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GLERL 2003 Milestone Reports
GLERL 2003 Milestone Home
GOAL: Protect, Restore and Manage Use of Ocean and Coastal Resources Through Ecosystem Management Approaches
OBJECTIVE 1: Rebuild and maintain sustainable fisheries.
SPECIFIC STRATEGY: Understand and describe, estimate fish distribution and abundance by developing better sampling technologies and procedures.
Milestone: Develop standard operating procedures for the application of fisheries acoustics in the Great Lakes Region: workshops I and II
Scientists: Dr. Doran M. Mason (GLERL) and Dr. Lars Rudstam (Cornell University)
Purpose: A thorough understanding of forage fish distribution and abundance is a key component of efforts to maintain the economically and internationally important salmonid sports fishery in the Great Lakes. The applications of acoustic methods have become an important tool in developing this understanding and this tool is currently used in all the Great Lakes and Lake Champlain. Acoustic surveys provide measures of abundance, distribution, and size of forage fish populations; providing the quantitative information essential for managing and maintaining sustainability of the multi-billion dollar Great Lakes salmonid fishery.
Figure 1: Example of fish survey acoustic data
Great Lake Fisheries Commission (GLFC), Great Lakes Research Consortium, and New York Sea Grant have supported several past workshops that have explored different aspects of the use of fisheries acoustics in the Great Lakes region. These have included an introduction to hydroacoustics, application of geostatistics, and importance of target strength determination (acoustic size of fish). The most recent effort was an inter-calibration exercise performed on Lake Champlain in 2000 by Mason (GLERL) and Schaner (Ontario Ministry of Natural Resources). The primary objective of this exercise was to compare the acoustic size and abundance estimates between 4 different frequencies that represented 3 different manufacturers (Biosonics, HTI, and Simrad) and three different signal processing software packages. These systems are representative of the frequencies, models and software used throughout the Great Lakes basin. The study found that several of these units gave comparable results, however, there were notable differences in abundance and size estimates both between frequencies and between systems. In addition, differences in analysis settings and software (thresholds, single fish filters, pulse length) provided significantly different results. These differences highlighted the need to develop a standardized protocol for data acquisition and analysis across the Great Lakes so that data collected from various scientific echo sounders are comparable. The series of workshops that form part of this milestone is a response to this identified need.
Based primary on the results of Mason and Schaner, a study group on fisheries acoustics was established and a series of workshops planned. The charge for this study group is:
- To develop a standard data acquisition protocol for collection of fisheries acoustics data in the Great Lakes (thresholds, single fish filter settings, pulse length). These are the parameters specified when collecting data in the field.
- To develop a standard processing protocol for estimates of fish density and biomass (density effects on in situ target strength, appropriate target-strength to length relationships for different species). These are the procedures used to translate acoustic data to fish abundance during processing.
- To develop recommendations for survey design including the use of geostatistics for density estimates, and recommendations for appropriate stratification of collected data. These are the decision made when designing the survey and when applying statistical procedures for expanding fish abundance obtained along a transect to whole lake estimates.
- To write a document that describes the standards developed from items 1-3 above, probably published as a GLFC technical report.
This milestone reports on the results of the first two workshops.
Figure 2: SIMRAD Acoustic Fish Survey equipment
EFFORTS: A series of workshops was planned, with 2 workshops organized per year over three years, with the ultimate goal to develop a standard operating procedure (SOP) for the application of fisheries acoustics in the Great Lakes. Members of the fisheries acoustics working group where selected and invited to participate. Working group members were selected based on the lake that they worked on and whether they had a background in fisheries acoustics. Through this process, we were able to form a working group with at least one person representing each of the five Great Lakes and Lake Champlain. Members were from state, federal, and provincial agencies (Ontario Canada), and from universities. In addition to the core working group members, we also have and will continue to invite national and international experts for various sub-tasks.
The agenda for the first workshop was to: (1) identify current applications of fisheries acoustics by each of the study group members, (2) discuss data collection and analysis problems, (3) definition parameters used by different programs that need to be standardized, (4) outline a document describing the standard sampling design for Great Lakes acoustics, (5) define tasks for the study group member, and (6) define the subject matter for each of the following workshops.
CUSTOMERS: Ultimately, the customers/beneficiaries of the SOP for fisheries acoustics in the Great Lakes are the recreational users- the public. This is realized through improved sampling technology that will provide more accurate information and knowledge for effective resource management and sustainable fisheries. The immediate customers are those who use fisheries acoustics technology to estimate the abundance of salmon prey fish, and those managers that require this information for wise management decisions (for example, determining the number of salmon to stock).
SIGNIFICANCE: A comprehensive review of current acoustic techniques in the Great Lakes and development of standard operating and analysis procedure is urgently needed for acoustics to reach is full potential in the Great Lakes. Estimates of forage fish abundances are a priority for resource managers partly because of the need to determine stocking rates of predators like salmon. Currently, the scientist and biologist involved with acoustic surveys in the Great Lakes often call on the expertise of the two study leaders to determine appropriate analysis methods (Rudstam for Erie, Ontario, and Champlain, Mason for Michigan, Superior and Huron). The set of workshops proposed here should allow us to develop comparable methods and lead to biological interesting analyses of the abundance and spatial distribution of forage fish across the Great Lakes.
SUCCESS: Workshop I was held January 9-10, 2003 in Ann Arbor Michigan. The agenda items as outlined under the section "Efforts" were successfully completed. Members of the core group were from the Michigan Department of Natural Resources, Illinois Natural History Survey, New York Department of Conservation, NOAA Great Lakes Environmental Research Laboratory, NOAA National Marine Fisheries Service- Northeast, University of Minnesota, Cornell University, University of Vermont, United States Geological Survey-Biological Resource Division, and Ontario Ministry of Natural Resources. Discussion of agenda items 1-3 led to an outline for the Great Lakes fisheries acoustics SOP. The outline of the SOP is reflected in the topics to be covered in workshops II-IV. The last two workshops will be devoted to topics identified in workshops II-IV that were not covered and for writing the SOP.
Topics for Workshops II-IV:
Workshop II Survey Design: Topics will cover sampling design (transect types, coverage, timing of survey, etc), additional sampling gear (fish trawls) and corresponding sampling design and strategy, and biases (boat avoidance, noise problems, etc).
Workshop III Acoustic Size (Target Strength- TS): Topics will cover species specific actual size to acoustic size (TS) relationships, TS estimates from trawls and models, separation of TS between fish and invertebrates, Sensitivity of TS estimates to fish behavior, fish density, depth, and body condition (gonads, fats).
Workshop IV Signal processing: Topics will cover spatial resolution of processing (horizontal distance and depth range to average over), statistical methods (uncertainty), and development of standard options for software parameterization and output.
Workshop II was held May 19-20, 2003 at the Cornell Biological Field Station. Core working group members, interested individuals (New York Sea Grant) and an invited guest attended. The distinguished guest was Dr. John Simmonds of FRS Marine Laboratory (Aberdeen, UK) and co-author of the text- "Geostatistics for Estimating Fish Abundance (2000)" published by Blackwell Science Inc. Two days were devoted to Geostatistics and survey design. Survey designs were evaluated for Lake Ontario, Lake Erie, Lake Michigan, and Lake Superior. Recommendations for improvement of survey designs were made. Agency personal responsible for the fisheries acoustic surveys in each of the lakes are currently evaluating those recommendations.
NEXT STEPS: Hold the remaining series of workshops and produce the SOP over the next two years.
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Last updated: July 22, 2003 mbl