Fish Hatchery Management - fisheries & aquaculture

350 FISH HATCHERY MANAGEMENTTrucks are the principal means of transporting fish. Most hatcheriescurrently use vehicles near 18,000 pounds gross vehicle weight (GVW)'However, units from 6,000 to over 45,000 pounds GVW often are used formoving fish.Automatic transmissions are becoming common in all trucks. Automaticshifting reduces engine lugging or overspeeding, and allows the driver toconcentrate on defensive driving rather than on shifting gears'Diesel engines also are gaining in popularity. Minimal service and longlife are attractive features but the high initial cost is a major disadvantage.Cab-over trucks are popular in many areas especially where a short turningradius is important. Conventional-cab trucks generally are quieter, havebetter directional stability, and a less choppy ride because of their longerwheelbase.A relatively new and promising innovation in warmwater fish transportationis the combined use of gooseneck trailers and pickup trucks. Theseunits are low in cost yet very versatile (Figure 108).Tank DesignMost new fish-distribution tanks are constructed of fiber glass or aluminum,but plywood, redwood, stainless steel, glass, galvanized iron, andsheet metal all have been utilized in the past.Aluminum is lightweight, corrosion-resistant, and easily mass-produced.Alloys in the range 3003H14 to 6061T6 will not cause water-quality problems.Fiber glass is molded easily into strong, lightweight tanks and can berepaired readily. Its smooth surface is simple to clean and sanitize. Aluminumand fiber glass appear equallT well-suited for fish-transport tanks.Most tanks constructed in recent years are insulated, usually with styrofoam,fiberglass, urethane, or corkboard. Styrofoam and urethane are Preferredmaterials because of their superior insulating qualities and theminimal effect that moisture has on them. A well-insulated tank miminizesthe need for elaborate temperature-control systems and small amounts ofice can be used to control the limited heat nses.Circulation is needed to maintain well-aerated water in all parts of thetank. Transportation success is related to tank shape, water circulation pattern,aerator type, and other design criteria'The ff factor is the basis for comparing insulation materials. It is theamount of heat, expressed in BTU's, transmitted in I hour through Isquare foot of material I inch thick for each degree Fahrenheit of temperaturedifference between two surfaces of a material. The lower the ff factor,the better the insulating quality. The following is a list of insulating materialsand their respective -K factors: