488 
Fishery Bulletin 108(4) 
August 2006 (n=459) 
Log e A/, = 8.645 - 0.381 (age) 
r 2 = 0.94 
Ns 
o o 
n 
10 12 14 16 18 20 
Age (days) 
Figure 6 
Regression plots of log p {abundance + 1 ) on age for ten-day cohorts of sailfish (Istiopho- 
rus platypterus) larvae collected from the northern Gulf of Mexico in 2005 and 2006. 
Regression equations and plots arranged by survey. 
shown to increase stage-specific production potential 
(Rilling and Houde, 1999). 
Hatch dates of sailfish larvae collected in this study 
indicate that spawning is protracted in the northern 
Gulf and peak activity occurs during July. To date, 
sailfish spawning has not been documented in the 
northern Gulf, but sailfish are known to have pro- 
tracted spawning in other regions of the Atlantic and 
Pacific oceans (de Sylva and Breder, 1997; Chiang et 
al., 2006; Richardson, 2007). Although the timing of 
sampling likely influences hatch-date distributions of 
sailfish in the Gulf, resulting in a multimodal distri- 
bution, spawning has been shown to occur from May 
to September in the western North Atlantic Ocean 
(de Sylva and Breder, 1997) and from April to Sep- 
tember in the eastern Pacific (Chiang et ah, 2006), 
corresponding to the spawning range observed in this 
study. Additionally, data from studies indicate that 
peak spawning occurs in mid to late summer because 
increased frequencies of mature ovaries have been ob- 
served in sailfish landed in July and August (de Sylva 
and Breder, 1997; Chiang et ah, 2006; Richardson et 
al., 2009a). 
Questions remain regarding the specific factors regu- 
lating observed variations in distribution, growth, and 
mortality of sailfish, as well as the extent of spawn- 
ing in the northern Gulf. Regardless, high densities 
and broad distributions of larvae combined with rapid 
growth and high production potential indicate that 
sailfish larvae spawned or hatched in the northern Gulf 
potentially contribute to Atlantic sailfish populations. 
This study provides strong evidence that the northern 
Gulf serves as an important spawning and nursery 
habitat for Atlantic sailfish. 
