SRAC Publication No. 390

June, 1990

SouthernRegionalAquacultureCenter

Transportation of Warmwater FishEquipment and Guidelines

Gary L. Jensen’

Fish transport is often the finalstep in production. Most laborand production costs have al-ready occurred, and any fish lossfrom death or injury, at thisstage, severely affects the profitmargin. Most fish losses fromhauling are the result of the ac-tivation of latent disease or-ganisms or osmoregulatoryproblems. Poor water quality,overcrowding and impropertempering cause serious fish los-ses. The ultimate goal is to pro-vide healthy fish that surviveafter stocking.

Water quality

Water quality is an importantfactor to manage while fish arecrowded and stressed in hauling.The major parameters that limitthe loading density of fish areadequate oxygen levels and buil-dup of toxic waste products suchas ammonia and carbon dioxide.Temperature, pH, loading den-sity and trip duration affect theseverity of these problems.

A suitable water supply isneeded for short-term holdingand hauling. Cool, uncon-taminated well water is

preferred. Oxygenate well waterthoroughly before it is used inthe transport tank to removecarbon dioxide and add dissolvedoxygen. Beware of high levels ofammonia and iron that can occurin well water. Ammonia can beremoved by aging water in atank, and iron can be removed byaerating water before use.

Pond water is less desirable be-cause it often has a heavy algaebloom and other organisms thatremove oxygen from the waterand produce ammonia as a wasteproduct. Pond water also is morelikely to have harmful fishpathogens than well or springwater. Clear pond water withouta heavy algae bloom can be usedfor short trips. Special care is

Custom designed transport truck using liquid oxygen for aeration. Note sizeof discharge opening for large fish and side location of drain.

needed when any surface wateris used to make sure that noharmful contaminants arepresent.

Fish condition

One critical factor to the success-ful handling and transport of fishis that fish be healthy and ingood condition before they arehauled. Another important con-sideration is the variability oftolerance to loading andtransport stress among species.Some species are very hardywhile others require specialprecautions. With so many vari-ables important in transportingfish, it is imperative that thehauler is knowledgeable about ac-ceptable loading rates for thespecific conditions. Start with asafe loading rate, and increaselater based on experience andresults.

Hauling tank systems

The hauling unit should be com-patible with its intended use. Alight pickup can handle a 100-gallon tank while a 3/4 ton pick-up can pull a gooseneck trailerwith two 350-gallon tanks.Water is heavy--one gallonweighs 8.3 pounds. Some unitsare attached to the frames orflatbed of trucks. Other units areportable and can be liftedmanually or with a winch and/orpulleys. Gooseneck trailers withelectric brakes are also used tocarry transport tanks. The pick-up truck used to pull thegooseneck is then available forother farm work. Speciallydesigned self-contained transportvehicles are common in situa-tions where they are usedregularly to haul large quantitiesof fish. A producer can savemoney by purchasing used equip-ment in good condition. Followrecommended gross weightlimits for vehicles and tonnageweight of the trailer for safetyreasons.

In the South, most hauling tanksare insulated unless trips are

—. .Typical long-haul truck delivery system utilizing blowers and oxygen. Thistractor-trailer rig with transport tanks in series can haul large quantitiesof fish.

short or tanks are for on-farmuse only. Insulation means littleor no ice is required to maintaintemperatures on long trips.Urethane foam, plastic foam andcorkboard are common insulat-ing materials used as filler be-tween tank walls.

Tank capacities range from 75gallons to 2,500 gallons with themost common tanks holding 100to 300 gallons. Tank depth isusually 28 inches to 32 inches.Most tanks are rectangular andmay have from one to eight com-partments with varying arrange-ments. More than onecompartment is needed if severalfish sizes or species requiretransport at the same time.Large or long tanks must containbaffles to reduce water sloshingthat can injure fish and createdangerous driving conditions.Welds in single, long tanks maybreak if the truck bed warps.This can be avoided if smaller,standard tanks with the samecarrying capacity are placed sideby side.

Most tanks are made of 3/16-inchaluminum or l/4-inch thickfiberglass. Uninsulatedfiberglass or marine plywoodtanks work well for short trips.

Metal tanks are less likely to bebroken or damaged. Anyhardware on the tank should bealuminum, stainless steel orother rust-resistant material.

The top doors or lids of the tankshould be large if fish will beloaded with a boom and fish bas-ket. Large doors make fishremoval easier if dip netting is re-quired.

The tank drain can be locatedeither in the rear or side of thetank. Side outlets allow easy un-loading of fish to holding vats orponds by means of chutes or ex-tended discharge pipes. Thesereduce rough handling caused bydip-netting. The discharge open-ing should be large enough toeasily pass the largest fishhauled and should be equippedwith a quick release gate or plug.Drain openings can be rectan-gular or round with round drainsusually 3 to 8 inches in diameter.These may be controlled with in-side rubber stoppers, outside ex-pansion plugs or threaded caps.A sliding inside gate, over thedrain opening, is useful to con-trol the rate of discharge and per-mit removal of outside cap orplug without releasing water orfish.

A sloped false bottom permitsthe complete discharge of waterand fish with minimal extra han-dling. The bottom of the drainopening should be flush with thetank bottom. A lip on this drainprevents total emptying of waterand fish.

Tanks should be equipped withan overflow drain to maintainwater level and allow agitatorsto function at the proper operat-ing depth. Electrical outlet boxesshould be available for easy hook-up of agitators. A central junc-tion box with wires leading toindividual outlets works well.

Another feature is an air vent orscoop to permit air circulation inthe space between the water sur-face and tank top. Adequate ven-tilation is important especiallyon long trips, to reduce accumula-tion of carbon dioxide.

Although uncommon in theSouth, tanks may have clear, ver-tical tubes or panels for deter-mining fish weights by calibratedwater displacement rather thanby scale weighing. This methodrequires that water transfer withfish be minimized. It is common-ly used in the trout industrywhere fish pumps and dewater-ing towers are used to move fishfrom production or holding unitsto transport tanks. Handling isminimal and efficient.

Aeration systems

A variety of methods can aeratewater during hauling. Becausefish are densely crowded and ex-cited--especially after loading--itis essential to have an aerationsystem that provides adequatedissolved oxygen (DO) rapidlyand efficiently. For most cases,maintain oxygen concentrationsabove 6 parts per million (ppm)at all times. Higher oxygenlevels, near air saturation, maylessen the effects of any am-monia buildup, especially on longtrips.

Most hauling units today usesome form of pure oxygen. Most

are equipped with compressedoxygen tanks but some haulersuse liquid oxygen (LOX) becauseit is cheaper, weighs less, andfewer tanks supply the sameamount of oxygen. A standardoxygen cylinder holds about 280cubic feet of oxygen and weighsabout 150 pounds. A LOX dewar(tank) holds about 4,500 cubicfeet of oxygen and weighs about780 pounds. Other sizes ofoxygen cylinders also are avail-able. Follow all recommendedsafety precautions when nearpure oxygen.

Both kinds of oxygen tanks canbe leased or purchased. A LOXdewar is more expensive. LOX ischeaper per cubic foot of oxygenthan compressed oxygen in mostlocations. For small fish loadsand short trips, compressedoxygen is adequate. Considercost, needs, service and con-venience in deciding whichoxygen source to use. Also, liq-uid oxygen should not be storedfor long periods because of gaslosses through pressure releasevalves at the rate of about 2 per-cent daily. Compressed oxygencan be stored indefinitely. Singlestage pressure regulators areneeded for each oxygen tank, andeach aeration line to a tank com-partment should have a flowmeter (lpm) to adjust supplyrates.

Various diffusers are used for dis-persing oxygen from the bottomof the tank compartment. Carb-on stones or rods, MicroporeTM

tubing, BioweaveTM, PorexTM, andothers work well. Aeration linesfrom the regulator to flow metersand drop lines to the diffusersare usually 3/8-inch ID flexibleplastic tubing or PVC pipe. Somediffusers are made of PVCframes that fit the bottom of thet a n k c o m p a r t m e n t .

Agitators are commonly usedeither alone or in combinationwith pure oxygen. Agitators canalso provide back-up aeration foremergency situations. For shorttrips agitators alone may sufficeThe combination of agitators

with oxygen diffusers works wellfor fish hauling. Agitators do nothave good mixing characteristicsalone, and low DO may result incorners of the hauling tank.Oxygen diffusers do not removecarbon dioxide efficiently be-cause of minor agitation at thewater surface, but under thehigh density hauling conditions,they supply oxygen efficiently.

Most agitators are 12-volt directcurrent (DC) units powered bythe vehicle’s battery and alter-nator. Alternators should beheavy-duty, and the vehicle’s en-gine should be kept runningduring a short stop to keep thebattery charged. One agitatorper compartment is used. Exces-sive agitation can be harmful todelicate scaled fish, and diffusedoxygen is preferred for small fish.

Other equipment andsupplies

To assure the successful deliveryof fish, other additional equip-ment and supplies are recom-mended. If you sell fish in manysmall lots along a route, an easi-ly attached or extendable sup-port for a hanging scale is useful.The scale should be in poundsand ounces and have a weighingbucket. You will need a suitabledip net to transfer fish.

An oxygen meter or test kit is im-portant for measuring oxygenconcentrations in transport andreceiving waters. Oxygen levelsand water temperature can bemonitored easily by using anoxygen meter with a long cableattached to the probe.

Gauges and manifolds that indi-cate the functional status ofagitators and flow meters can beput inside the truck cabin. Flowmeters may also be located ororiented for easy visual inspec-tion to make certain oxygen issupplied at all times during thetrip.

Water hardness, alkalinity andpH test kits should be used tocheck transport and receiving

waters, especially if fish areremoved from hard, highlyalkaline water to soft, acid waterwith low alkalinity. If you deliverfish to sites where chlorinatedwater is used, a chlorine test kitis helpful. Sodium thiosulfatemay be needed to dechlorinatewater.

Carry at least one extra agitatorand other essential spare parts,like fittings and hoses, at alltimes. A 12-volt submergiblepump or gasoline-engine pump isuseful for adding water in anemergency or for tempering fishby pumping pond water at thestocking site into the transportunit to exchange the water slow-ly and avoid any shock fromtemperature or water quality dif-ferences.

Pre-hauling handling andplanning

Fish must be in good health andgood condition before they areloaded into transport units. Fishin poor condition may die duringtransport or suffer delayed deathafter stocking. Withhold foodfrom fish for at least 1 to 2 daysbefore transport during warmermonths and 3 days or longerduring colder weather. Fish withempty stomachs are hardier, willnot regurgitate food in thetransport unit and will produceless metabolic waste. Do notstarve cannibalistic fish such asstriped bass or red drum longerthan 3 days before harvest.

If possible, use V-traps or har-vest basins in ponds to harvestsmall, delicate, scaled fish. Forlarger fish, harvest as many aspossible by seining or trappingas water level is lowered. Selectthe proper mesh size and net

material for harvest seines anddip nets to avoid injuring or gill-ing fish. Purchase treated nylonnets or treat with a net coatingfor seining catfish. Use soft 3/16-inch knotless nylon mesh netsfor delicate minnows.Polyethylene nets do not requirespecial treatment.

After fish are harvested, careful-ly remove debris and give fish aresting period of several hoursbefore they are handled again. Ifholding vats are available, youcan easily grade, clean and sortfish prior to shipment. Then thefish may be slowly tempered oracclimated to the expectedtransport water temperature.

If fish are to be held in ponds,maintain adequate aeration andwater quality. Secure live cars orharvesting seines to the pond bot-tom. Avoid holding large fish oractive species in cages. Do notoverload cages. If fish begin todie, diagnose the problem, thentreat and return fish to the pondrather than transport them.

Prophylactic treatment with ap-proved chemicals can reducepathogenic organisms that couldcause problems during or aftertransport. Paracide-F maybeused in holding vats for 15-minute to l-hour baths. Avoidovertreating with excessive dosesor combinations of chemicals. Beprepared to flush any treatmentwith fresh water if fish show anysigns of stress.

The transport unit and equip-ment, such as dip nets, should bedried and disinfected betweenloads of fish. This practicereduces the possibility of spread-ing disease pathogens from onegroup of fish to another. Tankscan be thoroughly air-dried or

treated with chlorine in a 10ppm solution for an hour.Household bleach (5 percentchlorine) or HTH (65 percentchlorine) can be used. Flushtanks thoroughly after chlorinetreatment. A 5 percent solutionof formalin can also be used todisinfect.

To avoid untimely delays, getgood directions to your destina-tion. Plan your trip to includeany drop-offs or water refreshen-ing. Be certain that all requiredpermits or licenses are in orderand carried in the vehicle in caseof an inspection check. Somestates require special markingson fish transport trucks. Checkwith the proper regulatoryauthorities for current informa-tion on laws and regulations ontransporting and marketing livefish before doing interstate busi-ness.

The following table provides in-formation on matching trucksizes with fish hauling tanks ofvarious capacities.

Truck size RecommendedTank Capacity

(short ton) (gallons water)

Tractor-trailer 5,0002.5 1,2001.5 600-8001.0 4000.75 3000.5 100

The information given herein is for educa-tional purposes only. Reference to commer-cial products or trade names is made withthe understanding that no discrimination isintended and no endorsement by theCooperative Extension Service is implied.

Acknowledgment

Special thanks to Gary Carmichael and Joseph Tomasso for providing useful information for thispublication.

This publication was supported in part by a grant from the United States Department of Agriculture, Number 87-CRSR-2-3218, sponsoredjointly by the Cooperative State Research Service and the Extension Service.