Oocyte maturation and ovulation in the Atlantic halibut, Hippoglossus hippoglossus (L.), examined using ultrasonography |
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| Authors: | R J SHIELDS J DAVENPORT C YOUNG P L SMITH |
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| Institution: | Sea fish Industry Authority, Marine Farming Unit, Ardtoe, Acharacle, Argyll, Scotland.;University Marine Biology Station, Millport, Isle of Cumbrae, Scotland.;Sea Fish Industry Authority, Marine Farming Unit, Ardtoe, Acharacle, Argyll, Scotland. |
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| Abstract: | High resolution ultrasound scanning was tested as a non-invasive technique for monitoring oocyte maturation and ovulalion in the Atlantic halibut Hippoglossus hippoglossus (L.). Female broodstock halibut were examined using a 7.5-Mhz linear ultrasound transducer, prior to and during spawning. Representative images of halibut ovaries are presented and discussed. Individual oocytes of spawning females were discernible during oocyte final maturation, due to the large increase in volume caused by water uptake. The yolky (vitellogenic) cocytes of pre-spawning fish were more reflective to ultrasound than hydrating oocytes. The resulting differences in depth of ultrasound penetration permitted easy distinction of pre-spawning from spawning females. In addition, short-term changes in the depth of ultrasound penetration were observed during repeated scanning of a spawning female, owing to progressive hydration of the oocyte batch destined for ovulation. Although of similar diameter, hydrating oocytes in the ovarian tissue could be discerned from eggs in the ovarian lumen because of the different acoustic properties of the surrounding media. The findings of the present study are considered promising for the future routine use of ultrasonography in halibut broodstock management. |
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