Post-Haul Mortality - Live Hauling of Fish

In certain markets, live fish can be sold for substantially higher prices than fresh dressed fish. A significant live-haul industry has developed in the U.S. and fish are commonly hauled 1,500-2,000 miles (25-30 hours) to market. The most common species hauled are tilapia, channel catfish, and rainbow trout; a smaller amount of marine rockfish, hybrid striped bass, and carp are also hauled. The most significant advancement in hauling technology in the last 20 years has been the use of bottled oxygen gas or liquid oxygen to maintain adequate dissolved oxygen levels. These types of systems can maintain significantly higher DO levels than systems using air. Some common stressors include harvest and loading procedures (pumping or out of water transfer), shaking as the transport vehicle is moving, low frequency sound from the vehicle and water treatment systems, crowding, and poor water quality (high ammonia and carbon dioxide levels, low dissolved oxygen), high light levels, or extreme water temperature. The physical shape and construction of the hauling unit may have an important impact on localized low DOs, physical damage to the fish, and survivability. Very little information has been published on the chemical and physical conditions in transport systems during long-distance transport and this limited data may not be representative of current commercial systems.

This research will be conducted with NWFSC staff in cooperation with private fish farmers in the Pacific Northwest. Specific sub-objectives will include the following:

(1) Documentation of water quality during transport and impact on mortality and product quality

(2) Design of efficient aeration systems for oxygen transfer and carbon dioxide stripping

(3) Determination of the impact of transport tank design and aerator type on the thermal balance during hauling.

The impact of this project will be increased survival and product quality of transported fish as a result of adopting the recommended protocols and utilization of the models. Project outputs will include peer-reviewed publications, popular publications, and conference presentations.
Following simulated hauling, fish from individual tanks will be transferred to 4 in diameter circular tanks for observation. Mortality will be recorded daily for 7 days.