TRANSPORTATION OF FISHERY PRODUCTS 323 



parent or other refrigeration plant. The system gets its name from the fact that 

 a eutectic solution is generally used in plates to maintain the desired tempera- 

 ture within the insulated van while the refrigerating machinery is not in opera- 

 tion. The eutectic plates may be frozen either by the parent plant equipment or 

 by a compressor driven by the truck motor or by an auxiliary motor forming part 

 of the equipment. The auxihary motor may be an electric motor which must be 

 plugged in to some convenient electrical outlet while the truck is standing still 

 (overnight), or it may be a gasoline engine separate from or in addition to the 

 electric motor. The hold-over period is a function of the amount of eutectic used 

 in relation to the usual factors entering into heat balance calculations. Similarly, 

 the temperature that will be obtained in the truck will depend upon those factors; 

 as it is not ordinarily controlled, outside conditions cause it to fluctuate some- 

 what. The hold-over system is simple and relatively inexpensive, but has the dis- 

 advantage of being inflexible with regard to holding temperature. 



Mechanical Systems. The mechanical systems that appear to be gaining favor 

 with truck and trailer operators are the packaged types already outlined under 

 railway transport sections. Mechanical units first used on trucks were moimted 

 under the trucks where air circulation was assured and radiation effects minimized. 

 This advantage was outweighed by the disadvantages of water and dirt hazards, 

 so that now mechanical units are mounted in the front of the van. In trucks the 

 units are mounted over the cabs and in trailers they are similarly mounted or 

 occupy a section on the floor across the front of the van. 



The Transport of Fish by Air 



The transport of fishery products by air is not of great commercial significance 

 and is' not likely to become so for some time. Numerous parcels of fishery products 

 of a specialty nature, such as live lobsters, have been and are being carried by 

 air, but they do not constitute an important portion of the total volvime shipped 

 and are therefore regarded as experiments. 



It is probably needless to observe that cost is the main inhibiting factor to great 

 expansion of air cargo traffic; therefore, air-borne fish cannot compete on a price 

 basis with that hauled by surface carriers. However, the great reduction in 

 elapsed time between catch and consumption of some fishery products can raise 

 these products into a superior or luxury class on a quality basis, and thus premium 

 prices can be assessed to take care of the extra transportation costs. The volume 

 of such traffic will of course depend upon the number of individuals willing to 

 pay premium prices for air-borne fish of assured quality. Although experiments 

 and surveys are under way in the United States and Canada to determine the 

 relation between premium prices (excess over ordinary market prices) and de- 

 mand in various income groups in some representative cities, these studies have 

 not progressed to the point where definite conclusions can be drawn. 



As far as is known the airplanes used in these experiments have no special 

 equipment for maintaining the required conditions for the carrying of fishery 

 products. The responsibflity for protection seems to be assumed by the shipper. 

 Protection is afforded by the container, which is usually of the standard "Insulpak" 

 variety consisting of an inner and an outer carton separated by insulating pads. 

 Chilled and wrapped fillets are placed in these cartons which are then kept at 



