Comparison of water quality in live shellfish retail holding tanks

Abstract

Background: Water quality in live retail shellfish holding tanks are vital in increasing shellfish quality and reducing risk of shellfish-associated outbreaks. Poor holding tank water conditions may not only cause mortality of shellfish, but also allow for harmful pathogens to contaminate the shellfish, proliferate in the holding tanks, and ultimately potentially affect consumer health. Shellfish are processed and handled at a variety of levels at the retail stage. Therefore, the purpose of this research project is to compare water quality in live retail shellfish holding systems between processing plants and retail food markets. Differences may indicate a need for attention at a particular level in order to effectively and efficiently reduce mortality and disease among shellfish, and thus potentially humans as well. Methods: 30 water samples were taken from the two types of locations with the help of the Department of Fisheries and Oceans (DFO), Ministry of Agriculture, and the BCCDC. These samples were tested for parameters including temperature, pH, nitrites, turbidity, and dissolved oxygen using a LaMotte Fresh Water Aquaculture Kit and a HACH 2100P turbidimeter. A two-tailed t-test was used to compare the means of each of the parameters among the two types of locations with live shellfish holding tanks. Results: The mean values for all parameters in both retail and processing met the requirements set by the BCCDC. However, temperature and dissolved oxygen showed statistically significant differences between retail markets and processing facilities. Nitrites, pH, and turbidity showed no statistically significant differences between the two types of locations. Conclusion: Differences in dissolved oxygen may have been due to salt levels, failing recirculation systems, or high levels of organic matter from sanitation issues. Differences in temperature may have been due to differences in holding tank size, or inconsistencies from using two different thermal measuring devices. High levels of nitrites were a concern as well due to overcrowding of holding tanks. More attention may be needed for these issues, especially during certain seasons such as Chinese New Years, in order to lower the risk to public health.