HANDLING FRESH FISH 279 



ern waters in uninsulated holds of wooden vessels, a ratio of 1 : 2 is com- 

 mon. More, rather than less, ice should be taken by fishing vessels because 

 it has been found that additional ice (compared to present practice) 

 should be allowed at the sides of the vessel and adjacent to the wing 

 boards of each pen. Any exposure of fish at these points due to melting 

 of ice contributes substantially to quality losses. 



Correct icing requires considerable care and experience, and every 

 vessel is a separate problem depending upon the construction, hold and 

 pen layout, and the relative heat transfer from the water and air outside 

 the hold. For eviscerated fish, the gut cavity or poke of the fish should be 

 well filled with ice, taking special care to pack the ice in the gill cavity 

 and around the nape. Preferably, each fish should be surrounded by ice 

 or the fish placed in alternate layers such that the ice is in actual contact 

 with the greater portion of each fish. 



Preservative Ices: In efforts to improve the keeping quality of fish in 

 ice, experimenters have incorporated a number of preservatives or germi- 

 cides in the ice. Sodium benzoate, benzoic acid, chloramine compounds, 

 fumaric acid, sodium hypochlorite, sodium nitrite, carbon dioxide, hydro- 

 gen peroxide, calcium propionate, disodium phosphate, and various anti- 

 biotics are among the many substances tried. Any such substance must 

 meet the approval of the United States Food and Drug Administration 

 for use with food products in this country. Proper care in the handling and 

 storage of fish, with adequate amounts of ordinary crushed or flaked ice, 

 will yield as much or more improvement in keeping quality than will the 

 casual use of any preservative-treated ice tested and accepted for use with 

 food fish to date. Any preservative ice that has been accepted for use on 

 fish will be of greatest value only if its use is combined with the best 

 handling practices. 



The introduction of the wide-spectrum antibiotics, especially chlor- 

 tetracycline (CTC) and oxytetracycline (OTC), about 1950 was followed 

 by more extensive laboratory and commercial testing for application to 

 fresh fish preservation than any other compounds to date. The consensus 

 in the considerable scientific literature favors use of five to ten ppm CTC 

 as a dip before icing or as an additive in the ice for extension of keeping 

 quality. 



In commercial operations, use of preservative ices generally add not 

 more than two or three days to the storage life of the fish, although in 

 some laboratory or experimental procedures extensions of up to two weeks 

 have been reported. Regulations of the United States Food and Drug 

 Administration provided in 1959 a tolerance of five ppm for use of CTC 

 on certain fish products in the fresh, uncooked and unfrozen form. Much 

 of the research on use of antibiotics in fish has been ably summarized with 

 a good literature review by Tarr^°. 



