This species is occasionally caught in the Mediterranean Sea with no known population information. It is unclear whether there are two separate stocks or a single population in the Atlantic (Collette et al. 2006). The most recent ICCAT stock assessment considers a single stock in the Atlantic (ICCAT 2007).

Catch for the Atlantic: recorded since 1956 when total catch was minimal; peaked in 1965 at nearly 5,000 t, then oscillated between 1,000 and 1,500 t until 1993; increased to 1,900 t in 1994; declined below 1,000 t from 1995–2004 (ICCAT 2007). During the 2006 marlin assessment it was noted that catches of Blue Marlin and White Marlin continued to decline through 2004. The estimate for 2005 was 597 t. The recent biomass most likely remains well below BMSY estimated in the 2002 assessment. Over the period 2001–2004 combined longline indices and some individual fleet indices suggest that the decline has been at least partially reversed, but some other individual fleet indices suggest that abundance has continued to decline. Confirmation of these recent apparent changes in trend will require at least an additional four or five years of data, especially since the reliability of the recent information has diminished and may continue to do so.

It is important to note that the decrease in catches is associated with ICCAT regulations that were put in place in 2001 regarding the mandatory release of live white marlin taken by pelagic longlines. In addition in 2003, there was the imposition of catch limits to 33% of the 1996 or 1999 reported values. Countries are now reporting their landings, not their total catch.

The most recent stock assessment (ICCAT 2007) used a Bayesian Surplus Production model to estimate biomass from 1990 through 2006. The remaining data series (1956–1989) are based on biomass estimates from the previous stock assessment (ICCAT 2003). Population declines were examined using a generation length estimated between 4.5 and 6.5 years. Over a three generation length period of 13 years, the decline was 8.67% and over a three generation length period of 20 years, the decline was 36.74%. These declines were calculated using the biomass estimate of the first to the last year of the range examined. Population reduction for Atlantic White Marlin was therefore estimated to be between 9% and 37%.

In addition, there is still a high degree of uncertainty regarding biological parameters for this species. Landings of White Marlin may also be misidentified with Tetrapturus georgii. The proportion of T. georgii has increased dramatically in catches from 2–32 % in the past decade, which increases the uncertainty of the status of White Marlin (Beerkircher et al. 2009).

Decreasing