Non-invasive method for collection of Clarias magur (Hamilton, 1822) spermatozoa: A novel approach for catfish domestication, aquaculture and conservation

Abstract

The current practice of captive breeding of Clarias magur involves killing male fish to obtain sperm for fertilisation. The sperm cannot be obtained by hand stripping because of the extremely low volume of seminal fluid in the testis. This sacrificial method of seed production has been applied to most catfish species. In this study, we reported an alternative approach that allowed harvesting of C. magur spermatozoa for artificial fertilisation without sacrificing male fish. Sexually mature C. magur males were anaesthetised and placed on the surgery table. A midline incision of 2.5 cm was made on the abdomen, and the testicular lobes were carefully lifted from the coelomic cavity. Using sterilised scissors and forceps, the testicular tissue was partially harvested, weighed to nearest 0.01 g, and macerated using a mortar and pestle in physiological saline. The abdominal incision was stitched using a surgical thread and topically treated with antimycotic ointment; subsequently, the fish were resuscitated in clean oxygenated water. Using the surgical technique, we harvested a maximum of 283 mg of testicular tissue, which corresponded to a count of 9.0 × 108 spermatozoa/mL, from a male fish weighing 210 g. By using the sacrificial approach, a maximum of 500 mg of testicular tissue, corresponding to a count of 16.0 × 108 spermatozoa/mL, was recovered from a male fish weighing 220 g. The surgically obtained spermatozoa were used to inseminate C. magur eggs; the cross resulted in healthy spawn with a fertilisation rate of 80%–98%. The results were similar to those obtained using the conventional sacrificial approach, which indicated the viability of partial surgical harvest of testicular tissue in seed production in C. magur for aquaculture without sacrificing male fish.