The time series of relative abundance and age structure from the Ross Sea shelf survey provides information about year class strength, variability, and autocorrelation, and hence is an important input into the Ross Sea stock assessment.
The objectives of the survey were to (i) continue monitoring trends in Antarctic toothfish (Dissostichus mawsoni) recruitment in the southern Ross Sea (core strata A–C); (ii) continue monitoring trends in abundance of larger (large sub-adult and adult) toothfish and biological characteristics in two areas of importance to predators: McMurdo Sound and Terra Nova Bay in alternate years; and (iii) collect and analyse a wide range of data and samples from these areas (e.g., demersal fish, benthic invertebrates, stomach and tissue samples, acoustic data), which will contribute to the Research and Monitoring Plan for the Ross Sea region MPA.
The estimated relative biomass index of toothfish showed an increase to the second highest in the survey time series in 2021. Biological data and samples were collected from more than 3,100 toothfish; samples and measurements were also collected on bycatch species. A total of 268 toothfish were tagged and released with an 89.6% tagging length overlap statistic. The catch limit of 65 t was not exceeded, mainly because catches in Terra Nova Bay were lower than in previous years. Collected toothfish otoliths were aged and included in the 2021 stock assessment.
Abstract:
This paper examined eggs and larval transport pathways of Antarctic Toothfish under extreme Southern Annual Mode (SAM) events in the continental slope-shelf regions of East Antarctica using a particle tracking model. Ocean currents datasets were calculated using a coupled ocean-sea ice-shelf model output “COCO.” Model simulation results indicated transport pathways of particles released from the east side slopes in the East Antarctic regions were different between the positive and negative SAM phases. While the Antarctic slope current (ASC) generally prevailed southwestward transports of particles from slopes to inner shelves regardless of release regions under both extreme SAM events, particles released from the northeast slopes were transported offshore by the Antarctic Circumpolar Current (ACC) or inner shelves by the combination of ACC and local recirculation system. The result suggests extreme SAM events caused the change in the transport of egg and larvae in the east slopes of the East Antarctic region.
Abstract:
The diet of Antarctic toothfish, Dissostichus mawsoni, collected from the 88.1 research subarea was analyzed by metabarcoding their stomach contents. As a result of metabarcoding analyzes of 436 stomach contents, which have been collected for three years (2018, 2019, and 2021), a total of 184 haplotypes and 38 species were obtained. As shown in previous studies, the main diet of D. mawsoni was fish species and relatively much lower proportions of cephalopods and crustaceans. Among them, both Macrourus caml and Cryodraco antarcticus were the two most abundant prey species, ranging from 25.41 % to 83.96 % with 64.43 % on average, supporting their importance as a diet of D. mawsoni in the 88.1 subarea. In the previous study, Chionobathyscus dewitti, Macrourus caml, and Macrourus whitsoni were the most dominant prey items in 88.3 and 58.4 subarea. Clustering analysis showed that prey compositions clearly reflected geographical distance, indicating that metabarcoding analysis of D. mawsoni stomach contents would be one of the efficient methods to monitor ecosystem sustainability in each research area. However, in addition to the geographical distance, the water depth where the fish were collected may also be one of the critical factors for the difference in the prey compositions. Long-term surveys should be conducted for statistical significance.
Abstract:
The stocks of Antarctic toothfish, Dissostichusmawsoni were a relatively economically and ecologically important fishery resource in the waters of Antarctic. However, there is not enough data and information to assess the robust stocks and deliberate proper measurements for sustainable utilize, especially relate to diet and feeding strategy which may lead to think about ecosystem based stock assessments and fishery managements. Therefore, the Korean scientists analyze diet composition and feeding strategy of D. mawsoni in the research block 88 as a part of Korean research plan for the exploratory longline fishery for Dissostichus spp. during 2021 season. This study was carried out based on the results of stomach content identification of the D. mawsoni caught in the research block 88 in CCAMLR conversion area from December 2020 to January 2021. The diet composition and feeding strategy of D. mawsoni were studied using 548 specimens (54 to 183 cm in body length) in the research block 88, respectively. D. mawsoni is a carnivore and piscivorous fish that mainly consumed fishes. Macrourus caml, M. whitsoni, and M. spp. of Macrouridae was dominant taxa. Chionobathyscus dewitti of Channichthyidae were the second largest dietary component in the fish diet of D. mawsoni. Its diet also included small quantities of mollusks, crustaceans, stones, and cnidarians. In this study, fishes were the dominant prey item in all size classes (<100 cm, n=65; 100-120 cm, n=83; 120-140 cm, n=72; 140-160 cm, n=99; ≥160 cm, n=32). The graphical method for feeding strategy revealed that D. mawsoni is an opportunistic and specialized predator on fishes and showed narrow niche width.
Abstract:
This paper presents the results from a three-year longline fishing research survey (2017 - 2019), conducted to improve understanding of Dissostichus spp. population connectivity, biological characteristics and spatial structure across CCAMLR Subareas 48.2 and 48.4. The results provide evidence linking D. mawsoni with the Antarctic continental shelf and indicate a potential D. mawsoni spawning region in Subarea 48.2. The movements of recaptured tagged fish indicate potential connections with the Lazarev Sea (Subarea 48.6) as well as the southern South Sandwich Islands. The results contribute to the information available for further refinement of the D. mawsoni stock hypothesis.
Abstract:
China submitted its first paper (CCAMLR-XXXVII/32) in 2018 to CCAMLR on the development of research and monitoring plan for CCAMLR MPAs, which attracted lots of comments and suggestions. In order to further contribute to the discussions on this issue, China revised the paper from the scientific perspective, taking into serious consideration of inputs received last year.
Abstract:
Scientific data are the basis of decision-making in CCAMLR. Over the years, CCAMLR members have carried out continuous research and monitoring on key components of Antarctic living resources and ecosystems. Findings all over the world are published in journals of multiple languages. To facilitate the CCAMLR’s management on the basis of science, this paper attempts to obtain, summarize and update the baseline data of emperor penguins and Adelie penguins in the Ross Sea region, as an example, through systematic collection and analysis of the data from the international literature in the past decades, management plans of the relevant Antarctic Specially Protected Areas (ASPA) and MAPPPD’s website, with the aim to establish an comprehensive knowledge on the penguins in this region. The paper further explores the possible reasons and trends of the penguin population fluctuations so that to provide guidance for future research.
Abstract:
The scientific background in support of the Weddell Sea Marine Protected Area (WSMPA) has been discussed in the SC-CAMLR for 3 years. Some agreements has been reached in the SC-CAMLR, while substantial issues remain outstanding. China has actively engaged in those discussions and have provided serious and constructive suggestions on the issue.
Abstract:
Fishing for Patagonian toothfish (Dissostichus eleginoides) in Subarea 48.3 has been carried out without interruption for over 40 years, with more than 25 years under CCAMLR management.
This paper discusses the observed long-term decline in the length composition of D. eleginoides in longline catches in Subarea 48.3 (Antarctic Atlantic, FAO Area 48.3). It is noted that the longline fishery in Subarea 48.3 has targeted immature fish less than 100 cm in length since the early 2000s. Unsustainable use of the Patagonian toothfish stock in Subarea 48.3 is discussed.
Abstract:
Information is presented on a Workshop for Training Russian Scientific Observers and Inspectors to work in fisheries in the CAMLR Convention Area held at the Atlantic brunch of VNIRO ‘Atlantniro” in Kaliningrad (16-20 August 2021).
The workshop program included a wide range of aspects related to scientific observation and inspection in krill, toothfish and crab fisheries in the CAMLR Convention Area. Program of the Workshop is shown.
Final tests were conducted and certificates awarded upon the conclusion of classes.