The Experts below are selected from a list of 177273 Experts worldwide ranked by ideXlab platform
D Wilsonchristopher - One of the best experts on this subject based on the ideXlab platform.
-
using Acoustic Data from fishing vessels to estimate walleye pollock theragra chalcogramma abundance in the eastern bering sea
Canadian Journal of Fisheries and Aquatic Sciences, 2011Co-Authors: H Resslerpatrick, H Towlerrichard, D WilsonchristopherAbstract: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 spatia...
H Resslerpatrick - One of the best experts on this subject based on the ideXlab platform.
-
using Acoustic Data from fishing vessels to estimate walleye pollock theragra chalcogramma abundance in the eastern bering sea
Canadian Journal of Fisheries and Aquatic Sciences, 2011Co-Authors: H Resslerpatrick, H Towlerrichard, D WilsonchristopherAbstract: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 spatia...
Edwin J Niklitschek - One of the best experts on this subject based on the ideXlab platform.
-
the use of fishing vessels to provide Acoustic Data on the distribution and abundance of antarctic krill and other pelagic species
Fisheries Research, 2016Co-Authors: J. L. Watkins, Dietolf Ramm, Georg Skaret, Sophie Fielding, X L Wang, X-y. Zhao, Keith Reid, Edwin J NiklitschekAbstract:A fishery for Antarctic krill (Euphausia superba) has existed for over 3 decades and the Commission for Conservation of Antarctic Marine Living Resources (CCAMLR) manages this fishery using precautionary catch limits, fishery Data collection and a scientific observer programme operating on the fishing vessels. A recent increase in the number of vessels fishing and the rising costs of undertaking scientific research cruises have focussed attention on being able to use fishing vessels to collect more extensive scientific Data sets. In 2011, CCAMLR’s Subgroup on Acoustic Survey and Analysis Methods (SG-ASAM) was tasked with assessing the use of Acoustic Data collected from fishing vessels to provide qualitative and quantitative information on the distribution and relative abundance of Antarctic krill and other pelagic species. SG-ASAM conceived a proof of concept programme and implemented the first stage in 2013 to determine the current setup of Acoustic equipment on participating fishing vessels and to establish whether these vessels could collect geo- and time-referenced Acoustic Data. To date Data have been received from 7 krill fishing vessels and SG-ASAM has now focussed on the development of Data collection protocols to enable fishing vessels to collect quantitative Acoustic Data along prescribed transects. While this development work continues, the willingness of fishing industry to participate in such studies has already been demonstrated by several fishing companies, and Norwegian- and Chinese-flagged fishing vessels are undertaking krill biomass surveys in two key fishery Areas in the South Atlantic sector of the Southern Ocean.
-
distribution density and relative abundance of antarctic krill estimated by maximum likelihood geostatistics on Acoustic Data collected during commercial fishing operations
Fisheries Research, 2016Co-Authors: Edwin J Niklitschek, Georg SkaretAbstract:Abstract There is a substantial harvest for Antarctic krill in the Southern Ocean, but little regular scientific monitoring of the resource. Recently, however, the Commission for the Conservation of Marine Living Resources (CCAMLR) has initialised a process to make use of Acoustic Data from commercial fisheries to increase the amount of relevant information available for making management decisions. We here provide an example where 34 days of Acoustic Data, collected during commercial krill fishing operations on the vessel ‘Saga Sea’ were processed to produce probability of presence, conditional density and relative abundance estimates on monthly, weekly and daily basis. Data were analyzed using a maximum likelihood time-series and geostatistical approaches, selected to account for the lack of sampling design, and likely correlation in space and time. The applied method showed low sensitivity of monthly estimates to different repeated measure criteria and location sub-settings. Most weekly estimates, but the last one, were also consistent with the full Data (monthly) estimate. Highly variable and lower estimates were obtained, however, from daily Data sets. Although our results suggest the method had provided an adequate treatment for time and space correlation, we were not able to evaluate potential bias due to preferential sampling of high density krill aggregations and/or limited area coverage within short time periods. The results suggest that this method, combined with some additional design based coverage by the fishing vessels, can be useful to obtain quantitative evaluations of krill density and distribution for management purposes.
Stan Kotwicki - One of the best experts on this subject based on the ideXlab platform.
-
correlating trawl and Acoustic Data in the eastern bering sea a first step toward improving biomass estimates of walleye pollock theragra chalcogramma and pacific cod gadus macrocephalus
Fisheries Research, 2007Co-Authors: Paul G Von Szalay, David A Somerton, Stan KotwickiAbstract:Abstract The charter vessels used for the annual eastern Bering Sea bottom trawl survey have recently been equipped with echosounders, which are relatively sophisticated compared to the traditional depth sounders, and are capable of collecting Acoustic backscatter Data of a quality approaching that of scientific echosounders. Because these echosounders provide a large amount of inexpensive and continuous backscatter Data between trawl stations, it is of interest to determine whether these Acoustic Data can be used in conjunction with the trawl catch Data to improve the precision of walleye pollock (Theragra chalcogramma) and Pacific cod (Gadus macrocephalus) trawl indices of abundance. Catch and Acoustic backscatter Data collected from 98 stations executed during the 2005 field season were analyzed to estimate the correlation between trawl catch per unit swept area and Acoustic backscatter integrated over various layers above the seafloor. The correlation for walleye pollock was good, with the highest correlation obtained for the layer between the seafloor and the headrope (r2 = 0.64). The correlation for layers above the headrope monotonically decreased with increasing height, indicating a lack of vertical herding by pollock. There was no correlation (r2 = 0.02) between trawl and Acoustic Data for Pacific cod, the only other important fish source of Acoustic backscatter.
Georg Skaret - One of the best experts on this subject based on the ideXlab platform.
-
the use of fishing vessels to provide Acoustic Data on the distribution and abundance of antarctic krill and other pelagic species
Fisheries Research, 2016Co-Authors: J. L. Watkins, Dietolf Ramm, Georg Skaret, Sophie Fielding, X L Wang, X-y. Zhao, Keith Reid, Edwin J NiklitschekAbstract:A fishery for Antarctic krill (Euphausia superba) has existed for over 3 decades and the Commission for Conservation of Antarctic Marine Living Resources (CCAMLR) manages this fishery using precautionary catch limits, fishery Data collection and a scientific observer programme operating on the fishing vessels. A recent increase in the number of vessels fishing and the rising costs of undertaking scientific research cruises have focussed attention on being able to use fishing vessels to collect more extensive scientific Data sets. In 2011, CCAMLR’s Subgroup on Acoustic Survey and Analysis Methods (SG-ASAM) was tasked with assessing the use of Acoustic Data collected from fishing vessels to provide qualitative and quantitative information on the distribution and relative abundance of Antarctic krill and other pelagic species. SG-ASAM conceived a proof of concept programme and implemented the first stage in 2013 to determine the current setup of Acoustic equipment on participating fishing vessels and to establish whether these vessels could collect geo- and time-referenced Acoustic Data. To date Data have been received from 7 krill fishing vessels and SG-ASAM has now focussed on the development of Data collection protocols to enable fishing vessels to collect quantitative Acoustic Data along prescribed transects. While this development work continues, the willingness of fishing industry to participate in such studies has already been demonstrated by several fishing companies, and Norwegian- and Chinese-flagged fishing vessels are undertaking krill biomass surveys in two key fishery Areas in the South Atlantic sector of the Southern Ocean.
-
distribution density and relative abundance of antarctic krill estimated by maximum likelihood geostatistics on Acoustic Data collected during commercial fishing operations
Fisheries Research, 2016Co-Authors: Edwin J Niklitschek, Georg SkaretAbstract:Abstract There is a substantial harvest for Antarctic krill in the Southern Ocean, but little regular scientific monitoring of the resource. Recently, however, the Commission for the Conservation of Marine Living Resources (CCAMLR) has initialised a process to make use of Acoustic Data from commercial fisheries to increase the amount of relevant information available for making management decisions. We here provide an example where 34 days of Acoustic Data, collected during commercial krill fishing operations on the vessel ‘Saga Sea’ were processed to produce probability of presence, conditional density and relative abundance estimates on monthly, weekly and daily basis. Data were analyzed using a maximum likelihood time-series and geostatistical approaches, selected to account for the lack of sampling design, and likely correlation in space and time. The applied method showed low sensitivity of monthly estimates to different repeated measure criteria and location sub-settings. Most weekly estimates, but the last one, were also consistent with the full Data (monthly) estimate. Highly variable and lower estimates were obtained, however, from daily Data sets. Although our results suggest the method had provided an adequate treatment for time and space correlation, we were not able to evaluate potential bias due to preferential sampling of high density krill aggregations and/or limited area coverage within short time periods. The results suggest that this method, combined with some additional design based coverage by the fishing vessels, can be useful to obtain quantitative evaluations of krill density and distribution for management purposes.
-
the r package echoviewr for automated processing of active Acoustic Data using echoview
Frontiers in Marine Science, 2015Co-Authors: Lisamarie K Harrison, Georg Skaret, Martin J Cox, Robert HarcourtAbstract:Acoustic Data is time consuming to process due to the large Data size and the requirement to often undertake some Data processing steps manually. Manual processing may introduce subjective, irreproducible decisions into the Data processing work flow, reducing consistency in processing between surveys. We introduce the R package EchoviewR as an interface between R and Echoview, a commercially available Acoustic processing software package. EchoviewR allows for automation of Echoview using scripting which can drastically reduce the manual work required when processing Acoustic surveys. This package plays an important role in reducing subjectivity in Acoustic Data processing by allowing exactly the same process to be applied automatically to multiple surveys and documenting where subjective decisions have been made. Using Data from a survey of Antarctic krill, we provide two examples of using EchoviewR: krill estimation and swarm detection.
