Enhancing fertility of the marine copepod Bestiolina amoyensis via multi-generational selective breeding

Copepods are a group of marine plankton that play an essential role in the energy transfer within marine ecosystems. They serve as vital prey for the larvae of numerous economically important fish, shrimp, and crabs species. Bestiolina amoyensis, a copepod species inhabiting nearshore warm waters, possesses numerous commercial advantages for aquaculture due to its small size, rapid reproduction, and strong adaptability, that make it well-suited for use as live prey in aquaculture systems. In this study, a breeding program targeting high fertility was designed and implemented. Fifty pairs of adult B. amoyensis were randomly selected to establish the base population (G0), with the total egg production used as the breeding index. In the selected group, offspring from maternal lines that ranked in the top 30% for total egg production were selected and eggs laid on the 4^th day by these selected pairs were used to establish breeding pairs for subsequent generations. In the control group, breeding pairs were established by randomly mating offspring of the G0 population. The selection procedure was repeated for five consecutive generations, with consistent selection criteria maintained only for the selected group. Additionally, the stability of selection effect was investigated by tracking both groups for an another 5, 10, 15 generations after the termination of artificial selection. After five generations of selection, the selected group showed a significant increase in total egg production, whereas no significant change was observed in the control group. By the fifth generation (G5), the selected group exhibited a 23.99% increase in total egg production compared with the control group, with a heritability (h²) of 0.46 ± 0.11. At the G5 generation, the population densities of the selected and control groups were 9075.00 ± 193.18 ind/L and 7200.33 ± 249.18 ind/L, respectively. After rearing for another 5, 10, and 15 generations without selection, the total egg production of the selected groups was 167.50 ± 2.47 eggs/female, 164.23 ± 2.46 eggs/female and 158.23 ± 3.14 eggs/female, respectively, indicating a gradual decrease. However, the selected group maintained significantly higher egg production than the control group (p < 0.05). The results demonstrate that the reproductive capacity of B. amoyensis can be enhanced through continuous selection, providing technical support for the large-scale and high-density cultivation of this copepod species.