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Although bluefin tuna are found throughout the Atlantic Ocean, spawning in the western Atlantic has been recorded predominantly in the Gulf of Mexico (GOM) in spring. Larval bluefin tuna abundances from the northern GOM are formulated into an index used to tune the adult stock assessment, and the variability of this index is currently high. This study investigated whether some of the variability in larval bluefin tuna abundances was related to environmental conditions, by defining associations between larval bluefin tuna catch locations, and a suite of environmental variables. We hypothesized that certain habitat types, as defined by environmental variables, would be more likely to contain bluefin tuna larvae. Favorable habitat for bluefin tuna larvae was defined using a classification tree approach. Habitat within the Loop Current was generally less favorable, as were warm-core rings, and cooler waters on the continental shelf. The location and size of favorable habitat was highly variable among years, which was reflected in the locations of larval bluefin tuna catches. The model successfully placed bluefin tuna larvae in favorable habitat with nearly 90% accuracy, but many negative stations were also located within theoretically favorable habitat. The probability of collecting larval bluefin tuna in favorable habitat was nearly twice the probability of collecting bluefin tuna larvae across all habitats (35.5 versus 21.0%). This model is a useful addition to knowledge of larval bluefin tuna distributions; however, the incorporation of variables describing finer-scale features, such as thermal fronts, may significantly improve the model's predictive power. [ABSTRACT FROM AUTHOR]

Catch statistics for the king mackerel ( Scomberomorus cavalla) recreational fishery off west-central Florida were derived from angler interviews conducted during 19 seasonal tournaments held in April–May and October–November of 2004 and 2005. Fishing location, number of fish per line per hour (catch per unit effort), and presence of baitfish from the tournament data were examined in the context of bathymetric gradients and other benthic features (e.g., wrecks or artificial reefs), and the location and persistence of oceanic fronts mapped using satellite imagery of sea surface temperature (AVHRR) and ocean color (MODIS and SeaWiFS). Generalized linear models were applied to identify the relationship between king mackerel catch rates and environmental data. The distance of fishing activity to the nearest front varied substantially, particularly when winds and front position were variable. However, baitfish presence with proximity to water clarity fronts (as defined by water-leaving radiance at 443 nm) significantly influenced successful king mackerel catch. Positive catch rates were significantly influenced by chlorophyll values and period (season and year). Additionally, intermediate water clarity (in the range 0.7–1.0 mW cm−2μm−1 sr−1) led to higher catch rates. Decreased water quality, primarily associated with a large Karenia brevis red tide, led to a lower number of catch and lower catch rates (122 king mackerel, 0.13 catch per unit effort) in fall 2005, compared to spring 2004 (179, 0.14), fall 2004 (360, 0.17) and spring 2005 (296, 0.21), despite a consistent seasonal effort. [ABSTRACT FROM AUTHOR]