Resource Ecology & Ecosystem Modeling (REEM) Program

Sculpin Reproduction and Maturity

The images below are photomicrographs of yellow Irish lord ovaries histological cross-sections stained with haematoxylin and eosin.  Note: Post-ovulatory follicles stage or a “spent” stage absent from initial sample collection. early perinuclear stage late perinuclear

Approximately 500 ovary samples have been processed, spanning all five sculpin species mentioned above. Histological preparation has been initiated by a laboratory contractor. Analysis is under way on samples received to assess maturity stage.

Based on a review of the histology of about 275 yellow Irish lord ovary samples collected during the months of June and July, several stages exist. It appears that the spawning period may begin in mid-July/early August for both the eastern Bering Sea and Aleutian Islands regions. The length of the spawning period is still under investigation, as more samples will need to be collected around this time period. Length and age-at-maturity (first, 50%, and 100%) estimates will be available for the yellow Irish lord after final processing of the 2006 and 2007 survey samples.

A greater sample size is needed for other sculpin species to assess maturity. Observations from samples collected during the summer indicate that ovaries are in a resting or spent stage for the Myoxocephalus sculpins. These observations were validated through a review of histology. A few great sculpin ovaries (from specimens > 55 cm) collected in late January-early March 2007 by observers in the eastern Bering Sea were large and full of eggs, indicating a possible winter spawning period. Ovary stages of bigmouth sculpin are still being reviewed. Fecundity will be investigated later this year for selected species.

By Todd TenBrink

 

early vitellogenesis oocyte

vitellogenesis or advanced yolk oocyte with migratory nucleus

vitellogenesis oocyte near hydration, nucleus has disappeared, yolk nearly fused throughout oocyte