Shipping live fish by truck can potentially spread diseases and transfer unwanted plants and animals. Certain species are prohibited in some states and the unintentional transport of prohibited species is against the law.
Public agencies that purchase live fish are now specifying that shipments must be free of specific species. To avoid these environmental, legal and marketing problems, the culture, harvesting, holding, grading and loading of fish must be done very carefully.
Prevention:
Every farm should have a biosecurity plan and conduct regular inspections for diseases and nuisance species. One important biosecurity measure is to wash and disinfect hauling trucks and tanks before returning to the farm.
When ponds are inspected regularly, unwanted plants or fish can be detected in the early stages of an invasion while it is still relatively easy to eradicate them.
A good guideline for fish farmers who ship live fish is the Arkansas Offcial Standards for the Certification of Commercial Bait and Ornamental Fish (Arkansas State Plant Board, 2007).
To participate in this program, farmers must follow a biosecurity plan; pay for a comprehensive, twice-yearly farm-level disease inspection program; and allow state inspectors to review fish health records and check vats and pond facilities for specific nonindigenous species.
Keeping diseases and problem species off the farm is the first step in keeping them from hitchhiking along with fish shipments.
Harvesting:
Most problems with hitchhiking species occur when fish are harvested and loaded directly onto a hauling truck without passing through holding vats. Often a farmer first becomes aware of an unwanted species during harvest.
For example, shad may show up in the seine along with catfish. If the catfish are bound for a nearby processing plant, this is probably not a concern. But if the catfish are live-hauled to stock a fishing lake, the shad would be a very unwelcome addition. It is essential for the farmer and the live hauler to inspect the fish in the net before loading.
Unwanted fish will need to be carefully hand-sorted by the seine crew, a diffcult task on commercial farms where thousands of pounds of fish are harvested at a time. Assign specific employees the responsibility to watch for and remove unwanted species.
The employee who empties the loading net into the hauling tank should also inspect each load to make sure that it is free of unwanted species. Depending on the intended market, it may be necessary to take the load to a holding shed first and sort through the fish to remove the unwanted species, although this is not practical or possible in many cases.
Holding, grading and sorting:
Some fish crops, such as baitfish, are routinely taken to holding sheds for purging, acclimation and grading. Once fish are in holding vats, they are easy to inspect for unwanted species. Plant fragments and some unwanted animals can be hand-picked. Grading removes unwanted organisms that are smaller or larger than fish of the desired species.
A strong flow of water sometimes sweeps unwanted species to the end of a vat for easy removal. Some tadpole species congregate in corners at the bottom of the vat and can be siphoned out with a hose.
Treatments:
Fish producers who use surface water that might contain zebra (Dreissena polymorpha) or quagga (Dreissena rostriformis bugensis) mussels (hereafter, dreissenid mussels) are in danger of shipping mussel larvae (veligers) along with their fish.
If fish are held in vats flushed with well water before shipment, the chance of including dreissenid mussel veligers in fish shipments is reduced but not eliminated.
A treatment protocol (Edwards et al., 2002) consisting of a 1-hour treatment with 750 mg/L of potassium chloride (KCl) followed by a 2-hour treatment of formalin at 25 mg/L effectively killed all of the veligers but not the fish species tested (walleye, Sander vitreus, and saugeye, Sander canadensis).
Adding 0.5% salt (NaCl) to reduce fish stress reduced the effectiveness of the treatment and left veligers alive, so this treatment is likely to be ineffective on farms with naturally salty water. Before using this treatment for other fish species and temperatures, contact your Extension fisheries specialist or another fish health professional.
It is essential to conduct preliminary trials with small numbers of the cultured fish species to make sure the treatment will not harm them. Two studies have shown that standard formalin treatments will also selectively kill tadpoles, although the effcacy varies with the species of frog.
Treatment of largemouth bass (Micropterus salmoides) fingerlings with 60 ppm of formalin for 24 hours killed all of the tadpoles but not the bass. A 1-hour exposure to 250 ppm of formalin also killed all of the tadpoles.
This is similar to the disease treatments used for some fish species. Formalin toxicity varies with fish species, temperature and pH (Helms, 1967; Carmichael and Tomasso, 1983).
Shipping:
Exchanging water in hauling tanks is often necessary during extended trips. Water exchange on long trips should be from groundwater sources only. Do not add water from any surface source because it might transmit a disease or contain unwanted organisms.
Using well water for exchange may be problematic during times of the year when well water temperatures are very different from the temperature of water in the hauling tanks.
Turnbacks:
What happens if you ship a load of fish to a buyer and you are not able to sell the fish? Maybe the buyer changed his mind, the quality was poor, or the check bounced. If any of your fish have touched someone else’s facilities, or even if the customer just stuck a dip net into a hole of your tank to look at the fish, then the returned fish must not be mingled with the rest of the fish on your farm.
Authors:
Paul W. Zajicek, Jeffrey E. Hill, Nathan Stone, Hugh Thomforde, Cortney Ohs,
Diane Cooper, Gef Flimlin, Brad McLane and William D. Anderson
