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<br />2008]
<br />
<br />RAZORBACK SUCKER LARVAE GROWrIcl
<br />
<br />17
<br />
<br />- 35
<br />~ 30
<br />~ 25
<br />....
<br />en 20
<br />c
<br />.!!! 15
<br />10
<br />5
<br />
<br />
<br />ca
<br />....
<br />o
<br />I-
<br />
<br />5
<br />
<br />15
<br />
<br />Days post-hatch
<br />
<br />+16.5C
<br />D. 19.5
<br />.22.5
<br />025.5
<br />
<br />25
<br />
<br />35
<br />
<br />45
<br />
<br />Fig, 1. Growth (change in total length) of razorback sucker lan'ae a~ a function of age (days post-hatch) for fish reared
<br />in laboratory aquaria at 4 different water temperahlres, Parameters for a response surface regression to estimate growth
<br />a~ a function of water temperahlre and age in days post-hatch are available (Table 2).
<br />
<br />TABLE 1. Mean total length (sample size, sf) of razorback sucker larvae at 4 constant-temperature treatments (n = 3
<br />tanks per treatment, S larvae per tank, means for individual fish) at 9, 23, and 37 days post-hatch; larvae began exoge-
<br />nous feeding 9 days post-hatch,Fbr the 23-day post-hatch measurement, the ,5 lan'ae were removed from the tanks,
<br />lightly anaesthetized, measured to the nearest 0.1 nun TL, and retul1led to the tanks, Mean mass of individual larvae at
<br />37 (lays post-hatch is also shown; no mass measurements were taken at other intervals, Lan'ae were fed brine shrimp,
<br />Artemin sp, nauplii ad libitum twice daily.
<br />
<br /> Mean growth rate
<br /> Mean total length (mm) Mean mass (g) (mm . day-I)
<br />Temperal:u re treatment CC) 9 days 23 days 37 days 37 days 9-23 days 23-37 days
<br />16.5 11.0 1.5,9 21.8 0,057 O,3S 0,42
<br /> (8,0,27) (14, 0.28) (13. 0,,59) (13, 0,00,5)
<br />19,5 11.0 16,7 27,2 0,136 0,40 0,75
<br /> (8,0.27) (15,0..52) (lA, 0,,52) (14,0,010)
<br />22,5 11.0 18.4 29.2 O,I7S 0..5.3 0.77
<br /> (8, 0,27) (IS. 0,29) (15, 0.37) (15. 0,008)
<br />25.5 11,0 19,5 31.2 0.231 0.61 0,84
<br /> (8,0,27) (IS, 0.42) (IS, 0,80) (15, 0.020)
<br />
<br />calculated days required for razorback suckers
<br />to achieve 25-mm TL under a slower growth
<br />rate (0.29 mm TL' d-I) at 200C (Clarkson and
<br />Childs 2000).
<br />
<br />RESULTS
<br />
<br />Growth of early life stages of razorback
<br />sucker was positively related to water temper-
<br />ature, and fastest growth occurred at 25.50C,
<br />the highest water temperature tested (Fig, 1,
<br />Table 1). Mean TL of razorback sucker~ 37
<br />days post-hatch was 21.8 mm (sx = 0.59) at
<br />16.50C and 31.2 mm (sx = 0.80) at 25SC.
<br />Growth was intermediate at 19SC and 22SC.
<br />Growth in length (mm TL . d-I) of early life
<br />stages of razorback sucker was faster between
<br />23 and 37 days post-hatch for all temperature
<br />
<br />treatments. Growth in both the early and late
<br />post-hatch periods was about twice as fast at
<br />25SC (0.61 mm TL . d-I and 0.84 mm TL .
<br />d-I, respectively) than growth rates in corre-
<br />sponding periods at 16SC (0.35 mm TL . d-I
<br />and 0.42 mm TL . d-I, respectively). Average
<br />weight of razorback suckers in the 25.50C
<br />treatment was about 4 times that of razorback
<br />suckers in the 16.50C treatment when the ex-
<br />periment ended. Mortalities during the exper-
<br />imental period were limited to 2 individuals in
<br />the 16SC treatment and 1 in the 19SC treat-
<br />ment; no adjustments to growth calculations
<br />were made for these fish.
<br />Growth was mostly linear over time for the
<br />16SC treatment and increased in a slightly
<br />exponential fashion over time in the 19.50,22.50,
<br />and 25.50C treatments. The response surface
<br />
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