Sperm Quality of Pond‐Reared and Wild‐Caught Penaeus monodon in Thailand 1

Sperm quality, as determined by visual examination and by reaction with “egg‐water” was not significantly different ( P > 0.05) for sperm obtained by electro‐ejaculation from ablated or non‐ablated pond‐reared Penaeus monodon . Nor was sperm quality different between pond‐reared and wild‐caught prawns. Normal sperm, determined by appearance, ranged from 17.1 to 21.0%, while reactive sperm ranged from 1.5 to 3.0%. There were, however, significant correlations ( P < 0.01) between spermatophore weight and prawn weight ( r = 0.73, N = 434). Male prawns weighing 4150 g produced on average spermatophores weighing 22.7 mg and containing 0.8 million sperm, while prawns weighing 61‐90 g produced on average spermatophores weighing 56.6 mg with 2.5 million sperm. Ablation did not increase spermatophore size or sperm quality, although it significantly increased mortality of ablated males. Male prawns could be re‐ejaculated at about weekly intervals with no change in sperm quality. Wild‐caught female prawns artificially inseminated with spermatophores from electro‐ejaculated males produced normal spawns with 51% average egg fertilization, and 41% nauplii hatch success. Nauplii hatch success following spawning increased from >60% for newly inseminated females to near zero after 30 days post‐insemination, indicating spermatophore depletion and/or deteriorated sperm quality during spermatophore storage in the thelycum. The findings of the present study indicate that electro‐ejaculation and artificial insemination are relatively simple and practical methods for improving captive reproduction performance of closed‐thelycum prawns such as P. monodon , and that pond‐reared and wild‐caught males produced sperm of similar quality.