Constraints on seedstock production in eighth generation domesticated Penaeus monodon broodstock

• Identified the key constraints on reproduction in eighth generation Penaeus monodon.
• Inferior reproductive performance exclusively linked to the females.
• Highlights the reproductive parameters that need improvement.

Improving the seedstock production of domesticated broodstock remains a high priority for the black tiger shrimp, Penaeus monodon, farming industry in Australia and other shrimp farming regions. In this study, wild-caught (W) broodstock were reciprocally crossed with eighth generation (domesticated-selected) broodstock (G8) and the reproductive performance was evaluated to identify the key parameters and gender influences currently constraining seedstock production from domesticated broodstock. Nauplii production was significantly lower in G8 than W broodstock and differences in nauplii production were found to be more influenced by the female than the male origin of the broodstock. The main constraints on nauplii production in G8 females were inferior egg hatch rates and egg production. The percentage of eggs that hatched was 44% lower in G8 females (24.3%) than W females (43.7%). The total number of eggs per spawning was 25% lower in G8 females (413,000) than W females (552,000) and the relative number of eggs spawned per gram female body weight was 37% lower in G8 females (2476) than W females (3909). In addition, a significantly higher percentage of the W females (70.8 ± 5.7%) matured to ovary stage 4 than G8 females (2.1 ± 2.1%). But there was no difference in the percentage of females that developed stage 3 ovaries or the percentage of females that spawned. There was no difference in the total number of sperm per spermatophore or sperm quality (based on acrosome reaction) between W and G8 males, which may explain the lack of any male effect on fertilization. Our results suggest that female broodstock quality may often explain the low nauplii output of domesticated broodstock.