Diet of Wahoo, Acanthocybium solandri, from the Northcentral Gulf of Mexico JAMES S. FRANKS, ERIC R. HOFFMAYER, JAMES R. BALLARD 1 , NIKOLA M. GARBER 2 , and AMBER F. GARBER 3 Center for Fisheries Research and Development, Gulf Coast Research Laboratory, The University of Southern Mississippi, P.O. Box 7000, Ocean Springs, Mississippi 39566 USA 1 Department of Coastal Sciences, The University of Southern Mississippi, P.O. Box 7000, Ocean Springs, Mississippi 39566 USA 2 U.S. Department of Commerce, NOAA Sea Grant, 1315 East-West Highway, Silver Spring, Maryland 20910 USA 3 Huntsman Marine Science Centre, 1Lower Campus Road, St. Andrews, New Brunswick, Canada E5B 2L7 ABSTRACT Stomach contents analysis was used to quantitatively describe the diet of wahoo, Acanthocybium solandri, from the northcen- tral Gulf of Mexico. Stomachs were collected opportunistically from wahoo (n = 321) that were weighed (TW, kg) and measured (FL, mm) at fishing tournaments during 1997 - 2007. Stomachs were frozen and later thawed for removal and preservation (95% ethanol) of contents to facilitate their examination and identification. Empty stomachs (n = 71) comprised 22% of the total collec- tion. Unfortunately, the preserved, un-examined contents from 123 stomachs collected prior to Hurricane Katrina (August 2005) were destroyed during the hurricane. Consequently, assessments of wahoo stomach contents reported here were based on the con- tents of the 65 ‘pre-Katrina’ stomachs, in addition to the contents of 62 stomachs collected ‘post-Katrina’ during 2006 and 2007, for a total of 127 stomachs. Wahoo with prey in their stomachs ranged 859 - 1,773 mm FL and 4.4 - 50.4 kg TW and were sexed as: 31 males, 91 females and 5 sex unknown. Stomach contents reported in this study were identified to the lowest taxon possible (depending on the stage of digestion) and analyzed for %N, %W, %F, IRI y %IRI. Stomachs contained pelagic/epipelagic fishes and squid, including evidence of species associated with pelagic Sargassum. Prey (309 identified items) belonged to 27 taxa and ranged in stomachs from only one prey in 74 stomachs (58% of total stomachs) to 9 prey in a single stomach. Dominant fish families in the diet were Carangidae, Coryphaenidae, Scombridae and Exocoetidae. A moderate ontogenetic shift in the diet was observed among three size classes of wahoo. The diversity of fishes in the diet suggests that wahoo is an opportunistic predator that feeds on a variety of regionally abundant prey. KEY WORDS: Acanthocybium solandri, wahoo, diet, Gulf of Mexico Dieta del peto, Acanthocybium solandri, en la Región Central del Norte del Golfo de Méjico Análisis del contenido estomacal fue usado en forma cuantitativa para describir la dieta del peto, Acanthocybium solandri, en el norte del Golfo de Méjico. En los torneos de pesca recreacional (n = 321) se presento la oportunidad de colectar estómagos de petos capturados en 1997-2007 registrando el peso total (kg) y largo de horquilla (mm.) del pez. Los estómagos fueron congelados y mas tarde descongelados para remover y preservar (95% etanol) su contenido, lo que facilito su examinación e identificación. Los estómagos desocupados (n = 71) constituyeron el 22% del total colectado. Colecciones de 123 estómagos que habían sido adquiridos y preservadas antes de Agosto del 2005 fueron destruidas durante el Huracán Katrina; sinembargo, otras (n = 65) colecciones preser- vadas ‘pre-Katrina’ fueron salvadas. Estas colecciones y el contenido de 62 estómagos colectados durante 2006 y 2007, formaron la base de este estudio (n = 127; 32 machos, 103 hembras, 5 sexo indeterminado). Los petos con presas en sus estómagos tenían un largo de horquilla entre 859 - 1,773 mm. y un peso total de 4.5 - 50.5 kg. El contenido estomacal reportado en este estudio fue iden- tificado hasta el mas bajo taxón posible (dependiendo del grado de digestión) y fue analizado utilizando el %N, %W, %F, y IRI de los organismos de presas. Los estómagos contienen peces pelágicos/epipelágicos y calamar, incluyendo evidencia de especies aso- ciadas con Sargassum pelágico. Las presas (309 identificadas) pertenecen a 27 taxas encontrándose una presa en 74 de los estóma- gos (58% del total de estómagos) y hasta 9 presas en un solo estomago. Las familias de peces dominantes en la dieta fueron Caran- gidae, Coryphaenidae, Scombridae, y Exocoetidae. Un moderado cambio ontogénico en la dieta fue observado entre los tres tama- ños del peto. La diversidad de peces en la dieta sugiere que el peto es un predador oportunistico que se alimenta de una variedad de presas que son regionalmente abundantes. PALABRAS CLAVES: Acanthocybium solandri, peto, dieta, Golfo de Méjico Proceedings of the 60th Gulf and Caribbean Fisheries Institute November 5 - 9, 2007 Punta Cana, Dominican Republic INTRODUCTION The wahoo, Acanthocybium solandri, is a migratory epipelagic fish in the family Scombridae with cosmopolitan distribution in tropical and subtropical seas (Iversen and Yoshida 1957, Collette and Nauen 1983). In the Western Central Atlantic Ocean (WCA) wahoo occur from New Jersey to Columbia, including Bermuda, the Bahamas, Caribbean Sea and Gulf of Mexico (GOM) (Fischer et al. 1978, Robins et al. 1986). Wahoo is a highly esteemed food fish throughout its WCA range where it supports valuable commercial and recreational fisheries, particularly in Bermuda (Luckhurst and Trott 2000), the southeastern Caribbean islands where it is an important artisanal pelagic fishery resource (Oxenford et al. 2003), and the northcentral GOM (Franks et al. 2000) where it is caught year-around and is among the most preferred species targeted by anglers. Wahoo are managed in U.S Atlantic waters through the Dolphin-Wahoo Fishery