A Low-Volume Flow-Through System for Rearing Pacific Oyster (Crassostrea gigas) Larvae

• Main Author: Fleener, Henry R.
• Other Authors: Langdon, Chris J., Thompson, Neil F., Waldbusser, George G., Milligan, Allen J., Fisheries, Wildlife, and Conservation Sciences, Oregon State University. Agricultural Experiment Station, Hatfield Marine Science Center
• Format: Master Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Crassostrea gigas; Pacific oyster
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/ft848z70b

Standard larval Pacific oyster (Crassostrea gigas) rearing systems can be described as either static or continuous flow. While rearing oyster larvae in static cultures can be a low-cost and simple method, static systems require significant husbandry effort, floorspace and can produce highly variable results due to environmental variance among cultures. As an alternative to static cultures, a low-volume, flow-through system was developed by modifying McDonald-style hatching jars to: 1) reduce floorspace needs for culturing larvae, 2) decrease labor by requiring fewer sieving and cleaning events, 3) reduce variability among replicates due to environmental effects, and 4) produce large numbers of spat per tank to increase capabilities of both commercial and research hatcheries. This flow-through system was named the Hatfield Ultra Density Larval System (HUDLS) and was based on the Cawthron Ultra Density Larval System (CUDLS) developed by the Cawthron Institute, New Zealand. HUDLS is fully comprised of off-the-shelf and 3D printed parts, using low-volume rearing tubes (4.3 L) with high exchange rates (24 day⁻¹). Multiple concentrations of microalgae used to feed the larvae were tested with targeted HUDLS outflow microalgae densities of 1K, 10K, 20K, 40K, and 80K cells mL⁻¹. An outflow algal density of 10K cells mL⁻¹ resulted in a significantly higher total number of spat produced per HUDLS tube (76,750 ± 9,877) than with other outflow algal densities. Initial larval stocking densities of larvae at 20, 40, 80, 160, and 320 larvae mL⁻¹ were also tested. While an initial stocking density of 160 larvae mL⁻¹ resulted in the highest mean spat yield (163,045 ± 78,341), there was a strong positive correlation between initial larval stocking density and the percent coefficient of variation (CV) among replicates (R2 = 0.909, p = 0.012), indicating higher variability in larval performance at higher larval stocking densities. Once the HUDLS was optimized, a final experiment was undertaken whereby larval performance of three ...