Effect of starvation on the growth and survival of
post-larval abalone (Haliotis iris)
R.D.
Roberts, C. Lapworth, R.J. Barker-2001
Aquaculture,
200(3-4): 323-338
Abstract:
The
starvation tolerance of post-larval abalone (Haliotis iris) was
determined by examining post-larval growth and survival after various
periods of starvation. Competent larvae (10 days old at 16°C) were induced
to attach and metamorphose with 2 µm GABA. Post-larvae were either fed
diatoms (Nitzschia longissima) or starved. In Experiment 1,
post-larvae were starved immediately after metamorphosis for periods of 1,
2, 4, 8, 15, 20, 25 and 30 days. Starved post-larvae grew relatively well
for several days after metamorphosis despite the absence of food (averages
of 10.4 and 17.8 µm shell length (SL) per day after 8 days for two
batches). Subsequent growth was minimal, averaging 1.7 and 0.7 µm day-1
over 6¯7 days for the two batches. There was no clear
relationship between period of starvation and growth rate when fed. Mean
daily growth rate over 3 weeks when fed ranged from ~15¯22 µm
day-1. However, the duration of starvation did have a significant
effect on survival. Survival of post-larvae fed after 1¯2 days
of starvation was 90¯100% after 3 weeks of feeding. Longer
starvation periods gave progressively lower survival and post-larvae starved
for 30 days all died within a week of being fed. In Experiment 2, post
larvae were fed for 3 weeks after metamorphosis, then starved for 0, 3, 7,
14 or 21 days. Growth rates of starved post-larvae averaged only 5¯6
µm day-1 in the first week (vs. 30 µm day-1 in
controls), and later declined to zero. Growth resumed within a week
following return to food, but the 14- and 21-day starvation treatments took
2 weeks to reach growth rates comparable to controls. The no-starvation
controls and the 3- and 7-day starvation treatments all had >70% survival
over 4 weeks after return to food. Survival in the 14- and 21-day starvation
treatments was 15¯20%, with almost all mortalities occurring in
the first week after return to food. These data suggest that Haliotis
iris post-larvae are relatively tolerant of starvation, so abalone
farmers have a week or so to remedy food shortages before major post-larval
mortality begins.