In view of its new found status in export market, ribbon fish resources need to be continually monitored. Mortality, one of the important parameter is reported for the Indian ribbon fish Trichiurus lepturus Linnaeus in the present communication. The average annual instantaneous rate of total (Z), natural (M) and fishing mortality coefficient (F) were estimated as 2.66, 0.77 and 1.89 respectively for the 1995 to 1997 period. The exploitation rate (U) and exploitation ratio (E) were estimated as 0.66 and 0.71 respectively, which is beyond the optimum thrust reduction in the fishing effort for this stock along the Maharashtra coast is necessary

Biradar, R.S.

Mohite, A.

Aquatic Commons

Journal of the Indian Fisheries Association 
28, 2001, 23-29 
23 
MORTALITY ESTIMATES OF INDIAN RIBBON FISH TRICHIURUS 
LEPTURUS OFF MAHARASHTRA COAST 
ASHISH MOHITE* 1 AND R. S. BIRADAR 
Central Institute of Fisheries Education 
(!CAR) Deemed University, 
Versova, Mumbai- 400 061. 
ABSTRACT 
In view of its new found status in export market, ribbon fish resources 
need to be continusly monitored. Mortality, one of the important parameter 
is reported for the Indian ribbon fish Trichiurus lepturus Linnaeus in the 
present communication. The average annual instantaneous rate of total (Z), 
natural (M) and fishing mortality coefficient (F) were estimated as 2.66, 0. 77 
and 1.89 respectively for the 1995 to 1997 period. The exploitation rate (U) and 
exploitation ratio (E) were estimated as 0.66 and 0.71 respectively, which is 
beyond the optimum Thursreduction in the fishing effort for this stock along 
the Maharashtra coast is necessary. 
Keywords : Mortality, Exploitation rate, Trichiurus lepturus. 
INTRODUCTION 
Rribbon fishes were never the main 
focus of attention oflndian fishermen, and 
were primarily consumed locally in fresh/ 
sundried condition or used as popular baits 
for capturing larger fishes like seerfish. 
They were also regularly exported in sun 
dried or salt- cured condition to countries 
like Sri-Lanka, Malaysia etc. However, it 
is only during the last decade that 
ribbonfishes have been able to gradually 
attain the status of one of the major marine 
resource of India. Presently frozen 
ribbonfishes are exported to more than 30 
countries around the world including China, 
Singapore, Republic of Korea, Japan etc. 
Recently, they have also been tried as a 
source of raw material for surimi processing 
in India. Further, there is an increasing 
demand for the cosmetics made from their 
skin and pearl essence obtained from their 
body. During the last 10 years, the Indian 
ribbonfishes have registered a three -fold 
increase in their annual landings (MPEDA 
1990, 1996, 1998), including a record 10,000 
t'onnes hike along the Maharashtra State 
(west coast of India). It is in this context, 
during the course of the present study, an 
attempt has been made to analyse the 
trends in mortality over the years. 
Mortality studies of the Indian ribbon 
fish Trichiurus lepturus, have been carried 
out by several workers like N arasimham 
(1983, 1994). Meenakshisundaram et al. 
* Present address : College of Fisheries, (Dr. B. S. Konkan Krishi Vidyapeeth), Ratnagiri-415 629. 
1 Formed part of thesis for partial fulfillment of Ph.D. degree submitted to CIFE (Deemed University) 
24 MOHITE AND BIRADAR 
(1986), Somvanshi and Antony (1989). 
Chakraborty (1990), Thiagarajan et al., 
(1992), Reuben et al., (1997) and 
Chakraborty et al., (1997) along both coasts 
of India. The present investigation was 
carried out to estimate fishing and natural 
mortality coefficient ofTrichiurus lepturus 
offMaharashtra coast specially on account 
of its new- found status as an important-
sea- food export commodity. 
MATERIAL AND METHODS 
The catch and length composition data 
during the period October, 1995 to 
September, 1997 was collected by 
undertaking at least three monthly visits 
to each landing centre viz. Mirkarwada at 
Ratnagiri and New Ferry Wharf and 
Versova at Mumbai, representing southern 
and northern zones of the Maharashtra 
coast respectively. Length frequency data 
·of total length in centimeters ofT. lepturus 
thus obtained on each sampling day, was 
then pooled up month-wise by grouping it 
into four em class interval. This month-
wise data collected for the two years of 
study period was further pooled to one 
calendar year by taking average values of 
the corresponding months and was then 
converted to the percentage of sample total. 
Estimates of growth parameters viz. La = 
128 em, K = 0.5 per year and t 0 =- 0.009 
years thus obtained from this basic data 
(Mohite, 1999) have been used as inputs in 
the present analysis. 
The mortality parameters were obtained 
by using FiSAT (FAO - ICLARM Stock 
Assessment Tools) computer software 
package developed by Gayanilo, et. al. (1996) 
comprising methods like Pauly's (1978) 
Rikhter and Efanov's (1976) and also 
Cushing (1968) and Srinath (1948) for 
natural mortality coefficient. Length 
converted catch curve (Pauly, 1983 b, 1984 
a & b), Jones and van Zalinge plot (1981), 
Beverton and Holt (1956) and Ault and 
Ehrhardt (1991) for estimation ofZ. 
Table 1: Total Mortality Coefficient (Z) for Trichiurus lepturus off 
Maharashtra Coast (For L011 = 128 em, K = 0.5 per year) 
Method z Remarks 
Jones & van Zalinge (1981) Z plot 2.24 -
Length converted catch curve 2.25 -
Ault & Ehrhardt (1991) method 2.66 For L' = 64.00 em 
L = 74.103 em and 
Lmax = 123.7 em. 
Beverton & Holt (1956) model 2.67 For L' = 64.00 em 
-L = 74.103 em 
MORTALITY ESTIMATES OF INDIAN RIBBON FISH 25 
RESULTS AND DISCUSSION 
The results of instantaneous rate of 
total and natural mortality coefficient of 
Trichiurus lepturus off Maharashtra, as 
estimated by different methods employed 
in the present investigation are given ·in 
Table 1 and 2 respectively. It is seen that 
annual "Z" varied from 2.24 to 2.67 while 
annual''M11 varied from 0.77 to 1.61. 
The "Z11 as recorded by various authors 
for T. lepturus (Table 3) along the west 
coast of India varied from a minimum of 
1.79 (Somvanshi and Antony 1989) to a 
maximum of off 3.82 Mumbai coast 
(Thiagarajan et al., 1992). Similarly, along 
the east coast, the lowest 11Z" value of 1.2 
was observed by Narasimham (1983) off 
Kakinada and Meenakshisundaram et al., 
(1986) off Andhra Pradesh coast, while the 
highest was 3.4 7 offVisakhapatnam coast 
by Ruben et al., (1997). 
The Ault and Ehrhardt (1991) method 
for the estimation of Z does not assume an 
infinite life span for the fish of the stock 
that is being analysed and is best suited for 
short lived tropical species (Gayanilo, et 
al., 1996). During the present study, 
however, the annual "Z" values as obtained 
by Ault and Ehrhardt (1991) method and 
Beverton and Holt (1956) model are almost 
same. viz., 2.66 and 2.67 repectively (Table 
1). Further, the annual "Z" as obtained by 
these two methods is close to the value 
obtained earlier by Chakraborty et al., 
(1997) for the Maharashtra coast for T. 
lepturus (Table 3). Hence, the value of 
instantaneous total mortality coefficient 11Z" 
= 2.66 as obtained by Ault and Ehrhardt 
(1991) method, had been selected for 
estimation of fishing mortality coefficient 
"FII. 
The instantaneous natural mortality 
coefficient "M" = 0. 77 for T. lepturus off 
Maharashtra was the lowest estimate 
obtained by Pauly's (1978) method while 
the highest value of 1.61 was obtained by 
Rikhter and Efanov's (1976) method (Table 
2). The natural mortality estimates ofT. 
lepturus for different regions along the west 
Table 2: Natural Mortality Coefficient (M) for Trichiurus lepturus off 
Maharashtra Coast (For Loo = 128 em, K = 0.5 per year) 
Method M Remarks 
Pauly's (1978) method 0.77 For T =28.72°C. 
Srinath (1998) method 0.84 -
Cushing's (1968) method 0.92 For Tmax = 6 years and 
95% of Loc = 121.6 em. 
For tmass = 0.883 years. 
Rikhter & Efanov's (1976) 1.51 (females) 
method 1.61 tmass = 0.8125 years 
(males) 
Table 3 : Mortality estimates for Trichiurus lepturus by different authors. 
Indian Annual Mortality Coefficients 
Coast Authors Region M z 
Present Study Maharashtra 0.77 2.66 
Coast (Pauly's Method) (Beverton & Holt method) 
w Somvanshi & North West 0.80 1.79 
Antony (1989) coast (Pauly's method) (Length Converted Catch Curve method) 
E Chakraborty Mumbai Coast 1.05 1.96 
(1990) (Cushing's method) (Beverton & Holt method) 
s Thiagarajan et al., West Coast 1.00 and 1.07 3.71 and 3.77 
(1992) (Calculated from Z & F) (Catch Curve method a..'l.d Cohort analysis) 
T Chakraborty et al., Maharashtra 0.75 2.62 
(1997) Coast (Pauly's method) (Length Converted Curve method) 
Narasimham Kakinada coast 0.90 1.20 
E (1983) (Sekharan's method) (Average Catch curve (Ricker 1975) 
Meenakshisundaram Andhra Pradesh 0.90 1.20 
A et al., (1986) coast (method not mentioned) (method not mentioned) 
Thiagarajan et al., East coast 0.95 and 1.12 3.15 and 3.32 
s (1992) (Calculated from Z & F) (Catch Curve method and Cohort analysis) 
Narasimham Kakinada coast 0.46 3.16 
T (1994) (Sekharan's method) (Beverton & Holt method) 
Reuben et al., Visakhapatnam 0.89 2.42 and 3.47 
(1997) coast (Pauly's method) (Catch curve and Beverton & Holt method) 
F E 
1.89 0.71 
0.99 0.55 
0.91 0.46 
2.71 0.730 
1.87 0.71 
0.30 0.25 
0.30 0.25 
2.20 0.70 
2.70 0.85 
1.52 0.63 
u 
0.66 
0.46 
0.39 
0.70 
0.68 
0.17 
-
0.84 
0.32 
0.57 
tv 
m 
0 
~ 
8 
t?;j 
§ 
td 
...... 
~ 
~ 
MORTALITY ESTIMATES OF INDIAN RIBBON FISH 27 
as well as east coast of India as computed 
by various authors is presented in Table 3. 
It can be seen that natural mortality 
estimates of T. lepturus along the west 
coast varied from a lowest of 0. 7 5 off 
Maharashtra coast (Chakraborty et al., 
1997) to a highest of1.07 off the entire west 
coast (Thiagarajan et al., 1992). Similarly, 
along the east coast the minimum estimate 
was 0.46 offKakinada coast (N arasimham, 
1994) while the maximum of 1.12 was 
recorded by Thiagarajan et al.,(1992) for 
the entire east coast. The values of annual 
"M" of0.77, 0.84 and 0.92 as estimated in 
the present investigation (Table 2) fall 
within the range of the estimates as obtained 
by (Table 2) appear to be on the higher side. 
Further, the value of instantaneous natural 
mortality coefficient "M'' = 0. 77 obtained in 
the present investigation for T. lepturus off 
Maharashtra coast using Pauly's (1978) 
method is quite close to the value obtained 
earlier by Chakraborty et al., (1997) for the 
same region and hence, has been used in 
further analysis including estimation of 
fishing mortality coefficient "F". 
The fishing mortality coefficient "F" 
obtained in the present investigation is 
1.89 (i.e. after selecting "Z" = 2.66 and "M" 
= 0. 77). The fishing mortality estimates of 
T. lepturus computed by various authors 
for different areas along both the coasts of 
India is given in Table 3. It can be observed 
that fishing mortality estimates of T. 
lepturus along the west coast varied from a 
minimum of 0.91 off Mumbai coast 
(Chakraborty, 1990)to a maximum of2.71 
off the entire west coast (Thiagarajan et 
al., 1992). Similarly, along the east coast 
the lowest estimate of0.3 was observed off 
Kakinada coast (N arasimham, 1994) and 
Andhra Pradesh coast 
(Meenakshisundaram, et al., 1986) while 
the highest of 2.20 was recorded by 
Thiagaraj'an et al., (1992) for the entire 
east coast. The value of instantaneous 
fishing mortality coefficient "F" =1.89 
obtained in the present investigation is 
quite close to the value obtained earlier by 
Chakraborty et al. (1997) for Maharashtra 
coast. 
The annual catchability coefficient "q" 
was derived by calculating "f' the average 
of trawler boat hours for the fishing seasons 
1995-96 and 1996-97 and by using the value 
of"F" as 1.89. The average annual trawler 
boat hours during the period 1995 to 1997 
was estimated to be 53,44, 726 hours (Mohite, 
1999). Fm'ther, it was estimated that out 
of the total T. lepturus landings of 
Maharashtra, for these two fishing seasons. 
97 per cent was exclusively contributed by 
trawlers (Mohite, 1999). Hence, trawler 
boat hours have been used for the estimation 
of "q" in the present analysis. Further, 
assuming that the value of"q" & "M" remain 
the same over the years, fishing mortality 
and total mortality can be estimated if 
fishing effort 'f is known. 
The exploitation rate and exploitation 
ratio estimates ofT. lepturus, as computed 
by various authors for different sectors 
along the Indian coast are presented in 
Table 3. It can be seen that the exploitation 
rate of T. lepturus along the west coast 
varied from a minimum of0.39 offMumbai 
coast (Chakraborty, 1990) to a maximum 
of 0. 70 off the entire west coast. 
(Thiagarajan et al., 1992). Similarly, along 
the east coast the lowest and the highest 
estimate of the exploitation rate of 0.17 and 
28 MOHITE AND BIRADAR 
0.82 both offKakinada coast were recorded 
by Narasimham in 1983 and 1994, 
respectively. Like wise, the lowest value of 
the exploitation ratio was recorded as 0.25 
off Kakinada coast (N arasimham, 1983) 
while the highest of0.66 was observed for 
the entire east coast by Thiagarajan et al., 
(1992). 
Thus the exploitation rate as well as 
exploitation ratio as determined in the 
present investigation are quite similar to 
those obtained earlier by Chakarborty et 
al., (1997) along the Maharashtra coast 
and Thiagarajan et al. (1992) along the 
entire west coast oflndia (Table 3) and are 
well beyond 0.5. Hence there is an urgent 
need to reduce fishing effort along 
Maharashtra coast for optimum 
exploitation ofT. lepturus. 
ACKNOWLEDGMENTS : 
The authors are grateful to Dr. S .A. H. 
Abidi, former Director, CIFE, Mumbai for 
his kind encouragement and facilities 
provided during the course of investigation 
and thank Dr. R. Pai, Associate Professor, 
College of Fisheries, Ratnagiri for going 
through the manuscript and providing 
invaluable suggestions. 
REFERENCE 
Ault, J. S. and Ehrhardt N. H., 1991. 
Correction to the Beverton and HoltZ-
estimator for truncated catch length-
frequency distributions. ICLARM 
Fishbyte 9(1): 37-39. 
Beverton, R. J. H. and HoltS. J., 1956. 
A review of methods for estimating ·. 
mortality rates in exploited fish 
populations, with special reference to 
sources ofbias in catch sampling. Rapp. 
P.- V. Reun. ClEM. 140:67-83. 
Chakraborty, S.K., 1990. Fishery, age, 
growth and mortality estimates of 
Trichiurus lepturus Linnaeus from 
Bombay waters. Indian J. Fish., 37 
(1): 1-7. 
Chakraborty, S.K., Deshmukh V.D., 
Khan M.Z., Kuber V. and Raje S.G., 
1997. Estimates of growth, mortality, 
recruitment pattern and maximum 
sustainable yield of important fishery 
resources ofMaharashtra coast. Indian 
J. Mar. Sci., 26: 53-56. 
Cushing, D.H., 1968. Fisheries biology. A 
study in population dynamics. Univ. 
Wisconsin Press, Madison, Wis., : 
200pp. 
Gayanilo, F.C. Jr., Sparre P. and Pauly 
P., 1996. FAO - ICLARM Stock 
assessment tools (FiSAT). Computer 
software package (ver. 1.1; September, 
1995) & User's manual. FAO 
Computerised information senes. 
(Fisheries) 8: 126 pp. 
Jones, R. and Zalinge van. N.P., 1981. 
Estimates of mortality rate and 
population size for shrimp in Kuwait 
waters. Kuwait Bull. Mar. Sci., 2 : 
273-288. 
Marine Products Development 
Authority, India, 1990. Statistics of 
Marine Products Exports, 1989 : 115 
pp. 
Marine Products Development 
Authority, India, 1996. Statistics of 
MORTALITY ESTIMATES OF INDIAN RIBBON FISH 29 
Marine Products Exports, 1994 : 254 
pp. 
Marine Products Development 
Authority, India, 1998. Statistics of 
Marine Products Exports, 1996 : 388 
pp. 
Meenakshisundaram, P. T ., 
Narasimham K.A. and Sastry Y.A., 
1986. The ribbonfish resources, R & D 
series for marine fisheries resources 
management CMFRI, Cochin, India. 
Mohite, A.S., 1999. Stock assessment of 
Trichiurus lepturus (Linnaeus, 1758) 
and study of gears employed in its 
fishery of Maharashtra coast. Ph.D. 
Thesis submitted to the Central 
Institute of Fisheries Education 
(Deemed University), Mumbai : 219 
pp. 
Narasimham, K.A., 1983. On the fishery, 
mortality rates and yield per recruit of 
the ribbon fish, Trichiurus lepturus 
Linnaeus, Indian J. Fish., 30 (1): 99-
101. 
Narasimham, K.A., 1994 Fishery and 
population dynamics of the ribbonfish 
Trichiurus lepturus Linnaeus off 
Kakinada. J. Mar. biol. Ass. India, 36 
(1&2): 23-27. 
Pauly, D., 1978. A discussion of the 
potential use in population dynamics of 
the interrelationships between natural 
mortality, growth parameters and 
mean environmental temperature in 
122 stocks. ICES, C.M., Demersal Fish 
Committee 21: 36 P. 
Pauly, D., 1983 b. Length - converted 
catch curves. A powerful tool for 
fisheries research in the tropics. (Part 
I), ICLARM Fishbyte, 1 (2) : 9- 13. 
Pauly, D., 1984 a. Length - converted 
catch curves. A powerful tool for 
fisheries research in the tropics. (Part 
II). ICLARM Fishbyte, 2 (1): 17-19. 
Pauly, D., 1984 b. Length - converted 
catch curves. A powerful tool for 
fisheries research in the tropics. (Part 
III : Conclusion). ICLARM Fishbyte, 2 
(3): 9-10. 
Reuben, S., Vijayakumaran K., 
Achayya P. and Prabhakar R.V.D, 
1997. Biology and exploitation of 
Trichiurus lepturus Linnaeus from 
Visakhapatnam waters. Indian J. 
Fish., 44 (2): 101-110. 
Rikhter, V.A. and Efanov V. N., 1976. 
On one ofthe approaches to estimation 
of natural mortality offish populations. 
ICNAF Res. Doc., 76NI/8 : 12 pp. 
Somvanshi, V. S. and Antony J., 1989. 
Population dynamics and assessment 
of Trichiurus lepturus Linnaeus stock 
in north - west coast of India. In : 
Studies on Fish Stock Assessment in 
Indian Waters Spl. Publ. No.2 (Fishery 
Survey of India) : 1-32. 
Srinath, M., 1998. Empirical relationships 
to estimate the instantaneous rate of 
natural mortality. Indian J. Fish., 45 
(1): 7- 11. 
Thiagarajan, R., Lazarus S., Sastry 
Y.A., Khan M. Z., Kasim H.M. and 
Scariah K.S., 1992. Stock assessment 
of the ribbonfish, Trichiurus lepturus 
Linnaeus, from the Indian waters, 
Indian J. Fish., 39 (3 & 4): 182-194. 


Mortality estimates of Indian ribbon fish Trichiurus lepturus off Maharashtra coast

http://aquaticcommons.org/16569/1/JIFA28_023.pdf

Mortality estimates of Indian ribbon fish Trichiurus lepturus off Maharashtra coast

Abstract

Similar works

Full text

Available Versions

Aquatic Commons