CCAMLR

The exploratory fishery for Antarctic toothfish (D. mawsoni) has been operating for ten years in Subarea 88.1 and for five years in Subarea 88.2. This report summarises the large amount of data collected on toothfish and the associated bycatch by all vessels participating in the fishery. All SSRUs in the two subareas except for 881D and 882C have now been fished. The 2007 D. mawsoni catch was the second highest on record with a total of 3431 t against a combined catch limit of 3579 t. The management of the SSRUs within the two subareas was changed for the 2006 season as part of a 3-year experiment (SC-CAMLR-XXIV). One of the aims of the experiment was to simplify the administration of the fishery by having fewer catch limits. This appeared to be moderately successful, with only one catch limit being slightly exceeded in the 2006 season, and two catch limits exceeded in the 2007 season. Although there was a large overrun of the catch limit in the North region, the overall catch limit for Subarea 88.1 was only exceeded by 2%. The catch limit was under caught in Subarea 88.2. The concentration of effort within smaller spatial areas in Subarea 88.1 has undoubtedly contributed to the large increase in tag recoveries over the past two seasons (Dunn et al. 2007).
The length frequency data from the Ross Sea fishery have been very consistent over the past 3–4 seasons. There is no evidence of any truncation of the overall length frequency distribution, and no evidence for a reduction in fish length in any SSRU over time. Although moderate numbers of small fish are caught in some years (e.g., on the Shelf in 1999 and 2001), these year classes are not seen in large numbers in later years in the fishery. So at this stage there is no evidence for strong variation in year class strength in the fishery.

Two regions of mitochondrial (mt) DNA: cytochrome b and cytochrome c oxidase subunit 1(COI) were sequenced in 9 species of Bathyraja skates from the Southern Oceans and New Zealand. Based on significant sequence divergence, the species that has been referred to as Bathyraja eatonii from the Antarctic shelf and slope is a species distinct from B. eatonii from the Kerguelen Plateau (the type locality), and is a new and undescribed species, and should be provisionally referred to as Bathyraja n. sp. cf eatonii. There was no sequence divergence among samples of B. n. sp. “dwarf” from the Ross Sea and South Atlantic. However, for Bathyraja n. sp. cf. eatonii and Bathyraja maccaini in the Ross Sea and South Atlantic Ocean, the DNA sequence divergences are indicative of differentiation among ocean basins; and for Bathyraja n. sp. cf. eatonii are similar to divergences among recognised Bathyraja species in the North Pacific Ocean.
Despite investigating four colour characters, eight meristic characters and six morphometric characters, relatively few were diagnostic for the Antarctic Bathyraja. Ventral colouration appeared reliable for distinguishing Bathyraja meridionalis and B. n. sp. dwarf, but dorsal colouration was unreliable. Proportional disc width showed substantial changes in shape between the juvenile and adult stages of Bathyraja n. sp. cf eatonii; hence, the common name “allometric skate” is proposed. Eight meristic characters were evaluated. Pectoral radials and monospondylous vertebrae were useful in diagnosing B. n. sp. dwarf, and midline thorns for B. meridionalis. The presence/absence of thorns around the eyes and on the scapular appeared to be a reliable character to distinguish species in the Ross Sea. A field key for identification of Ross Sea skates is provided.

Icefish (Channichthyidae) specimens were randomly collected by observers during the 2005–06 fishing season. These observers were placed aboard three longline vessels targeting Antarctic toothfish in the Ross Sea (Areas 88.1 and 88.2). Biological data from 303 returned specimens was collected. These data included species identification, fish length, weight, sex, meristics, reproductive biology, diet, and age estimation. All of the icefish sampled were identified as Chionobathyscus dewitti, and showed no significant difference in sex ratio. Meristic, diet and age data were consistent with previous research. Regression equations for converting standard length to total length and for defining length-weight relationships were calculated and presented for both male and female fish. Gonad maturity stage data showed that most fish were either immature or resting (mature). Gonado-Somatic Indices (GSI) were calculated and plotted against sample month. There was a weak positive trend in GSI between December and February, but this was limited, probably due to the short temporal distribution of the data. Length-at-maturity and age-at-maturity ogives indicated that 50% of the fish sampled were mature at about 340–360 mm (TL) and about 3–4 years of age and that 95% were mature at about 370–400 mm (TL) and 6–8 years of age. Counts of growth zones in sectioned otoliths were used to determine ages and von Bertalanffy growth parameters. Fish growth was rapid for both sexes, and females approached a significantly larger mean asymptotic maximum size than males. Maximum ages of 8 and 11 years were obtained for male and female fish, respectively. Diet analysis showed most icefish stomachs were empty and the few prey items recovered were generally in advanced stages of digestion. This may be due to regurgitation of prey during capture.

The mean mercury level for the D. eleginoides 1998 sample was 0.43 mg/kg-1, which is slightly lower than the permissible level of 0.5 mg/kg-1 set by the New Zealand Food Safety Authority (NZFSA). In contrast, mean levels of mercury for D. mawsoni were 0.10 mg/kg-1 in the 1998 samples and 0.16 mg/kg-1 in the 2006 samples, both of which are well below the permissible level.
Mercury levels were highly variable both within and between the five species studied. Once the factors length and year had been accounted for, the mercury levels in D. eleginoides were over four times greater than in D. mawsoni. The three prey species had intermediate mercury levels, with Whitson’s grenadier (Macrourus whitsoni) being only slightly lower than D. eleginoides, whilst the levels of ice fish (Chionobathyscus dewitti) and blue antimora (Antimora rostrata) were at low levels, similar to that of D. mawsoni. Mercury levels were positively correlated with fish length in four of the species. Mercury levels also showed positive trends with depth for D. eleginoides and C. dewitti, and with area for A. rostrata. Mercury levels showed no trends with any factors for M. whitsoni.
The low levels of mercury in D. mawsoni relative to its prey species and the four-fold difference in mercury concentrations between it and D. eleginoides were unexpected. Reasons for these different levels of bioaccumulation were explored including differences in diet, growth and longevity, and location. We conclude that these results can only be explained by a lower rate of mercury assimilation and/or a higher rate of mercury elimination by D. mawsoni.

This paper describes the interaction between sperm whales (Physeter macrocephalus) and the toothfish fishery (Dissostichus eleginoides) carried out by longline fishing vessels operating in two different fishing zones at 40º and 50º latitudes in the Southwestern Atlantic from March to May 2007. 62 hauls were performed in the northern zone (latitude 40º 00’ S), while 41 hauls were performed in the southern zone (latitude 50º 00’ S) at an average depth of -1282 m. 57.2% of the total number of hauls were observed. Onboard observers recorded: a) quantity and quality of fish parts remaining in the recovered longline; b) presence and number of sperm whales and c) comparative fishing yields with and without sperm whales effective predation. The observations were performed using both, the traditional Spanish longline and the Mammals and Birds Excluding Device (MBED). The longline with MBED sinking rate was determined in 1.14 m/seconds. In both fishing zones, the sperm whales presence was observed in 77.4 % of total observed sets and the effective predation was determined in 22.6 % with MBED. Effective predation was determined in 44 % of observed sets during the day period from 12:00 to 18:00 hours GMT. Lips and buccal parts were observed in 71 % of sets with traditional longline and in 27 % with MBED. The estimated fishing yields of northern and southern zones were 11.05 kg/hour and 15.53 kg/hour respectively, using the MBED and with sperm whales effective predation. In the southern zone the fishing yield increased to 23.03 kg/hour, using MBED but without sperm whale evidence of effective predation. No incidental mortality of birds was registered using both tory-line and MBED simultaneously, in spite of remarkable abundance of the southern black-browed albatross (Thalassarche melanophrys) and cape petrel (Daption capense) in 40.76 % and 23.13 % of total observed sets respectively.

Germany conducted a bottom trawl survey aboard R/V ‘Polarstern’ around Elephant Island and the South Shetland Islands from 19 December 2006 to 3 January 2007. Information on species composition, biomass, and size composition of the abundant fish species was provided. Estimates of total biomass for Elephant Island and the South Shetland Islands separately as well as biomass overall were provided for Notothenia rossii, N. coriiceps, Lepidonotothen larseni, L. squamifrons, Gobionotothen gibberifrons, Champsocephalus gunnari, Chaenocephalus aceratus and Chionodraco rastrospinosus. Biomass was found to be much lower than in 2002 and 2003 for C. gunnari, C. aceratus, C. rastrospinosus, G. gibberifrons, L. larseni and L. squamifrons while biomass was found to be higher in N. coriiceps around the South Shetland Islands and N. rossii in both areas. The proportion of juvenile G. gibberifrons, decreased further due to the production of poor year – classes since the late 1990’s. A concentration of N. rossii was found in the same location where aggregations of the species have been detected in 1975/76 and 1977/78 before they were depleted by the commercial fishery. Two concentrations of N. coriiceps were met in the South Shetland Islands. Given the low stock size of most species it is recommended to leave Elephant Island and the South Shetland Islands closed for commercial finfishing.

Pseudochaenichthys georgianus is a member of the unique Channichthyidae family, which lack haemoglobin. The distribution, length-frequency and summer diet are described from 14 bottom trawl surveys undertaken in the austral summers between 1986 and 2006. P. georgianus (50-590 mm Total Length) were caught throughout the South Georgia shelf from depths of 76 to 370 m, but very few specimens (

Since the 2001/2002 season CCAMLR has recognised the importance of the high level of hooks discarded in fish heads which ingestion by seabirds, especially wandering albatrosses which are large enough to swallow fish heads whole (SC-CAMLRR-XXI/BG/7). For example, in 2001/02 the scientific observer on the F/V Argos Helena estimated that >15,000 fish heads were discarded with hooks still in them. The hooks found in albatross colonies at South Georgia in years prior to 2001/02 were of the type used in the regulated fishery in Subarea 48.3 (SC-CAMLRR-XXI/BG/7). In 2007 overwintering scientists at Bird Island, South Georgia, have noted an increase in the occurrence of hook injuries to wandering albatrosses. The injuries appear to have two sources – injuries from the ingestion of discarded fish heads and offal, and injuries to birds that appear consistent with interactions during line hauling. This raises once again the importance of actions by CCAMLR to minimise or eliminate the discarding of fish heads containing hooks. CCAMLR–XXI noted the difficulty in getting the message to relevant fishers and indicated that alternative means should be considered. One alternative means would be the production and distribution by CCAMLR of a poster designed to educate fishers of the consequence to seabirds of discharging heads and offal containing hooks. The poster would be located in the processing areas of vessels, carry a simple and clear message, be inexpensive to produce and be produced in the languages spoken by crews. A draft poster will be submitted to WG-IMAF for discussion.

The Australian Fisheries Management Authority (AFMA) recently granted a permit for a trial of longline fishing in the Macquarie Island toothfish (Dissostichus spp.) fishery, which lies just outside the CCAMLR Area. Several threatened seabird species, including albatrosses and petrels have very small breeding populations on Macquarie Island and are potentially vulnerable to interactions with fishing vessels. The seabird bycatch mitigation measures adopted for the trial included a ban on offal discharge, night setting only, use of integrated weight longlines (CCAMLR standard); paired streamer lines and strict seabird bycatch limits.
The seabird bycatch limits categorised seabirds into three groups of species with a different limit for each group. The groupings reflected the varying conservation status of the seabird populations breeding on and foraging around Macquarie Island, and the vulnerability of each species to fisheries interactions. The group containing those species with the most critical conservation status and highest risk of interacting with fishing operations had a bycatch limit of one seabird; limits on the other categories were two and three individuals respectively. In addition, if three seabirds in total from categories 1-3 were killed as a result of interactions with fishing gear then longline fishing was to cease for the remainder of the season.

Longline fisheries worldwide have interactions that can be harmful or fatal to seabirds. We report preliminary testing of potential seabird deterrents in longline fisheries around the sub-Antarctic Kerguelen Islands. We compared White-chinned Petrel (Procellaria aequinoctialis) responses to mackerel (Scomber scombrus) baits treated with capsaicin and piperine mixtures, and untreated baits. Petrels readily consumed all untreated baits. However, there were significant differences among the six categorised responses to treated baits (capsaicin mixture: ?5 = 161.71, P