We have developed a Geographic Information System (GIS) and accompanying metadata to provide standardised and accessible information on the location and extent of spatial fisheries management measures in the Southern Ocean. We used the GIS in combination with catch data and the results of the 2007 CCAMLR bioregionalisation exercise to examine the relative spatial distribution of fishing activities, existing management, and ecological characteristics. Such analysis is a necessary part of systematic conservation planning for developing marine spatial protection. Our analysis of catch data focused on the Antarctic krill fishery, which accounted for 92% of catch biomass in the Southern Ocean in 2010/11 (CCAMLR Statistical Bulletin, 2012). 64% of the area managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) was open to directed fishing for at least one species during the 2010/11 season. However, catch limits were unevenly distributed within this open area due to regional differences in the occurrence of target species and level of fishing interest. There were important differences between pelagic bioregions in terms of the fraction of the bioregion that was open to fishing, and the distribution of catch within the open fraction. For example, 94% of the Antarctic shelf slope bioregion was open to directed fishing for toothfish compared to 32% of the Weddell Gyre & Ross Sea Banks bioregion. Only 26% of the total area open to krill fishing has ever been fished, and this fishing is concentrated in 3 of the 7 bioregions found in the open area. Information on the distribution of catches and catch limits among different bioregions could be used to prioritise protection for bioregions that are currently under-represented in marine protected areas (MPAs), or fished to a proportionally greater extent than other bioregions. However, systematic conservation planning should take appropriate account of uncertainties including those relating to scales of correspondence between datasets. Further development of the spatial management GIS could assist CCAMLR in many of its functions relating to fisheries and ecosystems research, monitoring and management (see also WG-EMM-12-XXX, Secretariat paper on development and management of the database).
Abstract:
A Tagging Program for Patagonian toothfish in the longline Argentine fishery outside CCAMLR´s waters was implemented. It was designed to study specific characteristics of the movement and migration of Patagonian toothfish in order to increase biological knowledge on the species and improve resource management in the South-Western Atlantic Ocean. The program started in 2004 and some 4900 juvenile toothfish were tagged and released by Observers form National Institute for Fisheries Research and Development (INIDEP). The chosen tag was an orange standard anchor T-bar tag, similar to those used in other CCAMLR’s toothfish tagging programs. The program was directed to juvenile fish preferably less than 82 cm length TL. Once a tagged specimen was retrieved on board, the tag was removed by the observer who registered its size, weight and recapture position. Otoliths were extracted. Since 2004 up today, 4,913 toothfish were tagged and 70 recaptured. In order to improve the results some recommendations are given.
Abstract:
At its 2011 meeting, the Scientific Committee agreed that a time series of relative recruitments from a well-designed survey could be a useful input into the Ross Sea stock assessment model and endorsed a proposal to carry out this work once the fishery had closed at the end of the 2011/12 season. The first survey was successfully completed in February 2012 and the results presented to the 2012 meeting of WG-SAM (Hanchet al. 2012). In this paper we provide a proposal to continue this time series.
The objectives of this second survey of the time series are as follows:
(i) To carry out the second of a time series of longline surveys to monitor pre-recruit (<110 cm TL) toothfish in the southern Ross Sea (strata A12–C12) using standardised gear in a standardised manner; and
(ii) To define additional experimental stations in adjacent areas to identify areas of high pre-recruit abundance which could be included as additional strata in future annual surveys.
Abstract:
CCAMLR Conservation measures currently require vessels to tag only toothfish with a high probability of survival, but no objective criteria are provided for this evaluation. Achieving this requires an objective evaluation of the probability of survival of each fish to be tagged, which in turn requires objective criteria that link observable characteristics to survival. This paper proposes criteria based on assessments of injuries and vitality used on other species and includes several options for implementation in CCAMLR tagging programmes.
Abstract:
Mark-recapture methodologies are commonly used to inform the management of fisheries. In addition to answering targeted research questions, tagging programmes are typically used to describe movement patterns relative to stock unit identification or to support spatial disaggregation of stock assessment areas, and in some instances to derive population abundance estimates. This paper is intended as a discussion tool to identify and prioritize tagging-related issues for further research drawing on the experience tagging programmes internationally. To the extent that CCAMLR tagging programmes are unique, an evaluation of potential programme biases and corresponding information needs is presented. The paper focusses on the design and implementation of toothfish tagging programmes, but many of the potential issues apply equally to other tagged species such as skates.
Abstract:
With the recognition that CCAMLR tagging programmes are used for abundance estimation of toothfish and skates, tagging operations need to be appropriately supported through documentation, training, and supplies. This paper reviews how tagging programme information could be effectively organised, provides a template training module for observers and vessel crew, and makes recommendations to update tagging protocols and to create a tagging checklist for use at the tagging station.
Abstract:
A reliable commercial tagging program is critical to the successful assessment and management by CCAMLR of a number of toothfish fisheries in Antarctica. The evaluation of the tagging programme relies on two key aspects (i) that the tagged fish have a good chance of survival and (ii) that the tagged fish are reliably detected when recaptured. Previous attempts to evaluate individual vessel tagging performance in relation to these two aspects has been thus far inconclusive because of confounding factors such as time and location of tagging and subsequent fishing effort, as well as size of fish tagged.
We propose that, by controlling for the spatial and temporal confounding factors using a case-control study design, we can derive meaningful indices of relative tagging performance of groups of fishing effort (e.g. vessel, vessel-trip). We developed indices to compare (i) the tag detection rate of recaptured fish and (ii) the tagging survival of released fish.
This method was applied to the toothfish tagging data in CCAMLR Subareas 88.1 and 88.2. Initial results show that the indices developed can provide evidence of significant differences in tagging performance between different groups of fishing effort. Preliminary investigation showed these indices are robust to the choice of the control group and the area included in the analysis. Subject to further checks, this method could be used to investigate the relative tagging performance of different components of the CCAMLR tagging program across all fisheries, and more generally the relative performance of spatially and temporally heterogeneous data sets.
Abstract:
At its 2011 meeting, the Scientific Committee agreed that a time series of relative recruitments from a well-designed survey could be a useful input into the Ross Sea stock assessment model and endorsed a proposal to carry out this work once the fishery had closed at the end of the 2011/12 season. The survey had two main objectives: (i) To establish the feasibility of developing a time series of longline surveys to monitor pre-recruit (<100 cm TL) toothfish in the south of SSRUs 881.J and 881.L in the southern Ross Sea using standardised gear in a standardised manner; and (ii) To carry out experimental depth-stratified fishing in 400–600 m depth adjacent to the survey boundaries to establish the most appropriate depth strata for future annual surveys.
The survey demonstrated it is possible to carry out a longline survey of pre-recruit toothfish from commercial fishing vessel in Ross Sea using standardised gear in a standardised manner. Based on a total of 45 sets in the three core strata (A12-C12) the survey had an overall c.v. of 9%, which met the target c.v. of 10%. The survey caught mainly 70–110 cm TL Antarctic toothfish. The survey provided new data on the depth distribution of pre-recruit fish in this area. Catch rates of pre-recruit toothfish were highest between 500 and 900 m and very low shallower than 450 m. The size distribution of toothfish was very similar between the four main strata suggesting no depth preference between 400 and 900 m. It is recommended that future surveys in this area should focus on depths greater than 500 m. The survey also demonstrated the feasibility of collecting samples for wider ecosystem monitoring.
Although the main aim of the 2012 survey was to monitor pre-recruit toothfish, the survey provided the opportunity to compare catch rates in 2012 with historical catch rates by San Aotea II and its sister ship Janas in earlier years of the fishery. The results of a standardized CPUE analysis suggest that there has been no significant change in catch rates in the southern Ross Sea over the past decade.
Abstract:
Currently the target tagging rate to be achieved by vessels fishing in the CCAMLR area is set in terms of the number of fish tagged per mass of fish caught thereby mixing “units” of measure. This note questions whether it is appropriate to set the tagging targets these terms and suggests that defining the target in terms of a percentage of the number caught may be more appropriate.
Abstract:
Using a modeling framework for toothfish population dynamics, fishing and data collection, this study investigated how the bias and precision of a CASAL assessment is influenced by various aspects of a tagging program, in particular the effects of the numbers of fish tagged, the duration of a tagging program, the size of tagged fish, and the type of auxiliary data used in the assessment.
The simulation study indicated that:
(1) A high tag size-overlap (at least 60%, better 100%) and high tagging numbers were important particularly in the early stages of an exploratory fishery to ensure some recaptures and maximise the likelihood of a robust assessment.
(2) Using catch-at-age data instead of catch-at-length data substantially improved all assessment estimates and was required for adequately estimate annual recruitment and year class strengths.
(3) For a simulated lightly fished stock, CASAL assessments with good quality tagging data had a low bias and reasonable precision for SSB0 and annual SSB estimates, however the precision of SSB status estimates in the final assessment year was relatively low. Bias and precision of CASAL assessments were better for the lightly fished stock than for a heavily fished stock.
(4) This modeling framework appears to be useful for evaluating data sampling strategies, assessment approaches and management strategies.