• Odors And Ornaments In Crested Auklets (Aethia Cristatella): Signals Of Mate Quality?

      Douglas, Hector D., Iii; Springer, Alan M. (2006)
      Crested auklets (Aethia cristatella) are small colonial seabirds that display an ornamental feather crest and emit a citrus-like odorant during the breeding season. In this study odors and ornaments were investigated as possible signals of mate quality. Crest size was negatively correlated with the stress hormone corticosterone in males, but this was not the case in females. Body condition was negatively correlated with corticosterone in females, but this was not the case in males. Corticosterone levels were interpreted as an index of physiological condition, and it was concluded that males with longer crests were more competent at meeting the social and energetic costs of reproduction. I hypothesized that the crested auklet odorant: (1) functions as a chemical defense against ectoparasites, (2) is assessed as a basis for mate selection, (3) is facilitated by steroid sex hormones. Laboratory and field experiments showed that synthetic replicas of the crested auklet odorant repelled, impaired, and killed ectoparasites in a dose-dependent fashion. Chemical concentrations in plumage were at least sufficient to repel and impair ectoparasites. Chemical emissions from breeding adult crested auklets peaked at the time of egg hatching when young are most vulnerable to tick parasitism. In males, chemical emissions were correlated with crest size, a basis for mate selection. Presentation of synthetic aldehydes elicited behaviors similar to those that occur during courtship. Captive crested auklets responded preferentially to synthetic replicas of their odor, and the highest frequency of response occurred during early courtship. These results show that the chemical odor could be a basis for mutual mate selection. Production of the chemical odorant may be facilitated by steroid sex hormones since octanal emission rates were correlated with progesterone in males. Finally it was determined that the chemical composition of odorants in crested auklets and whiskered auklets (A. pygmaea) differed in three key respects. This suggests that an evolutionary divergence occurred in the odorants of the two species similar to what has been suggested for ornamental traits. In conclusion, crested auklets appear to communicate with odors and ornaments, and these signals may convey multiple messages regarding condition, quality, and resistance to parasites.
    • Organic matter accumulation and preservation in Alaskan continental margin sediments

      Ding, Xiaoling; Henrichs, Susan M. (1998)
      Continental margin sediments provide a historical record of the sources and fate of organic matter (OM) originating both from the continents and from primary productivity in the overlying water column. However, since this record can be altered by microbial decomposition within the sediment, the history cannot be interpreted without understanding how decomposition can affect OM composition. Also, the margins accumulate much of the OM buried in ocean sediments; hence, knowledge of processes influencing preservation of OM in these sediments is essential to understanding the global carbon cycle. OM preservation was examined using two approaches. First, I studied sediments in the northeastern Gulf of Alaska to determine sources of OM and temporal changes in carbon accumulation. A large amount of OM, 45--70 x 104 tons/yr, accumulated in this region, about 50% from terrestrial sources. Most of the sediment cores showed little evidence of change in TOC, TN, or C and N stable isotope compositions due to decomposition within the sediment. Second, I investigated the processes that control OM preservation, focusing on the role of the OM adsorption to mineral surfaces. Because proteins are major constituents of sedimentary OM, I examined factors controlling their adsorption, decomposition, and preservation. Three hydrophilic proteins were strongly adsorbed by two clay minerals, an iron oxide, sub-oxic sediments from Resurrection Bay (RB), Alaska, and anoxic sediments from Skan Bay (SB), Alaska. The partition coefficients were large enough to lead to their preservation provided that the proteins did not decompose while adsorbed. Generally, adsorption of proteins to solid phases decreased decomposition rates, suggesting that adsorption is important in protecting these compounds from microbial attack. Greater protein decomposition rates were found in SB than in RB sediments, indicating that anoxia did not inhibit protein biodegradation. Naturally-occurring adsorbed proteins were extracted from SB and RB sediments using a detergent solution. Most of these adsorbed proteins were small (<12 kDa), indicating that only the proteins adsorbed within the micropores of particle surfaces are preserved long-term.
    • Organochlorines In Steller Sea Lions (Eumetopias Jubatus)

      Myers, Matthew John; Atkinson, Shannon; Krahn, Margaret; Rea, Lorrie; Castellini, Michael; Mellish, Jo-Ann; Burdin, Alexander (2009)
      Existing populations of Steller sea lions (Eumetopias jubatus ) have declined precipitously over the last half-century. Investigations into the cause of this downward trend have focused on many different possible factors. Toxicity caused by the accumulation of organochlorines (OCs), such as polychlorinated biphenyls (PCBs) and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane or dichlorodiphenyltrichloroethane (DDT), has been demonstrated in marine mammals and was considered here as one possible factor that may have contributed to the decline of Steller sea lions or their failure to recover. The focus of this project was to investigate the relationship of contaminant loads to hormone levels, specifically thyroid hormones and cortisol in Steller sea lions. Two approaches were taken to this study. Firstly, baseline hormone concentrations were identified for the thyroid hormones, thyroxine (T 4) and triiodothyronine (T3), and cortisol. This involves comparison and extrapolation. Secondly, possible risk effects were examined by comparing levels of OCs in captive and free-ranging Steller sea lions to known effects in related species with known physiological thresholds. Serum concentrations of total T4 were highest in Steller sea lions followed by total T3 concentrations. Concentrations of free T4 and free T3 were three to four orders of magnitude lower. Concentrations for all four thyroid hormone measurements tended to a lower level as animals matured beyond the neonatal stage. When thyroid hormones from captive sea lions were evaluated across seasons, all thyroid hormones were highest in the July to September period. Cortisol concentrations were similar in male and female pups. Cortisol varied with age but when considered in regards to time of year when sampled, followed a seasonal pattern. Cortisol was elevated in fall months in captive sea lions (non-pups), which is similar to what is seen in other marine mammals and is likely associated with the annual molt. Male pups from Alaska had lower levels of SigmaPCBs and SigmaDDT when compared to male pups from Russia. Female pups from Alaska were significantly lower in SigmaPCBs than Russian female pups as were female pups for SigmaDDT levels between areas. Anywhere from 12 to 64% (depending on rookery) of Steller sea lion pups investigated for contaminants had concentrations of SigmaPCBs that are high enough to cause physiological problems. Concentrations in blood taken monthly for 2 years in three captive Steller sea lions were similar at any given sampling time and followed a seasonal pattern with levels significantly higher in the summer months of July to September and lower in the three month winter period January to March. Concentrations of OCs in blubber samples collected quarterly for the captive females followed an analogous pattern to blood samples but the captive male sea lion was considerably lower and declined over the study period. A significant relationship between blubber contaminants and lipids was noted in the three captive Steller sea lions. Even though OC contamination has not been hypothesized to be the primary factor that precipitated the population decline, there is a potential for these chemicals to have a negative effect on the health of free-ranging Steller sea lions. These data suggest that concentrations of OCs in Steller sea lions may be high enough to cause endocrine or reproductive dysfunction and could potentially impact fertility or fecundity. Therefore, OC contaminants can not be dismissed as a contributing source to either the decline or the failure to recover of the Steller sea lion population.
    • Otters, sea stars, and glacial melt: top-down and bottom-up factors that influence kelp communities

      Traiger, Sarah B.; Konar, Brenda; Hardy, Sarah; Okkonen, Stephen; Edwards, Matthew; Litaker, Wayne (2017-08)
      Kelp beds are important features of the Alaska coastline and provide habitat, protect coastlines, and support commercial and subsistence harvests. Kelp beds are affected by top-down and bottom-up factors, which are changing due to human and climate-related impacts. The influences of these top-down and bottom-up factors on kelp beds are investigated in three chapters. My first chapter investigated the influence of glacial discharge on recruitment and early community development in subtidal kelp communities by monitoring benthic sessile algae and invertebrates on cleared rocks across a glacial gradient along with various physical and biological parameters in the summers of 2013-2014. It has been predicted that Alaska's glaciers will lose 30-60% of their volume by 2100. The melt from glaciers increases sedimentation and lowers salinity, impacting important habitat-providing kelp. I found that sites upstream from glacial discharge had higher kelp recruitment than downstream sites, and that up to 72% of the variation in community development was related to mobile invertebrates and kelp in the surrounding community. Glacially-influenced environmental factors did not explain any variation that was not already explained by biological factors. My second chapter explored whether patterns in the recruitment of the dominant canopy kelp, Nereocystis luetkeana and the subcanopy kelp, Saccharina latissima were a result of dispersal limitation or failure to grow to macroscopic size. My goals were to determine 1) whether glacial melt conditions affect adult fecundity (spore production) of either species, 2) how sedimentation affects early gametophyte growth and survival in each species, and 3) whether competitive interaction between species at the gametophyte stage is altered by sediments. I found that glacial melt conditions did not affect the fecundity of either species, but sedimentation affected survival and competition. Saccharina latissima was the superior competitor under high sediment conditions. Because glacially-influenced coastal areas often have little exposed hard substrate and predation by sea otters and sea stars on clams can provide hard substrate for kelp colonization, my third chapter examined methods for determining predation on clams by these predators without direct observation. I found that foraging pits of sea otters and sea stars could not be distinguished using quantitative measurements. In contrast, shell litter proved useful in quantifying relative foraging rates. Clam consumption by sea otters and sea stars was equal at all but one site. Collectively, my thesis chapters provide information on the effects of glacial discharge on microscopic and early kelp life stages in Alaska which can be incorporated into management practices.
    • Pacific walrus use of higher trophic level prey and the relation to sea ice extent, body condition, and trichinellosis

      Seymour, Jill-Marie; Horstmann-Dehn, Lara; Atkinson, Shannon; Barboza, Perry; Rosa, Cheryl; Sheffield, Gay; Wooller, Matthew (2014-05)
      The changing Arctic ecosystem may prompt Pacific walruses (Odobenus rosmarus divergens) to change their usual diet of lower trophic level prey (e.g., benthic invertebrates) by increasing the consumption of higher trophic level prey (HTLP). Prey-switching may have consequences to walrus populations through increased energetic costs, increased stress response, declines in body condition, and exposure to diseases, including the zoonotic parasite Trichinella spp. Trichinella is possibly transmitted to walruses via predation or scavenging on seals. The goal of this study was to quantify reliance on HTLP using stable carbon and nitrogen isotope ratios, and assess potential correlations among consumption of HTLP and sea ice extent, sex, Trichinella infection, body lipid stores, and cortisol concentrations used as an index of the stress response. Walrus diet is comprised of ~1-22% HTLP and reliance on HTLP may be correlated with sea ice extent in a complex way. Trichinella was present in ringed seal (Pusa hispida, 1/57), Arctic fox (Vulpes lagopus, 3-7/32), and polar bear (Ursus maritimus, 1/1), but was not detected in walruses (0/137) regardless of %HTLP in the diet. Walrus blubber and attached skin contained 44.6 ±12.4% lipid wet weight, which was lower than that found for other Arctic marine mammals; however, the inclusion of skin likely decreased our %lipid values. While the absolute value of %lipid from blubber and attached skin was not a suitable substitute for %lipid from blubber only, we were still able to detect the influence of biological factors, with sex-linked variability in walrus lipid stores observed. Cortisol analysis from full-thickness blubber resulted in a wide range of concentrations (2.77 to 34.04 ng/g), but showed that this stress hormone can be extracted from blubber. While neither %lipid nor blubber cortisol was correlated with the proportion of HTLP in walrus diet, they may serve as minimally-invasive methods for health monitoring of walruses. Overall, dietary plasticity of walruses is robust and switching to HTLP is not likely to have immediate adverse effects on the Pacific walrus population.
    • Paleoceanographic shifts in the Gulf of Alaska over the past 2000 years: A Multi-proxy perspective

      Boughan, Molly McCall; Finney, Bruce; Naidu, Sathy; Whitledge, Terry E. (2008-12)
      The Gulf of Alaska (GOA) is a dynamic region influenced by climate variability on time scales ranging from days to millennia. Recent regime shifts suggest interdecadal GOA primary productivity patterns, yet it is unclear whether such fluctuations extend beyond the instrumental record. This thesis examined the nature of prevalent climatic and oceanographic patterns before the twentieth century using several marine sediment core proxies for paleoproductivity and paleoceanography. Sediment cores were from two locations: Bay of Pillars, Kuiu Island, in southeast Alaska (56.63 ̊N, 134.35 ̊W), and a central midshelf location (GAK4) along the Global Ecosystem Dynamics (GLOBEC) Seward Line (59.25 ̊N, 148.82 ̊ W). Proxy data from these cores include: percentages of organic carbon, nitrogen and biogenic opal; organic carbon-to-nitrogen ratios; stable isotope ratios from sediment organic matter (δ13C and δ15N) and foraminifera tests (δ13C and δ18O); and foraminifera faunal analysis. Bay of Pillars proxy data suggest that the onset of the Little Ice Age (LIA) ca. 1200 AD coincides with pulses of decreased salinity and increased productivity. GAK4 proxy data indicate increased productivity and decreased terrestrial input over the past century; as well as fresher surface water was during the latter portion of the LIA (1716 – 1894) and positive Pacific Decadal Oscillation phases.
    • Paralytic shellfish poisoning: the relationship between Alexandrium abundance and psp toxins on Kodiak Island, Alaska

      Matweyou, Julie A. (2003-05)
      Paralytic shellfish poisoning (PSP) events have severe negative impacts on Alaska commercial shellfish fisheries as well as recreational and subsistence harvests. This study, designed to improve existing PSP monitoring programs, involved the use of a rapid sandwich hybridization assay to detect and quantify the relative abundance of Alexandrium catenella based on species-specific LSU rRNA targeted oligonucleotide probes. Blue mussel (Mytilus edulis) toxicity, expressed as saxitoxin equivalents, was determined using the ³H-Saxitoxin receptor binding assay. Shellfish toxicity was relatively low in both 2000 and 2001 compared to historically high values on Kodiak, but exhibited pronounced late spring and late summer peaks, in both years at four to seven sampling sites. Temporal and spatial variability in shellfish toxicity among sites, seasons, and years suggested dynamic, and possibly unpredictable, Alexandrium bloom events. Importantly, DNA probe data revealed a strong association between Alexandrium abundance and shellfish toxicity. The results also demonstrated that increases in Alexandrium abundance preceded elevated toxin levels in shellfish, indicating that this assay may prove useful as a monitoring tool to predict toxic events in shellfish before they are harvested. Water column nutrients and climate data were evaluated to determine if bloom-triggering mechanisms could be identified.
    • Pelagic nitrogen cycle in an arctic lake

      Whalen, Stephen Charles (1986-05)
      A mass balance for nitrogen was developed for the water column of Toolik Lake and the isotope tracers 15N and 14C were used to examine the phytoplankton ecology with respect to dissolved in organic nitrogen (ammonium and nitrate). The nutrient budget showed an oligotrophic ecosystem with important flux terms few and small in magnitude. Nitrogen input was primarily from inflowing rivers and was dominated by the dissolved organic fraction. Ammonium release from sediment provided the only other major source of nitrogen to the lake water. Toolik acted as a nitrogen sink, trapping 18% of the annual input. Retention was almost exclusively (98%) as dissolved organic nitrogen. Tracer experiments suggested chronic nitrogen deficiency in the phytoplankton, but indigenous populations were well-adapted for utilizing characteristically low levels of nutrient. Phytoplankton showed a high affinity for both nitrate and ammonium as well as a lack of discrimination between the two forms of inorganic nutrient. The ambient concentration was the most important factor regulating uptake, with light and temperature of secondary importance. More than 66% of the dissolved in organic nitrogen supporting phytoplankton productivity was derived from local recycling, with the remainder from sediment efflux and riverine input. Dissolved organic nitrogen from inflowing waters probably provided an additional, important source of nutrient for the phytoplankton.
    • Penetrative convection in sediments

      Musgrave, David L. (1983-05)
    • Phosphorus metabolism of several aquatic microorganisms

      Lang, Douglas; Brown, E. J. (1980-12)
      Several taxonomically diverse aquatic microplankton were described growing at phosphorus (P) concentrations that limit growth in many natural aquatic systems. Because natural aquatic systems are subject to periodic fluctuations in P levels, both steady-state (via continuous culture) and transient (via batch culture) growth were described. Complete growth kinetic descriptions of Synechococcus Nageli (strain A) and Scenedesmus quadricauda were used to predict the relative competitive abilities of these species when P was the growth-limiting nutrient. These descriptions, coupled to their morphological characteristics, were used to construct partial physiological profiles for each organism. The profiles indicate that S. Nageli (strain A) (a small unicellular blue-green alga) is better suited for growth in P-limited oligotrophic niches than is S. quadricauda (a green alga). However, results from kinetic experiments with these and several other microplankton, show that such physiological profiles are not necessarily indicative of profiles for taxonomically related species.
    • Physical And Biological Factors Affecting The Diel Vertical Migration Of Walleye Pollock

      Adams, Charles F.; Kelley, John J.; Coyle, Kenneth O. (2007)
      The mechanisms underlying diel vertical migration (DVM) in marine fishes are unclear, although it is generally thought that this behavior is influenced by light, hydrography, food availability and predator avoidance. In the North Pacific Ocean, walleye pollock (Theragra chalcogramma) undergo DVM as juveniles, ascending to the surface at night and returning to the bottom at dawn. Adults are generally considered demersal. The objective of this research was to examine the effect of light, temperature and prey availability on the DVM of adult pollock. The work was undertaken to further our understanding of pollock biology, and the mechanisms underlying DVM in marine fishes in general. The study was conducted in the northern Gulf of Alaska in April, August and November 2003. Trawls < 80 m in April, and < 50 m in August, suggested that at least some portion of the pollock population was ascending to within 20 m of the surface in spring and summer. In November, acoustic data and targeted hauls > 100 m indicated that adults were not ascending to the surface at night, and that DVM behavior was occurring at depth. Euphausiids were the primary component of the diet in April and August. Decapods, primarily the shrimp Pandalus borealis, were the main component of the diet in November. Pollock passed through the thermocline during their ascent to the surface at night in August, and there was no relationship between the mean depth of pollock and the isolume (line of equal light intensity) necessary for visual foraging. In contrast, there was a significant relationship between the biomass of adult pollock above the 200 m isobath and the isolume necessary for visual foraging in November. Pollock did not pass through the thermocline at this time. It was concluded that in August adults ignore the isolume and thermocline, simply tracking the movements of euphausiid prey to feed upon them near the surface at night. In November, when euphausiids are no longer in patches, pollock shoals migrate up and down with the isolume necessary for visual foraging to feed on decapods.
    • Physical environmental and biological correlates of otolith chemistry of Arctic marine fishes in the Chukchi sea

      Gleason, Christine Marie; Norcross, Brenda; Brown, Randy; Horstmann-Dehn, Larissa; Trefry, John; Christie, David (2012-08)
      Life history movement patterns in marine fishes can be determined by otolith chemistry if environmental variables are reflected in the otoliths. Arctic cod (Boreogadus Saida), Arctic staghorn sculpin (Gymnocanthus tricuspis), and Bering flounder (Hippoglossoides robustus) are abundant Arctic fishes in the Chukchi Sea with overlapping distributions. Physical environmental data, demersal fishes, bottom seawater, and sediment interface seawater samples were collected from the Chukchi Sea Offshore Monitoring in Drilling Area (COMIDA) cruise on July 30, 2009 and the Russian American Long-term Census of the Arctic (RUSALCA) cruise from September 3 to 30, 2009 in the Chukchi Sea. Magnesium (Mg), strontium (Sr), barium (Ba), and calcium (Ca) were measured with an inductively coupled plasma mass spectrometer (ICP-MS) on the most recent growth edge of otoliths and in whole fish blood, as well as Ba in bottom and sediment interface seawater. Environmental variables and fish age correlated with Arctic cod and Arctic staghorn sculpin otolith signatures while only environmental variables correlated with Bering flounder signatures. Elemental correlations were not always consistent for the variables tested among species. The complexity of this multi-element tool suggests otolith chemistry may not be useful to determine life history movement patterns of these demersal Arctic fishes in offshore waters.
    • Physiological and behavioral responses of tanner crabs (Chionoecetes bairdi) to handling, emersion and temperature

      El Mejjati, Sonya Y. (2006-12)
      Commercially harvested Tanner crabs (Chionoecetes bairdi) are exposed to physical stressors during capture and sorting including changes in temperature and oxygen availability. This study characterizes the physiological and behavioral responses of Tanner crabs exposed to air (emersion) at 8 and -15°C for various durations. Concentrations of glucose and lactate in hemolymph measured between 30 and 120 min following emersion for 45 min differed between animals exposed to 8 or -15°C. Glucose concentrations were higher among animals emersed at 8°C than those exposed to -15°C within the intervals sampled. Lactate concentrations were unchanged at intervals following emersion at 8°C, while they were elevated at 120 min following emersion at -15°C. Rates of oxygen consumption (VO₂) increased immediately following 15, 30, and 45 min emersion at 8°C, whereas 30 and 45 min emersion at -15°C resulted in depressed VO₂. All crabs survived handling and emersion at 8°C, while exposure to -15°C resulted in increased mortality. Thus, differences among physiological parameters corresponded with differences in percentage survival between the two temperature treatments. While not providing a causal relationship between survival and physiology, the metabolic responses of Tanner crabs following a simulated capture protocol provide a predictive index of subsequent survival.
    • Population biology and ecology of the North Pacific giant octopus in the eastern Bering Sea

      Brewer, Reid; Norcross, Brenda L.; Seitz, Andrew C.; Blanchard, Arny L.; Ormseth, Olav A.; Tamone, Sherry L. (2016-08)
      The North Pacific giant octopus (Enteroctopus dofleini) is an important member of pan-Pacific coastal ecosystems and represents a large incidental catch in Alaska; however little is known about the biology and ecology of this species, which hinders management. To improve our understanding of E. dofleini biology, I conducted a multiyear tagging study in a 25 km2 study area in the eastern Bering Sea (EBS). I used Visible Implant Elastomers to determine growth and movement patterns for E. dofleini and sacrificed octopus were examined to determine seasonal and sex-specific reproductive characteristics. Using tagging data and Cormack-Jolly-Seber models, I estimated survival and study-area abundance for E. dofleini and expanded the abundance estimates to neighboring areas where most of the incidental catch of octopus occurs. In this three-year study, a total of 1,714 E. dofleini were tagged and 246 were recaptured. In autumn when temperatures were warmest, E. dofleini had higher growth rates, moved more and both sexes were predominantly mature when compared to colder winter months. Size also played a role in E. dofleini ecology, with smaller octopus growing faster than larger octopus and larger, mature octopus moving more than smaller, immature octopus. The abundance estimate for octopus in the study area was 3,180 octopus or 127 octopus per km2, and annual survival was 3.33%. Using 20 years of data from the federal groundfish observer program, I estimated that the biomass for E. dofleini in the area where most of the incident catch occurs was 20,697 mt of octopus, an order of magnitude larger than the current biomass estimate for the entire EBS. Though the study area and the scale of the mark-recapture effort were limited, the survival and abundance estimates are from the same area where most of the octopus are in incidentally captured and represent an important first step in enhancing octopus management. However, the large estimates of biomass suggest the current management is too conservative and the estimates of survival suggest that management estimates of mortality are too low.
    • Population dynamics of steller sea lions, Eumetopias jubatus, in the Eastern Gulf of Alaska

      Maniscalco, John Michael; Springer, Alan M.; Iverson, Sara J.; Horstmann, Larissa-A.; Hollmien, Tuula E.; Adkison, Milo D. (2015-05)
      Steller sea lions (Eumetopias jubatus) were listed as endangered following a collapse of the western population beginning in the late 1970s. Low juvenile survival and reduced reproductive rates (natality) have been implicated as important factors in the decline. I conducted separate mark-recapture analyses to estimate juvenile survival and natality in an area of the western population where Steller sea lions have begun to show signs of recovery since the early 2000s. I then used these vital-rate estimates in a population matrix to estimate the strength of the recovery and assess which rates pose the greatest threats to recovery. First year survival was estimated at 80% for both males and females, but second-year survival dropped to a low of 40.6% for males and 64.2 % for females that were weaned at age 1. In contrast, survival was greatly improved (88.2%) for males and females that continued to suckle between ages 1 and 2. Cumulative survival to age 4 was double (35.7%) that estimated during the population decline. Natality was also higher in recent years (70%) than during the height of the decline in the 1980s (55%). The mean rate of population growth, based on matrix modeling of vital rates estimated in this study, was 4.1% per year between 2003 and 2013. By projecting these trends into the future, I estimated that the population in the study area may be fully recovered within 14 years, if density independent growth is to be expected in the near future. If density dependent factors come into play, the population will need another 37 years to fully recover. As would be expected from a long-lived, K-selected species, population growth rate was most sensitive to variation in adult survival, less sensitive to juvenile survival, and least sensitivity to natality. The findings of this study have important implications for Steller sea lion population management and suggest research priorities should be shifted from an emphasis on natality to an emphasis on survival rates and causes of mortality.
    • Population Structure And Behavior Of Pacific Halibut

      Seitz, Andrew C.; Norcross, Brenda (2006)
      Pacific halibut (Hippoglossus stenolepis) is not managed on regional scales with separate population dynamics, but rather as a single, fully mixed population extending from California through the Bering Sea. However, some of the evidence from which this paradigm was established is questionable and I hypothesize that there are separate spawning populations of Pacific halibut in three regions, the Gulf of Alaska, Bering Sea and Aleutian Islands, because these regions are geographically separated by land masses and/or deep water passes that may prevent movement by adults. Pop-up Archival Transmitting (PAT) tags were attached to Pacific halibut in each region to examine their movement and behavior. First, geolocation by ambient light was able to discern basin-scale movements of demersal fishes in high latitudes and therefore this technique provided a feasible method for providing scientific inference on large-scale population structure in Pacific halibut. Second, because seasonally low ambient light levels and inhabitation of deep water (>200 m) restricted geolocation by light during winter, an alternative method, a minimum distance dispersal model, was developed for identifying migration pathways of demersal fish in the Gulf of Alaska based on daily maximum depth. Third, the PAT tags provided no evidence that Pacific halibut in the southeastern Bering Sea and Aleutian Islands moved among regions during the mid-winter spawning season, supporting my hypothesis of separate populations. Fourth, geographic landforms and discontinuities in the continental shelf appeared to limit the interchange of Pacific halibut among areas and possibly delineate the boundaries of potential populations in the Gulf of Alaska and eastern Bering Sea, with apparent smaller, localized populations along the Aleutian Islands. This possible population structure may be reinforced by regional behavioral variation in response to the environment. Future research should be directed at quantifying the exchange of individual fish among regions for possible local area management plans that more accurately reflect population structure.
    • Predicting Distributions of Estuarine Associated Fish and Invertebrates in Southeast Alaska

      Miller, Katharine Bollinger; Norcross, Brenda; Iken, Katrin; Weingartner, Tom; Mundy, Phillip; Huettmann, Falk (2013-05)
      Estuaries in Southeast Alaska provide habitat for juveniles and adults of several commercial fish and invertebrate species; however, because of the area's size and challenging environment, very little is known about the spatial structure and distribution of estuarine species in relation to the biotic and abiotic environment. This study uses advanced machine learning algorithms (random forest and multivariate random forest) and landscape and seascape-scale environmental variables to develop predictive models of species occurrence and community composition within Southeast Alaskanestuaries. Species data were obtained from trawl and seine sampling in 49 estuaries throughout the study area. Environmental data were compiled and extracted from existing spatial datasets. Individual models for species occurrence were validated using independent data from seine surveys in 88 estuaries. Prediction accuracy for individual species models ranged from 94% to 63%, with 76% of the fish species models and 72% of the invertebrate models having a predictive accuracy of 70% or better. The models elucidated complex species-habitat relationships that can be used to identify habitat protection priorities and to guide future research. The multivariate models demonstrated that community composition was strongly related to regional patterns of precipitation and tidal energy, as well as to local abundance of intertidal habitat and vegetation. The models provide insight into how changes in species abundance are influenced by both environmental variation and the co-occurrence of other species. Taxonomic diversity in the region was high (74%) and functional diversity was relatively low (23%). Functional diversity was not linearly correlated to species richness, indicating that the number of species in the estuary was not a good predictor of functional diversity or redundancy. Functional redundancy differed across estuary clusters, suggesting that some estuaries have a greater potential for loss of functional diversity with species removal than others.
    • Primary production and nutrient dynamics of the southeastern Bering Sea shelf

      Rho, TaeKeun (2004-05)
      Understanding the relationships between the distributions of organisms and oceanographic conditions was one of the major goals of the Southeastern Bering Sea Carrying Capacity (SEBSCC) study. As a part of SEBSCC, this study focused on the response of nutrients and primary production to the variations of physical conditions, the general distribution of primary production, and the dynamics of phytoplankton growth, and nutrient utilization over the middle shelf and shelf break regions. The concentration of nutrients and primary productivity were measured over the shelf during 1997-1999. Shipboard nutrient and iron addition experiments were conducted over the middle shelf and shelf break region of the southeastern Bering Sea shelf during 2000-2001. The variations in physical conditions strongly affected the distribution of nutrients in the surface euphotic layer as well as in the deep layer. The offshore transport of the middle shelf water at mid-depth over the outer shelf may playa very important role in the export of materials, including regenerated iron, from the middle shelf to the shelf break. There were large seasonal and spatial variations in the development of the spring phytoplankton bloom due to the strength of upwelling and the slope of the front at the shelf break. However, annual primary production, estimated by combining carbon uptake data of the PROBES study and this study, were similar over the inner (133 g C m⁻² y⁻¹), middle (144 g C m⁻² y⁻¹) and outer (138 g C m⁻² y⁻¹) shelves and the shelfbreak (143 g C m⁻² y⁻¹). Nutrient addition studies showed that nitrogen availability was essential to continuous phytoplankton growth during summer, and that the interaction between ammonium and nitrate may play an important role in the dynamics of nutrient utilization. The iron addition study suggested that lack of iron did not affect the growth of phytoplankton over the middle shelf, but slightly suppressed growth at the outside edge of the shelf break region.