P18 U. S. BUREAU OF FISHERIES 
It was found that the pens in the hold of vessels having mechanical 
refrigeration are constructed in such a manner that cold air cannot cir- 
culate around them. Thus the fish in the topmost layers may be 
frozen upon arrival at port, while the lower layers remain at a tempera- 
ture conducive to rapid deterioration. To overcome this, the investi- 
gators suggested that the pens be SO constructed as to allow an open 
space of about 2 inches around all sides of each individual pen. 
It was found that one of the major factors contributing to dete- 
rioration of the fish is the physical damage trom punctures made in 
the flesh by the use of pitchforks in handling the fish aboard vessels, 
in unloading at the pier, and, in some instances, in the packing plants. 
Physical damage also is caused by the pressure of large pieces of ice 
which bruise and rupture the flesh when fish are stored on the vessel 
in deep pens, or bins. This pressure was found to be as high as 2.5 
pounds per square inch on the bottom layer of fish in a pen 5 feet 
deep. Bacterial contamination of the flesh 1s made easily possible 
through the ruptures and bruises caused by these practices. In pens 
30 inches deep, the pressure on the lower layer was 1 pound per 
square inch and bruismg was not excessive. It appears, therefore, 
that the storage pens should be as shallow as possible and that finely 
crushed ice should be used for refrigeration of the fish while in the 
pens. 
Studies on handling the fish in the packing plants reveal the need 
for instituting improved sanitary practices. Toward this end, the 
investigators prepared a set of suggestions Which was distributed 
among the owners of the packing plants. These suggestions are 
similar to those for the crab-packing plants as outlined on pp. 213 to 
216 of this report. 
During recent years some of the fish-packing firms in New England 
have been candling fish fillets to detect those which are unmarket- 
able. The method used in Boston caused considerable glare, and 
resulted in eyestrain to the inspectors. Attempts were made to 
remedy this situation by polarizing the light for the candling opera- 
tion. This proved successful in reducing the glare, but costs for 
general installation are somewhat high. A partial solution of the 
problem could be obtained by exposing a smaller illuminated area, 
thus reducing or entirely eliminating the stray light around the 
fillets. Special types of light bulbs which minimize glare also may 
be an aid in this connection. A detailed report of this study is now 
being prepared by the investigators. 
ULTRAVIOLET RAYS IN KILLING BACTERIA 
The work on this problem during the past year has been concerned 
with establishing the effects of intermittent irradiation on the keeping 
quality of haddock fillets stored under refrigerated conditions. The 
purpose of this work is to determine whether it would be possible to 
reduce bacterial contamination in fish while being prepared in the 
fish processing plants and while being held in cold-storage warehouses 
and retail display cases, by‘the use of ultraviolet lamps. A mechan- 
ical device, developed by the research workers at the College Park 
Laboratory, allowed a 30-second exposure of fish fillets to the rays of 
the ultraviolet lamps for each hour of storage in the experimental 
refrigerator. At 48-hour intervals during a total storage period of 
Pa 
