Report for April-May-June 2001)
in Distribution, Migration, and Growth of Juvenile
Sockeye Salmon in the Eastern Bering Sea, 1999 and
The Auke Bay Laboratory (ABL) Ocean Carrying Capacity (OCC) program conducted research cruises in the eastern Bering Sea during July and September 1999 and August 2000 to study the early marine distribution, migration, and growth of juvenile Bristol Bay sockeye salmon, Oncorhynchus nerka. The survey area was bounded to the west by Cape Cheerful and to the east by the Ugashik River, crossing the coastal, middle, and outer domains of the eastern Bering Sea. The 1999 and 2000 surveys were the first in a series of annual assessments to document variations in the biological characteristics (growth, migration, and distribution) of juvenile sockeye salmon leaving Bristol Bay. The objectives of the annual surveys are 1) to determine the extent of offshore migrations of Bristol Bay juvenile sockeye salmon and 2) to describe the physical environment of the eastern Bering Sea shelf occupied by juvenile sockeye salmon. The primary goal of the research is to establish and verify the linkages between adult sockeye salmon survival and annual variations in biological characteristics of juvenile sockeye salmon.
Our survey results to date suggest that the migration timing and distribution of juvenile sockeye salmon in the coastal waters of the eastern Bering Sea are influenced by environmental conditions. The July and September 1999 surveys occurred after a cold spring in the eastern Bering Sea, which was characterized by a delay in the breakup of lake ice in sockeye salmon nursery lakes and anomalously cold sea temperatures. During July 1999, juvenile sockeye salmon were mainly distributed in the coastal domain; we speculated that these salmon had not migrated farther offshore into the middle domain due to cold surface temperatures (<6ºC) within the middle domain. By September 1999, surface temperatures had warmed considerably in the middle domain (>9ºC) and juvenile sockeye salmon encountered west of long. 160ºW were mainly distributed within the middle domain. In contrast, our August 2000 survey followed relatively warm spring and summer temperatures and earlier timing of lake ice breakup than during 1999, and we observed increased sea surface temperatures in the middle domain and earlier offshore migrations of juvenile salmon away from coastal waters.
Differences in migration timing and habitat occupied by juvenile sockeye salmon in the eastern Bering Sea may influence early marine growth. During July and September 1999, zooplankton densities were greatest within the middle domain and within the coastal domain west of Port Moller. As mentioned earlier, juvenile sockeye salmon were mainly distributed in the coastal domain east of Port Moller during July and within the middle domain west of Port Moller during September. The distribution of juvenile sockeye salmon captured in September (within areas of higher forage densities) may explain the significantly higher growth and condition factor found for juvenile sockeye salmon captured during September than those captured during July. Furthermore, juvenile sockeye salmon caught during the August 2000 survey were significantly larger than those caught during the September 1999 survey (t = 2.576; p<0.01). Thus, it is quite possible that the increased early marine growth of juvenile sockeye salmon observed in August 2000 was due to increased sea temperatures promoting accelerated migration westward and offshore where zooplankton densities are greater.
Faster growing individuals may have a survival advantage over slower growing individuals since the survival rate of juvenile salmon apparently increases with increased size. Our results suggest that anomalously cold spring and sea temperatures in the eastern Bering Sea may have delayed juvenile sockeye salmon migration into areas of greater forage densities, therefore, reducing early marine growth rate. Similar observations of early marine distribution, migration, and growth of juvenile sockeye salmon encountered within the coastal waters of the eastern Bering Sea during the summer of 1971 (which followed an anomalously cold spring) were followed by dramatically reduced adult sockeye salmon returns to Bristol Bay 2 (1973) and 3 (1974) years later. If this qualitative comparison holds true, then we may expect lower than average returns of 2-ocean and 3-ocean sockeye salmon to Bristol Bay during the 2001 and 2002 summers, respectively.
By Ed Farley.
Surf Smelt Reproduction Confirmed in Northern Southeast Alaska
A small collection of juvenile surf smelt, Hypomesus pretiosus, was received from the ABL Steller sea lion forage study project in Berners Bay north of Juneau. Eulachon, Thaleichthys pacificus, and capelin, Mallotus villosus, are also common in Berners Bay. This confirms that surf smelt have a reproducing population in northern Southeast Alaska and that at least three species of smelt spawn in the Berners Bay vicinity.
By Bruce Wing.
Coral Reference Collection Established
Twenty-one specimens of octocorals were returned by the Smithsonian Institution in June 2001. The specimens had been identified by Dr. Frederick M. Bayer, curator emeritus, at the National Museum of Natural History. Sixteen distinct species from 10 genera were represented. The material was part of the 67 lots of octocorals, hydro-corals, and stony corals submitted last spring as a cooperative project to establish a reference collection of Alaska corals. Much of the material gathered in the past 2 years represents undescribed species or species previously known only from the type material.
By Bruce Wing.
High Seas Salmon Survey
The OCC program, along with scientists from the Fisheries Research Institute at the University of Washington, participated in a cooperative high-seas salmon survey aboard the Japanese research vessel Oshoro maru from 28 June to 10 July 2001. Immature and maturing Pacific salmon were captured by gill net, and over 500 salmon were sampled for diet and stable isotope analysis for the study of trophic dynamics of salmon in the Gulf of Alaska. All six species of Pacific salmon were captured with surface longlines, and 46 salmon were tagged with archival tags (data storage tags with temperature and pressure sensors).
By Jim Murphy.
Chinook Salmon Data Storage Tagging Study
A new cooperative study on chinook salmon, O. tshawytscha, by the ABL Marine Salmon Interactions and OCC programs was launched during the past quarter. The primary goal of the study is to learn more about habitat utilization and migration strategies of chinook salmon that live and grow, at least part of their lives, in Southeast Alaska marine waters. The study will focus on the use of new RL-42 data storage tags which continuously record both temperature and depth data. Jim Murphy is principal investigator for the study, with Bill Heard and Jack Helle as coinvestigators.
The RL-42 tags have a 3-year battery life, are fully encapsulated in clear urethane, measure 8 x 16 x 27 mm and weigh 5 g. Depth (pressure) data range and resolution are automatically scaled to incoming data with a 500-m maximum. The temperature sensor has a range of -5º to 35ºC with 0.20º resolution. Data from recovered tags is downloaded through a light-emitting diode to an optical reader attached to a host computer.
A total of 48 tags were deployed on chinook salmon in April and May 2001 at several locations in northern Southeast Alaska using both a chartered commercial troller and sport fishing vessel to capture fish. Most of the fish tagged were 80-100 cm in length with ocean ages of .3 or .4, however, three fish were ocean age .1 and nine were ocean age .2 fish. Additional chinook are scheduled for tagging later this year when the focus will be on younger ocean age .2 fish. With a 3-year battery life, the intent is to have tags recovered from younger, immature chinook after an extended time at liberty in the ocean. Through analyses of extended temperature and depth profiles of the fish’s environment we hope to improve our understanding of the seasonal movements of the fish. Of particular interest is the usual midsummer appearance of immature, feeder age-.1 and -.2 chinook salmon in the coastal and inside waters of Southeast Alaska, their later apparent disappearance for up to 8 months, and then their return.
A total of six tagged chinook have been recovered to date; four were recovered in the general vicinity of where they were tagged, one was recovered on the Taku River in British Columbia by a commercial fisherman, and one was recovered in the Queen Charlotte Islands by a sport fisherman. None of the data have yet been analyzed.
By Bill Heard.
In the past 3 months, research at the Little Port Walter Field Station (LPW) has focused on Endangered Species Act (ESA)-related studies of steelhead trout, O. mykiss. The 1996 brood that has been held in marine net pens was inventoried in mid-April to measure winter growth, sort out maturing fish, and move some to fresh water for final maturation prior to spawning. These fish all have internal PIT (passive integrated transponder) tags with a detailed record of growth, smoltification, and prior maturation (if any) history. Over-winter survival was very high (>90%), and the fish were in excellent condition. Sibling fish from the same brood that were coded-wire tagged and released as smolts in 1998 began returning in April and were collected for spawning and tag recovery at the Sashin Creek weir. Over 150 tagged adults were recovered from the 1996 and 1997 brood years. Growth and survival of these fish will be compared to captive siblings that have been held through their life in marine net pens at LPW.
Over 325 captive and released adults were spawned to continue the genetic studies initiated from the first spawnings in 1996. From these, 80 families representing eight distinct lines will be cultured separately until age 1 to measure family variability in growth and survival. At age 1 the fish will be pooled by line and cultured to age 2 when the groups will be evaluated for early maturation and smolting. Smolts will be coded-wire tagged and released to measure marine survival between groups to help determine, in part, if maintaining stocks of a normally anadromous fish in fresh water for many generations results in any maladaptation when attempts are made to re-anadromize these fish. The work is important in evaluating proposed recovery strategies for threatened and endangered stocks of steelhead trout and other salmonids. The 1999 brood fish were evaluated this June, and over 4,000 smolts from eight lines were coded-wire tagged and released. These fish will return from the ocean in 2003-2004.
Chinook Smolt Release
The 1999 brood year of tagged chinook salmon smolts representing the sixth generation of hatchery culture for the Chickamin and Unuk River stocks at LPW were released in May. The stock origin of these fish are from two important Southeast Alaska chinook rivers. More than 100,000 tagged smolts were released to maintain the two pure lineages of these stocks at LPW, which will be used for new research focusing on genetic and other interactions of hatchery and wild fish. This new research effort was made possible through increased funding for chinook work at ABL and LPW. Smolts released this year will result in a direct economic contribution to commercial fishermen when the fish are captured in 2-3 years and will also contribute to the sports fishery.
By Frank Thrower.
Hatchery and Wild Stock Chinook Study
The first returns of mature male and female chinook salmon from the 1996 study of the Chickamin River hatchery and wild brood lines will be captured at LPW during July and August 2001. Plans are underway to collect biological and genetic information from these fish and to spawn them as part of a breeding design to examine behavioral and life-history characteristics in the next generation. Scientists from the Northwest Fisheries Science Center and the University of Alaska will participate in the work this summer at LPW. Returns from the 1996 brood will be studied thru 2003. Returns from a similar study utilizing Unuk River chinook will be studied until 2005. Results from these studies will provide information to managers about the impacts and interactions of hatchery-produced chinook salmon.
By John Joyce.
Southeast Coastal Alaska Monitoring Project
The Marine Salmon Investigations Program has completed two of five monthly research cruises scheduled for 2001 in continuation of its Southeast Coastal Alaska Monitoring (SECM) Project. This project was initiated in 1997 to study the habitat use and early marine ecology of juvenile (age-.0) Pacific salmon (Oncorhynchus spp). From May through October annually, biophysical parameters are sampled in inshore, strait, and coastal habitats along a primary seaward migration corridor used by juvenile salmon in the geographic area extending from near Juneau westward through Icy Strait to 64 km offshore in the Gulf of Alaska. The project collects data on seasonal patterns and interannual variation in juvenile salmon distribution and abundance, predation on them by species such as spiny dogfish, walleye pollock, sablefish, and immature salmon, as well as data on zooplankton food abundance and the physical characteristics of these habitats that could affect salmon growth and survival.
In the SECM project’s fifth year of monitoring, sampling locations include a station in Auke Bay and three transects with four stations each in upper Chatham Strait, Icy Strait, and Icy Point on the outer coast. Stations sampled in prior years at Cross Sound, Taku Inlet, Lower Favorite Channel, and False Point Retreat were omitted to focus on key sampling locations and free up time for process studies. The standard fishing gear used is a NORDIC 264 surface rope trawl fished for 20 minutes from the NOAA ship John N. Cobb. Oceanographic samples taken include a 20-m vertical haul with a 0.5-m diameter, 243-µm mesh Norpac net; a double oblique bongo net system sample (0.6-m diameter opening, 333-µm and 505-µm mesh nets) to 200 m depth or within 20 m of bottom; a 0.6-m diameter opening, 202-µm mesh WP-2 net sample to 200 m depth; surface water samples for chlorophyll and nutrient determinations; and CTD casts for temperature and salinity profiles. To target the prey resource potentially most important to juvenile salmon in the water column zone they inhabit, a 20-m bongo sample series was added to augment the oceanographic samples collected.
The May cruise (JC-01-05) was conducted 19-25 May, approximately 2 weeks after the two large scale hatcheries in northern Southeast Alaska (Douglas Island Pink and Chum Hatchery, near Juneau, and Hidden Falls Hatchery, located on northeastern Baranof Island) had released approximately 130 million thermally marked chum salmon into local marine waters. The annual May cruise is timed to precede the departure of juvenile salmon from near-shore waters along the beaches; therefore, in May 2001 standard oceanographic sampling was conducted at the 13 stations, but trawling for juvenile salmon was limited to the 4 Icy Strait stations. In addition, juvenile pink and chum salmon (approximately 40-60 mm in fork length) were sampled on beaches in Icy Strait with a 37-m long beach seine. The primary purposes of this nonstandard sampling were 1) to collect specimens to document the arrival of hatchery chum salmon at locations distant from their release sites before they can be captured in deeper waters accessible by trawl , 2) to collect and preserve samples of juvenile pink and chum salmon at approximately 3-hour intervals to determine their diel feeding rhythms, 3) to obtain live specimens of each species for shipboard gastric evacuation experiments, and 4) to freeze specimens of each species for later bomb calorimetry to determine energy content (a measure of condition). Approximately 450 individuals were preserved, and 300 were frozen for these purposes. Diel samples of each species were preserved at approximately 07:00, 10:45, 14:00, 18:00 and 21:00 on 21-22 May. Evacuation sample series were started at 06:50 and sacrificed roughly 1, 2, 4, 6, 8, 11, 14, 24 and 32 hours later.
The June cruise (JC-01-09) was conducted 26 June to 2 July. Standard oceanographic sampling and surface trawling were conducted at the 13 stations. In addition, a diel sample series was collected by trawling at 3-hour intervals at an Icy Strait station over 2 days. Feeding periodicity will be determined from pink, chum, and coho salmon stomach samples collected on 29 May at 04:00, 07:00, 10:00 and 13:00, and on 30 May at 13:00, 16:00, 19:00 and 22:00. The evacuation experiments could not be conducted on this cruise because catches were too low to obtain sufficient specimens, and fish were in poor condition after trawling. For chum salmon, no catches exceeded 40-60 individuals, catches of pink salmon were even lower, and fish were badly descaled. The feeding periodicity samples will be repeated during the next SECM cruise (27 July - 2 August). The evacuation experiments also will be attempted during the July cruise. The fish should survive the trawl in better condition because of their larger size and because of a higher abundance of jellyfish, which cushion the fish in the cod end of the trawl.
By Molly Sturdevant, Alex Wertheimer, and Joe Orsi.
Auke Lake Sockeye Salmon Smolt Migration
The NMFS Auke Creek Weir provides the opportunity to enumerate and sample both upstream and downstream migrating salmonids. The ABL has compiled historical data series consisting of sockeye salmon adult and smolt counts and biological information. Preliminary data from 2001 indicate above average numbers of smolts are leaving the system and that some are unusually large. In Auke Lake sockeye salmon spawn in the larger tributaries and on submerged gravel beds in the lake. The production of wild sockeye smolts from Auke Lake was first estimated in 1961. From 1961 through 1979, smolt numbers were estimated several times, but some of the early smolt estimates are known to be incomplete. The pre-1980 smolt estimates lack continuity, and based on the pre-1980 escapements, it is obvious there has been a significant decrease in the number of smolts since the 1960s and early 1970s. The 1961 estimate of 90,000 smolts is the highest on record, and estimates from 1962 through 1979 ranged from 8,862 to 62,389. Since 1979, the entire smolt population has been counted at Auke Creek weir, and the number of wild smolts ranged from 1,719 to 33,616.
Hatchery-reared sockeye fry stocked in Auke Lake in 1974-75 and 1987-89 contributed to the smolt production in subsequent years. Sockeye enhancement in the late 1980s and early 1990s included the release of underyearling smolts that were reared in the hatchery and net pens in Auke Bay. Adults returning from enhancement projects contributed to the escapements and subsequent smolt production. The average number of wild smolts produced in Auke Lake, 1980-2001, is 16,897 (Figure 1 below). In 2001, a total of 21,428 sockeye smolts were counted at Auke Creek weir during the downstream migration. The downstream migration of sockeye smolts began in early May, and about 15,000 smolts migrated during the last week of the month. The migration midpoint was 27 May, 3 days later than average. All sockeye salmon smolts in 2001 were from natural spawning in the Auke Lake system. Scale analysis revealed that 41% (8,754) of the smolts were age-1, 1999 brood fish and 59% (12,674) age-2, 1998 brood fish. The 1998 brood completed the freshwater phase of its life history and produced a total of 16,429 smolts, slightly less than the average 17,259.
One measure of freshwater survival, the number of smolts produced per spawner, indicates that for the last 13 brood years fewer than 10 smolts were produced per spawner in Auke Lake. The 1998 brood production of eight smolts per spawner, was the highest in 7 years (Figure 2 below). In 2000, age-1 and -2 smolts averaged 77 and 131 mm, and 3.9 and 19.6 g, respectively (Figure 3 below). The age-2 smolts were some of the largest on record leaving Auke Lake. The long-term average for age-1 and -2 sockeye smolts leaving Auke Lake is 75 and 107 mm, and 3.9 and 12 g, respectively.
Total biomass zooplankton models indicate Auke Lake is capable of producing about 350 kg of smolts annually. The total biomass of sockeye smolts (estimated total weight of all smolts in a migration year) from Auke Lake in 2001 was 282 kg (Figure 4 below ). This was greater than the average of 142 kg and was the second highest on record for Auke Lake.
By Jerry Taylor.
First Frederick Sound Cruise of the Southeast Alaska Steller Sea Lion Prey Study Completed
The first cruise in Frederick Sound for the Southeast Alaska Steller sea lion prey study was completed during 22 May to 2 June 2001. The purpose of the study is to test the hypothesis that juvenile sea lion prey diversity and seasonality are related to Steller sea lion population trends. The study is a comparison study to one being conducted around Kodiak Island by the University of Alaska. During the Frederick Sound cruise, prey abundance was measured using echo-integration and a midwater trawl. Scat was collected to infer diet. Fish also were collected for proximate and free fatty acid analysis. Prior to the cruise, Alaska Department of Fish and Game (ADF&G) scientists satellite-tagged sea lions in the area; the location information from the tagged animals was very helpful for conducting our cruise. Mostly juvenile walleye pollock and some Pacific herring were found at depths less than 75 m, adult pollock were found from 75 to 250 m, and Pacific whiting were found deeper than 250 m. Both day and night sampling was conducted to determine if availability of fish sea lion foraging depths was affected by time of day. There was little day-night difference in fish depth difference except that some adult pollock were found at shallower depths during night. Sea lions were found at three haulouts in Frederick Sound near The Brothers (Sunset Island, Sail Island, Southwest Brothers Island); the number hauled out totaled about 1,300 animals.
Scientists aboard the vessel were Mike Sigler, Johanna Vollenweider, and Dave Csepp of ABL and Olivier Cheneval of the University of British Columbia. Quarterly sampling is planned for the Frederick Sound study area with the next cruise scheduled for September 2001.
By Mike Sigler.
Juvenile Sablefish Tagging Cruise
The annual juvenile sablefish tagging cruise in Southeast Alaska was conducted aboard the John N. Cobb in Saint John the Baptist Bay from 12 to 15 June and in Silver Bay from 15 to 16 June. A total of 110 fish were captured with hook and line jigging gear in Saint John the Baptist Bay in 128.5 rod hrs (0.86 fish/rod/hr); 105 fish were tagged and released. One previously tagged fish
(# 16132) was measured (length 46 cm) and released. No fish were captured in the vicinity of Silver Bay. An underwater video camera was used by the crew to document juvenile sablefish taking bait from the jigging gear without taking the hook. This type of video information may enable the design of more efficient jigging gear in the future.
By Dean Courtney.
Effects of Trawling
Members of the ABL Groundfish Program conducted an effects of trawling study off Kodiak Island, 11- 18 June. Program staff were Bob Stone (project leader), John Karinen, Pat Malecha, Jon Heifetz, and Phil Rigby. The study used Delta Oceanographic’s submersible research vessel Delta; the contracted sub tender AJ, and the contracted Kodiak fishing vessel Peggy Jo. The study area, 10 miles offshore of Cape Chiniak, was approximately 1,300 m by 600 m and consisted of three corridors: a control corridor and a corridor each for a single trawl pass and for multiple (six) trawl passes. The site is an area closed to trawling in approximately 140 m of water and with large numbers of sea whips distributed throughout.
Before and after trawling by the Peggy Jo, the control and treatment corridors were sampled using the Delta for strip transects and with a Shipek grab sampler for infauna, sediment, and carbon composition. The Peggy Jo used a Bering Sea 107/136 combination (flatfish) trawl. The vessel location was plotted with navigation equipment on board the trawler, and door spread and net height were measured with an acoustic mensuration system. Location of the net with an attached transponder was tracked from the AJ with a track point system operated by the Delta crew. Observed evidence of trawling consisted of shallow grooves on the seafloor from discs on the net’s footrope, bent and damaged sea whips, dislodged anemones, and narrow tracks from the trawl doors. Although damage to sea whips was evident in the multiple pass corridor, the numbers remaining and the lack of deep furrows was less impact than expected by the investigators. Such observations are very preliminary, and results from the analysis of the benthic samples and transect counts should be available in spring 2002.
By Phil Rigby.
Surveys of Heavily Fished Areas of the Gulf of Alaska
The Sustainable Fisheries Act of 1996 was passed to attain long-term protection of essential fish habitat and specifically requires that NMFS minimize adverse impacts to essential fish habitat by fisheries. There is little knowledge of what the bottom habitat looks like where major fisheries occur. Without knowledge of whether or where vulnerable habitat is at risk, measures adopted to minimize impacts may be ineffective or unnecessarily restrictive.
The ABL Groundfish Program is conducting a study to find, describe, and map habitat vulnerable to fishing impacts. Vulnerable habitat is believed to occur on rough, hard, or steep bottom. Vulnerable habitat in soft bottom areas such as sea whip beds or coral habitat in inshore areas where little trawling takes place is not the objective of this phase of our study. Rough bottom is believed to occur often on the shelf area near steep slopes. Rockfish are typically found on rough bottom, based on the type of gear used by trawlers targeting rockfish. Using the research submersible Delta during 19-23 June, the Groundfish Program characterized habitat on Portlock Bank, Alaska, in the vicinity of rockfish fishing grounds. Program staff were Robert Stone and Pat Malecha. Twelve dives at six sites were completed. Surprisingly, the bottom was primarily soft sediments and pebbles with few large rocks or rock outcroppings. Small hard corals and some damaged sponges were observed. In August, we plan to map the area using multibeam acoustic technology.
By Jon Heifetz.
Surveys of Habitat Areas of Particular Concern
Habitat Areas of Particular Concern (HAPCs) are types of Essential Fish Habitat (EFH) that are deemed especially vulnerable to anthropogenic impacts. Gorgonian corals, especially red tree coral (Primnoa sp.), are HAPCs that are thought to be particularly vulnerable to the impacts of fishing gear. The North Pacific Fishery Management Council (NPFMC) has proposed that specific sites in Alaska be closed to fishing that have significant amounts of gorgonian coral. Using the research submersible Delta during 25-30 June, members of the Groundfish Program surveyed the biological and physical aspects at two of these sites; one located off the southwestern tip of the Kenai Peninsula and the other near Yakutat. Program staff were Linc Freese and Pat Malecha.
By Jon Heifetz.
Estuarine Wetland Survey
Estuarine wetlands are among the most productive habitats for fish that sustain marine fisheries worldwide, yet little is known about their role in the productivity of Alaska fisheries. There have been no comprehensive surveys of the extent or quality of fish habitat in Alaska estuaries, however, there is evidence that some estuaries may be under stress from human activities. For example, nearly 60 coastal streams listed by the State of Alaska as impaired water bodies drain into estuaries. Consequently, estuaries in urban areas are currently considered habitat areas of particular concern by the Alaska EFH Core Team
In 1998, ABL scientists proposed research on EFH in Alaska’s estuaries to help NMFS managers develop an understanding of the functional role of estuaries in Alaska fisheries and coastal health. The objectives of the work are 1) to identify and describe EFH for species covered by fishery management plans (FMPs) in estuarine wetlands throughout Southeast Alaska; and 2) to develop means of estimating and predicting effects on estuarine EFH as coastal development takes place.
Previous research has documented the use of estuaries near Juneau by 19 species of fish in the NPFMC FMP. Groundfish (e.g., yellowfin sole, rock sole, starry flounder), anadromous salmon, and important forage species (sand lance, herring, eulachon, and many invertebrates) are plentiful in those estuaries. In addition, a habitat classification system is being developed to stratify and map estuarine fish habitat. Habitat types that have been identified and sampled include emergent marsh wetlands, mud flats, sloughs, and sand and gravel beaches. A demonstration geographic information system (GIS) was developed for the Mendenhall Wetlands near Juneau to test the use of existing digital imagery and maps in identifying estuarine EFH. Digital photography, NOAA charts, and National Wetland Inventory maps have been integrated with data on fish abundance and habitat classification gathered by NMFS scientists. A GIS that can be used to evaluate the extent and value of fish habitat in the Mendenhall Wetlands was developed from those data. The methods developed in this work can be used to generate a regional GIS for estuarine EFH and eventually to help provide more accurate GIS coverages for other EFH.
In July 2001, NMFS scientists began the process of ground truthing additional Alaska estuaries for comparison to EFH found in the Mendenhall Wetlands. Two sites in the Icy Strait and Cross Sound area (Mud Bay and Port Althorp) were sampled. Preliminary findings indicate a shift in fish diversity and water chemistry in estuaries nearer the outer coast. That information will be important in developing a regional GIS capable of estimating estuarine habitat quality and productivity.
By Mitch Lorenz.
2001 Sablefish Longline Survey
The AFSC has conducted an annual longline survey of sablefish and other groundfish in the Gulf of Alaska since 1987. The survey is a joint effort involving the ABL and the Resource Assessment Conservation Engineering (RACE) Division. Beginning in 1996, biennial sampling of the Aleutian Islands region and eastern Bering Sea was added.
The 2001 survey began 2 June and will end 3 September. The survey vessel is the chartered fishing vessel Ocean Prowler. As of this writing, the survey has sampled the eastern Bering Sea, the western Gulf of Alaska, and three seamounts. Orca whales (Orcinus orca) took fish from the longline at five stations in the Bering Sea which is similar to previous years. Catch rates appear to be up from last year’s survey for both areas. In the western Gulf 19,300 sablefish were caught and average length was 66 cm. The same stations produced 13,445 fish in 2000. Early indications are that there was a strong 1997 year class that is now showing up in survey catches.
A study initiated in 1999 to determine the extent, if any, of seamount-to-slope and seamount-to-seamount sablefish migration continued during 2001. Three seamounts were sampled during the vessel’s transit from Sand Point to Ketchikan at the end of Leg 2. Sablefish catches were down slightly from last year on Surveyor and Welker Seamounts. Dickens Seamount, which was sampled for the first time this year, is shallower and rockier than other seamounts we have sampled, and rougheye and shortraker rockfish made up about one third of the catch. Male sablefish outnumbered females by a wide margin on all three seamounts. About 1,000 sablefish were tagged and released on the three seamounts, bringing the total number of tags released on seamounts since 1999 to just less than 2,700. Twenty-one tags were recovered from sablefish tagged in previous years, and one sablefish which was tagged in the Aleutian Islands region in 1982 was recovered on Dickens Seamount.
By Chris Lunsford and Nancy Maloney.