Pond No. 5 



It was judged that the concrete tank would accommodate no more 

 than about six or seven fish on a permanent basis, Moreoverj a greater 

 number than this would introduce complications in the experimental work 

 which was being undertakeno Accordingly, on and after September 5j 

 attempts were made to introduce tuna to pond Noo 5 where it was hoped 

 to build up a reserve populationo This pond (figSo 4 and 6) is the 

 largest available on Coconut Islando It is about 65 feet wide and 350 

 feet longo The west end is blocked from the seaward approach by a 

 series of large screened gates,, 4 to 10 feet wide^ and 12 feet deep. 

 At the northeast corner the pond extends under a bridge and is blocked 

 from a shallow coral reef by 16 screened gates, 4x4 feetj, arranged in 

 a semicircleo About one-half of the pondj, along the southern wall, is 

 shallowj, ranging from about 2 to 5 feet in deptho The other half of the 

 pondj, along the northern wall, is a deep channel which averages about 

 9 feet at low water and about 12 feet at high water^ The bottom is of 

 crushed corals covered with siltj, with a few living coral heads in the 

 shallow parts. The walls are of smooth concrete. Screened gates in 

 the south wall open to ponds Noso 1„ 3^ -and 4„ 



The Salpa was backed to the concrete framework forming the 

 gates at the seaward approach and the tuna were dipped from the livewell 

 and transferred directly to the pondc Present in the pond at the time 

 the tuna were introduced were large schools of iao and nehu (which 

 could pass through the meshes of the screening), one barracuda about 

 2 feet in length, several moray eels about 2 to 3 feet in lengthy, and 

 several small carangids, pomacentridSj, and other reef fishes o 



Over the period September 5 to October 18^ the following fish 

 were introduced? 1 frigate mackerel (about 1 pound), 19 tunny of which 

 1 was large (about 6 pounds) and the others were small (l to 3 pounds )s 

 and 9 yellowfin (l about 2 pounds and the rest 6 to 8 pounds). For the 

 most part, the fish swam rapidly away from the gates on being placed 

 in the water. The frigate mackerel and the tunny headed for the deep 

 part of the pond whereas the yellowfin tended to swim leisurely 1 or 2 

 feet below the surface, at first following the walls but later keeping 

 to the center. Once established and feeding, they could be attracted 

 readily by food to the surface where they could be observed and counted. 



The frigate mackerel was introduced on September 24 and 

 disappeared 2 days later, at which time it was presumed dead. The 

 large tunny was introduced on September 5, It was seen daily until 

 September 10, at which time it was badly bruised and scarred, and had 

 not started feeding. Presumably it died the following night. 



The small tunny were introduced at intervals between September 

 27 and October 18, Only 5 of the 18 had died by October 20^4 2 within 



21 All but two tunny, and one of the yellowfin, died about November 

 10-12, 1951s following a period of coldp wet weather. 



15 



