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Evaluation of partial water reuse systems used for Atlantic salmon smolt production at the White River National Fish Hatchery

Summerfelt, S. T., Sharrer, M., Gearheart, M., Gillette, K., Vinci, B. J.
Aquacultural engineering 2009 v.41 no.2 pp. 78
Salmo salar, ammonium nitrogen, aquaculture tanks, body length, carbon dioxide, dissolved oxygen, feed conversion, fish culture, fish production, hatcheries, parr, raceways, river water, rivers, salmon, smolts, total suspended solids, water flow, water quality, water reuse, water temperature, Vermont
Eight of the existing 9.1 m(30 ft) diameter circular culture tanks at theWhite River National Fish Hatchery in Bethel, Vermont, were retrofitted and plumbed into two 8000 L/min partial water reuse systems to help meet the region’s need for Atlantic salmon (Salmo salar) smolt production. The partial reuse systems were designed to increase fish production on a limited but biosecure water resource, maintain excellent water quality, and provide more optimum swimming speeds for salmonids than those provided in traditional single-pass or serial-reuse raceways. The two systems were stocked with a total of 147,840 Atlantic salmon parr in May of 2005 (mean size 89 mm and 8.5 g/fish) and operated with 87–89% water reuse on a flow basis. By the time that the smolt were removed from the systems between March 28 to April 12, 2006, the salmon smolt had reached a mean size of 24 cm and 137 g and hatchery staff considered the quality of the salmon to be exceptional. Overall feed conversion was <1:1. The Cornell-type dual-drain circular culture tanks were found to be self-cleaning and provided mean water rotational velocities that ranged from a low of 0.034 m/s (0.2 body length per second) near the center of the tank to a high of 39 cm/s (2.2 body length per second) near the perimeter of the tank. The fish swam at approximately the same speed as the water rotated. System water quality data were collected in mid-September when the systems were operated at near full loading, i.e., 24 kg/m3 maximum density and 52.1 and 44.1 kg/day of feed in system A and system B, respectively. During this evaluation, afternoon water temperatures, as well as dissolved oxygen (O2), carbon dioxide (CO2), total ammonia nitrogen (TAN), and total suspended solids (TSS) concentrations that exited the culture tank’s sidewall drains averaged 14.8 and 15.9 8C, of 7.9 and 8.2 mg/L (O2), 4.0 and 3.2 mg/ L (CO2), 0.72 and 0.67 mg/L (TAN), and 0.52 and 0.13 mg/L (TSS), respectively, in system A and system B. Dissolved O2 was fairly uniform across each culture tank. In addition, water temperature varied diurnally and seasonally in a distinct pattern that corresponded to water temperature fluctuations in the nearby river water, as planned. This work demonstrates that partial reuse systems are an effective alternative to traditional single-pass systems and serial-reuse raceway systems for culture of fish intended for endangered species restoration programs and supplementation programs such as salmon smolt.