Water quality

Water Quality

Water quality is critical and by necessity one of the prime site selection criteria. Minimum and maximum acceptable water quality parameters are discussed elsewhere. Problems can develop in applying the given criteria. Water quality parameters can vary considerably on a seasonal basis, particularly salinity and temperature. Some local recreational, industrial, or agricultural activities of potential concern may be very seasonal in nature. Water quality measurements should be taken throughout the year. If the potential hatchery site is near rivers, the impact of runoff on salinity must be carefully assessed. Runoff can carry agricultural and industrial contaminants. Contamination discharges may not be visible for parts of the year. If the site is located close to present or prior industrial and agricultural activities, heavy metals and pesticide analysis may be required. Water quality conditions within the hatchery system can also change due to seasonal weather factors. Dry winds and elevated temperatures can produce high evaporation rates, particularly in outdoor maturation and nursery ponds. Incoming seawater salinity is likely to be highest under these conditions and may exceed acceptable limits. Many potential sites with good marine water quality have been rejected because of the unavailability of freshwater needed for salinity control during the dry season. Larval shrimp bioassays can help detect unforeseen water quality problems (Colt & Huguenin, 1992).