We made stock status assessments of Dissostichus eleginoides in SSRUs C and D in Division 58.4.4 a & b. Regarding SSRU C, the stock size was estimated by using following six methods; 1) comparative CPUE analysis, 2) modified Lincoln-Petersen 3) CASAL_base model, 4) CASAL_YCS_fix model, 5) CASAL_0_IUU model, and 6) CASAL_all_IUU model. This approach was made based on the WG-FSA’s recommendation stating that the sensitivity run of the CASAL model should be made by using levels of IUU ranging from zero to all observed IUU fishing, and using constant YCS (year class strength) in SSRU C. The CASAL_base model includes estimated variability of YCS for the period from 1989 to 2005, and assumed that a quarter of observed IUU fishing in the division had occurred in SSRU C. High estimated stock levels were obtained from CASAL_base (1230 tonnes), CASAL_YCS_fix (1230 tonnes) and CASAL_all_IUU models (1360 tonnes), medium level from CASAL_0_IUU model (710 tonnes), and low level from CPUE comparison (542 tonnes) and modified Lincoln-Petersen (446 tonnes).
The catch and tagging data in SSRU D were not enough to be applied to modified Lincoln-Petersen and CASAL models. Thus the stock sizes of D. eleginoides in SSRU D is estimated only by using CPUE comparison with the stock size estimates in SSRU C obtained from each method.
Since we have not obtained enough evidence to estimate plausible stock size, and accordingly have not been able to determine catch limit yet, we would like to conduct research repeated for at least 3-4 years in the same locations as in the 2012/13 season, with the same survey design and sample size of a total of 50 tonnes in SSRUs C and D for the 2013/14 as in the 2012/13, in order to promote successful stock assessment
Abstract:
A survey was conducted to collect data of stock status and various biological information of toothfish in SSRUs C and D of Division 58.4.4a & b (Ob Lena Banks) from April 25 to May 22, 2013. A total of 64 research hauls using normal trotline system were made in SSRUs C and D. Total catch of Dissostichus eleginoides (excluding those tagged and released) was 31.1 tonnes in the survey area from 64 longline sets. Mean CPUEs in terms of weight of D. eleginoides was 70.6 kg / km (CV = 79.1%) and 44.2 kg / km (CV = 91.9%) in SSRUs C and D, respectively. Both nominal and standardized CPUEs were relatively higher in 2011 but showed no clear tendencies with the years in SSRU C. Fish in single-hooked and good physical condition constituted 31.6 and 27.1 % of the total catch in SSRUs C and D, respectively. The possible maximum tagging rate was calculated to be 30.1 fish per tonnes and 23.5 fish per tonnes in SSRUs C and D, respectively. Accordingly sufficient numbers of fish suitable for tagging was captured by using the normal trotline system. A total of 233 fish of D. eleginoides in good physical condition and single-hooked were tagged and released during the survey, and 3 fish of D. eleginoides, which were tagged and released in SSRU C in 2007/08 and 2010/11, were recaptured in the same SSRU. No set was affected by killer whales in both SSRUs.
Abstract:
The correct age-length keys are essential for the stock assessment of Dissostichus spp. by CASAL model. However, the age estimations using the otoliths have been scarcely progressed in regions of data-poor fisheries. Therefore the analysis is an urgent task. We have made five reading tests using images of thin-sectioned TOP otoliths in December 2012 and May 2013. The coefficient of variation between “known ages” by AAD (Australian Antarctic Division) and those estimated by the first author (Taki) is lower than the threshold of 10 % for five tests, with one of them being close to 10 %. This suggests that his reading clear the standard by NIWA (National Institute of Water and Atmospheric Research Ltd, in New Zealand). He will continue to make the periodical reading test for TOP otolith sections. On the other hand, a total of 60 TOA otolith references by bake-and-embed method were provided by CCAMLR Secretariat in this February. We will make image processing for these references and also conduct the periodical reading tests using the images. In addition, we plan to train the second reader referring to the standard protocols by NIWA and AAD. We aim to establish the reading technical skill for TOA otolith sections by next year (2014). The size-age data will be applied to CASAL catch-at-length and catch-at-age models in 2015 and later.
Abstract:
Length frequency distributions (LFD) of catch collected as a random sub-sample from hauls are an important input to integrated fish stock assessments. Statistical tests for variables that significantly influence the LFD helps in evaluating how to account for important differences in availability and/or gear specific selectivity. A distribution-free model of LFD is described which is fitted to the set of length quantiles L for a predetermined set of corresponding probabilities P (in this instance 0.05, 0.1 to 0.9 in 0.1 increments, and 0.95), constructed from individual length measurements of individual hauls as sampling units or after pooling hauls to sampling units defined by combinations of discrete-valued covariates of gear type, spatial block, depth strata, and optionally the sex of sampled fish. The Ls were modelled as a Gaussian response variable using a Generalised Additive Mixed Model (GAMM) with cubic smoothing splines fitted to P for each combination of the covariates (i.e. gear type, depth strata and sex). Within-sampling unit error structure incorporated a statistical weight for sample size and a continuous autoregressive component due to the cumulative nature of the quantiles. Additional error terms included a random spatial block term and interactions of spatial blocks with other covariates. Graphical presentation of fitted splines along with standard error of difference bounds were used to investigate where differences were significant. The model has the advantage of greater generality and sensitivity in detecting differences compared to modelling a single quantile such as the median. In addition, fitting cubic splines allows modelling of standard sigmoidally-shaped cumulative LFDs as well as other more complex shapes, for example, due to multi-modality. The model and model testing using analysis of residuals and random effect estimates are demonstrated using LFD from commercial fishing for Patagonian toothfish at Heard Island (Division 58.5.2). The model supports fitting separate selectivity functions by gear, depth and sex in Division 58.5.2.
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Abstract:
The article is concerned with discussion of the Analysis of anomalous CPUE data from data-poor exploratory fisheries (WG-FSA-12/07). Key points of the paper were presented and discussed during the Workshop for the Analysis of the Anomalous High CPUE by Korean Vessels in the CCAMLR Area (2013,April 29th - May 1st, Busan, Korea). This paper attempts to explain possible reasons of anomalous high CPUE for Dissostichus spp. revealed by several vessels in the Subareas 58.4.1, 58.4.2 and 48.6. A number of objective and subjective factors, which can have a principal effect on results of the analysis of anomalous high CPUE, are described. The opinion has stated that a criterion of anomalous CPUE should be specified under condition of CPUE standardization of different types of longlines. There is a conclusion that a discussion on anomalous high CPUE in the specified areas using available data and techniques of their processing is bleak.
Abstract:
Ukraine has submitted a notification for research fishing over three seasons to assess the stock status of Dissostichus spp. in Subarea 48.2, starting in 2013/14. Research fishing will be limited to 80 tonnes of Dissostichus spp. in 2013/14. The notification was submitted on 30 April 2013 and in accordance with Conservation Measure 24-01 (paragraph 3).
Abstract:
Chile has submitted a notification for research fishing in Subareas 48.1 and 48.2 in 2014, 2015 and 2016 in accordance with Conservation Measure 24-01 (paragraph 3). The research will provide information on finfish distribution, abundance and size composition, with the objective of determining the current status of fish stocks in the study area. Research fishing will be limited to 100 tonnes of finfish per season. The notification was submitted on 4 June 2013.
Abstract:
Ukraine has notified its intention to participate in the exploratory fisheries for Dissostichus spp. in Subarea 48.6 and Division 58.4.1 in 2013/14. The research plan details the objectives, rationale and activities proposed for research fishing, in accordance with Conservation Measures 21-02 and 24-01.