The paper deals with the average yield of four spp of prawns viz. Metapenaeus dobsoni, Metapenaeus affinis, Parapenaeopsis stylifera and Penaeus indicus on conversion to peeled and deveined (PD), cooked and peeled (CP) and head less shell on (HL) forms in the different months of a year and the likely variations observed in the average yield

Krishna Iyer, H.

Rao, P.S.

Unnithan, G.R.

Aquatic Commons

E E YIE OF DIFFE 
FREEZIN 
NT 
G. RAJAGOPALAN UNNII'HAN, P. SREENIVASA RAO, *H. KRISHNA IYER 
Central Institute of Fisheries Technology, Cochin-6820 II 
The paper deals with the average yield of four species 
of prawns viz. Metapenaeus dobsoni, Metapenaeus affinis, Para-
penaeopsis stylifera and Penaeus indicus on conversion to peeled 
and deveined (PD), cooked and peeled (CP) and head less 
shell on (HL) forms in the different months of a year and 
the likely variations observed in the average yield. 
INTRODUCTION 
The prawn catch for the last few 
years has shown an increasing trend. The 
percentage of prawn catch to the total 
marine landings ranges from lO to 16% 
during this period. Side by side, the export 
of processed prawn products has also 
shown an increasing trend. Out of the 
prawn products exported from India frozen 
prawns comprises a major share both in 
terms of quantity and value. Important 
species of prawn used for freezing are 
Metapenaeus dobsoni (poovalan), Metapen-
aeus affinis (kazhandan), Parapenaeopsis 
stylifera (karikadi) Penaeus indicus (sea 
naran) and Penaeus monodon (kara 
chemmeen). Although these species were 
used for processing for the last so many 
years, no reliable estimate regarding the 
average yield of the said species has been 
worked out so far. Though some figures 
were published by Indian Institute of 
Foreign Trade (1970) they were not com-
plete by themselves as they failed to reveal 
the fluctuations in the average yield of 
these species over the different months 
of the year. Reliable estimates leading 
to conversion factors are required both 
by the fishery technologists and the prawn 
processing industry. The fishery tech-
nologists require such an estimate to verify 
the validity of the estimated landings of 
prawns with those exported. The industry 
requires such estimates for planning and 
production. This study was undertaken 
with a view to working out the conversion 
factors of the important species of pra-
wns used for processing so as to meet 
the needs of the technologists and the 
industrialists engaged in this field. 
MATERIALS AND METHODS 
Data on the total quantity of whole 
*Present address: National Institute of Oceanography, Cochin-] 8 
VoL B2 No. 1 1975 25 
'Rajagopalan Unnitfwn. Sreenivasa 'Rao & 'Kristina lyer: Yield of pranms for freezing and canning 
prawns of different species handled daily 
by the factories and the quantity of PD, 
HL, and CP produced after conversion 
were collected by visiting the processing 
factories and peeling centres attached to the 
processing factories regularly. These data 
were collected for a period of one year(i973) 
excluding the monsoon months June, July, 
August and September for the five im-
portant species of prawns. · Generally, 
smaU size prawns were converted to PD 
form for freezing and canning and bigger 
size were converted to HL form. In 
rare cases, the shell damaged and broken 
pieces also were converted to PD form. 
The data collected were compiled and 
the percentage yield on conversion to HL, 
PD and CP of the different species in the 
days of production in different months 
were worked out. Also, from the percentage 
yield worked out for the days, the average 
for the months as a whole was calculated 
and the standard deviat;on (SD) and the 
95% confidence interval . (CI) for the 
population mean were calculated. Analysis 
of variance technique was used for testing 
the significance of variation of the average 
percentage yield in the different months. 
For framing the ANOV A table, the per-
centages were converted to degrees using 
the angular transforn1ation. By this trans-
formation the variance was expected to be 
stabilised. 
RESULTS AND DISCUSSION 
Table I (a), (b), (c) and (d) give the 
mean, standard deviation and the 95% 
confidence interval for the population 
mean of the 4 species M. dobsoni, M.affi-
r;is, P. stylifera and P. indicus respectively 
on conversion from whole to PD and HL 
as the case may be for the different 
months under study. From Table I (a), it 
could be seen that the lowest average 
yield of M.~ dobsoni on conversion from1 
whole to PD was 41.46% in March and 
highest yield of 44.33% in May. Stand-
ard deviation was found to be the lowest 
in October and the highest in March and 
April. The spread of the confidence inter-
val for average yield was found to be 
short in October. Also, Jlf. dobsoni when 
converted to peeled form with tail on has 
shown a 3% increase in yield compared 
to peeled and deveined type. 
For Jlf. affinis (Table 1-b), the maxi-
mum average yield of 49.52% on conversion 
TABLE I (a) 
Month 
January 
February 
March 
April 
May 
October 
November 
December 
26 
Mean S D and 95% confidence interval 
M. dobsoni (poovalan) whole to PD. 
No. of days Mean yield SD 
observed % 
19 42.28 1.85 
18 43.72 1.93 
16 41.46 2.23 
20 41.75 2.22 
15 44.43 2.03 
14 42.00 1.30 
17 42.38 1.50 
17 43.65 1.73 
95% C I 
41.25 - 42.75 
42.66 - 44.68 
40.27 - 42.65 
40.71-42.79 
43.21 - 45.45 
41.25 - 42.75 
41.61 - 43.15 
42.75 - 44.53 
Fish. Techno!. 
'R.ajagopalan Unnitlian, Sreenivasa 'R.ao & 'Krisf!na lyer: Yield of prmvns for freezing and canning 
TABLE I (b) 
M. affinis (kazhandan) whole to PD. 
Month No. of days Mean yield SD 95% C I 
observed % 
January 23 4.6R9 2.27 45.91 - 47.87 
February 18 46.58 2.23 45.47- 47.69 
March 21 45.76 1.49 45.08 - 46.44 
April 25 47.78 3.05 46.52- 49.04 
May 17 49.52 2.11 48.44 - 50.60 
October 14 48.39 2.03 47.22 - 49.56 
November 23 46.60 1.78 45.83- 47.37 
December 17 45.97 2.10 44.89- 47.05 
TABLE I (c) 
P. stylifera (karikadi) whole to PD 
Months No. of Mean yield SD 95% C I 
o bservatioi1s % 
January 19 37.13 1.97 36.18 - 38.08 
February 15 36.37 0.71 35.98 - 36.76 
March 15 33.57 1.97 22.48 - 34.65 
April 23 35.46 1.43 34.84 - 36.08 
May 1l 35.82 1.71 34.67 - 36.97 
October B 33.64 1.67 32.64 - 34.65 
November 20 35.42 1.52 34.71- 36.13 
December 16 36.12 2.31 34.99 - 37.45 
TABLE I (d) 
P. indicus (naran) whole to HL 
Month No. of Mean yield SD 95% C I 
observations % 
January l3 64.83 4.95 61.84 - 67.42 
February 16 65.91 2.17 64.75- 67.07 
March 19 64.85 1.79 63.99 - 65.71 
April 18 66.13 1.19 65.54- 66.72 
May 7 66.00 3.21 63.03 - 68:97 
November 12 1 67.13 1.71 66.04 - 68.22 
December 17 67.06 1.42 66 33 - 67.69 
VOL 12 No. 1 1975 27 
'Rajagopalan Unnitftan, Sreenivasa 'Rao &: 'Krisftna lyer: Yield of prawns for freezing and canning 
ANOV A of mot'thly yield 
TABLE II(a) 
M. dobsoni (poovalan) whole to PD 
Source of ss DF MS F 
variation 
Bet: Months 41.1797 7 5.8828 5.19* 
Error 145.1897 128 1.1342 
Total 186.3690 135 
TABLE Il(b) 
M. affinis (kazhandan) whole to PD 
Source of ss DF MS F 
variation 
Bet: Months 67.3202 7 9.6171 6.21* 
Error 232.2108 160 1.5480 
Total 299.530 157 
TABLE II(c) 
P. stylif::ra (karikadi) whole to PD 
Source of ss DF MS 
variation 
Bet: Months 50.9709 7 7.2815 
Error 131.4775 119 1.1048 
Total 182.4484 126 
TABLE II(d) 
P. indicus (sea naran) 
Source of 
variation 
ss DF MS 
Bet: Months 27.5710 
Error 223.8967 
Total 251.4677 
6 4.5951 
94 2.3818 
100 
* 
ss 
DF 
MS 
CI 
28 
highly significant 
sum of squares 
degrees of freedom 
mean square 
confidence interval 
F 
6.59* 
F 
1.93 
from whole to PD was noticed in May 
Minimum yield noticed was 45.76% i~ 
March. Standard deviation was found to 
be the lowest during March and the highest 
during January and February. The shortest 
confidence interval for the mean yield 
was observed during March and the longest 
during ApriL The percentage yield of M. 
affinis from whole to HL was on an 
average 60%. 
Table I (c) gives the mean, standard 
deviation and the 95% confidence inte = 
val for the percentage yield of P. stylifera. 
For this species a maximum yield of 37.13% 
was noticed in January and a minimum 
of 33.57% during March. Comparatively 
smaller value for standard deviation was 
observed in February and larger value in 
December. The narrow confidence belt for 
mean yield was noticed in February. 
Regarding P. indicus (Table I-d) the 
maximum yield of 67.13% was observed 
during November and minimum yield of 
64.83% was observed in January. The 
mean yield for various months ranged 
between 64.83% and 67.13%. Standard 
deviation was found to be minimum during 
April and maximum during January as 
could be seen from the table. The shortest 
confidence interval for the mean yield 
was observed in April and the longest in 
January and May. The variability obser-
ved in the percentage yield of this species 
may be attributed to the non-uniformity 
in the size grade because a part of the 
P. indicus, processed at Cochin was coming 
from nearby states, which differ in size 
composition compared to those available 
locally. 
For P. monodon no monthwise data 
were available. For the year under study 
a total of 29 observations were made and 
on the basis of this, mean yield worked 
Fish. Techno!. 
'Rajagopalan Unnitlian, Sreeniuasa 'Rao & Kristina lyer: Yield of prawns for freezing and canning 
out from whole to HL was 67.41% with 
a standard deviation of 5.38%. The95% 
confidence interval worked out for this 
species was 65.79 to 69.03%. 
Table II a, b, c and d give the re-
sults of analysis of variance of the mean 
yield of the 4 species M. dobsoni, M. 
affinis, P. stylifera and P. indicus in 
different months. It could be seen from 
these tables that between month variation 
in the average yield of M. dobsoni, M. 
affinis and P. stylifera was highly signifi-
cant (p :S .01). By forming the critical 
difference at 5% level, the average yield 
in different months of the said three species 
was compared. It was observed that the 
average yield of M. dobsoni was significa-
ntly high during February and May, the 
yield of M. affinis was significantly high 
during May ond October and the yield 
of P. stytifera in January, February, April, 
May and December. The variation in the 
average yield of P. indicus was · found to 
be not significant between months. The 
significantly high yield observed in certain 
months in the case of M. dobsoni and 
M. affinis may be attributed to the fact 
that they were the months preceeding the 
effective spawning of these species (George, 
1970). 
Table III (a) gives the monthly yield 
of M. dobsoni and P. stylifera from whole 
to cooked and peeled. Though the species 
were cooked separately for 3 to 4 minutes, 
on peeling, the meat were put together 
so that no monthwise figures were obtained 
separately for the two species. However, 
from factory experience, the average yield 
of M. dobsoni converted from whole to 
cooked and peeled worked out to be 38% 
and that of P. stylifera to be 30 %. From 
Table III (a), it could be seen that the 
yield on conversion from whole to cooked 
Vor. 12 No. 1 1975 
TABLE UI(a) 
Average yield (%) of whole prawns 
to cooked and peeled. 
Month 
January 
February 
March 
April 
May 
Average yield 
35.0 
June 
July 
August 
September 
October 
November 
December 
TABLE III(b) 
35.4 
35.2 
35.3 
35.3 
33.3 
32.0 
30.9 
31.8 
32.3 
30.5 
34.9 
Analysis of Variance of cooked 
and peeled yield rates 
Source of ss DF MS 
variation 
F 
Bet: Months 299.9849 11 27.27 8.37 
Error 329.1303 101 3.26 
Total 629.1151 U2 
and peeled was high m the months 
December to May. 
Table IU(b) gives the analysis of variance 
of the monthly yield. The between months 
variation was highly significant (p :=: .01) 
and the cooked and peeled yield rate was 
found to be comparatively lower from 
June to November than from December 
to May. 
For canning, M. dobsoni, P. stylifera 
and smaU M. affinis are generally used. 
It was observed that under factory condi-
tions the blanched yield of peeled and 
29 
'Rajagopalan Unnitlian, Sreenivas(l 'Rao & 'Kristina lyer: Yidd of prawns for freezing and canning 
deveined M. dobsoni was about 45% and 
that of P. stylifera was about 38%. Thus 
the blanched yield worked out in terms 
of the net weight of whole prawns used 
for canning was on an average 19% for 
M. dobsoni and 152% for P. stylifera. 
ACKNOWLEDGEMENT 
The authors are grateful to late Dr. 
V. K. Pillai, former Director of CIFT, 
Cochin, for suggesting this problem and 
to Shri. G. K. Kurian, Director, CIFT, 
30 
Cochin, for permission to publish this 
paper. They are also thankful to the 
prawn processing factories in and around 
Cochin for their co~operation in carrying 
out this study. 
REFERENCES 
Anon, 1970. Indian Institute of Foreign 
Trade-Report; 3-A: 143. 
George, M. J. 1970. FAO Fisheries Repo-
rts; No. 57. 
Fish. Techno!. 


A study on the average yield of different species pf prawns used for freezing and canning

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A study on the average yield of different species pf prawns used for freezing and canning

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