Abstract

Overall, 1,145 dolphinfish larvae were collected, and C. hippurus was the more abundant of the two species accounting for 87% of the total catch. Larvae of both species were collected during all eight surveys, and frequency of occurrence was high overall with C. hippurus and/or C. equiselis larvae present at 59% of the stations sampled. Percent occurrence of C. hippurus ranged from 42% to 76% per survey while occurrence of C. equiselis larvae was lower ranging from 9% to 27%. Mean density across the 8 surveys for C. hippurus and C. equiselis ranged from 0.40 to 1.60 larvae/1,000 m3 and 0.02 to 0.20 larvae/1,000 m3, respectively. While density was significantly different among years sampled for both C. hippurus and C. equiselis (Figure 1), no intra-annual effect was detected for either species. Mean density of C. hippurus peaked in 2007 for C. hippurus (1.05 larvae/1,000 m3) and 2008 for C. equiselis (0.17 larvae/1,000 m3), while mean densities were low in 2010 for both species (0.40 C. hippurus larvae/1,000 m3, 0.07 C. equiselis larvae/1,000 m3). Increased densities of C. hippurus were observed in the eastern portion of our sampling corridor and the majority of this species was collected east of 91°W, a region largely influenced by the Loop Current and associated eddies. In contrast, C. equiselis larvae were more evenly distributed across the sampling corridor. Analysis of mean densities within different salinities indicate a positive relationship for C. hippurus abundance (Figure 2A,) with more than 90% of the catch found in waters with salinities > 32. A negative association between C. hippurus density and sea surface height anomaly (SSHA) was also observed (Figure 2B), with the majority (> 90%) of larvae collected at stations with SSHA of 12 cm or less. This suggests that C. hippurus larvae were abundant in cold core eddies (characterized by negative SSHA), and that larvae rarely occurred within warm core features (regions of high SSHA) in the Gulf. In contrast, no obvious relationship was detected between C. equiselis density and salinity or SSHA; however, catches were low overall for this species so additional sampling is necessary in order to elucidate spatial trends in C. equiselis abundance. In general, results showed that both species were abundant and broadly distributed across our sampling area, and their distribution and abundance is likely influenced by physicochemical condi-tions and the geographic position of mesoscale oceanographic features.

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