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| 181 publication(s) found. Page 1 of 13 |
| 1 | pdf | 207 | | Rodionov, S.N. 2004. A sequential algorithm for testing climate regime shifts. Geophysical Research Letters 31:LO9204: 1-4. See abstract |
| Empirical studies of climate regime shifts typically use
confirmatory statistical techniques with an a priori hypothesis
about the timing of the shifts. Although there are methods
for an automatic detection of discontinuities in a time series,
their performance drastically diminishes at the ends of the
series. Since all the methods currently available require a
substantial amount of data to be accumulated, the regime
shifts are usually detected long after they actually occurred.
The proposed sequential algorithm allows for early detection
of a regime shift and subsequent monitoring of changes in its
magnitude over time. The algorithm can handle the
incoming data regardless whether they are presented in the
form of anomalies or absolute values. It can be easily used
for an automatic calculation of regime shifts in large sets of
variables. |
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| 2 | pdf | 301 | | Ryer, C.H., Stoner, A.W., and Titgen, R.H. 2004. Behavioral mechanisms underlying the refuge value of benthic habitat structure for two flatfishes with differing anti-predator strategies. Marine Ecology Progress Series 268: 231-243. See abstract |
| Juvenile flatfish habitat is usually modeled on the basis of sediment grain-size, depth
and temperature. Recent evidence indicates that some juvenile flatfishes associate with emergent
structures such as sponge, shell and other biogenic and bed-form features of otherwise low-relief
shelf habitats. In laboratory experiments we examined the habitat preference and effects of habitat
structure upon predation vulnerability of sub-yearling (Age-0) Pacific halibut Hippoglossus
stenolepis and northern rock sole Lepidopsetta polyxystra. When given the choice between bare
sand or sand with 16% sponge coverage, halibut demonstrated strong preference for sponge, while
rock sole showed no preference. Larger Age-2 halibut (used as predators in the subsequent experiment)
also preferred sponge, but this preference declined with increasing hunger. When allowed to
forage for Age-0 flatfishes in either bare sand or sponge, predators consumed more prey in sand and
consumed more Age-0 halibut than rock sole. We were able to determine which behavioral processes
in the predator–prey interaction were modified by the presence of habitat structure. Predator–prey
encounter rates decreased in the sponge habitat as predator search was impeded: predators paused
more frequently and swam more slowly to maneuver through the sponges. Sponges also tended to
hinder the pursuit of prey. Rock sole utilized stereotypic flatfish defense-mechanisms, relying upon
immobility, burial and crypsis, and were less likely to flush at a predator’s approach than halibut.
Halibut have a less developed ability to mimic sediments, but a deeper/narrower body that confers
greater swimming speed, and were more likely to flush as a predator approached. Once they had
flushed and were pursued by a predator, halibut were more likely to escape than were rock sole.
These experiments support an accumulating body of evidence that emergent structure, in otherwise
low-relief benthic habitats, may play an important role in the ecology of some juvenile flatfishes.
Removal of emergent structure by towed fishing gear and other anthropogenic and/or natural disturbance
may influence patterns of distribution for juvenile halibut, as fish redistribute to less preferred
habitat, and may decrease survival rates through increased losses to predation. |
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| 3 | pdf | 305 | | Jurado-Molina, J., and Livingston, P. 2004. Sensitivity analysis of the multispecies virtual population analysis model parameterized for a system of trophically-linked species from the eastern Bering Sea. Ciencias Marinas 30(2): 1-12. See abstract |
| A sensitivity analysis of a multispecies virtual population analysis (MSVPA) model parameterized for the Bering Sea was
carried out using two methods for the analysis. In the first method, four variables related to the predation mortality M2 and
population size of age-1 walleye pollock (Theragra chalcogramma) and Pacific cod (Gadus macrocephalus) were chosen as
response variables. Results suggested that the response variables of walleye pollock were sensitive to the residual mortality M1 of
walleye pollock, the stock size of arrowtooth flounder (Atheresthes stomias) and ration of both predator species. Pacific cod
response variables were sensitive only to variables related to Pacific cod. These results reinforce the importance of cannibalism in
the dynamics of walleye pollock and Pacific cod. Results from the individual perturbation parameter analysis showed that the
changes produced by large positive perturbations in the “other food” parameter were small. The overall results suggest that the
MSVPA model can be considered robust. These results help to recognize the potential use of MSVPA as a tool to assist in
broadening the management of the fishery resources from the Bering Sea within a multispecies perspective. |
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| 4 | | 307 | | Wiggins, S.M., McDonald, M.A., Munger, L.M., Moore, S.E., and Hildebrand, J.A. 2004. Waveguide propagation allows range estimates for North Pacific right whales in the Bering Sea. Canadian Acoustics : . See abstract |
| The shallow and uniform water depth of the eastern Bering Sea shelf results in an acoustic waveguide.
Propagation within this waveguide produces waveform dispersion which is dependent upon range. We
present a means for using dispersed waveforms to determine range to calling whales from a single
autonomous acoustic recording instrument. The predominant North Pacific right whale (Eubalaena
japonica) call is frequency upswept from about 90 Hz to around 160 Hz and lasts approximately 1 s. The
regional bathymetry of the eastern Bering Sea middle shelf is relatively uniform and shallow (~ 70 meters
deep). This geometry provides a plane-layered waveguide in which right whale upswept calls can be
detected at ranges over 50 km and have multiple modal arrivals that become dispersed, displaying different
propagation velocities for different frequencies. Dispersion characteristics of modal arrivals are dependent
on the calling whale’s depth, the receiver’s depth, the water depth, the range from caller to receiver, and
various environmental parameters including water and sediment density and sound velocity. A model of
sound propagation for the eastern Bering Sea middle shelf is developed from right whale call dispersion
recorded on sonobuoys and seafloor acoustic recording packages, using individual calls recorded at
multiple instruments. After development of the model, waveform dispersion allows estimation of caller
range based on single instrument recordings. Estimating range between instrument and calling whales
provides a means to estimate minimum abundance for the endangered North Pacific right whale. |
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| 5 | pdf | 207 | | Rodionov, S.N., and Overland, J.E. 2005. Application of a sequential regime shift detection method to the Bering Sea ecosystem. ICES Journal of Marine Science 62: 328-332. See abstract |
| A common problem of existing methods for regime shift detection is their poor performance
at the ends of time-series. Consequently, shifts in environmental and biological indices are
usually detected long after their actual appearance. A recently introduced method based on
sequential t-test analysis of regime shifts (STARS) treats all incoming data in real time,
signals the possibility of a regime shift as soon as possible, then monitors how perception of
the magnitude of the shift changes over time. Results of a STARS application to the eastern
Bering Sea ecosystem show how the 1989 and 1998 regime shifts manifest themselves in
biotic and abiotic indices in comparison with the 1977 shift. |
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| 6 | pdf | 209 | | Gharrett, A.J., Matala, A.P., Peterson, E.L., Gray, A.K., and Li, Z. 2005. Two genetically distinct forms of rougheye rockfish are different species. Transactions of the American Fisheries Society 134: 242-260. See abstract |
| The variation in mitochondrial DNA (mtDNA) and at eight microsatellite loci was
analyzed in 700 rougheye rockfish Sebastes aleutianus sampled along the Pacific Rim from the
Oregon coast to the western Aleutian Islands and Bering Sea. The program STRUCTURE was
used to analyze the microsatellite genotypes and determine that the samples probably came from
two genetically distinct sources (type I and type II) by minimizing the strong Hardy2Weinberg
and gametic disequilibria observed in the total sample. The two types had nearly fixed differences
at one microsatellite locus (mSma 6), which corresponded to divergent mtDNA haplotype clusters.
We conclude that these two types are distinct species. The ranges of the two types overlapped but
were not coincident; in some areas, one or the other predominated. For example, most of the
Aleutian Island samples were type I fish. Although both types were caught in the same hauls in
some regions, often one or the other species was predominant in a haul. The differences in
distributions suggest a historic vicariant or ecological basis for their divergence. No phenotypic
characteristics have been confirmed that can be used to distinguish the two species visually.
Rougheye rockfish have high commercial value and their incidental catch has the potential to
greatly affect larger fisheries. The discovery of cryptic speciation in a commercially important
species underscores our need to learn more about the distribution and biology of these and other
groundfish species. |
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| 7 | pdf | 301 | | Spencer, M.L., Stoner, A.W., Ryer, C.H., and Munk, J.E. 2005. A towed camera sled for estimating abundance of juvenile flatfishes and habitat characteristics: Comparison with beam trawls and divers. Estuarine Coastal and Shelf Science 64: 497-503. See abstract |
| An inexpensive towed video camera sled was developed to provide abundance estimates for juvenile flatfishes and other benthic
taxa, and to characterize habitat features. The camera sled was compared with beam trawls and diver survey methods in Yaquina
Bay, Oregon, and in bays of Kodiak Island, Alaska. In Yaquina Bay the camera sled with a tickler chain (to induce flatfish
movement) yielded density estimates for juvenile flatfish (English sole, Pleuronectes vetulus) that were equivalent to those of the
divers, but greater than with a 1 m beam trawl or the camera sled without a tickler chain. Crab (Cancer magister) density estimates
were similar between the divers and the camera sled (with or without the tickler chain), but were underestimated with the beam
trawl. In Kodiak, densities of juvenile flatfish (northern rock sole, Lepidopsetta polyxystra) were similar between the camera sled
with a tickler chain, divers, and a 2 m beam trawl. Density estimates from the camera sled were obtainable for flatfish as small as 20
mm. Habitat features, such as empty bivalve shells, were underestimated with the beam trawl compared with the divers and the
camera sled. These results demonstrate the effectiveness of an inexpensive, simple to operate, towed camera sled in surveying
abundance and habitat associations of juvenile flatfishes, crabs, and other taxa. |
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| 8 | pdf | 303 | | Smith, C.T., and Seeb, J.E. 2005. Use of the 5'-nuclease reaction for single nucleotide polymorphism genotyping in chinook salmon. Transactions of the American Fisheries Society 5: 259-262. See abstract |
| We report the characterization of 13 single nucleotide polymorphism (SNP) genotyping
assays for chum salmon (Oncorhynchus keta). These assays are based on the 5′-nuclease
reaction and thus facilitate high-throughput genotyping with minimal optimization time.
Because data generated using these markers may be transported and combined across laboratories,
SNPs offer the potential to reduce the amount of redundant work being done in
mixture and migratory studies of chum salmon. |
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| 10 | pdf | 304 | | Heifetz, J., Wing, B.L., Stone, R.P., Malecha, P.W., and Courtney, D.L. 2005. Corals of the Aleutian Islands. Fisheries Oceanography 14(suppl. 1): 131-138. See abstract |
| A unique feature of the benthic habitat in the Aleutian Islands is the presence of a highly diverse and abundant coral
and sopnge community. Thse communities likely provide important habitat for a variety of fish and invertebrate species. Summaries of
historical data and recent direct obserations witha submersible indicate that the Aleutiani Islands may harbour the highest
diversity and abundance of cold-water corals in the world. There are 69 documented taxa (species and subspecies) of coral in the Aleutians
of which 25 are endemic. Within the Aleutian Islands, there is an increas in diversity of corals west of about longitude 169 degrees W.
This shift in diversity is consistent with the hypothesis of an ecological boundary in the vicinity of Samalga Pass. Given the endemism and high
diversity and abundance of corals in the Aleutians, there is evidence that this region is the evolutionary centre of origin for some
taxa of coldwater corals. |
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| 11 | pdf | 305 | | Jurado-Molina, J., Livingston, P.A., and Ianelli, J.N. 2005. Incorporating predation interactions in a statistical catch-at-age model for a predator–prey system in the eastern Bering Sea. Canadian Journal of Fisheries and Aquatic Sciences 62: 1865-1873. See abstract |
| Virtual population analysis and the statistical catch-at-age methods are common stock assessment models
used for management advice. The difference between them is the statistical assumptions allowing the fitting of parameters
by considering how errors enter into the models and the data sources for the estimation. Fishery managers are being
asked to consider multispecies interactions in their decisions. One option to achieve this goal is the multispecies
virtual population analysis (MSVPA); however, its lack of statistical assumptions does not allow the use of tools used
in single-species stock assessment. We chose to use a two-species system, walleye pollock (Theragra chalcogramma)
and Pacific cod (Gadus macrocephalus), to incorporate the predation equations from MSVPA into an age-structured
multispecies statistical model (MSM). Results suggest that both models produced similar estimates of suitability coefficients
and predation mortalities. The adult population estimates from the single-species stock assessment and MSM
were also comparable. MSM provides a measure of parameter uncertainty, which is not available with the MSVPA
technologies. MSM is an important advancement in providing advice to fisheries managers because it incorporates the
standard tools such as Bayesian methods and decision analysis into a multispecies context, helping to establish useful
scenarios for management in the Bering Sea. |
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| 12 | pdf | 305 | | Jurado-Molina, J., Livingston, P.A., and Galucci, V.F. 2005. Testing the stability of the suitability coefficients from an eastern Bering Sea multispecies virtual population analysis. Ciencias Marinas 30(2): 1-12. See abstract |
| A sensitivity analysis of a multispecies virtual population analysis (MSVPA) model parameterized for the Bering Sea was
carried out using two methods for the analysis. In the first method, four variables related to the predation mortality M2 and
population size of age-1 walleye pollock (Theragra chalcogramma) and Pacific cod (Gadus macrocephalus) were chosen as
response variables. Results suggested that the response variables of walleye pollock were sensitive to the residual mortality M1 of
walleye pollock, the stock size of arrowtooth flounder (Atheresthes stomias) and ration of both predator species. Pacific cod
response variables were sensitive only to variables related to Pacific cod. These results reinforce the importance of cannibalism in
the dynamics of walleye pollock and Pacific cod. Results from the individual perturbation parameter analysis showed that the
changes produced by large positive perturbations in the “other food” parameter were small. The overall results suggest that the
MSVPA model can be considered robust. These results help to recognize the potential use of MSVPA as a tool to assist in
broadening the management of the fishery resources from the Bering Sea within a multispecies perspective. |
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| 13 | pdf | 305 | | Livingston, P.A., Aydin, K., Boldt, J., Ianelli, J.N., and Jurado-Molina, J. 2005. A framework for ecosystem impacts assessment using an indicator approach. ICES Journal of Marine Science 62(3): 592-597. See abstract |
| Assessment of the historical, present, and future states of marine ecosystems and the effects
that humans and climate have on the state of an ecosystem are crucial to the scientific
advice required to implement an ecosystem-based fishery management system. Management
of federal groundfish fisheries in Alaska considers not just the target fishery, but also
the possible impact those fisheries might have on other species and the ecosystem.
Management actions have ranged from providing protection of endangered species in the
region to preventing new fisheries from starting on key foodweb components such as forage
fish. A scientific framework for providing ecosystem-based advice that puts the ecosystem
first has been evolving over the past few years. This framework provides a way of assessing
ecosystem factors that influence target species, the impact the target fishery may have on
associated species, and ecosystem-level impacts of fishing. An indicator approach that
describes ecosystem status, and trends and measures of human and climate influence has
been developed to provide advice to fishery managers. This approach is now being
expanded to utilize a variety of models to predict possible future trends in various
ecosystem indicators. Future implementation challenges include the refinement of these
predictive models, and the inclusion of climate into the models. Identification of sensitive
and meaningful ecosystem indicators is also required before a more formalized decisionmaking
process, one that includes ecosystem considerations, can be developed. Most
important, the culture of fishery management and research organizations needs to |
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| 14 | pdf | 307 | | Munger, L.M., Mellinger, D.K., Wiggins, S.M., Moore, S.E., and Hildebrand, J.A. 2005. Performance of spectrogram cross-correlation in detecting Right Whale calls in long-term recordings from the Bering Sea. Canadian Acoustics 33(2): 25-34. See abstract |
| We investigated the performance of spectrogram cross-correlation for automatically detecting North Pacifi c
right whale (Eubalaena japonica) calls in long-term acoustic recordings from the southeastern Bering Sea.
Data were sampled by autonomous, bottom-mounted hydrophones deployed in the southeastern Bering Sea
from October 2000 through August 2002. A human analyst detected right whale calls within the fi rst month
(October 2000) of recorded data by visually examining spectrograms and by listening to recorded data;
these manual detections were then compared to results of automated detection trials. Automated detection
by spectrogram cross-correlation was implemented using a synthetic kernel based on the most common
right whale call type. To optimize automated detection parameters, the analyst performed multiple trials on
minutes-long and hour-long recordings and manually adjusted detection parameters between trials. A single
set of optimized detection parameters was used to process a week-long recording from October 2000. The
automated detector trials resulted in increasing proportions of false and missed detections with increasing data
set duration, due to the higher proportion of acoustic noise and lower overall call rates in longer recordings.
However, the automated detector missed only one calling “bout” (2 or more calls within a 10-minute span)
of the 18 bouts present in the week-long recording. Despite the high number of false detections and missed
individual calls, spectrogram cross-correlation was useful to guide a human analyst to sections of data with
potential right whale calling bouts. Upon reviewing automatic detection events, the analyst could quickly
dismiss false detections and search recordings before and after correct detections to fi nd missed calls, thus
improving the effi ciency of searching for a small number of calls in long-term (months- to years-long)
recordings. |
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| 15 | pdf | 308 | | Buchheister, A., and Wilson, M.T. 2005. Shrinkage correction and length conversion equations for Theragra chalcogramma, Mallotus villosus and Thaleichthys pacificus. Journal of Fish Biology 67: 541-548. See abstract |
| Preservation of walleye pollock Theragra chalcogramma, capelin Mallotus villosus and eulachon
Thaleichthys pacificus by freezing decreased fork length (LF) up to 1.8, 5.6 and 2.7% and
reduced mass by up to 8.4, 3.5 and 1.1%, respectively. Shrinkage of walleye pollock standard
length (LS) was greater for fish in 95% ethanol v. 5% formalin and for fish in 10% formalin v.
frozen. Equations describing the shrinkage and loss in mass for these species are presented as
well as conversions between different length measurements (LS, LF and total length, LT) for
fishes that were frozen. |
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| 16 | pdf | 308 | | Lanksbury, J.A., Duffy-Anderson, J.T., Mier, K.L., and Wilson, M.T. 2005. Ichthyoplankton abundance, distribution, and assemblage structure in the Gulf of Alaska during September 2000 and 2001. Estuarine Coastal and Shelf Science 64: 775-785. See abstract |
| Autumn ichthyoplankton assemblage structure in the Gulf of Alaska (GOA) region has not previously been characterized.
Ichthyoplankton data from September 2000 and 2001 survey collections were analyzed to describe assemblages in the western GOA,
to examine interannual variation in assemblages, and to relate observations to oceanographic conditions. Taxa with the highest
frequency of occurrence (2000/2001) included Osmeridae (94/87%), Hexagrammos lagocephalus (57/45%), Sebastes spp. (35/47%)
and Bathymaster spp. (27/57%). Through the use of clustering techniques and ordination, three identifiable larval assemblages
common to both years were identified. Slope assemblages appeared well defined in both years, while nearshore and mid-shelf
assemblages tended to be more loosely associated and variable between years. Analyses of environmental variables (temperature,
salinity, water depth, distance from shore, and water transport) suggest ichthyoplankton assemblage structure is affected primarily
by bathymetry and circulation. We demonstrate that early autumn ichthyoplankton assemblage structure in the GOA is
fundamentally linked to variations in macro- (slope vs. shelf) and meso-scale topography (on-shelf proximity to land masses), and
suggest that these intrinsic associations may be modified by spatial and temporal variations in local hydrographic conditions. |
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