The longline catch in the EPO declined from 83,000 t to about 35,000 t in 1998, and has been replaced by a large purse-seine catch since 1993. The purse-seine catch in the EPO increased from about 8,000 t in 1993 to over 50,000 t in 1996 and 1997. It declined to 34,000 t in 1998. Because a comprehensive stock assessment for this species is hindered by the scarcity of data and the absence or poor quality of estimates for some key biological parameters, the current stock status is uncertain. Although the estimates require further developments, the preliminary results raise concern of overfishing and decline in adult biomass.
Some information is available on marlin stock structure and broad movement patterns.
However, BBRG highlighted gaps in other information required for the development of quantitative stock assessments. These are major gaps in information on age and growth, mixing rates and natural mortality. Historical catch and effort data are available for several commercial fleets, especially Japanese longliners. But catches of billfishes are often incidental to commercial fishing operations. Consequently, there is uncertainty over the reporting of discarded catches, and catch rates need to be standardised if they are to be used as an index of stock abundance.