Exuma Sound is a semi-enclosed body of water bounded by islands of the Bahamas. During July 2000, sampling for larval billfish was carried out throughout the Sound's surface waters as well as in adjacent open waters of the Atlantic Ocean. A total of 99 larval billfish (Istiophoridae) was collected. Ninety of the larvae were identifiable as blue marlin (Makaira nigricans) and three as sailfish (Istiophorus platypterus). The remaining larvae were also istiophorids, unidentified to species owing to damage; no larval Xiphias gladius were collected. Larval blue marlin densities ranged from 0 to 3.4 larvae/1000 m2; their sizes ranged from 3.1 mm notochord length to 22.6 mm standard length. Densities tended to be highest north-east of the Sound's central axis, especially within the two regions where exchange with the Atlantic is greatest. Mean densities tended to decrease in the direction of mean flow; mean lengths increased from 8.08 mm at the Sound's mouth to 14.7 mm standard length at its upper reaches. Length-based estimates of larval age ranged from 2.2 to 17.2 days. Given these age estimates and assuming passive surface transport, the blue marlin larvae collected were likely the result of recent spawning in waters that include Exuma Sound and may extend some 200 km south-east of its mouth. This study suggests that Exuma Sound functions as a nursery area for blue marlin, and possibly other billfish species, at least during the summer. Limited sampling just outside Exuma Sound, in the Atlantic Ocean proper, also yielded blue marlin larvae.

The Atlantic blue marlin Makaira nigricans larvae were collected from Exuma Sound, Bahamas and the Straits of Florida over three summers (2000)(2001)(2002). Sagittal otoliths were extracted and read under light microscopy to determine relationships between standard length (L S ) and age for larvae from each year and location. Otolith growth trajectories were significantly different between locations: after the first 5-6 days of life, larvae from Exuma Sound grew significantly faster than larvae from the Straits of Florida. Exponential regression coefficients were similar among years for Exuma Sound larvae (mean instantaneous growth rate, G L ¼ 0Á125), but differed between years for larvae from the Straits of Florida (G L ¼ 0Á086-0Á089). Differences in larval growth rates between locations resulted in a 4-6 mm difference in L S by day 15 of larval life. These differences in growth appeared to be unrelated to mean ambient water temperatures, and may have been caused by location-specific differences in prey composition or availability. Alternatively, population-specific differences in maternal condition may have contributed to these differences in early larval growth. # 2005 The Fisheries Society of the British Isles

Motile organisms are thought to play a role in biogeochemical cycles in tidal systems, but few studies have addressed links between animal activities and dissolved nutrients. Our observations and experiments indicated that movements, feeding, and excretion by fishes and shrimps resulted in subsidies of NH in the natural intertidal pool. Nekton residing in intertidal pools generated the equivalent of 5% of the total NH z 4 imported to the creek. At night, nekton in pools contributed the equivalent of 12% of the NH z 4 and 4% of the PO 3{ 4 imported from the subtidal channel. As the tide flooded the intertidal creek, nutrient enriched pool water was pulsed up the creek and into the intertidal basin. Tidally controlled patterns of nekton movements and feeding result in retention and reintroduction of nutrients to the upper reaches of intertidal creek basins. Accordingly, nekton contribute to the recycling of nutrients through a positive feedback loop that may enhance primary production and invertebrate prey within salt marsh creek basins. We conclude that nekton can be important and underappreciated contributors of dissolved nutrients in tidal systems.

Of the Atlantic istiophorid billfishes, larval age–size relationships and growth rates have been examined only for blue marlin (Makaira nigricans). Using otolith microincrement analysis, we describe age–length and age–weight relationships for larval sailfish (Istiophorus platypterus) collected from the Straits of Florida. Sagittae and lapilli were dissected from 70 larvae ranging from 2.8 to 15.2 mm in (notochord or standard) length. Comparisons between otolith images obtained by light microscopy and scanning electron microscopy indicated that increment widths were well within the resolving power of light microscopy. Indirect evidence and published descriptions of larval blue marlin otoliths suggest daily increment deposition. Estimated ages of specimens ranged from 3 to 18 days. Length data were fitted to age estimates with an exponential model (R2 = 0.85). The estimated size-at-hatch for sailfish was 1.96 mm notochord length, and the daily instantaneous growth coefficient was 0.14. A power curve with exponent 3.05 described the length–dry weight relationship for sailfish. The instantaneous growth coefficient for an exponential regression of dry weight, converted from length, versus estimated age was 0.41. Growth in the length of sailfish larvae from the Straits of Florida was very similar to that described for blue marlin larvae from Exuma Sound, Bahamas.