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Fishery Information Packet for the Petrel Bank Red King Crab Fishery, 2003
Abstract
1 The Regional Information Report Series was established in 1987 to provide an information access system for all unpublished division reports. These reports frequently serve diverse ad hoc informational purposes or archive basic uninterpreted data. To accommodate timely reporting of recently collected information, reports in this series undergo only limited internal review and may contain preliminary data; this information may be subsequently finalized and published in the formal literature. Consequently, these reports should not be cited without prior approval of the author or the Division of Commercial Fisheries.
... By the end of the fishery, approximately 8.5 million pounds of red king crab were collected. The Alaska Board of Fisheries allows for the placement of observers on catcher vessels [6]. Approximately 10 percent of the vessels in this fishery included observers, and these observers were asked to record in situ data at the time of three RADARSAT-1 passes covering the fishery during the time the fishery was open. ...
... Map of Bristol Bay Red King Crab Fishery[6]. ...
The National Oceanic and Atmospheric Administration (NOAA) National Environment Satellite, Data, and Information Service (NESDIS) provides synthetic aperture radar (SAR) derived products under a demonstration project named the Alaska SAR Demonstration (AKDEMO) to the US government community. The AKDEMO near real-time data and products include SAR wind images and vectors, hard target locations, and ancillary data. The hard target locations are available for use in fishery management by agencies such as the Alaska Department of Fish and Games (ADF&G), the National Marine Fisheries Service ( NMFS) and the United States Coast Guard (USCG). Vessel positions are obtained form hard target signatures through the use of a constant false alarm rate (CFAR) vessel detection algorithm developed by Veridian Systems Division. This algorithm has gone through testing and validation, using fleet information and vessel observer reports, during the Red King Crab fisheries in Alaska in 1999 and 2000. The goal was to maximize the number of ships found while minimizing the number or false alarms. Using general fleet location information, it was found that the minimum vessel size detected by the CFAR algorithm was 36 m using RADARSAT-1 ScanSAR wide mode data with a nominal spatial resolution of 100 m. Still, when comparing the CFAR results with the actual positions reported by the ship observers, vessels over 36 m were not always detected. This led to the hypothesis that the heading and perhaps wind conditions may have affected the ability of the SAR to detect the vessels. In 2001, vessel observers again reported their positions during SAR overpasses, this time also reporting heading and wind conditions. Unfortunately, due to high winds and waves, SAR was not able to detect the fishing fleet. In 2002, this was repeated, resulting in 3 days during the fishery opening when RADARSAT-1 was able to image the fishing fleet in the ScanSAR wide B mode. Approximately twenty ships each day in the a rea covered by the RADARSAT-1 data reported their position and heading. Results showing the dependence between RADARSAT-1 vessel detection and vessel heading are presented using the GIS platform.
... The survey has consistently Figure 1. Abundance of mature male red king crabs estimated from area swept methods and directed fishery catch in the Bristol Bay region (adapted from Zheng and Kruse, 1999;Granath, 2002;Bowers, 2003). visited 119 stations in this area covering $160 000 km 2 (Fig. 2). ...
Distribution and abundance of ovigerous female red king crabs (Paralithodes camtschaticus) in the southeast Bering Sea from 1975 to 2001 were investigated using data collected during National Marine Fisheries Service annual trawl surveys. Peak abundance of ∼140 million crabs was observed in 1978, and declined rapidly to a low of just over 6 million in 1986. Abundance fluctuated from ∼6 to 22 million from the late 1980s through 2001, with a single strong recruitment event that resulted in ∼35 million ovigerous females observed in 1998. Changes in abundance were accompanied by changes in distribution. During the late 1970s the population was typified by high abundance to the southwest, along the northern shore of Unimak Island and the Alaska Peninsula. By the mid-1980s the population's average center of abundance shifted substantially to the northeast and was found in central Bristol Bay. The distribution remained similar throughout the 1990s. Changes in distribution during the late 1970s and early 1980s coincided with changes in early summer near-bottom temperature. The 1970s were typified by a pool of very cold water (<1°C) within central Bristol Bay. This retreated in ∼1978, and was not observed in consecutive summers during the remainder of the time series. The northeastward shift in the population, measured as the distance between Unimak Pass and the average center of abundance, showed a negative correlation with the geographic extent the cold-pool. Abundance calculated for smaller spatial strata indicate that changes in distribution were not simply the result of relative abundance phenomena or solely generated by mortality in southwestern Bristol Bay, but also reflected regional increases in absolute abundance. Total broodstock abundance declined after 1978, but abundance in the western and northern areas of the region increased until at least 1982. The fact that distribution patterns change over time may have implications for population dynamics and fishery management. Changes in spatial population structure may affect recruitment patterns via changes in larval dynamics, and management might benefit if the causes of geographic displacement can be identified and predicted.
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