Addressing larval rearing challenges for Eastern oyster (Crassostrea virginica) aquaculture requires replicated studies. Small-scale systems are useful for replication; however, most studies use live algae and, to our knowledge, have not compared performance to large-scale systems. To that end, the objective of this study was to optimize small-scale system production fed with algae concentrate. We tested a variety of aeration techniques (see Table) in small-scale, 17 L bucket systems. Control systems were 4000-L or 1000-L tanks (Fig. 1). Water quality was monitored, and larvae were counted volumetrically and measured for 14 days. Survival, growth, and percent set were compared among treatments and across time.
During trial 1, production requirements prohibited running replicated controls; however, bucket-reared larvae started setting at Day 10, with no differences between aeration treatments. Slow growth and high mortalities plagued all treatments in Trial 2. During Trial 3, bucket-reared larvae grew significantly faster than controls, with the 1 mL air injector and 2-inch airlift suffering fewer mortalities. In Trial 4, control larvae were larger than all bucket larvae at Day 10 and produced more setters by Day 14 than the 1 mL air injector and the no aeration treatment. We hypothesize this was due to lower nighttime temperatures than previous trials. However, all buckets had fewer mortalities than the control tanks.
This study indicates that performance of small-scale systems using algae concentrate are therefore feasible for replicated larval studies. These systems and the algae concentrate are inexpensive and simple to maintain and may provide demonstration opportunities for schools or individuals interested in hatchery management. Due to the simplicity of these systems, further adjustments can easily be made to improve growth, survival, and set rate of larval oysters.