CCAMLR

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.

We propose to test three hypotheses to describe the reproductive ecology of Antarctic toothfish (Dissostichus mawsoni):

1) Antarctic toothfish eggs are buoyant and accumulate under sea ice. If true, this would retain eggs near the spawning locations under the vast sea ice extent and once broken up in the spring, may provide access to a productive pagophilic ecosystem for feeding as well as a transport mechanism for subsequent advection patterns, all of which could be impacted by climate change. This would have implications on the understanding where recruiting fish originate and how those patterns may be influenced by changes in sea ice or circulation patterns that affect observed recruitment patterns.

2) Antarctic toothfish spawn throughout the Pacific Antarctic fracture zone. Evidence to date only exists from the west of the region (SSRU 88.1B), yet adult Antarctic toothfish are found much further east and north of the CCAMLR Convention area, which is bounded by latitude 60°S. Obtaining a better understanding of the location and movement of adult spawning toothfish has direct implications on the understanding of those parts of the adult stock that contribute to recruitment, and hence the productivity of the stock assumed in the stock assessment.

3) Biological characteristics of the northern spawning population change as younger, fatter, female fish move to the north for spawning during winter. Evidence to date found no change in these characteristics in June, suggesting sampling later in the spawning season is needed.

We propose to conduct a scientific survey during the austral winter in the northern Ross Sea region to test these hypotheses. The longline and plankton survey is designed to cover key gaps in the knowledge of the life cycle of Antarctic toothfish in the Ross Sea by collecting biological samples from a range of locations in the northern regions of Subarea 88.1 and 88.2 and begin in September 2019. The survey will be coordinated with a corresponding survey targeting Antarctic toothfish spawning dynamics in the southern area of the South Pacific Regional Fisheries Management Organisation (SPRFMO) area at a similar time.

This paper outlines the specific research objectives and plan to achieve them for the third year of an agreed 3-year longline survey, in the wider context of connecting the recently undertaken surveys in Subarea 48.2 with the established fishery in Subarea 48.4. The overall research objectives include determining population connectivity between these Subareas, improving understanding of Dissostichus sp population structures in this region, and improving available data on bathymetry and associated distributions of benthic bycatch species. This plan includes a three-year data collection and two-year data analysis plan leading towards the development of a stock hypothesis for the eastern regions of 48.2 and southern regions of 48.4.