Abstract

We describe a two-phased project that examines "essential fish habitat" for blue marlin, Makaira nigricans. It builds on previous work and constitutes an intemational cooperative research effort involving government and university scientists and recreational and commercial fishers. Neuston sampling during July 2000 and July 2001 in the vicinity of Exuma Sound, Bahamas, yielded some of the highest densities of circa 2 - 17 day old blue marlin larvae ever reported. This indicates that the waters directly upstream of the Sound served as blue marlin spawning grounds and that the Sound itself may be an important nursery area, at least during the summer. These results have prompted implementation of the second phase of the project: "pop-up" satellite tagging of aduIts at locations both upstream and downstream of the Sound during the peak of the next spawning season (Le., June, 2002) followed by additional, larval sampling in the vicinity of the Sound during July, 2002. This work may provide valuable insight into the nursery role of Exuma Sound relative to open-ocean environments as well as into the extent of adult movement during the peak of their spawning periodo Concurrent with our work are three other studies that will complement our research:\i) An effort to combine genetic and traditional methods for identifying even badly damaged billfish larvae to species;\ii) An effort to age larval blue marlin from their otoliths; and\iii) An effort to determine the sex and reproductive status of tagged adults from a small sample of muscle tissue.\Collectively, these ongoing investigations may provide critical information for the protection of spawning and nursery habitats for Atlantic blue marlin and possibly other billfishes in the region. A future application for this work, if the study is expanded spatially and a time series is developed, is to assess whether abundances of larval blue marlin can be used as a fishery-independent index of spawning stock biomass.

PDF Preview