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Jarpa Review

Extract from the full Report of the JARPA review workshop 2007

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8. Overview of results in the context of the stated objectives of the JARPA programme and of stock management

Although the Terms of Reference (ToR) specified this overview to include how well the initial and revised objectives of the research had been met, it was inevitable that the discussions at the Workshop would give rise to suggestions for further and/or refined analyses. Thus it was unclear whether or not the conclusions of the Committee under this component of the ToR should or should not await consideration of the results of further analyses.

8.1 Contribution to minke whale management

The Workshop noted that the Southern Ocean Sanctuary established in 1994 covers most of the Antarctic waters south of 40°S and all of the waters to the south of 60°S; within the Sanctuary, commercial whaling is prohibited although the Government of Japan has an objection with respect to Antarctic minke whales. If catch limits were to be set at some time in the future, the present approach the Scientific Committee has agreed to use for providing advice to the Commission on commercial whaling catch limits is that specified by the RMP. When it last considered this issue in 1997, the Committee agreed to the statement below.

The results from the JARPA programme, while not required for management under the RMP, have the potential to improve management of minke whales in the Southern Hemisphere in the following ways: (1) reductions in the current set of plausible scenarios considered in Implementation Simulation Trials; and (2) identification of new scenarios to which future Implementation Simulation Trials will have to be developed (e.g. the temporal component of stock structure). The results of analyses of JARPA data could be used in this way perhaps to increase the allowed catch of minke whales in the Southern Hemisphere, without increasing depletion risk above the level indicated by the existing Implementation Simulation Trials of the RMP for these minke whales.

The present Workshop concurred with that view.

In its discussions of possible contributions to management, the 1997 Workshop also referred to:

  1. questions about long-term changes in abundance of minke whales in Areas IV and V;

  2. elucidation of the role of minke whales in the Antarctic ecosystem (including the possible ‘krill surplus’ model);

  3. elucidation of the effect of environmental change on cetaceans and variation of minke whale biological parameters; and

  4. elucidation of stock structure to improve management. Progress and conclusions on these are considered below.

8.1.1 Stock structure

The issue of stock structure is fundamental to the analyses of the data collected under JARPA, the interpretation of the results and a view of whether it has reached its stated aims and objectives. As noted in 1997, the Scientific Committee at that time had no clear definition of a ‘stock’ in a management context. Despite the ongoing work of the Working Group on Stock Definition, the Committee is still not in a position to provide such a definition, although it recognises that any definition has to be linked to the management implications of such a definition, particularly with respect to feeding areas. This is being investigated as part of the Committee’s TOSSM project. In an RMP context, the approach has been to use the available data to establish ‘plausible’ hypotheses and to examine the management implications of these in the context of Implementation Simulation Trials. Given this background, it is not surprising that the Workshop cannot conclude that this issue has been resolved for Antarctic minke whales in the JARPA research area at the present time; however, it recognises that considerable progress has been made in addressing the issue of stock structure since the 1997 review. For example, the Workshop agreed that there are at least two stocks of Antarctic minke whales present in the JARPA research area and that the data suggest an area of transition in the region around 150-165ºE within which there is an as yet undetermined level and range of mixing. The Workshop has made a number of suggestions and recommendations for future work (see Item 3). The results of this additional work will have major implications for determining the level to which the programme will meet its other objectives. It is also clear that this work is essential to any future Implementation Review under the RMP.

8.1.2 Stock abundance and trend

Information on stock structure is also important for the interpretation of abundance and trend information obtained during surveys on feeding grounds. As stressed earlier in the report, such surveys provide information on numbers of animals (and trends in those numbers) within a geographical area. Information on abundance and trends in abundance is relevant to aspects of all of the objectives of JARPA including the estimation of biological parameters and changes in those over time, and the role of whales in the Antarctic ecosystem. At the 1997 Workshop it had been agreed that more research was needed to develop a reliable method to use the JARPA data to obtain estimates of absolute abundance and trends.

There are general unresolved issues related to estimating abundance and trends in these waters that apply not only to the JARPA data but also to the IDCR/SOWER data that require further work by the Committee. Given that, it is not surprising that the Workshop has not developed agreed estimates of abundance and trend for Antarctic minke whales in the JARPA research area at the present time; however, it recognises that considerable progress has been made in addressing the issues related to abundance and trends and provided the recommendations given under Item 2 are followed, the Committee should soon be able to agree estimates. The Workshop draws attention to its comments on the confidence intervals surrounding the preliminary estimates of trends presented that suggest that even the revised estimates may only be able to detect very major changes in the abundance of animals using the JARPA area over long time periods. The implications of this latter finding for addressing the other objectives (e.g. biological parameter estimation) require further investigation. The abundance estimates will be valuable for any future Implementation Review under the RMP.

8.1.3 Estimation of biological (life history) parameters to improve the stock management of the Southern Hemisphere minke whale

As noted above, issues of stock structure are directly relevant to the question of biological parameter estimation. The 1997 review had noted that the information from JARPA had set the stage for answering many questions about long term changes in minke whales in the JARPA research area and had recommended that biological parameters be analysed by stocks. Some advance towards that had been made at the present Workshop in that estimates had been presented for one possible hypothesis based on the stock structure analyses undertaken thus far, in accordance with a Committee recommendation made in 2006. However, further work will be required as progress is made with respect to stock structure and mixing in accordance with the recommendations made under Item 3.  Given that background and notwithstanding further comments below, the Workshop cannot conclude that this objective has been fully met at present; however, the Workshop acknowledged that considerable effort had been put into attempting to obtain agreed estimates of biological parameters (and changes in these over time) for one stock structure hypothesis. In discussion of the analyses presented at this Workshop, the Workshop agreed that no marked trends in life history parameters were found for the JARPA period. However, problems were identified with the age data for the commercial period and for this reason, there were differing views on the reliability of estimates of historical trends in life history and population parameters prior to the JARPA period. It was also noted that the confidence intervals around the estimates of natural mortality estimated from the JARPA data alone spanned such a wide range that the parameter remains effectively unknown at present (narrower confidence intervals were estimated for the ADAPT-VPA analysis but this relies on commercial age data). The Workshop agreed that every effort should be made to try to resolve the issue of the commercial age data as this has important implications as to how well the objectives of the programme can be met.

8.2 Elucidation of the role of whales in the marine ecosystem

At the 1997 Workshop, it had been noted that the data on body condition and biological parameters should result in a better understanding of the status of Antarctic minke whales in the research area and be useful to test hypotheses related to aspects of the ‘krill surplus’ model. The importance of understanding the feeding ecology of Antarctic minke whales has been recognised by the Committee and formed an important part of its SOWER 2000 programme (IWC, 2000b). The importance of but the inherent difficulties in ecosystem modelling are also recognised by the Committee (IWC, 2004a;2007b). The Committee has long been unable to reach agreement on interspecific competition among baleen whales in the Antarctic, particularly with respect to the so-called ‘krill surplus’ model. The Committee welcomed the oceanographic and krill-related work undertaken since the 1997 Workshop. The Workshop also agreed that considerable relevant data had been collected by the JARPA programme on matters related to body condition and feeding. However, it is clear from the discussion under Item 5 that the simple nature of several of the analyses presented at the present Workshop means that relatively little progress has been made in addressing this objective, even allowing for the complexities of the subject. Issues related to the ‘krill surplus’ model remain as controversial as ever. The Workshop strongly recommended the establishment of an advisory group (Item 5.5) to ensure that the extensive dataset is used to its full potential and progress is made. It also agreed that it is essential that information on other krill predators as well as information on krill dynamics is incorporated into analyses of the role of whales in the ecosystem and notes that planned discussions in the IWC/CCAMLR joint workshop would assist in this.

8.3 Environmental change

At the 1997 Workshop, it was noted that the pollutant analyses undertaken by the JARPA programme should take into account the recommendations made at the 1995 IWC Workshop on Chemical Pollutants and Cetaceans (Reijnders et al., 1999a). The Workshop welcomed the presentation of the pollutant analyses at this Workshop, although there was some disagreement over the implications of the results drawn by the authors (see Item 6.3.1). The Workshop also welcomed the oceanographic work presented, noting that in addition to its potential to assist in the ecosystem work, it also has the potential to contribute to other environmental monitoring programmes in the Antarctic.