Seasonal changes in the diet composition and prey selection of walleye pollock (Theragra chalcogramma) in the northern Gulf of Alaska

2007 ◽  
Vol 84 (3) ◽  
pp. 378-389 ◽  
Author(s):  
Charles F. Adams ◽  
Alexei I. Pinchuk ◽  
Kenneth O. Coyle
Keyword(s):  
Seasonal Changes ◽  
Diet Composition ◽  
Prey Selection ◽  
Gulf Of Alaska ◽  
Walleye Pollock ◽  
Theragra Chalcogramma ◽  
Walleye Pollock Theragra Chalcogramma ◽  
Selection Of

Phenological and geographical patterns of walleye pollock (Theragra chalcogramma) spawning in the western Gulf of Alaska

2007 ◽  
Vol 64 (4) ◽  
pp. 713-722 ◽  
Author(s):  
Lorenzo Ciannelli ◽  
Kevin M Bailey ◽  
Kung-Sik Chan ◽  
Nils Chr. Stenseth
Keyword(s):  
Time Series ◽  
Additive Model ◽  
Gulf Of Alaska ◽  
Walleye Pollock ◽  
Theragra Chalcogramma ◽  
Geographical Patterns ◽  
Spawning Aggregations ◽  
Egg Distribution ◽  
Walleye Pollock Theragra Chalcogramma ◽  
Egg Density

Over 20 years of egg sampling data were used to reconstruct the geographical and phenological patterns of walleye pollock (Theragra chalcogramma) spawning aggregations in the Gulf of Alaska (GOA). The analyzed time series (1972, 1978–1979, 1981–2000) included a documented event of climate change (i.e., 1988–1989) and the rise and fall of the GOA pollock population abundance and harvests. We compared results from two generalized additive model (GAM) formulations: one assuming no change of egg distribution and phenology over the examined time series (stationary) and the other admitting such changes (nonstationary) across an epoch determined from the data. Results from both model formulations corroborate the existence of a high egg concentration in Shelikof Strait, historically the primary spawning area of pollock in the GOA. However, model results also highlight the presence of other secondary, and possibly transitory, centers of egg distribution at various locations along the shelf and slope regions of the GOA. In addition, results from the nonstationary (and statistically superior) formulation indicate that the abundance of the non-Shelikof aggregations has increased over time, along with a tendency for earlier occurrence and displacement toward shallower areas of the high egg density regions.

Transport, Distribution, and Abundance of Larval and Juvenile Walleye Pollock (Theragra chalcogramma) in the Western Gulf of Alaska

1991 ◽  
Vol 48 (1) ◽  
pp. 91-98 ◽  
Author(s):  
Sarah Hinckley ◽  
Kevin M. Bailey ◽  
Susan J. Picquelle ◽  
James D. Schumacher ◽  
Phyllis J. Stabeno
Keyword(s):  
Early Life ◽  
Gulf Of Alaska ◽  
Walleye Pollock ◽  
Theragra Chalcogramma ◽  
Life Stages ◽  
Early Life Stages ◽  
Early Juvenile ◽  
Walleye Pollock Theragra Chalcogramma ◽  
Eggs And Larvae ◽  
Egg Abundance

The spawning distribution of walleye pollock (Theragra chalcogramma) and subsequent southwesterly drift of eggs, larvae, and juveniles were investigated in Shelikof Strait, March–September 1987. In mid-March, a hydroacoustics survey found that spawning adults were concentrated in the deeper parts of Shelikof Strait, as were eggs collected in this area during an ichthyoplankton survey about 1 mo later. In May, a concentration of young larvae was found 100–150 km to the southwest of the spawning area. In late June and early July, the center of distribution of late larval and early juvenile walleye pollock was further to the southwest, between the Shumagin and Semidi Islands. By August and September, juveniles were mostly distributed downstream of the Shumagin Islands. The rate of drift of eggs and larvae through June was estimated at 4–6 cm/s. The trajectories of satellite-tracked buoys deployed in the region of greatest egg abundance revealed similar patterns to those of the early life stages of walleye pollock. These observations demonstrate that transport is an important factor determining the distribution of pollock larvae in downstream coastal nursery areas.

Biochemical Genetic Variation in Walleye Pollock, Theragra chalcogramma: Population Structure in the Southeastern Bering Sea and the Gulf of Alaska

1980 ◽  
Vol 37 (7) ◽  
pp. 1093-1100 ◽  
Author(s):  
W. S. Grant ◽  
F. M. Utter
Keyword(s):  
Population Structure ◽  
Genetic Variation ◽  
Bering Sea ◽  
Genetic Relationships ◽  
Gulf Of Alaska ◽  
Walleye Pollock ◽  
Theragra Chalcogramma ◽  
Starch Gel Electrophoresis ◽  
Walleye Pollock Theragra Chalcogramma ◽  
Biochemical Genetic

The distributions of biochemical genetic variants were used to examine the genetic relationships among populations of walleye pollock, Theragra chalcogramma, located in the southeastern Bering Sea and the Gulf of Alaska. Enzymatic proteins in tissue samples of fish collected from 14 locations were assayed for electrophoretically detectable variants. Twenty-eight loci were tentatively identified, 8 (28%) of which were polymorphic. Only two loci, ME-2 and 6PG, had variants in great enough frequencies to be of use in distinguishing populations. Significant differences between regions were detected using a log-likelihood test for heterogeneity. Variation in allelic frequencies within each region was minimal. Cluster analysis of genetic similarities between sample pairs revealed two major clusters roughly corresponding to the Bering Sea and the Gulf of Alaska. Our biochemical genetic data suggest that there are no distinct stocks within the southeastern Bering Sea nor within the Gulf of Alaska, but that there are minor genetic differences between fish in these two regions.Key words: Walleye pollock, Theragra chalcogramma; biochemical genetic variation, population structure, eastern Bering Sea, Gulf of Alaska, starch gel electrophoresis

scholarly journals Age validation of walleye pollock (Theragra chalcogramma) from the Gulf of Alaska using the disequilibrium of Pb-210 and Ra-226

2006 ◽  
Vol 63 (8) ◽  
pp. 1520-1529 ◽  
Author(s):  
Craig R. Kastelle ◽  
Daniel K. Kimura
Keyword(s):  
Accurate Determination ◽  
Gulf Of Alaska ◽  
Growth Zone ◽  
Walleye Pollock ◽  
Theragra Chalcogramma ◽  
Age Validation ◽  
Important Species ◽  
The North ◽  
Walleye Pollock Theragra Chalcogramma ◽  
Radiometric Ages

Abstract The walleye pollock (Theragra chalcogramma) is a commercially important species in the North Pacific, and harvest quotas are dependent upon accurate determination of ages. The two techniques (called methods A and B) currently used to interpret the growth zone patterns in walleye pollock otoliths were compared. The age distributions from these two techniques differed; method B produced ages twice that of method A. Validation of ages from walleye pollock has not been done previously. Radiometric ageing based on the ratio of Pb-210/Ra-226 was used to evaluate the accuracy of otolith growth zone counts, and it demonstrated that method A, which produced younger ages between 3 and 8 years, was correct. Walleye pollock grow older than the 3–8 year (method A) age range validated in this study. The experimental design was limited to a maximum method A age of 8 years, because available samples did not provide the minimum of 40 fish required for estimating a radiometric age. Our radiometric ageing study on walleye pollock appears to be the first to use the Pb-210/Ra-226 radiometric age-validation method in a boreal fish species where all samples were potentially young, 8 years or less. In previous studies, radiometric ages often approached 100 years. Also, only one presumed year class was used, which was sampled in successive years. Therefore, Ra-226 sample measurements were averaged to provide lower error.

scholarly journals Length-selective retention of walleye pollock, Theragra chalcogramma, by midwater trawls

2010 ◽  
Vol 68 (1) ◽  
pp. 119-129 ◽  
Author(s):  
Kresimir Williams ◽  
André E. Punt ◽  
Christopher D. Wilson ◽  
John K. Horne
Keyword(s):  
Gulf Of Alaska ◽  
Light Level ◽  
Walleye Pollock ◽  
Theragra Chalcogramma ◽  
Eastern Bering Sea ◽  
Walleye Pollock Theragra Chalcogramma ◽  
Abundance Estimates ◽  
Selective Retention ◽  
Survey Estimates ◽  
Hierarchical Bayesian Methods

Abstract Williams, K., Punt, A. E., Wilson, C. D., and Horne, J. K. 2011. Length-selective retention of walleye pollock, Theragra chalcogramma, by midwater trawls. – ICES Journal of Marine Science, 68: 119–129. Midwater trawls are commonly used during acoustic surveys of fish abundance to determine species and length compositions of acoustically sampled fish aggregations. As trawls are selective samplers, catches can be unrepresentative of sampled populations and lead to biased abundance estimates. Length-dependent retention of walleye pollock was estimated using small recapture nets, so-called pocket nets, attached to the outside of the trawl. Experimental haul sets comprising eight hauls each were conducted in the Gulf of Alaska in 2007 and 2008 and in the eastern Bering Sea (EBS) in 2007. Pocket-net catches were then modelled by fitting parameters for selectivity and escapement location along the trawl. Within- and between-haul variability was jointly estimated using hierarchical Bayesian methods. There was significant undersampling of juvenile (<25 cm) pollock, with the length-at-50%-retention (L50) estimated between 13.5 and 26.1 cm among haul sets. In the EBS set, L50 values were correlated with light level, escapement being greater at night. Trawl selectivity may be a significant source of error in acoustic-survey estimates of the abundance of pollock.

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