CCAMLR

Data are collected for use in scientific research, the results of which are used to inform management decisions made to achieve specific goals. Any data collection plan should be drawn from the goals the management wishes to achieve. The Scientific Committee has recommended the development of a specific data collection and research plan for the Subarea 88.1 and 88.2 fisheries (SC-CCAMLRXXVII paragraph 4.160 vi). The long-term goals of the Ross Sea fishery based on Article II of CAMLR can be summarised as: the target fished population is above a level which ensures stable recruitment; the ecological relationships between harvested, dependent, and related populations are maintained; and, prevention of changes or minimisation of the risk of changes in the marine ecosystem which are not potentially reversible over two or three decades, with the aim of making possible the sustained conservation of Antarctic marine living resources. Based on these goals and previous experience in the fishery, proposed medium term research objectives for the Ross Sea fishery for the next 5–7 years were developed in 2008. The outlined medium-term research objectives were used as the basis for the development of this Ross Sea region fisheries medium term data collection plan. This paper provides context with a brief summary of recent science, summarises the current fishery-dependent data collection, describes the proposed medium term research objectives, and develops an associated draft fishery-dependent medium term data collection plan. Feedback is sought from WG-FSA and TASO, in particular are there any substantive gaps in the proposed data collection requirements and can any feedback be provided on the approaches to optimising sampling rates, the proposed rotational approach to sampling certain species and which data collection could be undertaken by vessels and which data collection should be undertaken by observers.

ABSTRACT Since 2008 New Zealand has been developing an impact assessment framework to estimate the likely impacts of bottom longline fishing on Vulnerable Marine Ecosystems (VMEs), as required by Conservation Measure 22-06. The most recent iteration of the impact assessment (Sharp 2010) was recommended in 2010 by WG-SAM (paragraph 4.16) and WG-EMM (paragraph 3.20) as the basis by which Members submitting new and exploratory fishery notifications should estimate impacts on VMEs associated with their proposed bottom fishing activities, as well as the basis by which WG-FSA might complete cumulative impact assessments for all gear types combined at the scale of entire fisheries. Both WG-SAM and WG-EMM gave specific guidance as to how the framework might best be applied. This paper updates the impact assessment taking account of the specific recommendations of WG-SAM and WG-EMM 2010 and incorporating new information arising from WG-EMM 10/33, including the choice of improved input distributions representing key variables driving the impact simulation and the use of alternate assumptions in which lateral movement frequency is negatively correlated with depth. Impact estimates are summarized separately for each of 17 benthic bioregions defined in Sharp et al. (2010), and displayed as frequency distributions of fine-scale pixels experiencing different levels of impact, as advised by WG-SAM 2010 (paragraph 4.18). We conclude that the relationship between depth and lateral line movement is highly uncertain, but it is likely that improved understanding of this relationship will yield impact estimates that are slightly higher for shallow habitats on the shelf relative to previous estimates, and substantially lower for deep habitats. Overall estimates of impact remain low within all bioregions.

High resolution VME taxa bycatch data (at the longline segment level) have been collected for two fishing seasons, with 4 728 longline segments observed. Several regions with consistent presence of VME taxa bycatch are identifiable, as are several areas of dense fishing effort with no evidence of VME taxa. Identifiable sponge and/or gorgonian habitats occurred at a typical scale of 10-30 km², though some sponge habitats may have been larger. Other taxa were not clustered at small scales, but were at larger scales. Spatial analysis of these data allows the detectability of prevalent taxa to be estimated, along with changes in catch rate at different levels of observed bycatch. Results indicate that several VME taxa are detected between 60% and 80% of the time when present, and that probability of detection was higher near areas with other high bycatch observations. Video transects on the Ross Sea slope from New Zealand’s 2008 IPY voyage were used to characterise the fine scale distributions (i.e. < 600 m) of sponges, stony corals, and ascidians. The prevalence of six VME taxa also varies among four benthic bioregions developed for the Ross Sea. Together, the data show that vulnerable taxa occur in complex mosaic patterns of small patches dispersed within larger habitats. Confirmation of these results is necessary using independent methods such as underwater video and would provide a method to link bycatch observations to habitat density on the seafloor.

An important management objective for CCAMLR in the high seas region of the Antarctic is to develop appropriate methods of monitoring and managing impacts of bottom fisheries on vulnerable marine ecosystems (VMEs). We describe a spatially explicit production model that can be used to investigate a range of scenarios for simulating the effect and management of benthic impacts from longline fishing effort. Further, we update this paper with a set of simulations using a range of simple and extreme case studies to validate the underlying model and code. In general, the model simulations were carried out under a range of productivity assumptions, impact, and spatial scale, with and without management by areal closures. The management action simulated considered a range of areal closure radii and bycatch trigger thresholds. We conclude that spatially explicit production models can provide a useful tool for the investigation of impacts of fishing effort on benthic organisms. They have the advantage that they are relatively simple to construct, run, and interpret. In most cases, the results of the simulations suggested that management action of areal closures in the Ross Sea region are likely to result in an improved outcome relative to scenarios where there was no management action, but that the magnitude of simulated impacts under the plausible models was often very small. We also note that further work on these simulations are required — including investigating how changes in the distribution of future fishing may influence estimated impacts or how different assumptions of the underlying distributions of benthic organisms may influence recovery or management effectiveness. However, as the magnitude of these impacts in the scenarios tested were small, we recommend that research be focused, at least in the short term, to provide the observational or experimental data necessary to constrain important model parameters, to reduce uncertainty and provide more plausible scenarios.

In 2009 SC-CCAMLR identified a list of tasks to be considered intersessionally to progress a framework to manage the risk that bottom fishing in the CCAMLR Area may produce significant adverse impacts on certain benthic habitats, termed Vulnerable Marine Ecosystems (VMEs). One of the identified intersessional tasks was to produce a glossary of terms relevant to the management of VMEs (SC-CAMLR XXVIII, paragraph 4.251(iii)). In 2010 WG-EMM discussed a proposed VME glossary (WG-EMM-10/29) and recommended adoption of six key terms. Other VME relevant terms were also discussed but referred to WG-FSA (WG-EMM 2010, paragraph 3.2-3.3). This paper updates the previous VME glossary to reflect the definitions agreed by WG-EMM and proposes definitions for additional terms consistent with the previous advice within CCAMLR and new advice from WG-EMM. A conceptual diagram is also provided to illustrate the relationships between the terms and the means by which terms might be combined quantitatively to inform the evaluation of fishing impacts on VMEs.

Revised weight-length and length-length regressions are provided for Amblyraja georgiana and Bathyraja cf. eatonii. Significant differences between males and females occurred for all comparisons except for B. cf. eatonii length-length regressions. Some observer maturity staging data were unreliable, as indicated by comparison with lab staging, and the presence of very large skates scored as immature. For A. georgiana, this resulted in flatter maturity ogives for observer data than lab data, and different estimates of median length at maturity. The lab estimates were based on small datasets that did not cover the maturation range adequately, so using them instead of the observer estimates is not necessarily a good option. Logistic regressions differed significantly between the sexes for both datasets, but observer data suggested that females matured at a larger size than males, whereas lab data suggested the reverse. The differences between sexes may therefore be spurious, and an artifact of insufficient and inaccurate data. Until better data are available, length at maturity should be regarded as the same for both sexes. The median lengths at maturity estimated for both sexes combined were similar for both data sources: 65.9 cm for lab data and 66.5 cm for observer data, suggesting a reasonable overall value of 66 cm PL. There are still insufficient reliable data to estimate the median length at maturity of B. cf. eatonii, but it is probably around 65–75 cm for males and 70–80 cm for females. Reasonable point estimates are therefore 70 cm for males and 75 cm for females.

A dataset for the 2009 assessment of Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea was selected on the basis of data quality metrics for individual trips. Initial informative datasets were selected comprising trips with high (above median) rates of recovery of previously released tags, and/or where tags released on the trip were subsequently recaptured at a high rate. These trips were used to define a range for various data quality metrics considered to be informative with respect to tagging data. Other trips with data quality metric values within these ranges were added to the dataset. A retrospective analysis of this data selection method was undertaken to evaluate whether trip selection was stable over time. The 2009 dataset was reduced by omitting data from the two most recent years, and the data selection method applied to these 2007 and 2008 datasets. Results from this three year period indicate that additional, historical trips may be added to the data set as new tagging data become available. However, once selected, trips are also selected in subsequent years. This analysis indicates that the tagging data selection methodology developed for the 2009 assessment yields generally stable selections over time. The retrospective analysis period is, however, short, and stability of trip selection in future years as further data are added will also be of interest.

The toothfish fishery in the Ross Sea region (CCAMLR Subareas 881 and 882) has been operating since the 1996–97 fishing season. The fishery has increased to an annual Antarctic toothfish (Dissostichus mawsoni) catch of about 3000 t. Skates form a small proportion of the total catch (typically 2% or less). In this paper we summarise the current available fisheries and biological information for skates in the Ross Sea Region, including the data collected in the two “Year of the Skate” fishing seasons in 2008/09 and 2009/10. The composition of the skate catch by species is uncertain; it is estimated that about 33 000 starry skates were landed, and 55 000 released in the Ross Sea region by all vessels to the end of the 2009–10 fishing season, and about 4300 Eaton cf. skates were landed and 4600 released in the same region over the same period of time. There were also differences in the distribution of the two species, starry skates generally being found deeper and more to the west than Eaton cf. skates in the Ross Sea region. Scaled length frequencies showed no change in distribution between 2003 and 2008 for landed starry skates, whilst tagged starry skates had a lower proportion of large individuals than landed starry skates. Eaton cf. skates had a different length frequency, with a narrower distribution centred around a larger average size than starry skates. This larger distribution is consistent with other studies suggesting Eaton cf. skates might grow to larger sizes than starry skates. During the “Years of the Skate”, a total of about 3300 starry skates and 700 Eaton cf. skates were tagged and 13 starry skates and 3 Eaton cf. skates were recaptured and successfully linked to a tag event. In total there have now been a total of 179 tags recaptured but only 128 have been successfully linked. There was no evidence of growth retardation linked with the capture and tagging event. Tag loss rates of T-bar tags were similar to those calculated for toothfish. The “Years of the Skate” have been instrumental in collecting further data on skates, in particular length and tagging data. The quality of the tagging database has also improved since it has been centrally managed by CCAMLR. It has shown the value of collecting large amounts of data in specific years rather than small amounts of data in many years. An updated risk assessment of the skate population in the Ross Sea region should be carried out.

A species profile, covering aspects of the biology, fisheries and stock assessment of both toothfish species was first completed by Everson (2002). A new species profile, specifically for Antarctic toothfish (Dissostichus mawsoni, Norman), was developed by Hanchet (2006). That document concentrated on drawing together mostly unpublished data on D. mawsoni biology including distribution and overlap with D. eleginoides, stock structure, reproduction, age and growth, food and feeding, predation, and depredation. It focused primarily on the biology of D. mawsoni based on information collected from the Ross Sea fishery because that was where most of the work had been carried out. The aim of the current work was to update and revise the species profile of Hanchet (2006). It updates, collates, and summarises new biological data on D. mawsoni. Although the report still focuses primarily on data collected from the Ross Sea fishery, it also presents data from other areas and fisheries where available. It is intended that this report form the basis of a species profile of D. mawsoni as requested at the 2009 CCAMLR meeting (SC-CAMLR XXVIII).

The exploratory fishery for Dissostichus spp. Has now been operating for 14 years in Subarea 88.1 and for 9 years in Subarea 88.2. This report summarises the timing, depth, and location of fishing together with the catch of Dissostichus spp and bycatch species by year for the period 1997–98 to 2009–10. During the 2009–10 fishing year most of the catch in Subarea 88.1 came from the slope SSRUs 881H and 881I, with a reduced catch from 881K due to ice conditions. The catch limit in the north was all taken from 881C, whilst the catch limit from the shelf was taken mainly from 881J. Most catch from Subarea 88.2 was taken from SSRU 882E, with little fishing occurring in the other SSRUs, and the catch limit was under caught by 250 t. Unstandardised catch per set and catch per hook have varied considerably over time in each of the fisheries showing no trend in the main fisheries in Subarea 88.1 and SSRU 88.2E, but a slight decline in SSRU 882CDFG over the last two years. We carried out a more detailed characterisation of Patagonian toothfish catches for the first time. A total of 124 t of Patagonian toothfish has been reported from the fishery, with catches mainly coming from the northwest of the Ross Sea region (SSRUs 881A and 881B). Some observers appear to have problems distinguishing the two toothfish species, and many small (<100 cm TL) toothfish which have been reported as Antarctic toothfish should in fact be Patagonian toothfish. We recommend that observers be made aware of this issue, and that the species identification be independently checked through examination of a subsample of otoliths from these small fish. A major source of uncertainty in the current stock assessment concerns the recruitment dynamics. It has been suggested that a pre-recruit longline survey be developed to collect data to better estimate these parameters. We recommend WG-FSA consider whether such a survey would be worthwhile and identify several fishing grounds on the Ross Sea shelf where such a survey could be carried out.