Estimation of fecundity and oocyte measurements in Lophius americanus using Image J image analysis software

Monkfish (Lophius americanus) fecundity and egg size were estimated using Image J image analysis software. The auto-diametric method using digital image analysis to capture images, count and measure oocytes is much less labor intensive than the traditional gravimetric method of counting oocytes manually. Digital image analysis is a new method being applied to estimate fecundity in monkfish, which has a unique ovary type in that oocytes are embedded in a gelatinous matrix. Three subsamples of ovarian tissue taken from developing monkfish were pre-weighed and oocyte images were captured and then analyzed using Image J. The analysis produced counts and measurements (area, length and width). Oocyte length-frequency distributions were compared within and between individuals, and to oocyte maturity stages for the same individuals as determined by histology. Sample sizes that were greater than 100 oocytes per subsample appear to capture sufficient size variation of yolked oocyte stages. This is a good starting point for refining the method to use to evaluate if monkfish are fractional spawners, spawning multiple batches per year, and to estimate fecundity of monkfish.