Effect of size grading on the growth performance of shortfin eel (Anguilla australis) during its yellow stage

Figures & data

Table 1 Body weight, total length, survival, specific growth rate, biomass gain, feed intake, feed conversion ratio and age of four groups of shortfin eel (Anguilla australis) established by size.

	Large eels (> 135 g)		Small eels (≤ 135 g)
	L-graded n = 32	L-ungraded n = 31	S-graded n = 21	S-ungraded n = 19
Social interaction	Large eels with large eels	Large eels with small eels	Small eels with small eels	Small eels with large eels
Body weight (BW, mean ± SD, g)
Day 0	101 ± 12 g^1
Day 42	182 ± 29^a	183 ± 30^a	97 ± 20^b	94 ± 19^b
Day 109	321 ± 59^a	337 ± 69^a	144 ± 94^b	140 ± 85^b
Total length (TL, mean ± SD, cm)
Day 0	387 ± 21 mm^1
Day 42	421 ± 18^a	425 ± 21^a	374 ± 22^b	380 ± 20^b
Day 109	485 ± 25^a	492 ± 34^a	396 ± 46^b	404 ± 40^b
Specific growth Rate (SGR, mean ± SD)
Day 0–42	1.08 ± 0.27^a	1.10 ± 0.28^a	−0.05 ± 0.37^b	−0.15 ± 0.42^b
Day 42–109	0.84 ± 0.27^a	0.91 ± 0.30^a	0.31 ± 0.78^b	0.36 ± 0.69^b
Day 0–109	1.03 ± 0.18^a	1.08 ± 0.20^a	0.19 ± 0.55^b	0.16 ± 0.56^b
Survival (%)
	100	100	86	95
Biomass gain^2(BG, % of biomass at day 42, mean ± SEM of 3 tanks)
	76.0 ± 7.7^a	85.1 ± 10.5^a	38.2 ± 11.5^b	46.3 ± 6.4^b
Feed intake^2(FI, % of biomass at day 42, mean ± SEM of 3 tanks)
	78.9 ± 2.9^a	NC	54.9 ± 14.1^b	NC
Feed conversion ratio^2(FCR, mean ± SEM of 3 tanks)
	1.0 ± 0.1^a	NC	1.5 ± 0.1^b	NC

NC, not calculable. It was not possible to separately record the FI (and consequently, FCR) by L-ungraded and S-ungraded fish because they were reared together in the same tanks.

¹Mean values of the whole eel lot as calculated at day 0.

²Analyses from day 42 to 109.

The groups were conformed on the basis of weight at day 42. ^a,bValues in the same row with different superscripts are significantly different at P < 0.05.

Figure 1 Body weight development of four groups of shortfin eel (Anguilla australis) established by size. Each line represents a specimen.

Figure 2 Age of four groups of shortfin eel (Anguilla australis) established by size. The bottom and top lines of the box are the lower (Q1) and the upper (Q3) quartiles respectively. The line inside represents the median (Q2), whereas the black dot represents the mean. The end of the whiskers are the lowest datum still within 1.5 IQR of the lower quartile (Q1) and the highest datum still within 1.5 IQR of the upper quartile (Q3). Outliers' values are represented by a plus sign. IQR = Q3–Q1.