, worldwide. It is the primary survey gear for National Oceanic and Atmospheric Administration ecosystem surveys in U.S. oceans and prey fish assessments in the Great Lakes. Fish assessments for prey species, such as alewife, rainbow smelt, and bloaters, have been conducted, annually, in the Great Lakes since the 1970s by state, provincial and federal agencies. Assessment programs have consisted largely of bottom trawling; however, in recent years, simultaneous hydroacoustic/mid-water trawling programs have been developed. Trawl abundance indices are used to model stock-recruitment relationships and to understand population dynamics, which are vital to effective fisheries management and advancing scientific understanding of fish stocks.
One of the greatest challenges for the Great Lakes fisheries assessment programs is maintaining consistency of trawling gear through time. This is a challenge made more difficult by the proliferation of zebra and quagga mussels, which have been implicated in reduced sampling efficiency of traditional bottom trawls and have also been linked to changes in fish distribution resulting from changes in the lower food web dynamics.