RAUL H. PIEDRAHITA, Professor

Ph.D., Agricultural Engineering, University of California, Davis, 1984
Department of Biological and Agricultural Engineering
3056 Bainer Hall
Phone: 530-752-2780
Email: rhpiedrahita@ucdavis.edu

Current Research 

Professor Piedrahita's research interest is in the area of aquaculture, with an emphasis on water quality. Projects include the development of procedures and hardware for monitoring and treating water in aquaculture, and the creation of computer models of aquaculture production systems.

Aquaculture operations are receiving increased attention from the public and from regulatory agencies concerned with the potential environmental impact of effluents and land use changes. This attention adds a new dimension to long standing modeling work carried out at UC Davis. Models developed for the simulation of water quality and fish production in pond and tank systems, flow trough and recirculation, are also being used to investigate potential effluent water quality and ways of optimizing water recirculation systems to reduce the consumption of water.

Much of the organic matter in aquaculture waters is in the form of suspended solids. Techniques for solids removal are important both in water recirculation and in effluent treatment. Compared to conventional waste waters, aquaculture waters tend to have relatively low solids concentrations and high flow rates, making many of the techniques developed for other industries and for municipal waste waters impractical and uneconomical. In a project involving industrial and research collaborators, solids removal technologies utilized by the aquaculture industry in the Western States were evaluated for their effectiveness in improving the quality of effluents by reducing organic and phosphorus loads.

The focus of a recent project was the development of recirculation technologies and general culture and nutrition information for the California halibut. Culture techniques were developed for larvae through growout. An important aspect of the project was obtaining bioengineering data for this species, including rates of oxygen consumption and ammonia production, morphology, and allowable stocking densities and water velocities. The existence of regions of substantial oxygen depletion in the areas where the fish congregate on tank bottoms was documented, a finding that has important implications for tank design for this species and other flatfish.

A research network has been established with colleagues in France and Norway to study different aspects of carbon dioxide in aquaculture systems. Areas of interest to the group include the evaluation and standardization of practical carbon dioxide measurement methods for use in aquaculture, the physiological impact on fish of elevated carbon dioxide concentrations and the development of improved methods for carbon dioxide control in recirculation systems.

Representative Recent Publications

Jamu, D. M., and R. H. Piedrahita. 2002. An organic matter and nitrogen dynamics model for the ecological analysis of integrated aquaculture/agriculture systems. I. Model development and calibration. Environmental Modelling and Software 17:571-582.

Jamu, D. M., and R. H. Piedrahita. 2002. An organic matter and nitrogen dynamics model for the ecological analysis of integrated aquaculture/agriculture systems. II. Model evaluation and application. Environmental Modelling and Software 17:583-592.

Wong, K. B., and R. H. Piedrahita. 2003. Prototype testing of the appurtenance for settleable solids in-raceway separation (ASSIST). Aquacultural Engineering 27:273-293.

Conklin, D. E., R. H. Piedrahita, G. E. Merino, J. B. Muguet, D. E. Bush, E. Gisbert, J. Rounds, and M. Cervantes-Trujano. 2003. Development of California halibut, Paralichthys californicus, culture. Journal of Applied Aquaculture 14:143-154.

Huggins, D. L., R. H. Piedrahita, and T. Rumsey. 2004. Analysis of sediment transport modeling using computational fluid dynamics (CFD) for aquaculture raceways. Aquacultural Engineering 31:277-293.

Schrader, K. K., S. Acuña-Rubio, R. H. Piedrahita, and A. M. Rimando. 2005. Geosmin and 2-methylisoborneol cause off-flavors in cultured largemouth bass and white sturgeon reared in recirculating-water systems. North American Journal of Aquaculture 6:177-180.

Membership in Professional Societies

American Society for Agricultural and Biological Engineering
Aquacultural Engineering Society
World Aquaculture Society
US Chapter of the World Aquaculture Society
Latin American Chapter of the World Aquaculture Society

Courses Offered

ABT 161 - Water Quality Management for Aquaculture
ABT 163 - Aquaculture Systems Engineering
EBS 1 - Foundations of Biological Systems Engineering
EBS 220 - Pilot Plant Operations in Aquacultural Engineering
IAD 203N -

Research Support

California Sea Grant College Program
Western Regional Aquaculture Center (USDA)
California Department of Water Resources