Meeting Abstract

5.1  Thursday, Jan. 3  Slow-twitch oxidative muscle development in yellowfin tuna, Thunnus albacres DICKSON, Juleen*; DICKSON, Kathryn; California State University Fullerton; California State University Fullerton jdickson@fullerton.edu

The purpose of this study was to describe the development of slow-twitch, oxidative myotomal muscle (SM) in a size series of juvenile yellowfin tuna, Thunnus albacares. The SM powers continuous swimming and is important for generating the heat needed to maintain elevated SM temperatures in tunas. Fertilized eggs produced by yellowfin tuna maintained in shoreside tanks were raised to the juvenile stage, 40.08-74.03 mm fork length (FL), at the Inter-American Tropical Tuna Commission laboratory at Achotines Bay, Panama, and were frozen in liquid nitrogen. Larger juveniles (up to 344 mm FL) were collected by hook and line near fish aggregating devices off Oahu, Hawaii, and were frozen at -80�C. All samples were sectioned with a cryostat at a position along the body corresponding to 60% of FL, and the SM fibers were identified by staining for the mitochondrial enzyme succinic dehydrogenase. The Scion Image analysis program was used to calculate the amount of SM as a percentage of total cross-sectional area (%SM). As fish increased in length, there was an exponential increase in the total amount of SM and a gradual increase in %SM, at 60%FL. As the amount of SM increases with size, so does the potential for heat production, which is important for maintaining elevated SM temperatures when entering cooler waters to search for prey. Thus, the development of SM may limit the movement of yellowfin tuna juveniles into cooler waters.