REARING TILAPIA FOR TUNA BAIT 



SS 



JA^ FEB MAR APR MAY JlIN JUL AUG SEP OCT NOV DEC 



Figure 3. — Average miinthly maxiinum water tempera- 

 tures in brood-tank A in 1958 and 1959. 



The two years were fjenerally similar in the 

 amount of sunsliine recorded at the Paia station 

 (tifi:. 7). In the two montlis March and July, how- 

 ever, there was considerably more sunshine in 

 1959 than in 1958. 



Oxygen Concentrations 



1958. — Measurements of the concentration of 

 dissolved oxygen in the brood tanks showed a 

 marked diurnal variation (table 5). Oxygen 

 values at about 8 a.m. were frequently less than 



JAN FEB MAR APR MAV JUN JUL AUG SEP Oa NW DEC 



Figure 4. — Average niontlily minimum water tempera- 

 tures in brood-tank A in 1958 and 19J59. 

 519347 0—62 2 



JAN FEB MAR APR MAV JUN JUL AUG SEP OCT NOV DEC 



Figure 5. — Average monthly maximum air temperatures 

 at Paia, Maui, in 19.^8 and 19."i9. ( Data courtesy of 

 Hawaiian Sugar Planters Association.) 



1.0 ml./l., and on a few occasions wei'e less than 

 0.5 ml./l. These levels are dangerously low and 

 conceivably could have had a detrimental effect 

 on the .survival of eggs and young. 



On tiie basis of a 24-hour series of oxygen mea- 

 surements made in tanks at the Bureau of Com- 

 mercial Fisheries Biological Laboratory, Hono- 

 lulu, it would appear that our early morning 

 and afternoon sampling times were close to the 

 hours of minimum and maximum concentrations 



60 



JAN FEB M\K U'R MAY JUN JUL AUG SEP OCT NOV DEC 



Figure 6. — Average monthly minimum air temiM>ratures 

 at Paia, Maui, iu 1958 and 19,")9. (Data courtesy of 

 Hawaiian Sugar Planters Association.) 



