Proposed vessel calibration studies for NOAA ship Henry B. Bigelow
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Proposed vessel calibration studies for NOAA ship Henry B. Bigelow
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    "Standardized bottom trawl surveys have been an integral component of Northeast Fisheries Science Center ecosystem monitoring activities since the autumn of 1963 (Azarovitz et al. 1997). The autumn survey was supplemented by a spring survey starting in 1968 and a winter series was initiated in 1992. These surveys are designed to characterize spatial and temporal changes in the abundance of fish and macroinvertebrate species vulnerable to the sampling gear, demographic attributes of these species, and ecological interactions based on food habits studies and other observations. A stratified random sampling design has been employed for all surveys and biological samples are collected using a multi-stage cluster sampling design. Observations on lower trophic levels and oceanographic properties are also collected in conjunction with these surveys and in complementary ecosystem monitoring cruises. The NOAA Ship Albatross IV (Albatross) has been the principal research vessel employed throughout the series although the NOAA Ship Delaware II (Delaware) has also been used in selected bottom trawl surveys. An extensive series of calibration experiments has been undertaken to test for vessel differences and permit conversion of Delaware catches to Albatross catch units to account for these changes (Byrne and Fogarty 1985; Byrne and Forrester 1991). For general overviews of the design and analysis of comparative fishing trials, see Bergh et al. (1990) and Pelletier (1998). The Albatross is scheduled to be replaced by the NOAA Ship Henry B. Bigelow (Bigelow) in 2008, necessitating a new series of vessel calibration studies. The objective of the proposed experiments is to develop Bigelow-Albatross conversion coefficients to maintain consistent time series for the purpose of meeting stock assessment and ecosystem monitoring requirements. In addition to the vessel replacement, a change in the trawl gear used in standardized surveys from a Yankee No. 36 to a four-seam bottom trawl will be made at the recommendation of the MAFMC/NEFMC Trawl Advisory Panel (Brown 2007). Changes in selected sampling protocols, including tow speed and duration for the Bigelow are also recommended by the panel in conjunction with the gear change"--Introduction.
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