CCAMLR

Surveys of mackerel icefish, Champsocephalus gunnari, was undertaken in Division 58.5.2 in the vicinity of Heard Island during September 2010 and April 2011, to provide information on the population dynamics of this species, and to provide a basis for an assessment of short-term annual yield in the 2011/2012 CCAMLR season. This paper provides a preliminary assessment of yield for the area of Division 58.5.2 to the west of 79o 20’ E using standard CCAMLR methods. A predicted in 2010, the strong 4+ cohort that dominated the population declined rapidly in late 2010. Two new cohorts are present in the population, leading to a situation that is unusual for this region, with four or five successive year classes all present simultaneously. A catch limit of 103 t is recommended for the 2011/12 season.

Новая Зеландия является активным участником процесса АНТКОМ по планированию МОР и вместе с США представила в АНТКОМ документ семинара по МОР WS-MPA-25 (Sharp and Watters 2011), включающий проект новозеландского сценария МОР для региона моря Росса. В этом документе представлен новозеландский сценарий и метод планирования, при помощи которого этот сценарий был разработан, и приводится дополнительная информация, запрошенная семинаром АНТКОМ по МОР, для рассмотрения Научным комитетом.

In order to assess the level of confidence in the link made, as well as the time and effort  taken to make the link, the Secretariat introduced a tag recapture link status code to identify the level of effort involved in linking a tag recapture to its tagging event.  For the 2011 season 673 tags have been returned;  37% provide an exact match with tag numbers  held in the database, 22 % provide an exact match with tag numbers but had inconsistent ancillary data . For those tags that did not provide exact or unique matches only 63 (9%) could not be successfully linked using additional information.

An investigation into use the length-weight relationship of Dissostichus eleginoides and D. mawsoni to separate the two species was undertaken using data from the CCAMLR Scheme of Scientific Observation. Although the ability to discriminate the two species using length and weight measurement was inconclusive the process provided an opportunity to examine the variation in biometrics of both species by sex and by area and revealed some areas for future analysis.

A generic spatially-explicit age-structured model framework is in development that will enable to evaluate data collection protocols, assessment methods and management strategies. The model framework is programmed in R to promote transparency and interactions between researchers. It is based on the FLR framework and will incorporate links to external assessments programs such as CASAL. The model framework will have a number of modules representing the fish population dynamics, harvest by fishing fleets with different gear types or metiers, sampling of data, stock assessment, and implementation of fishery management decisions.
 

We used stable isotope and trace element chemistry from otoliths to test whether silverfish (Pleuragramma antarcticum) are distributed in independent, discrete populations in the Ross Sea, over the West Antarctic Peninsula, and around the South Orkneys; or whether the Southern Ocean circulation leads to connectivity. Otolith chemistry showed strong heterogeneity indicating four separate populations: i) in the Ross Sea, ii) on the southern Antarctic Peninsula in Marguerite Bay and off Charcot Island, iii) off Joinville Island, and iv) around the South Orkney Islands. This suggested that silverfish are not transported by the Antarctic Circumpolar Current, shelf processes on the West Antarctic Peninsula, or along the Weddell Front. However, the otolith chemistry combined with particle simulations suggested fish from Marguerite Bay may be advected along the southern Peninsula to Charcot Island by the Antarctic Coastal Current.

The present paper presents the brief results of the research in reproductive biology of the Antarctic greinadier M. whitsoni in the Ross Sea. It was stated that the eggs were released by batches. It was supposed that the similar character of spawning might be for some other Antarctic fish species. Some peculiar features of the reproductive biology Moray cod M. evseenkoi, Antarctic toothfish D. mawsoni and other fishes are provided.

In 2010, two toothfish species, Patagonian (D. eliginoides) and Antarctic (D.mawsoni) toothfish, were registered during the fishery on Dissosyichus spp. on the shelf edge and slope of Bouvet Island. Their commercial concentrations were found also on the neighboring underwater plateaus surrounding the island. The vertical distribution of two species was differentiated distinctly, with the crossover point at depth of 1300 m. For both species the size and weight compositions were studied; indices of stomach fullness and qualitative diet composition as well as maturation stages of gonads and their weight were determined; gonadosomatic indices (GSI) were calculated. The sex ratio in catches and vertical distribution of toothfish in the fishing area were analyzed also.     
 

In 2010 on the southern slope of Bouvet Island, I found L. kempi at still greater depth in the course of fishery for toothfish onboard of 1 Insung Korean longliner. In the first case, mature specimens with absolute length (TL) of 39–45 cm and weight of 0.8–1.3 kg
were found in stomachs of Antarctic toothfish caught at depths of 1500–1900 m. In the second case at 54°32′7 S and 03°46′8 W, three specimens of striped-eyed rock cod were caught (one female and two males) at a depth of 2033 m.
 

Preliminary studies on the age, growth and size at sexual maturity of Dissostichus eleginoides sampled in the 2007/08 season in the Ob-Lena Bank were carried out. The ages of 214 of 3,013 fish sampled by Observers were estimated last year. Then, we took several advice and comments about the methods of otolith readings by experienced readers of AAD. One of these is that the first ring was generally identified within the primordium and thus many of age counts were overestimated. The Japanese experienced reader (who is different from the last year’s reader) recounted annuli for the 214 otolith samples and count annuli for the newly added 338 samples (thus total of 552 samples) referring these advice and comments. The estimated ages ranged from 5 to 48 years for males and from 4 to 48 years for females. Ten to fifteen years gave large contribution to the total age groups for both sexes. Females grew at a faster rate and reached a larger size than males. The individuals with 80 cm total length, which are generally thought to begin to mature, corresponded to 10.6 year for females and 11.4 year for males. On the other hand, the age at 50 % maturity for females and males was estimated to be 12.3 and 12.5 year, respectively, assuming animals with maturity stage > I.
However, the results in reading for 40 reference samples provided by AAD were less consistent with those read by the AAD readers. The Japanese reader tended to overestimate for < 30 years, but underestimate for > 30 years, as compared to AAD readers. This means that the present results on age, growth and size at sexually maturity is less reliable. The main reason for the underestimation for older ages was due to the consistently counting on the ventral side of the section.
We would like the AAD readers and CCAMLR member give further advice on the present results during the WG-FSA or intersessionally. We would recount the annuli for the present 552 otolith samples following their advice. Furthermore, we would count annuli for the newly added 300 samples from the 2007/08 survey and depict the average image of growth pattern in Ob-Lena Bank using total of ca. 800 samples in the next WG-FSA.