CCAMLR

A random stratified trawl survey was conducted in May 2000 to assess the abundance of icefish, Champsocephalus gunnari, and juvenile pre-recruit toothfish, Dissostichus eleginoides, on the Heard Island Plateau and Shell Bank. Abundances and length density plots of these species plus two principal bycatch species Lepidonotothen squamifrons and Channichthys rhinoceratus are given for each stratum. A total of seven surveys have been conducted in the Heard Island and McDonald Islands region since 1990 and results from each survey are presented so that inter-annual comparisons can be made. Abundance of D. eleginoides, L. squamifrons and C. rhinoceratus in each stratum are relatively steady, varying by a factor of 2-3 between years, but C. gunnari abundance can vary by a factor of about 20 between years. This is the result of occasional strong year classes entering the fishery and dominating the population for about 2 years before disappearing, as has been documented in other locations.

For the last 3 years, WG-FSA has accorded high priority to development of a method to integrate different indicators of stock status into assessments using the generalised yield model (GYM). In this paper, we propose a method, based on use of the sampling/importance-resampling algorithm, for incorporating information on trends in standardised CPUEs into GYM assessments. The use of the method is illustrated using data for D. eleginoides in Subarea 48.3. As the method requires only very small adjustments to the computer program implementing the GYM assessments, we propose that this method should be adopted for use during the 2000 meeting of WG-FSA.

Fish Heaven is a simple spatially explicit age structured fish model, containing the basic features of standard fish modeling with a number of optional extras. It was designed within an object oriented framework to allow for the possible extension in a number of directions. In particular it was designed with the view of testing the efficacy of different statistical sampling regimes given various plausible spatial structures of fish stock.
The model has a simple age and space structured population governed by the normal life history parameters and subject to both environmental stochasticity (if desired) as well as demographic stochasticity. It is a spatially explicit model in which fish will tend to distribute themselves according to their density and the underlying habitat quality variable. On top of this, fishing occurs. This includes a wide range of fishing options. The software has been constructed to allow for it to be extended to include more complex fishing management practices.
The manual for the software, Fish Heaven Version 1.0.0, forms the body of the paper. Although Version 1.0.0 of the software is complete it is still seen as a piece of software in development. Currently the software is designed to allow environmental simulations with fishing while capturing various statistics about the status of the system. Analysis of the output must be done with a separate piece of software, such as a statistical package, reading in the output files of Fish Heaven. A number of extensions are planned for the software and these are described in the appropriate sections of the manual as 'further improvements'.
The manual and software are both contained in the file FishHeav.zip. This is on the CD of Australian Antarctic Division software and additional copies are available from the Australian Antarctic Division. The manual contains colour pictures, although black and white copies of the manual still contain all of the necessary information. The copy of the manual in FishHeav.zip is a pdf file and includes all the coloured pictures.
The executable has been compiled for Windows NT but should run on any 32bit Windows operating system. It requires no additional libraries to run and takes up less that 1.4M of disk space. When running the size of the spatial grid is the limiting factor on memory requirements but is not terribly restrictive.

A brief description of hawl-by-hawl data sets from Ukrainian commercial vessels fishing tooth-fish in Subdivision 48.3 during 1986-199 1 is presented. The fishery was mainly carried out in summer months off the eastern South Georgia and at Shag Rocks. The length frequency modes amounted to 95-100 cm, which exceeded modes for the latest years of fishery. Using the generalized additive model the catch per effort estimates for 1986-99 were standardize. The fishery efficiency in 1986-95 was approximately similar, while in 1996-99 it decreased sharply. It is shown that significance of such factors as a month and depth is low, and a modified model developed without these factors consideration provides more accurate estimates.

Biostatistic data obtained by Soviet research and commercial vessels in 1970 to 1991 have been used to study length-age composition of Champsocephalus gunnari from different locations of South Georgia Island Subarea. An analysis of Ch.gunnari length-age groups spatial distribution over Eastern, Northern, Western, Southern Island Shelf and near Shag Rocks allowed for revealing similarity of Ch.gunnari length-age composition structure at early years of life for fish inhabiting areas to the south of Island and near Shag Rocks and finding a difference between those two groups and the eastern group. Larger number of "mature" fish in the west is related to migration from eastern area of maturing individuals as they grow. It has been defined that a part of western group of fish at the age of 2-3 years had been migrating towards the Shag Rocks. It has been found that predomination of recruitment over remaining fish had been characteristic of the whole population irrespective to absence or presence of fishery. It is obviously a natural character of the population under consideration. Ch.gunnari could rapidly set up and restore high abundance in Subarea just owing to that character in conjunction with pelagization of species, earlier age of sexual maturity as compared to notothenia and favourable oceanographic conditions.

An attempt has been made to study icefish as an object of acoustic survey basing on the acoustic and biological data obtained by Russian RN ATLANTIDA in the area of South Georgia Island (January-February 2000). Estimation of possible target strength values was made by a comparison to TS of other fish species having similar body structure and morphological characters, as well as taking into acount chemical and physical body properties. There has been proved a comparability of Ch.gunnari length frequencies obtained from the catches by midwater trawl to those estimated with TS in situ measurements for fish recorded within the pelagic zone. Basing on the analysis of acoustic measurements and results of commercial fleet operation, there has been showed availability within the pelagic zone by daytime of Ch.gunnari, biomass of which would be out of bottom trawl survey access. It has been indicated that one of directions of improving Ch.gunnari stock state estimation could be an application of acoustic method to evaluate biomass distributed within the pelagic zone. The latter rises the problem of carrying out acoustic trawl survey to estimate Ch.gunnari biomass and distribution of species pelagic and pre-bottom concentrations.