Fecundity of shortspine thornyhead (Sebastolobus alascanus) and longspine thornyhead (S. altivelis) (Scorpaenidae) from the northeastern Pacific Ocean, determined by stereological and gravimetric techniques*

Fecundity was estimated for shortspine thornyhead (Sebas- tolobus alascanus) and longspine thornyhead (S. altivelis) from the northeastern Pacific Ocean. Fecun- dity was not significantly different between shortspine thornyhead off Alaska and the West Coast of the United States and is described by 0.0544 × FL 3.978 , where FL =fish fork length (cm). Fecundity was esti- mated for longspine thornyhead off the West Coast of the United States and is described by 0.8890 × FL 3.249 . Contrary to expectations for batch spawners, fecundity estimates for each species were not lower for fish collected during the spawning season compared to those collected prior to the spawning season. Stereological and gravimetric fecundity estimation techniques for shortspine thornyhead provided similar results. The stereo- logical method enabled the estimation of fecundity for samples collected ear- lier in ovarian development; however it could not be used for fecundity esti- mation in larger fish. distinguished from reserve oocytes by diameter or yolk presence (Macer, 1974). Collection date for samples is important. If samples are collected too early in oocyte development, some