WG-FSA-SAM-06

The standard procedure used to extract catch-weighted length frequencies can only make use of CCAMLR data for D. eleginoides in Subarea 48.3 collected in the seasons 1992/93 and from 1994/95 onwards. The procedure cannot use the earlier data collected between 1984/85 and 1991/93, and data from 1993/94 because of a mismatch in Flag State which presently occurs between the length and catch data Read More
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Trawl surveys are used in CCAMLR waters to estimate abundance of juvenile toothfish (Dissostichus eleginoides) and icefish (Champsocephalus gunnari). Documentation of some past trawl surveys has been insufficient to allow members of WG-FSA to fully interpret the survey results. This document suggests a standard pro-forma for reporting trawl survey results to WG-FSA based on Read More
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This paper develops a Bayesian mark-recapture model for estimating both fishing and natural mortality, and integrates catch-at-age data into the estimation model, to aid in distinguishing between natural and fishing mortality. The model essentially follows tagged cohorts, with the estimated parameters being the  fishing and natural mortality vectors for that particular cohort.

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Length-at-age data for the Patagonian toothfish (Dissostichus eleginoides) caught by trawl in Heard Island fishery were fitted using a von Bertalanffy (VB) growth model taking into account variable probability (VP) sampling of fish that were aged. Sub-sampling of random length frequency (LF) data used to obtain the samples of fish for ageing used length-bin sampling involving a Read More
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This report updates the estimates of the biological parameters for Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea (Subareas 88.1 and SSRUs 88.2A–B). We present revised estimates of the von Bertalanffy growth curves, length weight relationship, and natural mortality based on CCAMLR observer data collected from commercial fishing operations in the Ross Sea. In addition, we Read More
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A descriptive analysis of the toothfish tagging programme carried out in Subareas 88.1 and 88.2 since 2001 is presented. The paper updates tag-release and tag-recapture data for fish that were both released and recaptured from New Zealand vessels. It also presents release and recapture data for non- New Zealand vessels for the first time. However, tag data were only available for all of Read More
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This report outlines developments towards evaluating bias in abundance estimates for the current tagrecapture programme for Antarctic toothfish in the Ross Sea. We present an initial approach that uses the current data on catch (C2 data), tag-recovery effort and tag-release data from Dunn et al. (2005c), but ignores movements of tagged and untagged fish.

The results suggest that as Read More
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We provide an update of the Bayesian sex and age structured population stock assessment model for Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea (Subareas 88.1 and SSRUs 88.2A–B), by including tag-recapture data for 2005–06 from New Zealand vessels. The updated assessment resulted in a similar, though slightly higher, estimate of initial and current biomass as the 2005 base case Read More
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Two Operating Models (OMs) reflecting an “Optimistic” and a “Pessimistic” current status for the toothfish resource in the Prince Edward Islands region that were developed last year are updated given further data. These models are for use for initial trials of candidate Management Procedures (MPs) which could provide future TAC recommendations for this resource. Deterministic projections Read More
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During the year 2005 meeting of the WG-FSA two different methods for assessing Patagonian toothfish stock in CCAMLR Subarea 48.3 were available to the Working Group: CASAL and ASPM (WG-FSA-05/16; WG-FSA-05/73). Although the underlying basic age-structure population dynamics models in both cases were similar, there were considerable differences in assumptions and implementations of the two Read More
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This paper follows preliminary work in 2005 in developing an integrated assessment for Patagonian toothfish in Division 58.5.2. It focuses on developing a “base-case” assessment, which is primarily based on the 2005 assessment implemented in the Generalised Yield Model (GYM) using survey data of the abundances of juvenile fish but adding fishery catch-at-length data, including a standardised Read More
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This paper reviews the data used to estimate the abundance of juvenile Dissostichus eleginoides in Division 58.5.2 and examines the sensitivity of the assessment of yield to these results. Primarily, it is proposed to revise the use of historical survey data by reassigning them to the strata established in 2003. In addition, the sensitivity of the estimates of abundance to the latest length- Read More
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The study of animal movement and distribution has been a central focus in ecology since the inception of the science. However, continuous-time, discrete state models have received relatively little application in data analyses or prediction in studies movement. Here we develop a continuous time, discrete state stochastic model, a continuous time Markov chain (CTMC), for analyzing movement Read More
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