How CCAMLR Collects its Data

The data used by CCAMLR’s scientific working groups are collected by:

•  Members fishing in the Convention Area;
•  scientific observers on Members’ vessels (who collect data on the fishing operations and the catch, report on compliance and advise operators and owners); and
•  scientific surveys carried out by Members’ research vessels.

Since 1987, most fisheries data collection protocols and methods have been standardised to ensure that data from all sources are compatible.

Collection of Data on Target Species     [Return to table of contents]

Fisheries Catch and Effort Data

These data are collected by CCAMLR Members and link the size of the catches to how often, and for how long, a vessel fishes (i.e. the fishing ‘effort’). Such data also indicate where the vessel was fishing. The Convention Area is divided into statistical units which are thought to be biologically or environmentally distinct, and therefore to contain relatively discrete stocks of certain species. However, some species straddle the boundaries of these units. This is particularly true for krill, Patagonian toothfish, lanternfish and squid. Therefore, to fully understand the dynamics of these species, data are required from across statistical or biological boundaries, including from areas adjacent to the Convention Area.

Harvested Species Abundance      [Return to table of contents]

Fish, krill and squid abundances are estimated by Members’ research vessels independently of any fishery and often by collaborative programs involving more than one Member. Two types of surveys are predominantly undertaken:

• ‘Acoustic surveys’ cover quite large areas. High-frequency sound is transmitted vertically into the water column and then reflected back to the ship by any objects it intercepts (the ‘target’). The pattern of reflection varies with a shoal of fish reflecting differently to a swarm of krill, for example. The reflected sound is processed electronically making it possible to identify the target species and estimate its density. The latter is then scaled by area to estimate overall abundance of the species concerned.

• ‘Trawl surveys’ use either trawl or plankton nets to standardise what is caught by some set towing distance or time. Trawl nets tend to catch bigger animals which are part of the breeding stock. On the other hand, plankton nets tend to catch juvenile and smaller animals. After repeated survey tracks, which are usually followed in some random order, the abundances of targeted species are estimated and scaled over the entire area of interest.

Biological Information        [Return to table of contents]

Such information relates mainly to the growth, reproduction and natural mortality of the species being harvested. It is collected on board commercial fishing vessels by their crews and by national or international observers. It is also collected by research vessels.

• Data on the age composition of harvested animals, and how fast they grow, provides key information for fisheries managers to estimate the effects of fishing on a species and/or its potential yield. In fish, age is calculated from measuring an animal and then determining the number of growth rings on its scales or otoliths (earbones). Such rings are laid down regularly throughout life, though not necessarily annually. With enough measurements, it is possible to link the age of animals in the catch with their length composition. The problem for krill is slightly different as they do not have growth rings. However, since krill born in the same year or season (cohorts) tend to grow at similar rates, cohort age is then usually determined from the length composition of the krill in the catch. It may also be determined from other indices such as eyeball size or the chemical composition of the exoskeleton.

• Knowing the age at which a animal breeds, and also when and where it breeds, means that fishing can be regulated by ensuring that animals breed at least once before being caught so as to avoid compromising the stock’s potential/reproductive yield. The reproductive state of animals in a fishery’s catch, along with plankton catches, provides information on the spawning times and locations.

• Natural mortality (M)† is notoriously difficult to estimate in any species which is also subjected to fishing-induced mortality (F). For example, if the number of animals of a certain length decrease in any one year, it is difficult to determine the exact causes which can be naturally or fishery induced. Fisheries scientists employ a variety of estimation methods to address such problems and the resultant estimates can vary widely.

From the above, it should be obvious that considerable uncertainties surround estimates of the key biological parameters used to asses stock yield. While these cannot be ignored, CCAMLR has developed models (see below) which attempt to take such uncertainties into account in the formulation of risk-averse management action. Indeed, trying to account for potential uncertainties through conservative management action is a key feature of CCAMLR’s attempts to apply the ‘precautionary approach’.

Collection of Data on Dependent Species      [Return to table of contents]

An integral part of CCAMLR’s ecosystem approach endeavours to monitor selected species that depend on, or are related to, commercial target species and fisheries. The CCAMLR Ecosystem Monitoring Program (CEMP) aims to detect and record significant changes in selected stocks of these species to distinguish between changes arising directly from harvesting from those which occur naturally as a result of physical or biological variability in the environment.

The species being monitored have been selected from:

• key prey species – these exhibit some potential for harvesting and currently include krill (E. superba and E. crystallorophias), Antarctic silverfish (Pleuragramma antarcticum) and early life-stages of fish; and

• important predator species – these feed mainly on key prey species (at this stage particularly krill), have a wide geographical distribution, and occupy an important position in the ecosystem. They currently include Antarctic fur and crabeater seals as well as Ad?ie, chinstrap, gentoo and macaroni penguins, Antarctic and cape petrels, and black-browed albatross.

CEMP monitoring sites have been chosen to try to distinguish between broad-scale and local-scale changes, and to contrast differences between fished and non-fished areas.

The biological parameters being measured in CEMP species are broadly similar to those for species targeted by the fishery. However, the types of data vary for the species being monitored as an index of their dependence on the species targeted by the fishery (e.g. the duration of birds’ foraging/feeding trips and the weight of birds arriving to breed etc., give some indication of how effective a population has been in its feeding on krill).

The environmental parameters monitored by CEMP include sea-ice and hydrographic conditions.