FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Water Supply 



The water used at the Paia plant came from 

 wells located in tlie same general area. It was 

 pumped to a storage tank at a higher elevation 

 and returned by gravity flow to the tilapia plant, 

 arriving tliere under considerable pressure. Anal- 

 ysas showed a salt content ranging from 60 to 80 

 grains per gallon. Tlie water was suitable for 

 iri-igation but was not approved for human con- 

 sumption. The brood tanks, as well as the fry 

 tanks, had an independent water supply, and none 

 of the water was recirculated in 1958. Early in 

 1959, a pmnp and sand filter box were installed 

 and the water in brood-tank A was filtered and 

 recirculated during the balance of the year. 



The total amount of water used was 9,285,890 

 gallons in 1958 and 13,100,000 gallons in 1959. 

 The amounts used and cost by months are given in 

 tables 2 and 3 for the 2 years. The amounts used 

 were greater in 1959 than in 1958 because (1) of 

 the addition of 3 holding tanks, (2) a supply of 

 bait-size fish was held over from the previous year, 

 and (3) the peak in production was earlier in 1959 

 necessitating the use of more fiy tanks throughout 

 the year. 



Tam.e 2.- 



-Amoiint and cost of uYifcr used at the Paia 

 hatchery, 19.')8 



Month 



January-April 



May 



June 



July-August 



September-October-., 

 November-December, 



Total 



Gallons 



» 1, 792, 303 



385, 762 



634. 878 



2, 239, 367 



2, HO, 700 



1, 692, 890 



9, 28S, 890 



Cost" 



$107. 54 

 23.15 

 38.09 

 134. 36 

 152. 44 

 101.57 



557. 15 



Average 

 cost per 

 month 



$26.88 

 23. 15 

 38 09 

 67. 18 

 76.22 

 60.78 



' 6 cents per thousand gallons. 



2 Large volume because of fry-tank leakage. 



TABI.E .3.- 



-Amovnt and cost of water used at the Paia 

 hatchery, ]!).'■,;) 



Two air compressors and a system of air lines 

 were installed in March 1959 to aerate the water 

 in the brood tanks and increase its oxygen con- 

 tent dui'ing tlie hours of darkness, when the oxy- 

 gen content usually reaches a vei*y low level. In 

 April 1959, a 120- foot lead-sheathed, soil-heating 

 cable, i"ated at 3.65A-220V and capable of pro- 

 ducing 800 watts, or 6.7 watts per foot, was in- 

 stalled in each brood tank with the objective of 

 raising water temperatures and inducing early 

 spawning. The amount and cost of electricity 

 used in 1959 for the operation of the filter pmnp, 

 the air compressors, and the heating cables are 

 given in table 4. 



Table 4.- 



-Aniouiit and cost of electricity used at the Paia 

 hatchery, 1959 



 6 cents per thousand gallons. 



1 Mar. 27, filter pump placed in use; Apr. 10, heating cable and 1 aerator 

 in use; Apr. 27, second aerator in use; July 1, heating cables turned off; Aug. 

 10, filter pump turned off. 



3 Heat and power put on separate meters June 13. 



' Meter service charge. 



ENVIRONMENTAL CONDITIONS 

 Temperature Variations 



The monthly averages of maximum and mini- 

 mum water temperatures in brood-tank A, as 

 measured by a thermograph, are plotted in figures 

 3 and 4. The daily fluctuation in temperature 

 ranged from 5° to 9° F. In 1958, the highest 

 water temperature was recorded in September and 

 the lowest in December. In 1959, the maximum 

 occurred in July and the minimum in November. 



Maximum air temperatures at the Paia station 

 were higher from March through November in 

 1959 than in 1958 (fig. 5). The minima, on the 

 other hand, were lower in 1959 than in 1958 for 

 the .summer months. May through August (fig. 6), 

 but higher for the period February to April. As 

 a result of the generally warmer air conditions 

 during the spring months of 1959, we actually 

 have no way to evaluate the eifect of the heating 

 cables on water temperature and spawning. 



