Understanding the spatial distribution of the release of tagged fish and the subsequent spatial coverage of fishing effort to recapture tagged fish is an important consideration when interpreting the biomass estimated from mark recapture data. In 2015, the Scientific Committee identified that measures of spatial overlap and potential bias in the development of tag-based biomass estimates are an important focus topic for WG-SAM (SC-CAMLR-XXXIV, 2015, para 3.83). This paper outlines developments towards new biomass-weighted spatial overlap summary statistics for tagging data. The method calculates two statistics: (i) a single measure of the degree of spatial overlap between the release of tagged fish and subsequent fishing effort for tag recovery, labelled the tag spatial overlap (TSO) statistic and (ii) a measure of the potential bias in the biomass estimate calculated from non-homogenous spatial mark-recapture data, labelled the tag spatial bias (TSB) statistic.
We apply the method to a single case study area, SSRUs 88.2H to illustrate its use. We found that the median tag spatial overlap statistic in 2012 was 70% (95% CIs 53–80%), and the median tag overlap bias was 88% (95% CIs 64–114%). In 2014 the median tag spatial overlap statistic 60% (95% CIs 50-69%), and the median tag overlap bias was 192% (95% CIs 141-268%).
The TSO statistic and TSB statistic provide a simple; and intuitive approach to indexing the degree of spatial overlap and potential bias from mark recapture data, with few assumptions required on the distribution of fish, movement, or catch history. Potential uses of these statistics could include a measure of the total spatial distribution of effort through time in research or developing fisheries, and a measure of the change in bias of mark-recapture estimates through time.
Abstract:
This paper evaluates present regulation of cabled net monitoring instrumentation and suggests an adjustment in the CCAMLR requirements that enable the industry and researches onboard the krill vessel to collect more and better monitoring and research data.
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This paper evaluates present reporting procedures for the continuous fishing method and proposes a change in the CCAMLR requirements that produces more robust and correct catch statistics.
Abstract:
Exploratory fishing for toothfish (Dissostichus spp.) in East Antarctica (Divisions 58.4.1 and 58.4.2) began in 2003. Robust stock assessment and catch limits according to CCAMLR decision rules remain to be determined for these Divisions. The 2015/16 season was the first of a three-year research plan which was developed by Australia (WG-FSA-15/47 Rev. 1) under Conservation Measure 41–01. Australia will present to WG-SAM-2016 a full report on the fishing operation, catch composition, tagging and biological sampling undertaken by Australia during 2015/16 in SSRUs 58.4.1E and 58.4.1G. Here, we evaluate the original research plan set out in WG-FSA-15/47 Rev. 1, and propose continuation of this research in the 2016/17 season. Ongoing standardised longline fishing, in conjunction with fish biological measurements, tagging and aging, will be used to develop a stock assessment/s for Divisions 58.4.1 and 58.4.2, and inform the necessary considerations of spatial structure, biomass and connectivity of toothfish populations. In addition, environmental data from CTD (conductivity, temperature and depth) and video loggers will contribute to models of toothfish habitat use. These models will inform spatial management approaches for toothfish, and the conservation of representative areas of benthic biodiversity. Additional outcomes include mapping of the bathymetry of fishable areas, and improved understanding of the distribution, relative abundance, and life histories of bycatch species.
Presentar antecedentes y el objetivo de contribuir con un barco mas en la pesca de investigación en la Subárea 48.6 que aumentaria las chances de cuota de pesca de investigación y asi el número de peces observados y marcados, a efectos de lograr un nivel que permita robustecer el tamaño del stock estimado. Este documento presenta un Plan de investigación para el período 2016/17 - 2018/19, en el marco de la Medida de Conservación 41-04.
Abstract:
The current season (2015/16) is the first one of the second three-season research in data-poor fisheries. In the present report, the next season research plan in Division 58.4.2 was made using the updated CCAMLR C2 and Observer data.
The stock sizes for a research block (58.4.2_1) were estimated by the Petersen estimator and the CPUE x seabed analogy method using updated CCAMLR C2 data and reference area sizes.
Understanding of the resource structure through clarification of their life history is essential to establish stock assessment and robust stock/ fisheries management of Dissostichus spp. population(s) in data- poor exploratory fisheries. During the second three-season research, we will continue enhanced tagging program, and collection and analysis of biological data including otoliths and gonads to clarify migration route and associated life stages of the fish.
To this end, we propose to follow the current research style in the current research blocks for the next research with the sample sizes estimated following the procedure recommended at the WG-FSA in 2013 in order to maximize the expectation of tag-recapture to the extent possible under the precautionary exploitation rate.
Abstract:
The current season (2015/16) is the first one of the second three-season research in data-poor fisheries. In the present report, the next season research plan in Division 58.4.1 was made using the updated CCAMLR C2 and Observer data.
The stock sizes for five research blocks (58.4.1_1, 58.4.1_2, 58.4.1_3, 58.4.1_4 and 58.4.1_5) were estimated by the Petersen estimator and the CPUE x seabed analogy method.
Understanding of the resource structure through clarification of their life history is essential to establish stock assessment and robust stock/ fisheries management of Dissostichus spp. population(s) in data- poor exploratory fisheries. During the second three-season research, we will continue enhanced tagging program, and collection and analysis of biological data including otoliths and gonads to clarify migration route and associated life stages of the fish.
To this end, we propose to follow the current research style in the current research blocks for the next season research with the sample sizes estimated following the procedure recommended at the WG-FSA in 2013 in order to maximize the expectation of tag-recapture to the extent possible under the precautionary exploitation rate.
Abstract:
The subarea 88.3 is a large area contained from 105° W to 70° W where has been closed to directed fishing following the results of a Chilean survey activities in 1998 (SC-CCAMLR-XVII/BG/7). Previous three research surveys conducted by the New Zealand and the Russian flagged vessels since 1998. It was noted that 8 D. Mawsoni were tagged by the New Zealand in the 2004/05 season and 123 D. Mawsoni were tagged by Russian flagged vessels in the 2010/11 and 2011/12 season (WG-FSA-05/53, WG-FSA-11/36 & WG-FSA-12/13). It was also noted that no tagged fishes were recaptured during the previous research activities. Considering this large region, the Republic of Korea notes that only 95 research hauls and 131 tagged fishes from three research activities (in total since 1998) were not enough likely to recapture. it was further noted that there was no research activities more than two consecutive years in the past despite the Scientific Committee has agreed that research fishing should be conducted such that it results in an assessment of a stock in 3-4 years time (SC-CAMLR XXVIII, paragraphs 4.165). During the 2015/16 season the Korean flagged vessel, Greenstar, conducted 1st year research in this area. Total of 566 D. Mawsoni were tagged and released. Although the Greenstar set 108 research hauls in the Subarea 88.3 she did not find any recaptures of previous surveys. In second research year, the Greenstar is planning to revisit to the areas where the tagged fishes were released to further understand toothfish movement and migration with recapture data.