CCAMLR

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.

A tagging survey in SSRUs B and C in Division 58.4.4 a & b was initiated in the 2010/11 fishing season with the aims of providing the data required for assessments of the population structure, size, movement and growth of Dissostichus spp. in the centred area of Division 58.4.4 a & b. An approximate stock biomass level of Dissostichus spp. in the survey area (SSRUs B and C in Division 58.4.4 a & b) was estimated using simple Petersen, CPUE x area, and CPUE comparison methods. The medial estimates using simple Petersen (1583 and 2751 ton) were similar to those under the two scenarios analyzed at WG-FSA in 2010 (1580 and 3036 ton), although the 95 % confidence intervals were wide due to small numbers of recapture. The estimations using other two methods were a half to a quarter smaller than those using simple Petersen. The medial stock biomass estimated under the two scenarios at WG-FSA in 2010, which allowed determining the sample size as 53 tonnes for the 2010/11 survey, are identical with those estimated using the simple Petersen. Therefore we think that the result using the simple Petersen is more plausible and proposed sample size as 53 tonnes for the next 2011/12 survey is appropriate. We propose to continue the mark-recapture experiment in SSRUs B and C in the 2011/12 season, with nearly same survey design as in the 2010/11. A total of 71 research hauls will be allocated in the same locations on 7.5-minute latitude x 15-minute longitude grid points except one haul which are newly allocated in the northeast of SSRU B instead of an unconducted haul in the 2010/11. To apply mark-and recapture studies, tagging rate of 5 fish / ton will be conducted. The comparison test with the experimental gear, which consists of three segments of Trot line system and Spanish line system respectively, will be conducted at 14 hauls, due to understanding of differences in the physical conditions of tagged fish between those caught on Spanish lines and those caught on trotlines.

A survey was conducted in order to collect information for the stock status and various biological information on toothfish in Division 58.4.4a & b (Ob Lena Bank) by using a commercial bottom longline vessel, Shinsei Maru No. 3, from March 30 to May 2, 2011. This report described the results during the survey in two SSRUs (B & C) of Ob Lena Bank. Total catch (excluding fish released alive) of Dissostichus eleginoides and other by-catch species was 37.8 tonnes in the survey area in 70 longline sets. D. eleginoides showed the highest catch of 35.4 tonnes, contributing 93.6 % to the total catch. Mean CPUEs of D. eleginoides for 56 hauls where only trotline system was adopted in the SSRUs were 8.5 indiv. / km (CV = 53.5%; 15.3 indiv. / 1,000 hooks) in terms of number and 62.3 kg / km (CV = 76.0%; 111.2 kg / 1,000 hooks) in terms of weight. The mean CPUE in terms of weight in SSRU B (49.0 kg / km (CV = 85.1%)) was significantly lower than that (93.7 kg / km (CV = 61.7%)) in the same SSRU in the 2009/10 survey, although the CPUE in terms of number was same level between the years.  This may be due to the catch of small fish in the shallow area < 500 m in the 2010/11. A total of 189 individuals of toothfish with good physical condition were tagged and released during the survey, and 4 D. eleginoides, which were tagged and released in SSRU C during the 2007/08 and 2009/10, were recaptured in the same SSRU. The overlap of size between the fish released with tag and that of overall catch was considerably high (θ=95 %). There was a significant difference in physical composition between Spanish line and trotline (χ² test, P < 0.001), with the higher percentage of dead fish for trotline. It seems that smaller fish < 70 cm are more damaged than larger ones for trotline, as in BANZARE Bank. A total of ≥130 killer whales（Orcinus orca）were observed at the 35 hauls. Most of whales observed and the predatory damaged toothfish occurred in SSRU B.

A survey was conducted in order to collect information for the stock status and biology of toothfish in the southeast sector (24 allocated hauls) of Division 58.4.3b (BANZARE Bank), using a commercial bottom longline vessel Shinsei Maru No. 3, from May 7 to 16, 2011. Shinsei Maru Trot line system was used as fishing gear for 19 hauls. Comparison test using trotline and Spanish line systems were made for 5 hauls. Total catch (excluding fish released alive) of Dissostichus spp. and other bycatch species was 12.0 ton in the SE sector, where the catch limit of 15 ton was set. Mean CPUE of Dissostichus spp. was 58.8 kg / km (CV = 66.7%; 105.9 kg / 1,000 hooks) for the hauls where only trotline system was employed. This was lower than 69.6 kg / km (CV = 51.3%; 125.0 kg / 1,000 hooks) in the 2009/10 survey, although there was no significant difference. Total of 62 individuals of toothfish with good physical condition were tagged and released during the survey. No toothfish was recaptured. The overlap of size between the fish released with tag and that of overall catch was considerably high (85 % for D. mawsoni and 79 % for D. eleginoides). There was a significant difference in physical conditions of D. eleginoides between Spanish line and trotline (χ2 test, P < 0.05), with the higher percentage of bad condition (54.6 %) for trotline. It seems that smaller fish < 80 cm are more damaged than larger ones for trotline system in D. eleginoides.
An approximate stock biomass level of Dissostichus spp. in the survey area was estimated to be 174-175 ton, using CPUE x area and CPUE comparison methods. From this, the appropriate sample size in the next year survey was calculated to be 5.2 ton based on the criterion for the depleted stock shown in WG-FSA-10/42. However, the estimated biomasses using the two methods seem to be a quarter – a half underestimated compared to those using GYM at WG-FSA in 2010 in case of Ob-Lena Bank, and therefore we think that the total allowable size of 15 ton (ca. 3 times of 5.2 ton), along with the same survey designs as in the 2010/11, is appropriate for the next survey.
 

This paper is the second update to CCAMLR and the ATCM since the publication of the SCAR Antarctic Climate Change and the Environment (ACCE) report (Turner et al., 2009a). The ACCE report was a first step in compiling a comprehensive assessment of scientific information on the climate system and ecosystem responses to change in the Antarctic and Southern Ocean region. The present paper, developed by the new SCAR ACCE Expert Group, highlights some recent advances in our knowledge of Antarctic climate science and associated impacts on the environment.