CCAMLR

Antarctic Krill, Euphausia superba, is the key species of the Southern Ocean ecosystem. Earlier analysis suggested decrease in krill abundance by 50% since the mid 1970’s to early 2000’s in the Southwest Atlantic Sector, which has been specifically linked to a decrease in extent and duration of sea-ice coverage. More recent studies suggest more complex and/or dynamic nature of krill population trajectory as well as its link with decadal climatic events.

Krill population dynamics is thought to be strongly linked to sea ice, and their reproductive output and recruitment success been related to extent, timing and the duration of winter sea ice cover. The underside structures of sea ice are generally thought to provide good feeding ground as well as nursery grounds for overwintering larvae.

How will changing sea ice dynamics affect krill life history, their dynamics, and their distribution? This is a fundamental question for designing our future management approach for the krill fishery.

The intention of this paper is to provide the Working Group with a summary of our recent efforts published last year to improve the mechanistic understanding of the interaction between krill larvae and sea ice (WG-EMM-18/P04 and P05).

Following the submission of a first draft Conservation Measure for establishing a MPA in the Weddell Sea (WSMPA) to CCAMLR 2016, Germany has carried out further work on the WSMPA proposal with a view for a revised CM proposal to be submitted by the EU to CCAMLR 2018.

This document informs SAM about the following revisions carried out to the WSMPA proposal which would fall under the remit of SAM or might be of interest to participants at SAM 2018:

1. Unifying the previously two separate WSMPA parts into one coherent WSMPA by closing the gap on the eastern coast of the Antarctic Peninsula;
2. Adjustment of the habitat of adult Antarctic toothfish in statistical areas 48.6 and 48.5 as a result of further analyses and modelling of the habitat of adult Antarctic toothfish;
3. Establishment of scientific reference areas in statistical subarea 48.6 for monitoring the effects of harvesting on Antarctic marine living resources;
4. Changes to the WSMPA Management Plan and the WSMPA Research and Monitoring Plan, inter alia, by taking into account the outcome of the CCAMLR Workshop for the Development of a D. mawsoni Population Hypothesis for Area 48.

The document also seeks the advice of SAM 2018 as regards the design of the fisheries research zone (FRZ) foreseen in the draft WSMPA Conservation Measure and the establishment (number, location and size) of unfished scientific reference areas in the habitat for adult Antarctic toothfish in statistical subarea 48.6 (see point 3 above), which could be used for comparative studies into the potential impacts of D. mawsoni fishing operations on the ecosystems and food webs, of which this species is a part.

Casal2 (pronounced Casal-two) has replaced CASAL, New Zealand’s integrated fish stock assessment pack-age since 2002. Casal2 replicates most of CASAL’s functions such as many stocks, fisheries, and areas; age-or length-based dynamics; the use of several data sources (e.g., abundance indices, age frequencies, andtagging), but it has been extended into a generalised modelling tool and it uses more efficient program-ming practices and tools than CASAL. CASAL has enabled a more efficient use of resources for stockassessments, such as allowing a wider range of staff to conduct assessments, helped communicationbetween members of the Assessment Working Groups, enabling a focus on fits of the models and modelstructure since standardised methods meant that model components were known and rigorous testingensured confidence that the code base was validated. Design decisions taken at an early stage in CASAL’sdevelopment now limit its expansion. Re-coding CASAL was New Zealand’s best option to retain the ben-efits of CASAL and to control its own destiny over progress in new stock assessment techniques, such aseasy use in management strategy evaluations. We have replicated many CASAL assessments successfullyand so will release the first version of Casal2 in 2016 as an open source package under the GPL-2.0 licence. A pre-release download of an executable,draft manual, examples, and source code are available from ftp://ftp.niwa.co.nz/Casal2/windows/Casal2.zip.

The Casal2 software implements an updated generalised age-structured marine population model that allows more flexibility in specifying the population dynamics, parameter estimation, and model outputs than CASAL. Models are built with user-defined categories such as area, sex and maturity. These structural elements are generic and not predefined (as they are in CASAL), but are easily constructed. Casal2 models can be used for a single population with a single anthropogenic event (i.e., a single fishery), or for multiple species and populations, areas, and/or anthropogenic or exploitation methods.

Casal2 is open-source and is available at https://github.com/NIWAFisheriesModelling/Casal2

Initial comparisons of CASAL and Casal2 show that these programs provide the same stochastic results, and identical empirical results for estimation of key productivity parameters. We invite Members to test Casal2 on their stock assessments and / or on simulation data. Any issues should be registered through the github website. We also suggest that one or multiple assessments of toothfish be included in the Casal2 unit-testing.

This paper provides a summary of research carried out during New Zealand’s 2018 voyage to the Ross Sea region, and gives notice of a New Zealand 2019 research voyage to the Ross Sea region. The Ross Sea Environment and Ecosystem Voyage 2018 (TAN1802), took place from 9 February to 21 March 2018, departing from and returning to Wellington, New Zealand. Science objectives for the voyage were aligned with the Ross Sea region Marine Protected Area Research and Monitoring Plan, under New Zealand’s Antarctic and Southern Ocean science directions and priorities 2010-2020. The voyage was successful, achieving all objectives in part and most in full, including: (1) establishing a long-term experiment to monitor outflow of Antarctic Bottom Water at the continental shelf-break in the Cape Adare region; (2) surveys of seabed habitats and fauna at previously un-surveyed sites on Iselin Bank, Scott C seamount, and locations on the Pacific-Antarctic ridge; (3) characterisation of marine microbial community structure and function across the region; (4) characterisation of zooplankton community structure; (5) surveys of mesopelagic fish and krill distributions; (6) research into interactions between marine aerosols and cloud formation, and (7) documenting marine mammal distributions, including biopsy sampling of humpback whales. Preliminary research goals and study areas for the 2019 voyage are described and align with the Ross Sea region Marine Protected Area Research and Monitoring Plan. Results from the analyses of the data from the survey will be presented to CCAMLR and published in the peer reviewed literature, as appropriate, once completed.

Data on the distribution and abundance of mid-trophic level organisms (MTLOs) in the pelagic open-ocean ecosystem are normally sparse or absent. Consequently, ecosystem models are limited in their ability to support decision-making for issues ranging from fisheries management to ecosystem resilience to climate change. We used acoustic data collected at 38 kHz frequency across the Southern Ocean (SO) between 2008 and 2014 to develop explanatory and predictive models for acoustic backscatter, a proxy for MTLO abundance in the epi- and mesopelagic zones. Boosted regression trees and generalised additive mixed models were used to develop simple predictive models for backscatter in the epi- and mesopelagic zones, using sea surface temperature, time of day (day/night) and depth. The resulting models predicted backscatter reasonably well in the Pacific sector of the SO, and in an independent dataset in the Indian sector of the SO. Our predictive models may provide a tool for inferring abundance and distribution of MTLOs in other parts of the SO.

Mid-trophic level organisms (MTLO) of open-ocean marine ecosystems play a key role linking primary and tertiary consumers. Despite their importance, characterisation of MTLO is limited due to sampling difficulty, and is largely obtained through active acoustics. Acoustic data collected from vessels of opportunity transiting across the Southern Ocean between New Zealand and the Ross Sea provided the opportunity to study distribution and abundance of MTLO over 7 yr. Analyses were performed to identify spatial (vertical and horizontal) and temporal (annual, seasonal and diel) patterns in 28 acoustic transects collected between 2008 and 2014. Mean acoustic backscatter (s_a) at 38 kHz varied between years, but overall was reasonably stable, being in the same order of magnitude across all transects. Backscatter consistently and significantly decreased from north to south. Although this latitudinal pattern could be related to MTLO abundance, trawl samples collected in 3 research voyages suggest that it may also reflect differences in species composition and size distribution; consequently, indices based on bulk backscatter must be interpreted with caution. Vertical distribution of backscatter showed clear diel vertical migration patterns and 4 distinct vertical bands (i.e. epipelagic, transition, mesopelagic and deep mesopelagic), with seasonal differences in concentration and behaviour. Deep mesopelagic layers stopped north of the Ross Sea, which may relate to the temperature limitation of contributing organisms. Predicted climate change effects in the Southern Ocean could modify the spatial distribution of MTLO and have impacts on top predators relying upon the mid-trophic level as their main food source.

This paper provides data layers relevant to establishing the baseline for the Ross Sea region Marine Protected Area (MPA). We provide data used to investigate environmental and ecological spatial patterns as part of the design and evaluation process for the Ross Sea region MPA, including spatial maps and information on key Ross Sea ecosystem processes, and data layers used to determine the pelagic and benthic bioregionalisations. We also include data layers which we consider likely to be useful in contributing to defining the “baseline” state of the Ross Sea region.

We provide a photographic reference set for Antarctic toothfish (Dissostichus mawsoni) from the Ross Sea region. The photographs were derived from the four otolith reference set blocks used by New Zealand with the “sister” otoliths provided to CCAMLR for use by other Members. Two photographs are provided for each otolith; one of the prepared otolith surface alone, and a second with symbols marking the location where each annulus was counted. The photographs link to an excel spreadsheet providing data on each otolith. We recommend that the CCAMLR Secretariat make this reference set available via the CCAMLR website for use by Members.

At its 2011 meeting, the Scientific Committee agreed that a time series of relative abundance from a well-designed survey would be a useful input into the Ross Sea stock assessment model. In this paper we provide results of the seventh annual survey in the time series. The objectives of this survey included monitoring sub-adult (≤ 110 cm TL) toothfish in the south of SSRUs 881.J and 881.L in the southern Ross Sea (Strata A–C) using standardised gear in a standardised manner; and monitoring trends in larger (large sub-adult and adult) toothfish in two areas (both situated in SSRU 881.M) of importance to mammalian toothfish predators: McMurdo Sound in 2018, and Terra Nova Bay surveyed in 2017. The estimated relative biomass index of toothfish for the core strata showed a decrease from 2017 to a value equal to the average index early in the time series, and length and age frequency data showed the progression of cohorts through the population that were observed in previous surveys. Notification of research for the agreed 2019 fixed-effort survey is included with a catch limit of 65 t.