Effects of depressed pH on reproduction, growth and survival of flagfish, Jordanella floridae (Good and Bean)

Abstract

Breeding communities of flagflsh {Jordanella floridae) were exposed to adjusted pH levels of 6.0, 5.5, 5.0, 4.5 and 4.0 for 21 days. Control water (pH 7.5) received no acid treatment. Egg production was significantly reduced (p<.05) at pH 6.0 relative to control, and a termination, of spawning occurred below this test level. Control eggs were Incubated at test levels where spawning had not occurred. Hatching success was Impaired at pH 4.5 with a significant decrease (p<.01) at pH 4.0. Hatching time was variable but no significant relationship was found between hatching time and hydrogen ion activity. Fry mortality was significantly increased (p .01) with decreasing pH between treatment groups pH 6.0, 5.5 and 5.0. All fry died within 72 hours at pH 4.5 and no fry survived the first 24 hours at pH 4.0. The final mean weights and lengths of the fry were significantly reduced (p<.01) at pH 5.5 relative to control. Spawning resumed within three days following the return of the pH 4.5 test levels to control conditions. A histological examination of the ovaries from the control and pH 5.5 females revealed no obvious differences. Results of the present study concur with other reproductive Investigations of flagflsh, brook trout and fathead minnows Indicating a pH decline below 6.5 may result in reproductive impairment.