The BET and BBL swordfish fishery is expanding rapidly off the east coast of Australia and is now a significant fishery. The warning 'trigger', set by AFMA, of 800t of BBL caught this year has been exceeded. There is now an urgent need to gain an understanding of the stock structure of this fishery. There are now grave concerns, both within the Pacific and the Indian Ocean, on the possibility of over exploitation of these species.

Very little is known scientifically on these species (Whitelaw and Unnithan. 1997). Critically there is no verifiable information on the size at maturity and age-structure of populations of BET and BBL in the western Pacific.

Stock assessments require knowledge of size at maturity, size at age, growth rate and estimates of the variability in these parameters within the stock.

For management plans to be devised and implemented it is necessary to expand our biological knowledge. A first step in a structured stock assessment of a fishery is to determine whether ages of individuals can be estimated from their bony parts (otoliths and spines). There is a need to develop verifiable age estimation techniques for stock assessment studies.

Refs;
Whitelaw, A.W. and Unnithan, V.K. 1997. Synopsis of the distribution, biology and fisheries of the bigeye tuna, with a bibliography. CSIRO Marine Laboratories Report 228. 62pp.