Natural mortality is assumed to be 0.3 per year for all year classes and for both the North and the South Atlantic stocks. The available tagging data for North Atlantic albacore do not allow for the reliable estimation of M as it is confounded with emigration from the main tagging area (i.e. Bay of Biscay). Ortiz de Zárate and Bertignac (2002) estimated a combined parameter: natural mortality plus emigration from the Northeast Atlantic area was between 0.56 and 0.84. These estimates would not be inconsistent with the M value assumed by ICCAT.

More recently, Santiago (2004) compared natural mortality values obtained from different authors. Results were 0.322 and 0.325 according to Rikhter and Efanov (1976) and Pauly (1980) respectively and a vector of mortality of (0.541, 0.416, 0.351, 0.311, 0.285, 0.293, 0.318, 0.348, 0.385, 0.429, 0.486, 0.560) for ages 1-12 respectively following Chen and Watanabe (1988)’s method. This suggests that there is not enough reason to change the actual value assumed by ICCAT.