Live feeds production continues to be one of the primary constraints to marine finfish aquaculture. Since most marine finfish species require live prey at first feeding, the efficient production of suitable live feeds (quantity, size, and nutritional content) continues to limit commercial-scale production. This limitation is even more significant with species that require copepods as primary prey. Although copepods can significantly improve growth and larval survival in many marine fish species, their inherent production challenges have resulted in limited integration into most commercial-scale rearing protocols.
Over the past decade, Oceanic Institute (OI) overcame many of those challenges and has developed intensive, large-scale copepod production technologies capable of exceeding 100 million nauplii per day. These copepods have been used to successfully rear several coral reef fish species, such as coral grouper, blue-fin trevally, red snapper, flame angelfish and yellow tang. Additionally, fish species that haven’t previously required copepods (such as pacific threadfin and mullet) have shown increased survival when copepods were integrated into their culture protocols. However, notwithstanding our recent advances in production methods, the mass production of copepod nauplii is still fundamentally limited due to their inherent biological tendency to produce less nauplii at high adult densities. Specifically, culture densities > 4 adults/mL yield < 5 nauplii per female per day, whereas culture densities < 2 adults/mL yield much greater nauplii production (i.e. > 15 nauplii per female per day). Due to this biological limitation, copepods are currently cultured at low densities (i.e. 1-2 adults/mL) in an effort to produce adequate nauplii for hatchery needs. These low-density, high-volume cultures are labor intensive and relatively costly to maintain, and these restrictions represent a significant obstacle to large-scale copepod production.
One study recently showed that copepods can be selectively bred for increased fecundity, with substantial gains obtained in just a few generations (25% increase in total lifetime egg production within 6 generations of selection). The current study seeks to determine if similar performance gains can be realized when selectively breeding for copepods which remain reproductive at high adult density. If culture density can be increased without negatively impacting reproductive performance or physical characteristics of the copepods, significant production efficiencies can be realized whereby more copepod nauplii can be produced while occupying the same footprint and utilizing the same amount of labor. It is conceivable that this type of significant improvement to large-scale production of nauplii would rapidly advance the commercial-scale application of this technology. If this project objectives are achieved, current capacity of marine fish hatcheries will drastically increase, which ultimately will lead to significant gains in the number of successfully reared fish larvae. Results of the completed project will be presented at the conference.