2.5. Statistical analyses Ž
. Single-factor ANOVA P - 0.05 was used to determine whether there was a dietary
treatment effect on SL, SGR, FCE, and DFC. When null hypotheses were rejected, Ž
. Tukey’s HSD multiple range tests
P - 0.05 were used to determine significant
differences among treatments. Transformation of data was deemed unnecessary after Ž
testing for homogeneity of variances by box plot analysis. Two-factor ANOVA P - .
0.05 was used to determine overall effects of light and water volume exchange rate on algal food quality for abalone. Simple linear regressions were used to determine if
significant relationships existed between specific variables.
3. Results
3.1. Abalone growth and surÕiÕal Ž
. Abalone survival was high
Table 2 , except in one of the replicates with N. luetkeana, which was eliminated from the analysis. The remaining containers exhibited
no significant difference in survival and all abalone appeared healthy upon visual inspection at termination of the study.
Most of the difference in dulse nutritional value was attributed to light supplementa- Ž
. tion ANOVA; P - 0.01 , as water exchange rate alone had no effect on abalone growth
Ž .
Ž .
ANOVA; P 0.05 . There was also an interaction effect ANOVA; P - 0.05 between light and exchange rate on the nutritional value of dulse for abalone.
Ž Shell growth differed among abalone fed on the seven dietary treatments ANOVA;
.
y1
P - 0.01 , ranging from 51.56 mm SL d for abalone fed on 0 hr1 = diets to 62.81
y1
Ž .
mm d for abalone fed on 24 hr35 = diets Table 2 . Growth rates of abalone fed on
24 hr35 = and 24 hr1 = diets were different from that of abalone fed on the 0 hr1 = Ž
. diet Tukey’s HSD test; P - 0.01 .
All of the dulse diets resulted in higher SGR than that of abalone fed on N. Ž
. luetkeana, although differences were not always significant Table 2 . SGR of dulse-fed
y1
Ž .
y1
Ž .
abalone ranged from 1.23 d 0 hr1 = to 1.42 d
24 hr35 = . As with SL data, Tukey’s test indicated that both the 24 hr35 = and 24 hr1 = diets supported
Ž .
greater growth than the 0 hr1 = diet Tukey’s HSD test; P - 0.01 . 3.2. Feed conÕersion efficiency
Ž .
Ž Among the dulse treatments, FCE ranged from 18.2 0 hr1 =
to 22.6 24 . Ž
. hr35 =
Table 2 . Two-factor ANOVA indicated that both water volume exchange Ž
. Ž
. rate
P - 0.001 and light supplementation P - 0.05 had an effect on FCE. Water
Ž volume exchange rate and light supplementation also had an interaction effect ANOVA;
. Ž
P - 0.01 on FCE. FCE of abalone fed on the 24 hr35 = diet was higher Tukey’s; .
P - 0.001 than for abalone fed on all other diets, indicating that abalone converted this Ž
. diet into tissue more efficiently. FCE of abalone fed on N. luetkeana 19.21 was
G. Rosen
et al.
r Aquaculture
185 2000
121 –
136 128
Table 2 Ž
. Ž
. Ž
. Ž
. Ž .
Survival, shell length SL increase, specific growth rate SGR , feed conversion efficiency FCE , and daily feed consumption DFC mean1 SD of juvenile red
Ž abalone after 8 weeks of feeding on experimental dulse diets. Values in the same column followed by a common letter are not significantly different Tukey’s HSD
. test; P 0.05
Ž Calculations are based on either ash-free dry weights or wet weights of abalone tissue and algae. P. mollis diets differed by their culture conditions hours of
. supplemental illumination, h, and number of seawater volume exchanges per day, = . ns 4 for the dulse treatments, while ns 3 for the N. luetkeana treatment.
y1 y1
Ž . Ž
. Ž
. Ž .
Ž . Diet
Survival SL increase mm d
SGR d FCE
DFC Dry wt.
Wet wt. Dry wt.
Wet wt. Dry wt.
Wet wt. 24 h, 35=
100 62.813.49 a
1.420.07 a 1.400.08 a
22.600.66 a 13.510.59 cd
5.680.18 b 10.640.33 b
24 h, 1= 100
61.212.56 a 1.410.04 a
1.380.04 ab 18.680.35 b
24.900.98 a 6.830.24 a
5.700.23 d 24 h, 6=
97.5 59.785.03 ab
1.330.08 ab 1.290.07 ab
19.600.85 b 15.150.34 c
6.060.41 ab 8.710.60 c
0 h, 6= 100
56.223.98 ab 1.360.03 ab
1.330.12 ab 20.081.66 b
14.330.41 d 6.070.59 ab
9.490.65 bc 0 h, 35=
100 54.603.50 ab
1.270.09 ab 1.220.07 ab
19.550.93 b 12.910.35 d
5.730.34 b 9.640.62 bc
0 h, 1= 100
51.563.49 b 1.230.10 b
1.230.12 b 18.190.53 b
19.381.30 b 5.910.46 b
6.470.51 d N. luetkeana
100 53.934.04 ab
1.190.13 b 1.170.08 b
19.211.34 b 6.260.35 e
5.420.13 b 19.000.41 a
comparable to most FCE values of abalone fed on dulse diets when expressed in terms of ash-free dry weight, but was lower than for all dulse diets when calculated on a wet
Ž . Ž
. weight basis Tukey’s; P - 0.001
Table 2 . 3.3. Daily feed consumption
Feed consumption ranged from 5.42 BW d
y1
for abalone fed on N. luetkeana to
y1
Ž .
6.83 BW d for abalone fed on the 24 hr1 = dulse diet Table 2 . Two-factor
ANOVA indicated that light did not have an effect on ash-free dry weight consumption Ž
. of dulse ANOVA; P 0.05 , but the effect of water volume exchange rate on DFC was
significant. There was also a significant interaction effect between light and exchange Ž
. rate on DFC. The highest DFC 24 hr1 = differed from those of abalone fed on 24
Ž .
hr35 = , 0 hr35 = , and 0 hr1 = dulse diets Tukey’s HSD test; P - 0.01 . Although all dulse diets, on an ash-free dry weight basis, resulted in higher DFC rates than for
abalone fed N. luetkeana, on a wet weight basis, Nereocystis was consumed at about twice the rate as the 6 = and 35 = dulse diets and three times the rate as the 1 = dulse
Ž .
diets Table 2 . 3.4. Chemical composition of abalone diets
Ž Protein content of dulse samples was lower earlier in the study than at the end Table
. Ž
. Ž
. 3 , ranging from 10.9 24 hr1 = to 15.7 24 hr35 = of dry weight in July, and
Ž .
Ž .
13.9 24 hr1 = to 18.2 0 hr6 = in September. The general trend was similar at both dates, however, with protein content primarily affected by water exchange rate.
This was especially evident in the July samples, in which protein increased with Ž
. increasing number of seawater volume exchanges from 1 to 35 per day. Likewise,
September samples exhibited relatively low protein in the 1 = diets, but the difference Ž
. between 6 = and 35 = samples was not as apparent Table 3 . Light conditions did not
appear to have an effect on protein content in July, but protein was somewhat higher in the absence of supplemental illumination in September. Protein content of wild N.
Ž .
luetkeana was comparable to that of dulse diets in July 13.5 , but was the lowest Ž
. Ž .
among all diets tested in September 10.8 Table 3 . In July, a strong positive
Ž
2
correlation between protein and ash content of dulse diets was observed r s 0.95, .
n s 6 . Ash data were not available for September samples; thus, no comparison was possible.
By multiplying measured N values by 6.25, CHN analysis resulted in similar protein Ž
. estimates to those obtained biochemical analyses Table 4 . In July, dulse protein
Ž .
Ž .
estimates ranged from 12.9 24 hr1 = to 19.1 24 hr35 = , while in September, Ž
. Ž
. they ranged from 15.7 24 hr1 = to 19.7 0 hr6 = . CrN ratios decreased with
Ž .
increasing exchange rate in both July and September Table 4 . In September, there appeared to be a relationship between protein content of dulse
Ž
2
. and SGR of abalone in the 0 h light treatments r s 0.88, n s 3 , but not in the 24 h
Ž
2
. light treatments r s 0.12, n s 3 . The relationship between protein and SGR was not
Ž
2
. Ž
2
. apparent in July for 0 h light r s 0.32, n s 3 or 24 h light r s 0.03, n s 3 dulse
treatments.
G. Rosen
et al.
r Aquaculture
185 2000
121 –
136 130
Table 3 Ž
. Ž
. Ž
. Comparison of the chemical composition mean1 SD of diets fed to abalone during week 1 July 24, 1997 and week 8 September 16, 1997 of the experiment
Six diets were based on P. mollis, cultured with or without 24 h artificial light supplementation and seawater volume exchange rates of 1, 6, or 35 d
y1
. Dry weight, ash, and residual data not available for September samples
Diet Sample date
Dry weight, Ash,
Protein, Soluble
Lipid, Residual,
percentage percentage
percentage carbohydrate,
percentage percentage
of wet wt. of dry wt.
of dry wt. percentage
of dry wt. of dry wt.
of dry wt. 24 hr35=
July 13.1
41.0 15.7
13.6 2.8
26.9 September
– –
16.7 17.7
3.2 –
24 hr6= July
15.2 33.9
14.4 17.5
3.3 31.9
September –
– 16.5
17.2 2.7
– 24 hr1=
July 22.2
21.8 10.9
22.0 2.4
43.0 September
– –
13.9 20.7
2.3 –
0 hr35= July
13.9 38.2
15.0 14.2
3.0 29.6
September –
– 17.1
15.1 3.1
– 0 hr6=
July 14.4
36.0 14.1
18.2 2.3
29.4 September
– –
18.2 17.9
2.6 –
0 hr1= July
17.9 26.7
11.2 22.3
3.0 36.8
September –
– 15.3
24.6 2.4
– N. luetkeana
July 8.5
51.6 13.5
1.9 2.5
30.5 September
– –
10.8 1.6
2.2 –
G. Rosen
et al.
r Aquaculture
185 2000
121 –
136
131 Table 4
Ž . Ž
. Ž
. Comparison of the total carbon C , nitrogen N , Cr N ratios, and estimated protein contents of the seven diets fed to abalone during week 1 July 24, 1997 and
Ž .
week 8 September 16, 1997 of the experiment Ž
. The first six diets were different cultures of P. mollis, which varied by number of hours of artificial light supplementation 0 or 24 h and seawater volume exchanges
Ž .
0, 6, or 35 per day. Protein was estimated by multiplying N by 6.25. Values are based on one representative sample of food that was fed to abalone. Estimated protein from biochemical analysis is provided as a basis for comparison.
Diet Sample date
C, percentage N, percentage
Cr N ratio Estimated
Estimated of dry wt.
of dry wt. protein
protein Ž
. Ž
. CHN analysis ,
biochemical analysis , percentage of dry wt.
percentage of dry wt. 24 hr35=
July 22.9
3.1 7.5
19.1 15.7
September 24.5
2.9 8.6
17.8 16.7
24 hr6= July
24.6 2.5
10.0 15.3
14.4 September
26.0 2.8
9.2 17.8
16.5 24 hr1=
July 28.9
2.1 14.0
12.9 10.9
September 27.7
2.5 11.1
15.7 13.9
0 hr35= July
22.3 2.9
7.6 18.4
15.0 September
24.5 3.1
7.8 19.6
17.1 0 hr6=
July 24.7
2.6 9.6
16.1 14.1
September 26.1
3.2 8.3
19.7 18.2
0 hr1= July
27.2 2.1
13.0 13.1
11.2 September
28.6 2.5
11.3 15.8
15.3 N. luetkeana
July 20.9
3.0 7.0
18.7 13.5
September 19.7
2.1 9.4
13.2 10.8
Soluble carbohydrate content of dulse was inversely correlated with protein content, Ž
2
. Ž
particularly in July dulse samples r s 0.93, n s 6 . Levels ranged from 13.6 24 .
Ž .
Ž .
hr35 = to 22.3 0 hr1 = of dry weight in July, and 15.1 0 hr35 = to 24.6 Ž
. Ž
. 0 hr1 = in September Table 3 . Soluble carbohydrate extracted from N. luetkeana
samples was much lower than that for dulse, with 1.9 present in July and 1.6 present Ž
. in September Table 3 . Samples of N. luetkeana in July contained 30.5 residual
material that was likely largely composed of insoluble carbohydrate. Residual matter in Ž
. Ž
. Ž
. dulse ranged from 26.9 24 hr35 = to 43.0 24 hr1 = in July Table 3 . Data for
September residual material were unavailable due to the lack of ash weights for these samples.
Ž .
Ž .
Lipid ranged from 2.3 0 hr6 = to 3.3 24 hr6 = of dry dulse weight in July, Ž
. Ž
. Ž
. and 2.3 24 hr1 = to 3.2 24 hr35 = in September Table 3 . Although lipid
content increased with exchange rate in September, no such relationship existed in July Ž
. Table 3 . Samples of N. luetkeana collected from the wild contained 2.5 lipid in July
Ž .
and 2.2 in September Table 3 . Ž
. Ž
. Ash content of dulse in July ranged from 21.8 24 hr1 = to 41.0 24 hr35 = ,
Ž .
Ž and increased with increasing exchange rate of seawater Table 3 . Dry weight per-
. centage of wet weight , on the other hand, decreased as flow rate increased, and ranged
from 13.1 of wet algae weight in the 24 hr35 = dulse diet to 22.2 in the 24 hr1 = Ž
. diet Table 3 .
4. Discussion
