Estimation of Whole Volume of Green Shelled Mussels using their Geometrical Attributes Obtained from Image Analysis

Figures & data

Table 1  The Nikon D300 camera control settings for back-lighting images

Camera settings	Back-lighting
Exposure mode	Manual
Shutter speed	¼ s
Aperture	f/11
Exposure Compensation	0 EV
ISO sensitivity	200
White balance	Preset manual
Image size (pixels)	2144 × 1424

Figure 1 (a) Volume calculation by the cubic spline method. The black square is the size reference (4 cm × 4 cm). The divisions of the mussels, and the coordinates used to calculate the cross sectional areas (Eq. (5)) are shown. (b) The change of the total calculated volume of a mussel as affected by the number of divisions. After about 16 divisions, the calculated volume stabilizes. The volume of the same mussel, calculated based on two different images are also displayed. (c) Distribution of the calculated density frequency of the mussels used. (d) Volume calculated by cubic splines (using the combinations S1-T1 and S2-T2) versus the experimentally measured volume of the mussels.

Table 2  Parameters of the fitted equations to volume versus view area

Measured volume versus view area top (S1)
Y = A + BX		Y = A.X^B		Polynomial fitting
A=	−21.82 ± 6.66	A=	0.32 ± 1.65	C0=	2.432
B=	2.07 ± 0.19	B=	1.42 ± 0.14	C1=	0.690
R^2=	0.94	R^2=	0.93	C2=	0.019
SS=	181.00	SS=	172	R^2=	0.943
				SS =	170
Measured volume versus view area bottom (S2)
Y = A + BX		Y = A.X^B		Polynomial fitting
A=	−20.72 ± 6.18	A=	0.34 ± 1.59	C0=	−5.952
B=	2.04 ± 0.17	B=	1.41 ± 0.13	C1=	1.211
R^2=	0.94	R^2=	0.93	C2=	0.011
SS=	181.00	SS=	173	R^2=	0.946
				SS=	178

Table 3  Prediction of whole volume by using the top and side view areas of mussels

Equation	Combination	a	b	c	R^2
z = a + bx + cy	S1–T1	−22.09 ± 2.43	1.19 ± 0.2	1.39 ± 0.3	0.97
	S2–T2	−21.62 ± 2.15	1.11 ± 0.17	1.55 ± 0.26	0.97
z = a + bx^3 + c / y^0.5	S1–T1	100.82 ± 9.7	(2.95 ± 0.31)10^−4	−297.95 ± 39.81	0.97
	S2–T2	101.15 ± 7.93	(2.90 ± 0.26)10^−4	−293.44 ± 31.75	0.98

z: volume (cm³); x: top view area (cm²); y: side view area (cm²); a, b, c: parameters determined by fitting equations to data.

Table 4  Parameters of the fitted equations to weight versus view area

Measured weight versus view area, top (S1)
Y = A + BX		Y = A.X^B		Polynomial fitting
A=	−30.79 ± 9.02	A=	0.25 ± 1.81	C0=	−23.593
B=	2.57 ± 0.25	B=	1.54 ± 0.17	C1=	2.169
R^2=	0.93	R^2=	0.91	C2=	0.006
SS=	387	SS=	395	R^2=	0.928
				SS=	386
Measured weight versus view area, bottom (S2)
Y = A + BX		Y = A.X^B		Polynomial fitting
A=	−29.87 ± 9.60	A=	0.26 ± 1.88	C0=	−26.072
B=	2.56 ± 0.27	B=	1.53 ± 0.18	C1=	2.345
R^2=	0.92	R^2=	0.90	C2=	0.003
SS=	442	SS=	453	R^2=	0.917
				SS=	442

Table 5  Parameters of the fitted equations to meat weight versus whole weight

Y = A + BX		Y = A.X^B		Polynomial fitting
A=	2.92 ± 4.34	A=	0.69 ± 2.17	C0=	7.792
B=	0.32 ± 0.07	B=	0.84 ± 0.19	C1=	0.158
R^2=	0.71	R^2=	0.70	C2=	0.001
SS=	218	SS=	221	R^2=	0.717
				SS=	216

Figure 2  (a) Length, width and thickness frequency distributions of the mussels, measured by image analysis. (b) Volume calculated by using Length, Width, and Thickness data using Eqns. 10, 11 and 12. (c) Distribution of the frequency of the condition index of the mussels, calculated by using Eq. (2). (d) Distribution frequency of the aspect ratio (length / width) of the S₁, S₂ views and T₁, T₂ views of the mussels.

Figure 3 (a) Correlation between volume and perimeters of various view areas. (b) Volume calculated using Eq. (17) vs measured volume.