Importance of the Straits of Florida spawning ground to Atlantic sailfish (Istiophorus platypterus) and blue marlin (Makaira nigricans)

Abstract

Much of the uncertainty in managing highly migratory pelagic species results from the scarcity of fisheriesindependent data relevant to determining long-term trends in abundance, migratory movements, and the relative importance of different spawning grounds. To address these issues, we used an ichthyoplankton-based method to quantify the overall level of spawning of sailfish (Istiophorus platypterus) and blue marlin (Makaira nigricans) in the Straits of Florida (SF). We estimated that during the 2 years (2003)(2004) of the study, 4.60 · 10 11 sailfish eggs and 4.49 · 10 11 blue marlin eggs were produced on an annual basis in this region. These egg production values, when combined with estimates of annual fecundity for each species and the most recent stock assessment estimate of total biomass, indicate that about 2.1% of Western Atlantic sailfish spawning and 1.6% of Atlantic-wide blue marlin spawning occurs in the SF. Additionally, popup satellite tags deployed on sailfish at the start of the spawning season revealed their short residency times in the SF, suggesting that a large (%13%) transient portion of the sailfish population is responsible for the SF egg production. Overall, this study provides a critically needed fisheries-independent method of quantifying spatial and temporal trends in the abundance of highly migratory species. The application of this methodology in the SF indicated that aboveaverage levels of sailfish and blue marlin spawning occur in this area and, possibly more importantly, that the SF is a migratory bottleneck for these species.

Reply to Safina and Walter et al.: Multiple lines of evidence for size-structured spawning migrations in western Atlantic bluefin tuna

“…Longline sampling of adult fish in the Slope Sea for studies of reproduction and population structure is a top priority. We also agree with Walter et al (1) that larval surveys and analyses should be designed that allow for the implementation of the larval production method (14) in both the Slope Sea and the Gulf of Mexico. This approach can provide an independent rigorous comparison of the relative magnitude of spawning in the two regions.…”

Satellite telemetry reveals physical processes driving billfish behavior

“…They are believed to reach maturity at 2 years of age [95] and live up to 20 years [96]. Larvae have been identified near the Dominican Republic [38], the Bahamas [97], and the Florida Straits [46,81], cooccurring in these areas, respectively, with larvae of white marlin, sailfish, and both these species plus swordfish, suggesting that these regions are essential habitat for both spawning adults and developing larvae. Larvae and eggs have also been identified near Hawaii [83].…”

Ocorrência e identificação de larvas de Istiophoridae e ovos de Xiphiidae na Costa Sudeste Brasileira

“…TIDWELL et al (2007) state that information about the billfish first stages of development, nursery areas, larvae habitat preferences and eating habits is still scarce, especially for the Southern Atlantic. Studies on Istiophoridae and Xiphiidae larvae are most concentred in the Northern Atlantic, such as those by DE SYLVA (1963), JOLLEY (1977), BAGLIN (1979), HARVEY (1990), SOUZA et al (1994), DE SYLVA and BREDER (1997) and RICHARDSON et al (2009)…”