Water Quality in Tilapia Transport: From the Farm to the Retail Store

Abstract

Nile tilapia Oreochromis niloticus are routinely transported 1,200–1,400 km from Idaho to live markets in the greater Vancouver, British Columbia, area. Direct hauling mortality is typically very low, but significant economic losses occur during retail holding owing to a deterioration in physical appearance that results in fish that cannot be sold and their subsequent mortality. To address this problem, information was collected on hauling systems and protocols, holding systems and water management protocols, and water quality in the retail holding systems. During hauling, fish are exposed to high levels of dissolved oxygen, carbon dioxide, and bacteria. The transfer of fish from hauling systems to retail holding systems can subject them to rapid changes in temperature, dissolved oxygen, carbon dioxide, and pH. Problem areas in retail holding include low water temperatures, high un-ionized ammonia concentrations, and elevated levels of gas supersaturation. Determination of the causes of high mortality in transportation and retail holding is difficult to clearly identify because of sampling difficulties and commercial restrictions; improvements in hauling protocols may depend on simulated hauling experiments followed by commercial verification.

Received November 8, 2010; accepted March 21, 2011

ACKNOWLEDGMENTS

This project was supported by Western Regional Aquaculture Center Grant2008–38500–19230 from the U.S. Department of Agriculture Cooperative State Research, Education, and Extension Service (now the National Institute for Food and Agriculture).

Notes

^aBased on flatbed truck only; last delivery from semitrailer truck not observed.

^bStandard flow in liters per minute (1 atmosphere and 21°C).

^aThe variables pH, conductivity, dissolved oxygen, and temperature were measured continuously from approximately 1600 to 0800 hours; the measurements for the other variables are based on single grab samples during the daytime.

^bFarm C supplies fish to farm B for hauling.

^cFarm D does not routinely supply tilapia to the live market.