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Groundfish Assessment Program

Deep-Sea Coral Distribution and Habitat in the Aleutian Islands

Two studies were completed in the Aleutian Islands in summer 2004 on the distribution and habitat of deep-sea corals and the biological communities associated with these corals. The first study used the piloted submersible Delta in June and July. The second study in late July used the RV Roger Revelle as a support vessel for the remotely operated vehicle (ROV) Jason II.

The Delta was used to complete the second and final phase of a project to assess Aleutian Islands coral habitat in waters less than 365 m deep (the maximum depth at which the submersible can operate). The North Pacific Research Board and the AFSC funded this component of the study. Participating ABL scientists were Robert Stone (chief scientist) and Eloise Brown. Scientists visited 10 sites and collected video of the seafloor on 23 strip transects. Previously undocumented beds of sponges, predominantly demosponges, were documented on an additional six dives. More than 150 coral specimens were collected for molecular and morphological taxonomic identification and for studies on reproduction. More than 100 sponge specimens were also collected, and 5 of the first 10 specimens analyzed microscopically were confirmed as species new to science.

On 24 July, the Roger Revelle departed Dutch Harbor, Alaska, with a team of biologists, fisheries scientists, and geologists to study deep-sea coral habitat in the central Aleutian Islands. The team, including Robert Stone (chief scientist) and also ABL scientist Jon Heifetz used the ROV Jason II (Woods Hole Oceanographic Institute) to document coral and sponge habitat. The team also collected deep-water specimens -- many new to science -- for ecological and taxonomic studies. This cruise was the final component of a comprehensive study initiated in 2003 and funded by NOAA Fisheries and the North Pacific Research Board through NOAA’s Undersea Research Program. The team hopes to use their findings to construct a model to predict where coral habitat is located throughout the Aleutian Islands region. The model will provide fisheries managers with a powerful tool to conserve the region’s coral habitat.

Dives were made with the Jason II at 10 sites in the Central Aleutian Islands, at depths ranging from 131 m to 2,948 m. Video footage of the seafloor was collected along strip transects ranging from 13.2 to 2.4 km in length. Corals and sponges were widely distributed at the study sites, with an apparent change in density, diversity, and species composition at a depth of approximately 1,400 m. Samples were collected at stations along transects and included 260 corals, 45 sponges, 165 miscellaneous invertebrates, and 82 rocks. Preliminary results indicate that representatives from all seven coral families known to occur in the North Pacific were collected and that several of the collected sponges represent new species.

By Robert Stone

2004 Sablefish Longline Survey

The AFSC has conducted an annual longline survey of sablefish and other groundfish in Alaska from 1987 to 2004. The survey is a joint effort between the Center’s ABL and Resource Assessment and Conservation Engineering (RACE) Division. The survey replicates as closely as practical the Japan-U.S. cooperative longline survey conducted from 1978 to 1994 and also samples gullies not sampled during the cooperative longline survey. In 2004, the twenty-sixth annual longline survey of the upper continental slope of the Gulf of Alaska and eastern Aleutian Islands was conducted. One hundred forty-eight longline hauls (sets) were completed between 5 June and 1 September by the chartered fishing vessel Alaskan Leader. Sixteen kilometers of groundline were set each day, containing 7,200 hooks baited with squid.

Sablefish (Anoplopoma fimbria) was the most frequently caught species, followed by giant grenadier (Albatrossia pectoralis), Pacific cod (Gadus macrocephalus), and shortspine thornyhead (Sebastolobus alascanus). A total of 90,226 sablefish were caught during the survey. Sablefish, shortspine thornyhead, and Greenland turbot (Reinhardtius hippoglossoides) were tagged and released during the survey. Length-weight data and otoliths were collected from approximately 2,600 sablefish. Killer whales (Orcinus orca) took fish from the longline at several stations in the western Gulf of Alaska near Dutch Harbor; this also commonly occurred during past surveys. Sperm whales (Physeter macrocephalus) were present during haul-back at more than 20 stations and many were observed taking fish from the line. This is a substantial increase over previous surveys. A sperm whale depredation analysis is currently being done to determine the effects these whales may have on the catch. Results should be available in the 2005 sablefish assessment. The majority of sperm whale interactions occurred in the west Yakutat and central Gulf of Alaska areas.

Several special projects were conducted during the 2004 longline survey. Coral caught on the line was collected for identification and sample preservation. A seabird occurrence study was conducted for the third year to document where and when certain seabird species occur in Alaska waters. In addition, the Alaska Department of Environmental Conservation (ADEC) is conducting a monitoring project for environmental contaminants in Alaskan fish. Approximately 50 specimens of sablefish caught on the longline survey were collected throughout the Gulf of Alaska and Bering Sea and sent to ADEC for contaminants analysis.

By Chris Lunsford

Joint Research on Spiny Dogfish in Yakutat Bay, Alaska

Little is known about the life history or ecological role of spiny dogfish (Squalus acanthias) in the North Pacific Ocean. In this study, scientists from ABL and the University of Alaska Fairbanks School of Fisheries and Ocean Sciences, Juneau Center, conducted joint research on spiny dogfish in Yakutat Bay, Alaska. Spiny dogfish were captured for tagging and biological sampling from a 30-ft sport-fishing boat chartered from 27 to 29 July 2004. A total of 59 spiny dogfish were tagged and released. Electronic archival tags were surgically implanted in 37 spiny dogfish. A fluorescent pink disc tag with the words “reward for tag inside fish” was attached to the first dorsal fin of each electronically tagged spiny dogfish. The ABL offers a $200 reward for the return of electronic archival tags from spiny dogfish. An additional 22 spiny dogfish were tagged only with externally attached, modified disc tags. The modified disc tags were uniquely numbered on one side with the ABL address printed on the other side.

A total of 118 spiny dogfish were taken for biological sampling of age, maturity, and diet, including 96 females (80–110 cm total length) and 22 males (80–90 cm total length). Age will be determined from dorsal spines. Maturity and diet were examined on the boat. Most (80%) of the spiny dogfish examined were immature. One female was pregnant with eight very young embryos. Most stomachs were empty, but the few items found suggest that spiny dogfish in the Yakutat region are opportunistic predators with a high incidence of invertebrates in their diet. Items found in stomachs in order of incidence of occurrence included several species of jellyfish, razor clams, shrimp/krill, and unidentified forage fish species.

By Dean Courtney

Pacific Herring/Steller Sea Lion Study Initiated in Southeast Alaska

  Map of herring schools
Figure 3.  Map of Southeast Alaska showing locations of herring schools.

In September 2004, a study assessing over-wintering Pacific herring stocks in Lynn Canal, Southeast Alaska was initiated. The purpose of the study is to quantify herring as a prey resource for Steller sea lions inhabiting a haulout on Benjamin Island. Benjamin Island is a seasonal haulout attended by more than 800 sea lions during the winter months. Scat analyses have shown herring to be the most frequently occurring prey item for sea lions at this site. Specific objectives of the study are to estimate the spatial predictability of herring schools on monthly, weekly, and daily time scales. Secondly, the seasonal biochemical composition of herring will be analyzed to quantify the schools as a nutritional source for sea lions. In addition, the cardiac fatty acids of the fish will be examined for the development of a tool to discriminate herring stocks.

On 27 and 28 September, the first research cruise of the study was conducted by ABL scientists J. J. Vollenweider and Dave Csepp on a chartered gillnet vessel. A portion of Lynn Canal was surveyed with hydroacoustics along a zigzag transect line, traversing deep trenches in which herring are known to reside (Fig. 3 above). Herring schools were observed along the transect line. Some of these were pelagic, while others appeared to be commencing their benthic schooling behavior characteristic of winter. One particularly large school spanning approximately 200 m was found from a depth of 23 m down to the bottom at 55 m. Single humpback whales were the only marine mammals observed feeding on the schools. Herring samples were collected at three locations using vertical sampling gillnets and jigs. Additional cruises are planned each month through April 2005.

By J. J. Vollenweider

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