CCAMLR

The diet of Antarctic toothfish Dissostichus mawsoni captured by bottom longline in the Ross Sea was studied during the 2001 (3937 stomachs examined) and 2002 (5426 stomachs examined) summer fishing seasons. Fish sampled in 2001 were caught in 317-2154 m depths and ranged in length from 58–190 cm total length (TL) while fish sampled in 2002 were caught in 815-1623 m depths and ranged in length from 62–197 cm TL. A high proportion of stomachs sampled were empty (34% in 2001 and 49% in 2002) and the remaining stomachs often contained prey in advanced stages of digestion, making prey identification difficult. Fish were the most important prey category (86% of stomachs in 2001 and 78% in 2002), in particular icefish (family Channichthyidae) and Whitson’s rattail Macrourus whitsoni. Squid, bait, and prawns were also important prey items.

Considerable progress was made on the survey database in early 2002. However, this work had to be postponed because of a higher priority need for developing a web-based data system for the Catch Documentation Scheme. Work on the survey database in 2002 included:
• revision of the database model;
• documentation of the database specifications;
• development of data uploading routines;
• revision of data extraction routine for CMIX and trawlCI; and
• processing of historical data.
The survey database consists of some 50 tables and 50+ stored procedures and triggers. A detailed description of the database specifications is given in ‘Technical Specifications for the Survey Database (see document in ‘\FSA 2002\Survey Database’ on the server). The primary tables are: Survey; SurveyEvent; CatchSummary; CatchLWSM; and Specimen. Data from sixteen surveys have now been uploaded to the survey database.
Substantial further work is required to complete key elements of the database, as well as tidy up and transfer existing CCAMLR data to the new survey database. Future work may also include the development of a stand-alone database for at-sea entry of survey data.

The role of fish in the Antarctic food web in inshore and offshore waters is analysed taking as an example the coastal marine communities of the southern Scotia Arc (South Orkney Islands and South Shetland Islands) and the west Antarctic Peninsula. Inshore, the ecological role of demersal fish is more important than that of krill. There, demersal fish are major consumers of benthos and also feed on zooplankton (mainly krill in summer), and are links between lower and upper levels of the food web; they are common prey of other fish, birds and seals. Offshore, demersal fish depend less on benthos and feed more on zooplankton (mainly krill) and nekton, and are less accessible as prey of birds and seals. There, pelagic fish (especially lanternfish) are more abundant than inshore and play an important role in the energy flow from macrozooplankton to higher trophic levels (seabirds and seals). Through the higher fish predators, energy is transferred to land in the form of fish remains, pellets (birds), regurgitations and faeces (birds and seals). But in the wide context of the Antarctic marine ecosystem, krill (E. superba) plays the central role in the food web because it is the main food source in terms of biomass for most of the high level predators from demersal fish up to whales. This has no obvious equivalent in other marine ecosystems. In Antarctic offshore coastal and oceanic waters the greatest proportion of energy from the ecosystem is transferred to land directly through krill consumers, such as flying birds, penguins, and seals. Beside krill, the populations of fish in the Antarctic Ocean are the second most important element for higher predators, in particular the energy-rich pelagic Myctophidae in open waters and the pelagic Antarctic silver fish P. antarcticum in the high Antarctic zone. Although the occurrence of these pelagic fish inshore has been scarcely documented, their abundance in neritic waters could be higher than previously believed.