MCAF Cooperative Research Summary

Transcription

1 MCAF Cooperative Research Summary Test Deployment of a Towed Camera Sled for Weathervane Scallop Habitat and Stock Assessment from a Commercial Scallop Fishing Vessel Work on this project began in April, 2011 when FV Arctic Hunter arrived in Kodiak after completing the Bering Sea snow crab season. Personnel involved in the cooperative effort were John Lemar, Tommy and Bobbie Minio, and Josh xxx from the Alaska Scallop Association (ASA), and Gregg Rosenkranz, Ric Shepard, and Ryan Burt from the Alaska Department of Fish and Game (ADF&G) Kodiak office. To enable deployment of Alaska CamSled from Arctic Hunter, the vessel's starboard scallop winch and one scallop dredge were removed and stored at the ADF&G-Kodiak warehouse for the duration of the project. After the CamSled vehicle and control module were loaded and secured aboard the vessel (Figure 1), an adapter plate was fabricated by a local metal shop which allowed us to mount the CamSled winch on the foundation that normally holds the scallop winch. An electrical contractor was employed to connect vessel power to the CamSled control module and winch, which runs from its own electric/hydraulic power pack. For CamSled launch and recovery, a stainless steel eye was fabricated and attached to the sled's lifting bar (Figure 2), and the Arctic Hunter starboard cargo winch was rigged with a hook with spring loaded gate that could be opened by pulling on an attached line. This enabled us to lift CamSled over the starboard rail using the cargo winch and disconnect the hook when the vehicle was overboard, partially submerged, and tension was taken by the CamSled winch. After connecting the fiber optic tow cable to the sled, initial launch and recovery tests were conducted in Chinak Bay (Figure 2). This allowed us to practice deployment multiple times with no electronics mounted on the sled. Once we were satisfied with launch and recovery procedures, Arctic Hunter returned to the dock, and ADF&G staff began mounting components and cabling on the sled and testing the system. During this phase, ADF&G employees worked on CamSled while ASA fishermen worked on Arctic Hunter and Provider in preparation for the 2011/12 scallop season. The first sea trials with Arctic Hunter and fully rigged CamSled occurred on 27 April in Chiniak Bay. Technical problems with two strobe lights and a defective sonar head led us to haul back after a short tow; launch and recovery went smoothly and a few thousand images were recorded. Rocky habitat was encountered unexpectedly due to the non-performing sonar (Figure 3), but the sled was not damaged.

2 After replacing the sonar head and working on the CamSled lighting system, more sea trials were conducted in Chiniak Bay on 30 April. We towed CamSled for about two hours with all systems working properly. Communication between the vessel operator in the Arctic Hunter pilothouse and CamSled operators in the module was over low-power VHF radio. At-sea operations occurred 1 May to 3 May off the eastside of Kodiak Island in scallop fishing grounds of Chiniak Gully and again on May 19 in Chiniak Bay during a final day trip. Literally thousands of scallops were digitally captured (e.g., Figure 4), and in situ images of a number of mating pairs of Tanner crabs Chionoectes bairdi were also obtained (Figure 5). Overall, we towed CamSled over 220 km and recorded approximately 590,000 images documenting benthic habitat and associated fauna. Additionally, eight 10-minute dredge tows were made in Chiniak Gully to compare performance of ADF&G's lined 8 foot scallop survey dredge with the standard 15 foot dredge used by the scallop fleet. The dredge tows also allowed ADF&G to collect scallop specimens which were individually processed to collect shell height-meat weight data that will be used to convert counts and measurements of scallops from image review to scallop biomass estimates. CamSled equipment and ADF&G's scallop dredge were removed from Arctic Hunter on 20 May 2011 and the scallop winch was remounted on its foundation. ADF&G staff were extremely pleased with the joint research effort. Arctic Hunter is considerably larger than the ADF&G research vessel Pandalus that was used during development of CamSled. The extra deck space allowed us to easily switch between sampling with CamSled and two different scallop dredges, and the vessel's beam contributed to stability that made it possible to deploy CamSled over the side (rather than off the stern). Space under the shelter deck was used for processing scallops from dredge tows. Synergy between ASA fishermen and ADF&G staff was also good. One of ADF&G's research goals is basic mapping of scallop beds and scallop habitat in all fishing areas, an endeavor that will definitely be easier to accomplish with help from scallop vessel operators.

3 Figure 1. CamSled and control module on deck of Arctic Hunter. The CamSled winch is partially visible on forward upper deck. Figure 2. John Lemar, Gregg Rosenkranz, and Tommy Minio during initial launch and recovery testing on Arctic Hunter.

4 Figure 3. Image of rocky habitat in Chiniak Bay recorded by CamSled, 27 April 2011.

5 Figure 4. Mosaiced image of weathervane scallops on sandy mud habitat of Chiniak Gully recorded by CamSled, 1 May 2011.

6 Figure 5. Image of mating Tanner crabs in Chiniak Gully captured by CamSled, 1 May 2011.