Certain allometric relations of the spiny lobster Panulirus polyphagus are derived. While the relation between tail length and tail weight is made for both the sexes together, separate relations are derived for the sexes in the case of tail length versus total length. For conservation and economic purposes, it appears that the undersized ones are to be released alive

Kesavan Nair, A.K.

Mathai, T.J.

Aquatic Commons

Fish. Techno!. (1979) 16, 83-85 
n Certain liometric Relations of the piny lobster 
Panu!irus polyphagus (Herbst) 
T. JOSEPH MATHAP AND A. K. KESAVAN NAIR 
Central Institute of Fisheries Technology, Cochin-682 029 
Certain allometric relations of the spiny lobster Panu!ims polyphagus are derived. 
While the relation between tail length and tail weight is made for both the sexes 
together, separate relations are derived for the sexes in the case of tail length versus 
total length. For conservation and economic purposes, it appears that the under-
sized ones are to be released alive. 
Tail length = 88.3400 + 0.4104 
X (tail weight) 
83 
Spiny lobsters popularly called as rock 
lobsters are commercially very important 
in view of its export potential. Of the six 
species of spiny lobsters recorded off Indian 
coasts, Panulims polyphagus is the most 
predominant species off Goa. The same 
species is reported to be the most prevalent 
one off Bombay (Anon, 1962; Chhapgar & 
Deshmukh, 1961; Deshmukh, 1964). The 
relations derived here are restricted to P. 
polyphagus only. The lobster tails are 
graded according to their weight before 
they are packed for export. Difficulties 
have arisen to find the total length and 
weight of lobster caught in relation to the 
tail length and tail weight of the finished 
products. An attempt has been made by 
the authors to relate the tail length and tail 
weight and the total length and tail length 
of P. polyphagus and the results are reported 
in this communication. 
Standard error of the regression 
co-efficient = 0.0202 
Materials and Methods 
340 lobsters were collected from private 
trawlers at Panaji in 1972. The total 
length, total weight, carapace length, tail 
lengthand tail weight were measured. 
Results and Discussion 
Tail lengths are plotted against tail 
weights (Fig. 1). Correlation co-efficient 
(r) was found to be 0.94, suggesting a 
linear relationship. For the purpose of 
conversion, a regression line of tail length 
on tail weight was fitted as follows: 
*Present address: Goa Research Centre of Central 
Institute of Fisheries Technology, Panaji, Goa 
Vol. 16 
280 
260 
240 
220 
200 
180 
IGO 
f. 0·94 
120 
100 
80 
60 .... 
40 
20 90 100 IZO 140 ISO 1110 .2,90 2 20 
T~d length 
Fig. 1. Tail weight (g) x tail length (mm) of male 
and female 
84 T. JOSEPH MATHAI AND A.K. KESAVAN NAIR 
Table 1. Analysis of covariance 
df ;Ex2 ;Exy ;Ey2 Regression Deviations from regression 
co-efficient df ss ms 
Within males 99 29,202.19 52,813.63 102,770.91 1.8085 98 7,254.81 74.0287 
Within females 99 52,074.75 85,292.75 144,914.75 1.6379 98 5,214.55 53.2097 
196 12,469.36 63.6191 
Pooled, within 198 81,276.94 138,106.37 247,685.66 1.6992 197 13,014.31 66.0625 
Difference between slopes 544.95 544.95 
<x2, <xy and ;Ey2 are the corrected sums of squares and products. X and Y have usual meanings 
c . 544.95 
ompanson of slopes: F = 63 .62 = 8.57 with 1 and 196 df (Significant at 1% level) 
Table 2. Analysis of variance of tail length 
Source ss df ms 
Total 85,957.2188 199 
Between 4,680.2813 1 4,680.2813':' 
sexes 
Error 81,276.9375 198 410.4895* 
* Significant at 0.1 % level 
Table 3. Analysis of variance of total length 
Source ss df 
Total 256,771.18 199 
Between sexes 9,085.52 1 
Error 247,685.66 198 
* Significant at 1 % level 
Table 4. Percentage composition 
ms 
9085.52~' 
1250.94':' 
of tail 
weights of lobsters sampled 
Tail Weight Percentage composi-
grades g tion 
U/1 0- 28 0.826 
1/2 29- 56 16.528 
2/3 57- 84 55.371 
3/4 85-112 15.702 
4/5 113-140 4.958 
5/6 141-168 2.479 
6/7 169-196 0.826 
7/8 197-224 0.826 
8/9 225-252 0.826 
9/10 253-280 1.652 
360 
340 
320 
300 
280 
~260 
~ 
...J 
~ 24 
r-
220 
200 
180 
1601: 
0 0 
I 
90 110 
I I I I I I I 
1::10 150 110 190 210 
Tail length 
Fig. 2. Totallengthx tail length (male) 
As it was not possible to differentiate 
the sexes in the finished products at the 
processing factories, the form of relation-
ship between tail length and tail weight 
could not be derived separately for male 
and female. Tail lengths were plotted against 
total lengths separately for males and 
females (Figs. 2 & 3). The corre-
lation co-efficients between the two measure-
ments were 0.96 for males and 0.98 for 
females. As these values were quite high, 
1979 
ALLOMETRIC RELATIONS OF SPINY LOBSTER 85 
analysis of covariance was made with the 
original measurements to ascertain whether 
the form of relationship between total 
length and tail length were the same for 
both the sexes. (Table I). The F-value 
was found significant at I % level. The 
slopes of the regression lines therefore are 
to be considered different indicating that 
the forms of relationship between total 
length and tail length, are different for 
males and females. A combined regression 
line for males and females would not 
hold good and individual relations were 
worked as follows: 
Males: Total length= -5.6915 + 1.8085 
><(tail length) 
Standard error of regression 
co-efficient = 0.0503 
Females: Total 1ength=Il.63I8 + 1.6379 
X (tail length) 
Standard error of regression 
co-efficient=0.0320 
Tail length 
Fig. 3. Total length x tail length (female) 
The average total length and tail length 
for females were 203 mm and Il5 mm res-
pectively, while they were 216 mm and 125 
Vol. 16 
mm respectively for the males. From the 
analysis of variance of tail length (X) and 
total length (Y), the average tail and total 
lengths were found significantly different 
for the sexes. (Tables 2 and 3). This may 
be due to the difference in growth rates and 
sizes in the sexes. The grades accepted 
by the factories and the percentage compo-
sition of tail weights of P. polyphagus 
sampled and graded are furnished in 
Table 4. 
The predominant size group, namely, 
29-112 g (corresponding to the grades 1/2 
to 3/4) constituted 87.6% of the total lobs-
ters sampled. The mode lies in the grade 
2/3 and the corresponding weights are in 
the range of 57-84 g (55.371 %). Their 
tail length taken from the regression lines 
are in the range of 112-123 mm. The 
corresponding total lengths of males and 
females are in the range of 196-216 mm and 
195-213 mm respectively. But the tail 
weight of 29 g and over, that fall under the 
predominant size group is acceptable to the 
industry. The tail length corresponding to 
a tail weight of 29 g is calculated from the 
equation as 100 mm. The corresponding 
total lengths for males and females are 
calculated to be 175.5 mm and 175.7 mm 
respectively. Apart from purposes of con-
servation, for economic reasons also larger 
lobsters are preferred to younger ones, to 
get better grades of tail. Widening the 
mouth of the trap will also allow the entry 
of young ones and consequently in traps, 
all sizes will be caught. The young ones 
that are thus trapped are to be released to 
the water alive. 
The authors are grateful to Shri G. K. 
Kuriyan, Director, Central Institute of Fisheries 
Technology for providing all the facilities to carry 
out this work. They are also grateful to Dr P. N. 
Kaul and Shri R. Balasubramanyan for the 
criticism of the paper. 
References 
Anon (1962) Indian Fish. Bull. 9, I8 
Chhapgar, B.F. & Deshmukh, S.K. (196I) 
J. Bombay nat. Hist. Soc. 58, 632 
Desbmukh, S. K. (1964) J. Bombay 
nat. Hist. Soc. 61, I50 


On certain allometric relations of the spiny lobster Panulirus polyphagus (Herbst)

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On certain allometric relations of the spiny lobster Panulirus polyphagus (Herbst)

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