CCAMLR

Analytical data on determination of reproductive potential of Antarctic toothfish D. mawsoni in the Pacific (SSRUs 88.1, 88.2, 88.3), Indian Ocean (SSRUs 58.4.1 и 58.4.2) and Atlantic (SSRU 48.6) Antarctic areas are presented. Morphological indices of females and males, indices of gonads, fecundity, and condition by Fulton are described. Spawning time and regions for Antarctic toothfish are discussing.

Using a modeling framework for toothfish (Dissostichus spp.) population dynamics, fishing, and data collection, this study investigated how the bias and precision of biomass estimates from an integrated tag-based assessment are influenced by various aspects of a multiyear tagging program, particularly the effects of the size of tagged fish compared with the size of fish in the catch (tag size-overlap), numbers of tagged fish, duration of the tagging program, using catch-at-length or catch-at-age data as auxiliary data, and stock depletion levels. Biomass estimates generally improved with more and better-quality tagging data. The results showed that even when tag releases were distributed over a relatively large number of size classes, low recapture numbers collected in short tagging programs with a 100% tag size-overlap were sufficient for robust and unbiased assessments. Particularly in the early stages of the tagging program, a high tag size-overlap was imperative to maximize the likelihood of a robust assessment. Biomass estimates were largely unaffected by the stock depletion level; however, using catch-at-age compared with catch-at-length improved recruitment estimates and resulted in more conservative biomass estimates.

This paper presents an updated assessment for Patagonian toothfish (Dissostichus eleginoides) at the Heard and the McDonald Islands (Division 58.5.2) with data until the start of August 2013. Compared to the last assessment in 2011, this assessment updated the growth model and compared the effects of a range of alternative fishery structures and model assumptions for year class strength (YCS) on stock assessment estimates and projected catch limits that satisfy the CCAMLR decision rules. Re-defining the fishery structure was based on a method by Candy et al. (2013) that suggested a simplification of the longline hauls into two sub-fisheries that were depth-stratified but not regionally-explicit. Alternative trawl sub-fisheries were evaluated within the assessment model in different scenarios.

All evaluated scenarios produced similar spawning stock biomass (SSB) patterns and estimates of current status. Across scenarios with YCS estimation, estimates of virgin spawning biomass (B₀) ranged from 89 448 - 101 847 tonnes, and SSB status in 2013 ranged from 0.63 - 0.69 of B₀. A model scenario that ignored information on YCS variation resulted in an SSB status of 0.58 in 2013, but was considered to be less realistic. The impact of altering the sub-fishery structure for trawl on model estimates was relatively small, however the selectivity functions for the different trawl sub-fisheries varied substantially indicating that a separation of the trawl sub-fisheries is appropriate. The scenario with estimating a YCS from 1992-2009 compared to 1984-2009 was the preferred model, since the estimated YCS pattern was more consistent and did not show an early period with stronger inter-annual fluctuation.

Based on this assessment, we recommend that the catch limit for the 2013/14 and 2014/15 seasons be set at 3005 tonnes.

The annual Random Stratified Trawl Survey was undertaken in Division 58.5.2 in the vicinity of Heard Island during April 2013. This paper provides a preliminary assessment of mackerel icefish population structure, abundance and yield for the area of Division 58.5.2 to the west of 79° 20’ E using standard CCAMLR methods. A large cohort of fish, estimated to be 3+, dominates the population in both abundance and biomass. Two scenarios for harvest are presented – a typical two year projection of the population, and a projection accounting for the fact that the abundant 3+ year class is likely to be unavailable beyond 2013/14. Under the first scenario, a catch limit of 764 t is recommended for 2013/14 and 571t for 2014/15, while under the second scenario, a catch limit of 1267 t is recommended for 2013/14 and 0 t for 2014/15.

The fisheries targeting Patagonian toothfish (Dissostichus eleginoides) and mackerel icefish (Champsocephalus gunnari) in the Australian Fishing Zone surrounding Heard Island and McDonald take three species of skates, Bathyraja eatonii, B. irrasa and B. murrayi, as their most common bycatches. A tagging program has operated in these fisheries since 2001 to learn more about the movement and biology of these species. In the 13 years, over 12,000 skates have been tagged, with 112 recaptures, a recapture rate of less than one percent. The average distance between release and recapture for each of the three species was 4 nm, and the longest distance travelled was 23 nm. The skates appear to move equally in all directions. Most recaptures occurred within the first three years, with the maximum time at liberty of nearly eight years for one B. irrasa. Range of movement in depth was between -266 m and 280 m from release to recapture, with B. irrasa tending to move in depth more than the other two species. Growth increments for tagged and recaptured B. eatonii indicated growth of ~20mm/year for both sexes between 600 and 1000mm total length, indicating maximum ages of several decades. In combination with biological and catch and effort data, the ongoing program of skate tagging will continue to contribute data which will be used for better informed risk assessments in the future.

The annual random stratified trawl survey (RSTS) at Heard Island and McDonald Islands (HIMI) was completed during April of 2013. The catches of D. eleginoides for 2013 were half that of 2012 and lower than the long-term (2006-2012) average. Conversely, mackerel icefish catches were seven times the long term average. Catches of Channichthys rhinoceratus were higher and those of Lepidonotothen squamifrons lower than average. Skate catches in 2013 were slightly higher than the average RSTS take.

The catch of invertebrates in the 2013 survey was 6 t, which was lower than the long term average. This year there was a large abundance of jellyfish (Cnidaria) which formed about half of the catch of invertebrates. Catches of individual invertebrate taxa were generally much lower than in previous years.

Lengths and biological measurements were taken for 13,000 fish, 276 pairs of otoliths collected and 179 toothfish were tagged.

A revision of the research plan and preliminary results of the Spanish exploratory longline fishery for Dissostichus spp in Divisions 58.4.1 and 58.4.2, submitted to the XXXII-WG-SAM, taking into account the advice made by the Working Group, is presented.

The Spanish vessel Tronio started the research plan in the 2012/13 season using the Spanish bottom longline system. One depletion experiments was completed in each of the SSRU surveyed (58.4.1H and 58.4.1G). Three prospecting-phase clusters of sets did not reach the threshold to start the depletion.

A new prospective estimation of the local biomass (B_LOC) of the two localized areas where the depletion experiments were performed is done as well as an estimation of the biomass of the SSRUs (B_SSRU), maximal and minimal, considering areas with high and low densities, with a better fit of the regression and lower residuals than the previous analysis.   
 
An analysis of relevant sea-ice conditions in the last 11 seasons in these areas along with a summary of the activities and results from the survey is also presented related to the sampling scheme, collected samples and species involved.

Data were collected at Bird Island and King Edward Point, South Georgia, at Signy Island, South Orkneys and at Goudier Island, Antarctic Peninsula for the period April 2012 to March 2013. Surveys of beached marine debris at Bird Island recorded a total of 145 and 134 items during winter (April to September 2012) and summer (October 2012 to March 2013) respectively. Surveys at Signy Island (operational during summer only; 25 November 2012 to 20 March 2013) recorded a total of 13 items of beached marine debris. Entanglements of 13 Antarctic fur seals were observed at Bird Island, 15 at King Edward Point and zero at Signy Island and Goudier Island. In total, 85 items of marine debris were found in association with seabird colonies at Bird Island, most commonly in association with wandering albatrosses (45 items). There were no reports of beached marine debris at Goudier Island, and no incidences of hydrocarbon soiling at any of the four sites during the reporting period. Overall, the occurrence of beached marine debris was below the long-term mean at Bird Island during both summer and winter and was the lowest recorded in 23 years of summer surveys at Signy Island, possibly due to sea-ice coverage at the three survey beaches between November and January. The incidence of marine mammal entanglements was below the long-term mean at Bird Island and Signy Island but above the mean at King Edward Point. Debris associated with seabird colonies was below the mean level for wandering albatrosses, grey-headed albatrosses and giant petrels, but above the mean for black-browed albatrosses.