POND AND TANK EXPERIMENTS WITH EXTRACTS OP FOOD AND OTHER MATERIALS 



Catching and Establishing the Fish 



Two little txinny ( Euthynnus afflnls ), originally established during the 

 siiimner of 1952 In the large Fond No. 5 at Coconut Island (Tester et^ al. 1954) sur- 

 vived the winter and formed the nucleus of a new population which was established 

 during July and early August 1953. To the two survivors were added 12 ttmny and 

 9 yellowfln ( Neothunnus macropterus ) at the end of June. As In the previous year, 

 the fish were caught by trolling with the Salpa and were transported In the ves- 

 sel's llvewell to Pond No. 5. Of the 21 fish Introduced to the pond only one, a 

 tunny, failed to become established, that Is, to start feeding. This great suc- 

 cess, compared with that of previous years. Is attributed to the presence of the 

 two survivors, which acted as leaders of the new fish. 



Mortality among the established txmny was moderate between July 1 and 

 October 1, 1953: 5 of the 13 died, leaving 8 which have survived to the time of 

 writing (January 1954). Although the 9 yellowfln appeared to be In good condition 

 at the time they started feeding, all had died by the middle of September. The 

 reason for this mortality, which took place Irregularly throughout the period. Is 

 unknovm. 



Two tunny originally established during the summer of 1952 In a concrete 

 tank (Tester e_t al. 1954) survived the winter and wej?e used In experiments during 

 the early summer. One jumped from the tank and died on July 19, 1953. The other, 

 which was partially blind, died 3 days later. 



Feeding the Fish 



From April 25 to July 17, 1953, the tunas In the pond were fed exclu- 

 sively on frozen squid from the mainland. They were fed 4 times a week (Tuesday, 

 Thursday, Saturday, and Simday) at a rate of about 2 pounds of squid per fish per 

 week. Following July 17, 1953, they were fed daily for 1 week on squid, 1 week 

 on skipjack flesh, 1 week on frozen shrimp from the mainland, and thereafter 4 

 times a week on skipjack flesh. The change in diet was associated with experiments 

 (to be discussed later) probing the possibility of food-conditioned responses. 



The tunny In the tank were fed on tuna flesh 4 times a week throughout 

 1952 and until they died In 1953. 



Materials and Testing Procedures 



One himdred and sixty-nine experiments were conducted during the siimmer 

 of 1953, 162 in the pond and 7 in the tank. Of these, 94 involved extracts of 

 "natural" foods and the other 75 involved solutions or suspensions of chemical 

 materials. Pertinent data on these tests are included In the appendix to this re- 

 port. The tests are numbered in sequence with those presented in appendix I of 

 Tester et al. (1954) . They are referred to by nvunber in the sections which follow, 

 e.g. #4^. 



"Natural" foods from which extracts were made included skipjack ( Katsu - 

 wonus pelamls ) flesh, skipjack viscera, skipjack blood, dolphin ( Coryphaena 

 hippurus ) ovarie s , anchovy ( Stolephorus purpureus ) , hammerhead shark \ S phy ma sp.) 

 flesh, mainland squid, mainland shrimp, and marine plankton. The materials were 

 prepared in a similar manner: fish, squid, or shrimp flesh was chopped either by 

 hand or in a grinder, placed in a Waring Blendor and macerated after adding tap 

 water, further diluted v/ith water, and allowed to stand for several hours in a 

 refrigerator. Either the whole extract was tested, or the clear portion was sepa- 

 rated by decanting or centrifuglng and tested. The procedure was the same for 

 blood and plankton except that the initial chopping was not necessary. A self- 

 digested skipjack viscera preparation supplied by Hawaiian Tuna Packers Ltd. was 

 also used In preliminary tests. In some preparations 95-percent ethyl alcohol. 

 Instead of water, was added prior to maceration in the Blendor. 



