Using acoustic data from fishing vessels to estimate walleye pollock abundance in the eastern Bering Sea.

2011 ◽  
Vol 129 (4) ◽  
pp. 2695-2695
Author(s):  
Taina Honkalehto ◽  
Patrick H. Ressler ◽  
Richard H. Towler ◽  
Christopher D. Wilson
Keyword(s):  
Bering Sea ◽  
Walleye Pollock ◽  
Acoustic Data ◽  
Eastern Bering Sea ◽  
Fishing Vessels

Using acoustic data from fishing vessels to estimate walleye pollock (Theragra chalcogramma) abundance in the eastern Bering Sea

2011 ◽  
Vol 68 (7) ◽  
pp. 1231-1242 ◽  
Author(s):  
Taina Honkalehto ◽  
Patrick H. Ressler ◽  
Richard H. Towler ◽  
Christopher D. Wilson
Keyword(s):  
Bering Sea ◽  
Low Cost ◽  
Walleye Pollock ◽  
Theragra Chalcogramma ◽  
Accurate Information ◽  
Commercial Fishing ◽  
Acoustic Data ◽  
Eastern Bering Sea ◽  
Fishing Vessels ◽  
Walleye Pollock Theragra Chalcogramma

Eastern Bering Sea walleye pollock ( Theragra chalcogramma ) support one of the world’s largest fisheries. Because of walleye pollock’s high recruitment variability and relatively short life span, timely and accurate abundance indices are needed for fisheries management. Walleye pollock are surveyed biennially with an acoustic-trawl (AT) survey and annually with a bottom trawl (BT) survey. The latter tracks the demersal portion of the population using chartered fishing vessels, whereas the AT survey tracks the younger, midwater portion using research vessels and is critical for evaluating prerecruit abundances. Acoustic data collected from commercial fishing vessels conducting the BT survey were analyzed to provide information on midwater walleye pollock abundance at relatively low cost. A retrospective analysis of AT survey data identified a suitable index area to track midwater walleye pollock abundance. The BT survey acoustic data in that area tracked the AT survey abundance and captured its broad spatial patterns. This study is unique because commercial vessel acoustic data were used to estimate a new annual abundance index whose performance can be evaluated by a biennial research vessel survey. The new index will benefit managers by providing more accurate information on near-term abundance trends when dedicated research ship time is not available.

scholarly journals Geostatistical simulations of eastern Bering Sea walleye pollock spatial distributions, to estimate sampling precision

2007 ◽  
Vol 64 (3) ◽  
pp. 559-569 ◽  
Author(s):  
Paul D. Walline
Keyword(s):  
Bering Sea ◽  
Walleye Pollock ◽  
Geostatistical Simulation ◽  
Normal Space ◽  
Total Biomass ◽  
Spatial Distributions ◽  
Acoustic Data ◽  
Eastern Bering Sea ◽  
Abundance Estimates ◽  
Length Frequency Data

Abstract Walline, P. D. 2007. Geostatistical simulations of eastern Bering Sea walleye pollock spatial distributions, to estimate sampling precision. – ICES Journal of Marine Science, 64: 559–569. Sequential Gaussian and sequential indicator geostatistical simulation methods were used to estimate confidence intervals (CIs) for biomass estimates from six echo-integration trawl surveys of eastern Bering Sea walleye pollock (Theragra chalcogramma) biomass. Uncertainty in the acoustic and the length frequency data was combined in the calculation of CIs. Sampling in 2002 provided evidence for isotropy in the spatial distribution. Variogram models were characterized by long ranges (75–122 nautical miles for non-zero acoustic data, for example) compared with the smallest dimension of the survey area (∼100 nautical miles) and small nugget effects (∼20% of the semi-variance in transformed normal space for acoustic data). The 95% CIs obtained for the abundance estimates did not vary greatly between years and were similar to those from a one-dimensional transitive geostatistical analysis, i.e. ± 5–9% of estimated total biomass.

scholarly journals Comparison of the biophysical and trophic characteristics of the Bering and Barents Seas

2005 ◽  
Vol 62 (7) ◽  
pp. 1245-1255 ◽  
Author(s):  
George L. Hunt ◽  
Bernard A. Megrey
Keyword(s):  
Bering Sea ◽  
Barents Sea ◽  
Single Species ◽  
Atlantic Water ◽  
Walleye Pollock ◽  
Fish Stocks ◽  
Eastern Bering Sea ◽  
The Barents Sea ◽  
Shelf Seas ◽  
Bottom Waters

Abstract The eastern Bering Sea and the Barents Sea share a number of common biophysical characteristics. For example, both are seasonally ice-covered, high-latitude, shelf seas, dependent on advection for heat and for replenishment of nutrients on their shelves, and with ecosystems dominated by a single species of gadoid fish. At the same time, they differ in important respects. In the Barents Sea, advection of Atlantic Water is important for zooplankton vital to the Barents Sea productivity. Advection of zooplankton is not as important for the ecosystems of the southeastern Bering Sea, where high levels of diatom production can support production of small, neritic zooplankton. In the Barents Sea, cod are the dominant gadoid, and juvenile and older fish depend on capelin and other forage fish to repackage the energy available in copepods. In contrast, the dominant fish in the eastern Bering Sea is the walleye pollock, juveniles and adults of which consume zooplankton directly. The southeastern Bering Sea supports considerably larger fish stocks than the Barents. In part, this may reflect the greater depth of much of the Barents Sea compared with the shallow shelf of the southeastern Bering. However, walleye pollock is estimated to occupy a trophic level of 3.3 as compared to 4.3 for Barents Sea cod. This difference alone could have a major impact on the abilities of these seas to support a large biomass of gadoids. In both seas, climate-forced variability in advection and sea-ice cover can potentially have major effects on the productivity of these Subarctic seas. In the Bering Sea, the size and location of pools of cold bottom waters on the shelf may influence the likelihood of predation of juvenile pollock.

scholarly journals Evaluating total uncertainty for biomass- and abundance-at-age estimates from eastern Bering Sea walleye pollock acoustic-trawl surveys

2016 ◽  
Vol 73 (9) ◽  
pp. 2208-2226 ◽  
Author(s):  
Mathieu Woillez ◽  
Paul D. Walline ◽  
James N. Ianelli ◽  
Martin W. Dorn ◽  
Christopher D. Wilson ◽  
...  
Keyword(s):  
Bering Sea ◽  
Walleye Pollock ◽  
Target Strength ◽  
Acoustic Backscatter ◽  
Trawl Survey ◽  
Data Types ◽  
Total Uncertainty ◽  
Functional Relationships ◽  
Eastern Bering Sea ◽  
Trawl Surveys

Abstract A comprehensive evaluation of the uncertainty of acoustic-trawl survey estimates is needed to appropriately include them in stock assessments. However, this evaluation is not straightforward because various data types (acoustic backscatter, length, weight, and age composition) are combined to produce estimates of abundance- and biomass-at-age. Uncertainties associated with each data type and those from functional relationships among variables need to be evaluated and combined. Uncertainty due to spatial sampling is evaluated using geostatistical conditional (co-) simulations. Multiple realizations of acoustic backscatter were produced using transformed Gaussian simulations with a Gibbs sampler to handle zeros. Multiple realizations of length frequency distributions were produced using transformed multivariate Gaussian co-simulations derived from quantiles of the empirical length distributions. Uncertainty due to errors in functional relationships was evaluated using bootstrap for the target strength-at-length and the weight-at-length relationships and for age–length keys. The contribution of each of these major sources of uncertainty was assessed for acoustic-trawl surveys of walleye pollock in the eastern Bering Sea in 2006–2010. This simulation framework allows a general computation for estimating abundance- and biomass-at-age variance–covariance matrices. Such estimates suggest that the covariance structure assumed in fitting stock assessment models differs substantially from what careful analysis of survey data actually indicate.

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