CCAMLR

Longline fisheries have expanded throughout the world’s oceans since major commercial distant-water pelagic fleets began fishing for tuna and tuna-like species in the early 1950s. Along with the more recent development and expansion of demersal longline fleets for species such as Patagonian toothfish, these vessels are a major source of mortality to several species of seabird. Vessels can set many thousands of baited hooks in a day across many kilometres of water. These waters are often used as foraging areas by wide-ranging seabirds. Attracted by baits and offal, the birds can be caught on the baited hooks and subsequently drown. To provide a greater understanding of the potential impact of the Southern Ocean’s longline fleets on seabird populations, this paper describes the trends in longline effort of the major pelagic and demersal fisheries in southern waters. The total reported effort from all longline fleets south of 30?S has been well over 250 million hooks per year since the early 1990s. However the spatial and temporal distribution of this effort has not been constant. While effort from the Japanese pelagic distant-water longline fleet declined through the 1990s, the Taiwanese fleet expanded dramatically. Likewise demersal fishing for toothfish increased markedly during the mid-1990s. These fisheries, along with substantial illegal longline fisheries, may be placing the long-term viability of many Southern Ocean species of seabird in jeopardy.

Regression equations relating total length (TL), pelvic length, disc width and weight are provided for Amblyraja georgiana by sex, and for both sexes combined. For all regressions, there were significant differences between the two sexes: females are broader and heavier than males at lengths greater than about 90 cm TL. There were insufficient data to adequately define length-length and length-weight relationships for Bathyraja eatonii, but preliminary regressions are provided for the two sexes combined. It is probable that large females are larger and heavier than males of the same size. The regressions for these species should be used with caution.
The length at 50% maturity for male A. georgiana is about 91 cm TL, and females appear to mature at a similar or slightly greater length. The length at 50% maturity of male and female B. eatonii could not be accurately determined, but may be around 90–100 cm, and greater than 100 cm, respectively.
To date, c. 6000 skates have been tagged in sub-area 88.1 over the 1999–2000 through 2001–02 seasons. Returns suggest some long-term survival, small-scale migration within-season, and limited movement between seasons. Results are considered preliminary, given the short time span of the programme, and the confounding effect of spatial variation in fishing effort between seasons, resulting largely from changes in annual ice pattern.

This report provides the first analysis of standardised catch per unit of effort (CPUE) from the exploratory fishery for Antarctic toothfish Dissostichus mawsoni, which has operated in Subarea 88.1 for five seasons, from 1997 to 2002. Two analyses are presented. The first (all-ground) analysis reviewed catch from 1998 to 2002 (excluding the 1997 season as insufficient data were available), and included a number of areas that had been fished for only one season. The second (main-ground) analysis reviewed CPUE from the two main vessels involved in the fishery, and reviewed their catch from the main area of the fishery which had been consistently fished over most seasons.
For the all-ground analysis, variables area, season, length of line, soaktime, latitude and month in season entered the model, in order. This model explained 32% of the data variability, but was influenced by exploratory fishing activity. For the main-ground analysis, variables area, length of line, season, month, latitude, soaktime and type of set (research or exploratory) entered the model, in order. This model explained 34% of the data variability, because it excludes fishing grounds that were fished for only one season. Annual indices from both models show an increasing trend over the duration of the fishery, except for the 2001 season. Fishing in 2001 was poor, as bad weather and thick ice conditions precluded access to the main fishing grounds. The index for 2002 is the highest in the series, which suggests that the New Zealand toothfish fishery is not under stress from the current level of fishing activity. However, both models have relatively low predictive power, and are a relatively poor fit to the data, and these trends should be interpreted with caution. This is due to the exploratory nature of the fishery, and the unbalanced nature of the distribution of effort among seasons. As only four years of data are available for analysis, these trends are considered to be preliminary indications only.

Little is known about the bycatch of skates, rays and macrourids in the target longline fishery for toothfish in the Ross Sea. Following concerns about the accuracy of reporting of bycatch raised by the 2001 CCAMLR bycatch subgroup, the processes for recording bycatch in this fishery were reviewed and the accuracy of data recording was investigated. Current systems were considered to be appropriate, and current bycatch protocols were found to perform adequately against CCAMLR guidelines. Insufficient data have previously been available to evaluate the usefulness of a standardized CPUE analysis of macrourid bycatch in this fishery. The review of data suggest that the toothfish fishery has not yet had a detectable effect on the CPUE, and hence probably the abundance of rattails. Standardised CPUE analysis may be a useful method for the on-going monitoring of this bycatch species, and continued monitoring of CPUE is suggested.

Results from the 2002 season of the New Zealand toothfish fishery in Subarea 88.1 & 88.2 are reviewed and compared to previous seasons. Catch and effort data and biological information for Antarctic toothfish (Dissostichus mawsoni) and Patagonian toothfish (D. eleginoides) are presented. The catch for the 2002 season was almost double that for 2001, and CPUE was the highest for any year. The principal bycatch species continues to be the rattail Macrourus whitsoni, with skates, particularly Amblyraja georgiana, the only other significant bycatch.

A summary of current research underway in New Zealand on seabirds vulnerable to fisheries interactions is provided in two referenced tables, one describing population research and the other describing foraging range data available.