POWELL, Mickie/L*; SOWER, Stacia/A: Seasonal Estradiol Production in Three Size Classes of Atlantic Hagfish

Hagfish are considered to be the oldest form of extant vertebrates in the Class of Agnatha. During the past ten years they have become the focus of a growing commercial fishery on the East Coast. Since there is little information on age determination, age and time of reproduction, seasonality of reproduction and growth, the level at which a sustainable fisheries can be maintained is unknown. The goal of our studies is to further our understanding of growth and reproduction by testing the hypothesis that M. glutinosa exhibit seasonal reproductive growth. The specific objectives of this study were to determine gonadal development by histological analysis and estradiol production in the gonads of three size classes (small 20-35 cm, medium 35-45 cm, large 45-55+cm) of M. glutinosa trapped 25-30 miles off the New Hampshire coast at a depth of approximately 150 m from April to August 2001. The small group contained females and immature hagfish, the medium group contained males and females and the large group contained only females. Mature eggs were found only in the large size class and the greatest number of eggs 1 cm or larger were in the July sample. Estradiol production was measured in a section of gonad tissue incubated with pregnenolone for 48hr at 4�C. The greatest change in estradiol production was in the small size class between April and June, increasing from 1.79 to 5.77ng estradiol/g wet wt of gonad tissue. The highest estradiol production was measured in the small size class in June. This study and earlier studies from this lab indicate that Atlantic hagfish may have annual reproductive cycles. Supported by UNH/UME NOAA Sea Grant R/FMD-168 and NA16G1035 and UNH.