Image credit: FAO
Review: Abdel Rahman El Gamal (Founder of the website)
Unlike many fish species, African catfish males (Clarias gariepinus) –for anatomical features- do not release sperm under abdominal massage after treatment with hormones. Instead, males are sacrificed, opened, and testes are removed out of the abdomen and squeezed to release the milt as required for egg fertilization.
As a consequence, for each sacrificed male, a new male broodstock needs to be added to make-up the deficit in male population. When the size of the founder stock is barely sufficient to start with and cannot afford losing a male specimen after another, this issue would be a problem. Similarly, in selective breeding programs and is specific genetic studies, the use of the same male is repeated and needs to go beyond a single use.
Research initiatives have been conducted to save catfish males rather than sacrificing them. These initiatives include the use of a 2-ml syringe with needle to draw some sperm through a small incision in the belly of tranquilized males. Also, the partial ablation of male testes has been promoted to save males and has probably attracted researchers more.
The ablation of testes is done through the removal of about three quarter of the testes to be used as usual in egg fertilization. The healing of the incision point in African catfish occurs within about 14 days post-surgery. The regeneration of removed testis, and so the subsequent use of the same male may take about 45 days post-surgery implying the possibility of several re-uses of the same male depending on temperature and other husbandry practices bearing in mind that proper feeding should be ensured after ablation in order to hasten the development of the gonads.
In all situations where incisions are operated, the wound is stitched using veterinary stitching material and the operation is done while male is properly anesthetized.
It may worth noting that the adaption of “saving a male” approach would depend on educational level of hatchery operators and would be also influenced by the abundance of male broodstock bearing in mind that if a continuous supply of male broodstock is easy, commercial producers most likely would continue sacrificing males rather than putting extra efforts trying to save them.