Sharks have ample opportunity to damagj the catch because 

 tuna caught by longline remain in the v^rater for varying periods 

 before they are brought aboard. During this period they are sus- 

 ceptible to attack by the sharks in the deep waters. However, the 

 greatest damage appears to be done during hauling, when sharks 

 inhabiting the surface layers attack the fish. These sharks have 

 been found in varying abundance throughout the equatorial waters, 

 usually with larger numbers occurring close to land. The amount of 

 shark-damaged tuim for all three cruises is disturbing (table 13), 

 but it is probable that it can be considerably reduced by rapid 

 mechanical hauling of the hooked fish„ In addition, a number of 

 the fish classed as shark-bitten in table 13 could have been 

 salvaged for canning. 



Acceptability of the catch for canning is another vital 

 problem in evaluating the possibilities for a longline fishery,, 

 The catches of Smith cruises 7 and 11 were sold to canneries in the 

 Territory of Hawaii. Rejection by the cannery of the catch from 

 Smith Cruise 7 amounted to about one-third by weight of all species. 

 Records are not available for examining the distribution of the 

 rejections by sizes or species for this cruise. The acceptability 

 was based entirely on color of the cooked flesh. The color becomes 

 apparent only after precooking and partially dismembering the fish, 

 at which time weights and species identification become uncertain. 

 For the next landing, that of Smith Cruise 11 (table 14), about 

 half of the fish were tagged and monitored through the cannery. Of 

 the tagged sample, all bigeye tuna were rejected^ only 10o9 percent 

 by number, or 11.2 percent by weight of the yellowfin were rejected. 

 TCniile more evidence is required for final conclusions, it appears 

 that rejections are economically prohibitive for bigeye and un- 

 desirably high, though not necessarily prohibitive^, for yellowfin. 

 The tendency toward dark-colored flesh was greater among the large 

 yellowfin than the smaller ones, VJ'ith more knowledge of the 

 categories of fish tending toivard undesirably dark flesh and the 

 relative distribution of these categories of fish on the fishing 

 grounds it may be possible, by selective fishing, to reduce the pro- 

 portion of undesirable fish in the catch. 



38 



