Brenda Norcross | University of Alaska Fairbanks (original) (raw)

Papers by Brenda Norcross

www.oilspill.state.ak.us 907/278-8012 This publication was released by the Exxon Valdez Oil Spill... more www.oilspill.state.ak.us 907/278-8012 This publication was released by the Exxon Valdez Oil Spill Trustee Council and produced at a cost of $4.73 per copy. The Exxon Valdez Oil Spill Trustee Council conducts all programs and activities free from discrimination, consistent with the Americans with Disibilities Act. This publication is available in alternative communication formats upon request. Please contact the Trustee Council Office at 907/278-8012 to make necessary arrangements. Any person who believes she or he has been discriminated against should write to: The EVOS

Seafloor Geomorphology as Benthic Habitat, 2012

Publisher Summary Albatross Bank is located in the Gulf of Alaska's outer continental shelf n... more Publisher Summary Albatross Bank is located in the Gulf of Alaska's outer continental shelf near Kodiak Island. Geologically, it sits in a broad forearc above the Alaska subduction zone, 50–100 km north of the trench and 250 km south of the Alaska arc volcanoes. Earthquakes and vertical tectonic processes from active plate collision form the general morphology of the region. Bedrock at the outer shelf is composed of Miocene and younger sedimentary strata, mostly flat lying, and hosts seeps that vent methane-bearing fluids. Albatross Bank is influenced by strong ocean currents. The Alaskan Stream flows along the shelf break and continental slope in a generally southwest direction. Assessment of biological communities is based on analysis of submersible observations of fishes and macroinvertebrates. The focus was on the abundance and community composition patterns of fishes relative to substrate types and water depth. Rockfishes were the most abundant group, accounting for 69% of the fishes observed. This study employed statistical methods to study associations between fish communities and benthic habitat, and hence identified habitat types that may be useful as surrogates in a search for potential habitat of these fish communities.

[Missing plankton, jellyfish, seine, trawl, bird and CTD data sets from this study] Sound Ecosyst... more [Missing plankton, jellyfish, seine, trawl, bird and CTD data sets from this study] Sound Ecosystem Assessment (SEA) aerial surveys, 1995 - 1997: We show that aerial visual surveys are a cost-effective method to assess distribution and abundance of forage fish and seabirds and produce repeatable results with an acceptable level of error. We fulfilled our main objectives concerning forage fish assessment: 1) develop an appropriate survey design incorporating detection error, surveyor bias, and survey constraints, 2) determine the accuracy of fish species and age class discrimination, 3) determine the repeatability of aerial measurements, and 4) determine the spatial resolution of aerial measurements needed for ecological analyses. We also fulfilled our secondary objective to develop abundance estimates for jellyfish aggregations and seabirds. We developed an adaptive modified line transect methodology and model incorporating a detection curve for Pacific herring (Clupea pallusi), Pacific sand lance (Ammodytes hempems), and black-legged kittiwakes (Rissu triductylu) and a detection correction factor for fish schools. We established survey condition constraints and an optimal survey altitude range of 274 - 366 m based on school size and sightability of seabirds. We developed logging software to obtain flight path and sighting coordinates and incorporated measurements of schools using a sighting tube. The altitude dependent flight swath or transect width for fish schools was estimated from the detection curve at 474 m at an altitude of 305 m. The detection correction factor was estimated at 0.727 resulting in an undercounting rate of approximately 37.5%. Using double counting, individual surveyor bias was estimated at 6.5% for school counts and 7.0% for school surface area estimates; these rates are lower than those reported for wildlife aerial surveys. Error in fish species identification was estimated from validation data at 3.9% for herring, and 20. 2% for sand lance; we were not able to discriminate age classes [...]

These data are part of the ASGARD component of the Arctic Integrated Ecosystem Research Program (... more These data are part of the ASGARD component of the Arctic Integrated Ecosystem Research Program (IERP), sponsored by the North Pacific Research Board (NPRB), Collaborative Alaskan Arctic Studies Program (formerly the North Slope Borough/Shell Baseline Studies Program), Bureau of Ocean Energy Management (BOEM), and the Office of Naval Research Marine Mammals and Biology Program. To investigate the dynamics of the spring season in the northeastern Chukchi Sea, we conducted trawl surveys in June 2017 to explore fish abundance and life history parameters. Demersal fishes were targeted with a 3 m plumb-staff beam trawl, while pelagic fishes were targeted using an Isaacs-Kidd midwater trawl. Catches were processed (see methods). Files included in this dataset are as follows: Pelagic: Trawl Deployment Data, File Name: "201x_ASGARD_Chukchi_IKMT_haul_Norcross_MONYEAR.csv" Catch Data, File Name: "201x_ASGARD_Chukchi_IKMT_catch_Norcross_MONYEAR.csv" Fish Lab Specimen Data, ...

The goal of this project was to develop a detailed characterization of nearshore Arctic fish comm... more The goal of this project was to develop a detailed characterization of nearshore Arctic fish communities and their habitats in order to better understand the ecological function of the coastal habitats fringing the Arctic Large Marine Ecosystem. Our approach was to characterize Arctic fish communities in nearshore habitats by observing seasonal changes in the communities in a variety of habitats near Pt. Barrow, Alaska and relating those changes in local environmental conditions. Through a series of weekly surveys during the ice free periods in 2013 and 2014, we characterized the nearshore fish community structure and demographic patterns among dominant species, examined the feeding ecology and energetics of nearshore fish species, used stable isotopes to elucidate food web interactions, characterized the shallow water habitats with an autonomous vessel and examined the meteorological and oceanographic forcing between the Elson Lagoon and Beaufort Sea water masses. This dataset incl...

The primary authors of the GEM Program Document are Molly McCammon,

ICES Journal of Marine Science, 2008

Ormseth, O. A., and Norcross, B. L. 2009. Causes and consequences of life-history variation in No... more Ormseth, O. A., and Norcross, B. L. 2009. Causes and consequences of life-history variation in North American stocks of Pacific cod. – ICES Journal of Marine Science, 66: 349–357. Life-history strategies of four Pacific cod (Gadus macrocephalus) stocks in the eastern North Pacific Ocean are outlined. Southern stocks grew and matured quicker, but reached smaller maximum size and had shorter lifespans than northern stocks. The trade-offs resulted in similar lifetime reproductive success among all stocks. Growth was highly dependent on latitude, but not on temperature, possibly because of differences in the duration of the growing season. Comparisons with Atlantic cod (Gadus morhua) revealed similar latitude/growth relationships among Atlantic cod stocks grouped by geographic region. In Pacific cod, greater size and longevity in the north appeared to be adaptations to overcome environmental constraints on growth and to maintain fitness. An egg production-per-recruit model suggested tha...

Fisheries Research, 2012

ABSTRACT Visible Implant Elastomer (VIE) tags represent a viable approach for long-term tracking ... more ABSTRACT Visible Implant Elastomer (VIE) tags represent a viable approach for long-term tracking of North Pacific giant octopus (Enteroctopus dofleini) in Alaska. Over a two year period, 1730 E. dofleini were tagged with individually identifiable VIE tags and 238 E. dofleini were recaptured in a 25 km2 area. Of the 238 E. dofleini recaptured, 31 were at liberty for 60 days or more with a maximum time at liberty of 374 days. This study shows that long-term retention of VIE tags may prove to be a vital tool in determining important life-history information for octopus species.

Continental Shelf Research, 2013

Canadian Journal of Fisheries and Aquatic Sciences, 2002

The densities of young-of-the-year and 1-year-old Pacific herring, Clupea pallasi, in Prince Will... more The densities of young-of-the-year and 1-year-old Pacific herring, Clupea pallasi, in Prince William Sound, Alaska, were estimated using acoustic surveys from June 1996 to March 1998. Four bays were surveyed with acoustic transects that were repeated three times in 24 h. Species composition and size structure were determined from net collections. Averaging over the 24-h period allowed the best use of all data, as observations between the three replicates were similar but sporadic, possibly resulting from the different seasonal daynight cycle in these northern latitudes. The average instantaneous natural mortality rates for young-of-the-year Pacific herring were 0.009 (standard deviation (SD) = 0.002) and 0.016 (SD = 0.012) for the 1996 and 1997 cohorts, respectively. The average instantaneous natural mortality rates for 1-year-old Pacific herring were 0.003 (SD = 0.007) and 0.008 (SD = 0.005) for the 1995 and 1996 cohorts, respectively. Combining our estimates with those in the pri...

... JOHN F. PIATT is a research wildlife biologist with theU.S. Geological Survey, Biological Res... more ... JOHN F. PIATT is a research wildlife biologist with theU.S. Geological Survey, Biological Resources Division, 1011 E. Tudor Road, Anchorage, AK ... C. Armistead made Figure 1. M. Litzow, F. Mueter, J. Orr, D. Somerton, and 2 anonymous reviewers reviewed manuscript. ...

Canadian Journal of Fisheries and Aquatic Sciences, 2021

Juvenile fish winter mortality, whether through starvation, predation, or disease, depends in par... more Juvenile fish winter mortality, whether through starvation, predation, or disease, depends in part on feeding history. Assessing mortality risk thus requires metrics that can distinguish well-fed from poorly fed individuals. To investigate the effects of winter feeding and spring re-feeding after winter fasting on young-of-the-year Pacific herring (Clupea pallasii), captive herring were maintained on different feeding rations for 20 weeks under ambient winter and spring conditions and evaluated for differences in size, gut mass, RNA/DNA ratio, body composition, and swimming performance. Lipid and moisture levels were inversely related indicators of feeding history, differing most between full-ration and fasted herring. Fasted herring that were re-fed in spring had evidence of compensatory growth without impacting swimming performance. Minimal growth and reduced gut mass observed even among fully fed herring suggest limits to winter feeding benefits. Metabolically processing stored f...

Deep Sea Research Part II: Topical Studies in Oceanography

Abstract Abundances of small pelagic fish can change dramatically over time and are difficult to ... more Abstract Abundances of small pelagic fish can change dramatically over time and are difficult to forecast, partially due to variable numbers of fish that annually mature and recruit to the spawning population. Recruitment strength of age-3 Pacific Herring (Clupea pallasii) in Prince William Sound, Alaska, is estimated in an age-structured model framework as a function of spawning stock biomass via a Ricker stock-recruitment model, and forecasted using the 10-year median recruitment estimates. However, stock size has little influence on subsequent numbers of recruits. This study evaluated the usefulness of herring recruitment models that incorporate oceanographic and biological variables. Results indicated herring recruitment estimates were significantly improved by modifying the standard Ricker model to include an index of young-of-the-year (YOY) Walleye Pollock (Gadus chalcogrammus) abundance. The positive relationship between herring recruits-per-spawner and YOY pollock abundance has persisted through three decades, including the herring stock crash of the early 1990s. Including sea surface temperature, primary productivity, and additional predator or competitor abundances singly or in combination did not improve model performance. We suggest that synchrony of juvenile herring and pollock survival may be caused by increased abundance of their zooplankton prey, or high juvenile pollock abundance may promote prey switching and satiation of predators. Regardless of the mechanism, the relationship has practical application to herring recruitment forecasting, and serves as an example of incorporating ecosystem components into a stock assessment model.

Arctic Science

We describe a fecundity-hindcast model that incorporates Arctic cod Boreogadus saida acute toxici... more We describe a fecundity-hindcast model that incorporates Arctic cod Boreogadus saida acute toxicity data, field studies of Arctic cod larval distribution and abundance, natural mortality estimates for Arctic cod eggs and larvae, and an oil spill fate model in Alaska Beaufort Sea. Three orders of magnitude of spill events (1,000 tons, 10,000 tons, 100,000 tons) were evaluated for both physically and chemically dispersed oil. Using worst-case assumptions in our model, a 100,000-ton spill of crude oil treated with dispersants resulted in 266 million m 3 of water that exceeded our acute toxicity threshold, compared to a volume of 71 million m 3 for a 100,000-ton spill not treated with dispersants, and resulted in exposure of about 2 million Arctic cod larvae remaining from an initial 87 million eggs. This represents the reproductive output of about 7,300 adult females. Adult Arctic cod populations in the Alaska Beaufort number in the 10s to 100s of millions. The results show that even with an order of magnitude variation in exposure, the effect of dispersing a large oil spill on the regional cod population is expected to be insignificant (~0.7%). The recent hiatus in Arctic oil and gas development affords an opportunity to acquire additional data to further strengthen this conclusion.

To develop a series of statistical models linking walleye pollock recruitment in the Eastern Beri... more To develop a series of statistical models linking walleye pollock recruitment in the Eastern Bering Sea to climatic and oceanographic conditions at regional and larger spatial scales~ predictor variables were carefully selected based on four general hypotheses that have been advanced to explain variations in pollock recruitment. Inthe first hypothesis, Wyllie-Echeverria and Wooster (1998) relate survival oflarval and/or juvenile pollock to the severity of winter ice conditions and to the size and temperature of the resulting pool of cold bottom water, i.e., cold pool~ on the shelf. The second and third hypotheses incorporate aspects ofthe recently proposed oscillating control hypothesis of Hunt et al. (2002). They relate pollock survival to the presence or absence of an ice-related spring bloom (Hypothesis 2) and to summer stratification and temperatures on the middle shelf region (Hypothesis 3). The fourth hypothesis examines the advection/predation hypothesis of Wespestad et al. (2000), which relates pollock recruitment to the degree of spatial separation between juvenile and cannibalistic adults. The degree of separation, in tum, is believed to be related to the passive drift oflarvae into favourable or unfavourable areas. To examine the evidence for and against each of the proposed hypotheses~ thus far we have obtained relevant predictor variables based on the literature and from available data sets and constructed a limited set of statistical models of recruitment. Our overall objective is to model relationships between the recruitment or survival of larval and juvenile walleye pollock (ages 0-2), stock size, and relevant environmental variables using linear and non-linear models. These models will be used to assess the performance of each predictor variable and to assess the strength of evidence for a given hypothesis. The best models for each hypothesis will be combined into one or several models for predicting walleye pollock recruitment in the Eastern Bering Sea. The performance of the final predictive model(s) will be evaluated in a retrospective analysis and their use in stock assessment will be examined.