Fecundity Estimation of American Goosefish Lophius americanus in the Western North Atlantic Ocean

Goosefish (Lophius americanus), also called monkfish in the markets, is a valuable fishery species from the Gulf of Maine to Cape Hatteras, North Carolina. Although the reproductive potential of a fishery stock is often measured as an aggregate of spawning stock biomass, many studies have demonstrated that egg size and quality are better parameters for estimating reproductive potential. Counting eggs, particularly using the traditional gravimetric method, can be very labor intensive. In this study we investigate the application of a faster method, the auto-diametric method, which used digital image analysis to capture images and to automate the counts and measurements of oocytes.  Goosefish gonad samples (n = 180) were collected and preserved in 10% neutral buffered formalin for at least a month prior to processing for histology and fecundity.  Prespawning females with cortical alveolar (stage 3: n = 28) and vitellogenic (stage 4: n = 61) stage oocytes, as the most advanced oocyte stages, were determined by histology. Fecundity and egg size were estimated using Image J image analysis software from three subsamples of ovarian tissue. Oocyte images were then captured in sequential quadrants using a Zeiss Microscope to produce counts and measurements (area, length and width). Oocyte length-frequency distributions were compared to oocyte maturity stages determined by histology and also within and between individuals.