5 posts from June 2009
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5 June 2007 Pribilof Canyon
"Sea Whips" are a member of the Pennatulacean corals. At over 2 meters high, Halipteris willemoesei is the tallest coral recorded in Pribilof Canyon. We will refer to three sources of data on its distribution and ecology: a trawl-ROV study by Brodeur (2001), the NOAA Groundfish Observer online database, and the Greenpeace Bering Sea Canyons Submarine Expedition (2007).
In the Brodeur (2001) study, the author reports observing dense aggregations of Pacific Ocean Perch (Sebastes alutus) (>30 fish per minute) occupying "forests" of Halipteris willemoesii colonies. Colonies were evenly spaced about 2 m apart. This study contrasted these findings with areas in which no sea whips were found ... Pacific Ocean Perch were also absent.
The NOAA Groundfish Observer database invertebrate bycatch maps (right)show that seawhip bycatch in the pelagic trawl fishery occurred in the head of the canyon as well as on the shallower shelf just above the canyon in 2006.
Submarine pilots also observed dense aggregations of Halipterus willemoesii in upper Pribilof Canyon during dives in 2007 (left). Like Brodeur, many observations of these sea whips revealed a close association with Pacific Ocean Perch, especially when whip density was higher.
We are looking forward to seeing whether the sonar backscatter data can detect seawhips on the flat, sedimentary seafloor terrain they occupy.
4 June 2009 Pribilof Canyon
Based on previous surveys in this region, it appears as if
typical seafloor type in the upper canyon is compacted sediment with some sand or silt over the top. In this canyon seafloor image, Plumarella seafan corals are densely distributed (right), with a few sponges among coral colonies.
Clean, current-swept gravel bottom is also common at two sub dive sites in the upper portion of Pribilof Canyon (left). In this image, largemouth sculpin, seastars, brachiopods, brittle stars, small demosponges and possibly a conical scleractinian coral are among the invertebrates occupying one dive site in the upper canyon (depth approx 280 m).
3 JUNE 2009
We left Captain's Bay, Unalaska Island in the wee hours of this morning, headed directly to Pribilof Canyon. Seas were calm, with a lovely sunset. We arrived at the canyon this afternoon.
Since most of the crew were both tired and about to split up into shifts to work through the 24-hour days, we gathered in the survey room for likely the last time during the voyage.
Our destination is the mushroom-shaped canyon laying just south of the Pribilof Islands (right). The canyon edge is about 25 km south of St. George Island.
Michelle and Candace will be observing data returns from time to time to see whether backscatter is useful for interpreting the seafloor substrata or biotic features.
Weather has been picking up through the day, .
Meanwhile, BioGea Team is plotting submarine and ROV dive sites in a GIS database and reviewing underwater film footage of those sites.
02 JUNE 2008 DUTCH HARBOR, ALASKA
The 230' hydrographic survey ship, Mt. Mitchell arrived at Captain's Bay, Unalaska Harbor early this morning!
Captain and crew just spent a week crossing the Gulf of Alaska, then another week in the Bering Sea searching for oceanographic moorings along the ice edge and near the Pribilof Islands. They are in great spirits and busy changing equipment, personnel and topping up supplies for the Pribilof Canyon seafloor mapping expedition.
The ship has served on many Alaskan voyages and has a "following" in nearly every port! Visitor Brenda Tellman is gracing the bow with Captain Lawrence.
The Mt. Mitchell took PMEL field staff to service buoys at central and southern Bering Sea sites last week. Here, they are demobilizing -- removing gear from the Mitchell to ship to Seattle for data retrieval. The buoyed arrays are moored at traditional locations in the Bering Sea to collect oceanographic data on current speed, direction, temperature, salinity, and other parameters.
Exploring Dutch Harbor-Unalaska!
Ship and survey crew spent much of the day tending to chores and taking in shoreside opportunities not available at sea. Many explored the open terrain of the island on foot or by vehicle. Intrepid runner, AB Linda Mancuso ran 18 miles over the Unalaska Pass, while others drove around sight seeing and savouring local restaurant fare.
Personal use king crab fishing opened in Dutch Harbor at Midnight, so w
Candace and I worked this afternoon with ADF&G Observer Program staff Mary and Melissa, to review the diversity of
corals, sponges and bryozoans their field crew have collected in Aleutian and Bering Sea fisheries. This huge collection is in excellent shape and a great resource for training observers in Melissa's "Living Laboratory". We are trying to determine which species may have sufficiently dense skeletons and size to be detected by sonar backscatter returns. Paul Wilkins of the NOAA Fisheries and Monitoring Division toured us around the online databases which archive information on coral, sponge and bryozoan bycatch in federal fisheries. These data show some bycatch of corals and sponges in Pribilof Canyon -- especially in the non-pelagic trawl fisheries.
Candace Stepetin on the traditional Mt. Ballyhoo hiking trail. Many seafarers hike the mountain before setting out to sea, as it provides a phenomenal view and a stretch of the legs before long journeys at sea. The view shows Unalaska and Dutch Harbor, including the original village and tremendous commercial fishing infrastructure supporting fleets, processing and shipping products harvested from the Bering Sea grounds.
We wrapped up our shore excursions by 2230 hours and set sail northeastward toward Pribilof Canyon shortly after midnight.
01 June 2009 Anchorage to Dutch Harbor, Unalaska Island, Alaska
PRIBILOF CANYON SEAFLOOR MAPPING EXPEDITION 2009
During our submarine expedition to the Bering Sea Caynons in 2007, we conducted 14 dives in Pribilof Canyon and 4 ROV surveys. We distributed our dive effort around the canyons at roughly equidistant intervals, to cover the depth ranges reachable in the deepworker submarines -- a maximum of 630 meters. The ROV could reach 1,100 meters. At that time, we navigated using the best available bathymetric (seafloor depth) information available.
Most of that data was based on relatively crude surveys from the 1960's, making it difficult to plan dives to precisely hit our depth and seafloor feature targets. OK, we were essentially "flying blind"! Our current mission is to map the canyons for purposes of future submarine research navigation and for many other purposes.
Pribilof Canyon and the connected Pribilof Domain waters surrounding the Pribilof Island Archipelago are recognized for their unique, highly productive characteristics by scientists in many disciplines --- geologists, fisheries biologists, oceanographers, benthic ecologists, foodweb specialists -- concur that the region's physical and biotic attributes are outstanding relative to the shelf break and shelf regions nearby. How unique and quantifying facets of the canyon geo-bio setting are challenges we continue to address.
Since so many marine scientific disciplines rely intimately upon modelling, and modelling requires a fundamental understanding of the geomorphology of the canyons, Dr. Dave Scholl and I underscored the importance of obtaining fine scale bathymetric data for the canyon system during our address at the Marine Science Symposium (Anchorage, January 2008). Dave, who first mapped the canyons with Dave Hopkins in the late 1950s, was startled to find that very little mapping effort has been conducted in that area in nearly 50 years!
Finally, a team with the right stuff has been assembled to map
the canyon.
St. Paul Islander, Candace Stepetin and I are focusing on biogeographical exploration of Pribilof Canyon. We will be examining areas already surveyed visually by submarine and ROV in previous years to observe the depth profiles, geomorphology of the area, and to ascertain whether the backscatter component of the sonar returns being used on this survey are capable of detecting seafloor features documented by sub.
The team is gathered in Anchorage on weather hold ... awaiting our flight to Cold Bay and westward to Dutch Harbor this afternoon.
