Larger Predatory Fishes of the Meso- and Bathypelagic Domains: Linking the Planktivores and Top Predators

• Main Authors: Cook, April B., Sutton, Tracey
• Format: Still Image
• Language: unknown
• Published: NSUWorks 2017
• Subjects: Marine Biology; Oceanography and Atmospheric Sciences and Meteorology; toothed whales
• Online Access: https://nsuworks.nova.edu/occ_facpresentations/453; https://custom.cvent.com/D31C0AA42FDF42E9918B4DC41EF12A96/files/6314bb125e384ddca5641556a530f63c.pdf

Mesopelagic fish biomass has been estimated at 7-10 billion metric tons, an order of magnitude higher than previous estimates. This upscaling has resulted from the acoustical quantification of net avoidance, particularly avoidance of smaller, research-sized nets such as rectangular midwater trawls (RMTs) upon which previous estimates were based. Net avoidance by fishes is size-dependent, thus our greatest underestimation is likely that of the larger deep-pelagic fishes. Here, we present results from a research program in the Gulf of Mexico that used a large, dual-warp pelagic trawl in concert with an openingclosing RMT to sample from 0-1500 m depth. A total of 129 quantitative samples were obtained with the large trawl, representing over 337 million cubic meters of water filtered. Results showed a stark difference in both the size class and taxonomic composition of fishes collected with the two gears. Some of the larger, predatory deep-pelagic fishes collected were dragonfishes, anglerfishes, great swallowers, pelagic eels, and snake mackerels. Aspects of faunal composition, abundance, biomass, and size distributions will be presented. These larger deep-pelagic fishes are preyed upon by top predators such as sharks, billfishes, tunas, toothed whales, and deep-demersal fishes. Thus, data from this study will help improve our understanding of the links between zooplanktivorous micronekton and apex predators. The inclusion of large deep-pelagic fish biomass should dramatically improve ecosystem modeling efforts aimed at understanding carbon flow in the deep ocean interior.