A multi-year research plan as outlined in CM 41-04 (2012, 2013, 2014) was initiated in Statistical Subarea 48.6 by Japan and South Africa during the 2012/13 fishing season. Two vessels participated in the research project in each of the three fishing seasons and the progress achieved during the first 3.5 years is reported.
The emphasis of the progress report is on block 486_2, since more tag returns have been recovered from this block and a preliminary stock assessment has been attempted using data mainly from block 486_2.
Abstract:
We present preliminary results on age and growth of Dissostichus mawsoni for the second season (2013/14) of the Spanish research fishing in the 58.4.1 Division obtained for growth rings on otolith readings. It is included the age-length key and growth parameters estimates by sex. Growth parameters obtained using length-age pair values are: L∞: 175.7, k: 0.1078 and t0: 1.528 for females; L∞: 150.3, k: 0.1491 and t0: 1.809 for males; and L∞: 169.8, k: 0.1087 and t0: 1.168 all combined. These results are very similar to those reported previously for the first season (2012/13) although they differ slightly with the values used in the Ross sea assessment for males.
Abstract:
The second year survey and observations of Dissostichusspp. in statistical subarea 48.2 on board the Ukrainian vessel SIMEIZ were conducted in accordance with the recommendations of the Scientific Committee and Commission. The second year survey design was amended in comparison with the one of the first year and approved by WGs SAM, FSA and SC CCAMLR. Obtained data used for the preliminary biomass estimation of the target species and making decision for the future fishing on that fishing ground. During the survey the fragments of IUU nets were taken on board.
Abstract:
The third year research plan of Ukraine in subarea 48.2 by the fishing vessel SIMEIZ is provided. The survey design remains the same as in the second (2016) year. Ukraine proposes to divide the stock (the catch limit) in the researched area on two blocks – Northern and Southern, in order to reach maximum coverage of the subarea by the research stations.
There is no abstract available for this document.
There is no abstract available for this document.
Abstract:
The stock of Antarctic toothfish (D. mawsoni) in CCAMLR subarea 48.4 was conservatively estimated from tagging returns to be 1068.7 tonnes. In previous years the harvest rate used for Patagonian toothfish (D. Eleginoides) in Subarea 48.3 (γ = 0.038) has been used as a precautionary harvest rate which would imply a 2016/17 yield of 40.6 tonnes compared to the 2015/16 TAC of 39 tonnes.
Abstract:
Net monitor cable systems have been prohibited in CCAMLR trawl fisheries since 1994. This paper advocates a change in the CM 25-03 that opens for use of such cable. It is argued that this is beneficial for management as well as fishery.
Abstract:
The first winter longline survey of Antarctic toothfish in the northern Ross Sea region was successfully completed during June and July 2016. A total of 55 longlines sets were completed in the 4 strata, and 55.2 t of Antarctic toothfish and 3.4 t of Patagonian toothfish were caught. Spawning and spent Antarctic toothfish were captured late in the survey on undersea features to the northwest of stratum 1. Gonad staging and gonadosomatic indices suggest that males in spawning condition may aggregate earlier than females and that spawning begins in early July. There were a higher proportion of male fish caught during the survey than during the summer fishery (73% vs. 60–65%), and the sex ratio varied substantially among sets. Nineteen toothfish eggs were captured using a plankton net in the top 200 m of the water column, and eggs from two running ripe females were successfully fertilised and reared for several days in flow through incubators. Egg buoyancy measurements, conducted with fertilised eggs in density gradient cylinders, are being analysed and compared with CTD data to indicate the depth of neutral buoyancy. We recommend that a survey be carried out from mid-July through August to further document the temporal extent of spawning, although much of the likely spawning habitat is under sea ice at that time.
Abstract:
We describe the typical steps involved in demersal longline fishing operations for toothfish in CCAMLR fisheries and link those steps to the variables recorded as part of the CCAMLR catch and effort data reporting system. We then describe statistical properties of the recorded variables and how they may vary among gear type and other factors that make them useful to understand fishing activities and for error trapping or data validation.
During this process we identified some unusual values for some variables; some are explainable while others are obvious errors. We suggest that identifying values outside normal maximum ranges can be used to target additional error-checking or seek additional information using other associated vessel records. Other unusual values, although potentially in error, are more difficult to evaluate given the wide range of influences that may affect recorded values for a given parameter.
There are strong functional relationships identified between some of the variables. For example, a catch with high numbers of large fish increases the time taken to haul a line as each fish is required to be gaffed aboard and removed from the line. This effect is compounded by fish size and the requirement to tag fish, which further slows the hauling process. We investigate some of these relationships and their use in identifying erroneous data. The analyses show that many of the useful metrics that could be derived, are likely to be influenced by multiple variables. Therefore, multivariate analyses are needed to control for the influence of multiple variables before we interpret patterns in the data. We also recommend additional information be included in the data recording forms to improve interpretation for some variables.