Minimizing time fed rotifers maximizes hybrid striped bass larval growth in recirculating aquaculture systems

Authors: Fuller, Adam

Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2020
Publication Date: 4/23/2020
Publication URL: https://handle.nal.usda.gov/10113/7019797
Citation: Fuller, S.A. 2020. Minimizing time fed rotifers maximizes hybrid striped bass larval growth in recirculating aquaculture systems. North American Journal of Aquaculture. 80:208-214. https://doi.org/10.1002/naaq.10146.
DOI: https://doi.org/10.1002/naaq.10146

Interpretive Summary: Hybrid striped bass (HSB) represent a valuable sector of the U.S. aquaculture industry. Despite their commercial importance, one factor limiting the growth of the HSB industry is the lack of refined methods to rear larvae in tanks, including the lack of knowledge about optimal rearing conditions, feeding behavior, and efforts to reduce the time larvae spend utilizing live foods, especially rotifers. The rotifer culture stage of freshwater and marine larviculture remains the most resource and experience intensive portion of tank culture larviculture operations, including significant time, equipment, space, supplies, as well as expertise requirements. Therefore, goals of this study were to determine the earliest time HSB larvae could be weaned off of rotifers and onto Artemia nauplii at an optimum (26 deg C) and suboptimum (18 deg C) culture temperature and compare total length and survival of the resulting larvae. There was no difference in survival in HSB larvae based on how many days they were fed rotifers at either 18 deg C or 26 deg C. However, there was a difference in larval survival between the two rearing temperatures. At the end of the study, larvae from the 18 deg C system were shorter (8.00 mm) than those reared in the 26 deg C system (9.59 mm), and total length and body depth of larvae varied significantly (P<0.0001) among treatments by temperature, the number of days they were fed rotifers, and the interaction of temperature and the days they were fed rotifers. These results demonstrate that minimizing time larvae were fed rotifers maximized growth. This study also showed that Artemia is a suitable diet for six-day-old larval HSB and that these larvae can easily be weaned from rotifers at both optimum (26 deg C) and sub-optimum culture temperature (18 deg C) while maintaining suitable growth and with no significant drop in survival. Research is needed to determine the appropriate amount of time HSB need to be fed Artemia nauplii as well in order to minimize the time HSB are required to be on live feeds in order to wean to a dry diet more quickly while optimizing growth and survival.

Technical Abstract: Hybrid striped bass (HSB) Morone chrysops x M. saxatilis represent a valuable sector of the U.S. aquaculture industry. Despite their commercial importance, one factor limiting the growth of the HSB industry is the lack of refined methods to rear larvae in tanks, including the lack of knowledge about optimal rearing conditions, feeding behavior, and efforts to reduce the time larvae spend utilizing live foods. Four-day-old HSB larvae were stocked into two recirculating aquaculture systems (72.0-73.9 larvae/L) maintained at 18 deg C and 26 deg C. Larvae were fed three times daily with either rotifers (60 rotifers/mL/tank/d) or Artemia (12 /mL/tank/d) according to the designated replicated treatment for 2 to 12 days in 2-day increments where larvae were progressively weaned from rotifers onto Artemia. The number of days fed rotifers (DFR) had no significant effect (P=0.3987) on survival of larvae reared at either 18 deg C (46.6%) or 26 deg C (30.2%). However, there was a difference in larval survival between the two temperatures (P<0.0001). At the end of the study, larvae from the 18°C system were shorter (8.00 mm TL) than those reared in the 26 deg C system (9.59 mm TL), and total length and body depth of larvae varied significantly (P<0.0001) among treatments by temperature, DFR, and their interaction. These results demonstrate that minimizing time spent feeding on rotifers maximized growth of HSB larvae. This also indicates that Artemia is a suitable diet for six-day-old larval HSB and that the fish can easily be weaned from rotifers at both optimum (26 deg C) and sub-optimum culture temperature (18 deg C) while maintaining suitable growth. Notably, this was achieved with no significant drop in survival. Additional research is needed to optimize Artemia nauplii feeding regimes to minimize the time HSB are required to be on live feeds in order to wean to a dry diet more quickly while optimizing growth and survival.