INTRODUCTION:

The mathematical relationship between the length and weight of fishes is of great importance in relation to morphology, biology, growth rate and population dynamics and it also enables to estimate fish population. A perusal of previous literature on the length-weight relationship of fishes reveals its species dependence and its difference among populations (Bwathondi and Pratap, 1981; Seshappa, 1981; Safran, 1992). Natarajan et al., (1977) reported the difference in the length-weight relationship of intraspecific populations of fishes inhabiting in same water body. Generally it is expected that the weight of fishes would vary as the cube of length (Brody, 1945; Lagler, 1952; Rounsefell and Everhart, 1953; Brown, 1957).

But the actual relationship may depart significantly from this, as fishes normally do not retain the same shape or body outline throughout their life span and the specific gravity of the tissues may not remain constant (Le-Cren, 1951).

The length weight relationship of mackerels has been investigated by several workers (Pradhan, 1956; Rao, 1962; Sekharan, 1962; Luther, 1973; Yohannan, 1977; Udupa and Bhat, 1983; Azad and Udupa, 1989 and Gopakumar, 1991). The important contributions on the length-weight relationship of Sardinella gibbosa is that of Ganapati and Rao (1957), Sekharan (1968), Rao (1981) and Bwathondi and Pratap (1981). The noteworthy work on the length-weight relationship of Encrasicholina devisi is that of Syda Rao (1988a). The length –weight relationship of nemipterids has been recorded from east and west coasts of India (Krishnamoorthy, 1971; Vinci and Nair, 1974; Acharya and Dwivedi, 1981; Murty, 1983; Mohan and Velayudhan, 1984 and Hamsa et al., 1994).

Even though all these works are available, the length-weight relationship of the locational population of the common fishes of the south west coast of India are few. This aspect has been taken into consideration and the length-weight relationship of the common edible marine fishes viz, Rastrelliger kanagurata, Sardinella gibbosa, Encrasicholina devisi and Nemipterus japonicas of Trivandrum area was studied during the present investigation.

MATERIALS AND METHODS:

The samples of fishes were collected from the catches of Shanghumugham and Valiyathura beaches during a period of one year from January to December 1991.

Soon after the collection the fishes were brought to the laboratory. The water on the body surface was wiped with blotting paper. The total length and weight of all the specimens were recorded to the nearest mm and mg respectively. The data were pooled and subjected to regression analysis, to determine the growth pattern of fishes. No separate analysis was conducted for males and females, so common equation was derived for each species.

RESULTS:

The regression analyses of length-weight relationship of the four species of marine fish under study are given in Table I. The length-weight relationship of Rastrelliger kanagurata revealed a linear relationship which can be represented as TW=3.2392 log TL-2.3777. The ‘b’ value of 3.2392 explained the isometric growth rate of this species.

The linear relationships of Sardinella gibbosa revealed a regression equation of TW=1.47454 log TL-0.27006. The ‘b’ value of 1.47454 reveals its allometric growth pattern.

Encrasicholina devisi also showed allometric growth rate, since it has the ‘b’ value of 2.54733. The relationship can be expressed as TW=2.54733 log TL-1.69993.

The length-weight relationship of Nemipterus japonicas also reveals an allometric growth form. The ‘b’ value was found to be 1.56103. The linear relationship can be expressed as TW= 1.56103log TL-0.2365.

Table I: Regression equations for length- weight relationship

Species	r value	Regression equation
Rastrelliger kanagurata	0.97818	Log Wt=3.2392 Log Tl=2.3771
Sardinella gibbosa	0.95494	Log Wt=1.47454 Log Tl=0.27006
Encrasicholina devisi	0.93219	Log Wt=2.54733 Log Tl=1.69993
Nemipterus japonicus	0.86592	Log Wt=1.56103 Log Tl=0.23650

DISCUSSION:

Cubic law is the usual way to express the length-weight relationship of fishes which is expressed as

W= aL^b

Where W= Weight of fish

L= Length of fish

a,b= Constants

The value of ‘b’ has significance with growth pattern of the fish. The value of ‘b’ falls around ‘3’ in fishes having isometric growth rate. Those showing significant variation from ‘3’ are said to have allometric growth rate. Deviation from isometric growth rate is common among fishes.

Earlier workers (Pradhan, 1956; Rao, 1962; Luther, 1973; Yohannan, 1977 and Gopakumar, 1991) showed no difference in the length-weight relationship of males and females. Hence in the present study a common equation was derived for both males and females. Pradhan (1956) reported ‘b’ value of 3.1737 for the mackerels of Karwar which showed isometric growth rate of this species. Tampubolon (1986) reported a ‘b’ value of 3.377 for

Rastrelliger kanagurata of the Malacca strait. The results of the present study revealed ‘b’ value of 3.2392 in Rastrelliger kanagurata, which is almost equal to that obtained by (Luther 1973; Rao, 1962; Conand, 1987; Azad and Udupa, 1989).

The length-weight relationship of sardines depends upon the species and stage of maturity. Kumar and Balasubramanyan (1989) reported ‘b’ values of 2.3645, 3.0024 and 3.8056 in males, females and immature forms respectively for Sardinella logiceps. In Sardinella albella, Sekharan (1968) reported that the regression coefficient of very small fish, larger indeterminates and the sexes are found to be significantly different. The ‘b’ value was found to be 3.6391 for very small fishes, 3.2803 for indeterminate, 3.1757 for females and 3.0518 for males. According to him the ‘b’ value of Sardinella gibossa is also size dependent and it showed a maximum value of 3.9545 in very small fishes. The difference between regression coefficients of indeterminates male and females were most probably not significant and hence a pooled regression estimate was made and reported ‘b’ value of 3.1497. A significant difference in regression coefficient was noticed only among very small fishes and larger fishes. Since very small fishes were not included in the present study such a comparison was not possible. Bwathondi and Pratap (1981) reported ‘b’ value of 1.4453 in S. gibbosa of Kunduchi Creek, which reveals its specific variation. The results of the present study revealed ‘b’ value of 1.47454 which forms the allometric growth rate of S. gibbosa observed by Bwathondi and Pratap (1981).

The mathematical relationship length-weight varied among different species of anchovies. Venkataraman (1956) reported ‘b’ value of 3.3270 for Thryssa mystax of Calicut and Nalluchinnappan and Jeyabaskaran (1991) reported it to be 3.1067 for Tuticorin coast and 2.717 for the Northern Arabian Sea by Hoda (1979). In Stolephorus indicus from San Miguel Bay, Cino (1982) observed ‘b’ value of 3.325. Hoedt (1984) reported ‘b’ value of 3.914 for Encrasicholina devisi of Cleveland Bay and Conand (1987) reported it to be 3.328 for New Caledonia. Dalzell and Wankowski (1980) reported ‘b’ value of 3.340 for E. devisi of Ysabel passage.

The ‘b’ value of males and females of Encrasicholina devisi of Mangalore area were 3.1063 and 3.1975 respectively Syda Rao, (1988a). But in Stolephorus bataviensis it was found to be 2.5945 and 2.2556 Syda Rao, (1988b). According to him in E. devisi, no significant difference was noticed in the regression equations of the sexes but in S. bataviensis, there was considerable variation. Only a common regression estimate was made in the present study for both male and females. The present results revealed a ‘b’ value of 2.54733 showing allometric growth rates which deviated from the reports of Syda Rao, (1988a) in E. devisi and is in agreement with the observations of Syda Rao, (1988b) in S. bataviensis. The intraspecific variations in the ‘b’ value of E. devisi may be due to the difference in the geographical conditions of the location of sample collection.

The length-weight relationship nemipterid fishes varied from place to place and species to species. Mohan and Velayudhan (1984) reported a ‘b’ value of 2.97258 for Nemipterus delagoae of Vizhinjam and Hamsa et al., (1994) reported as 3.0508 for N. delagoae of Tuticorincoast. Krishnamoorthi (1971) reported the ‘b’ value of males and females of Nemipterus japonicas collected from Andhra-Orissa coasts as 2.0769 and 2.9423 respectively.

Acharya and Dwivedi (1981) reported a ‘b’ value of 2.8069 for males and 3.0634 for females of N. japonicas of the Bombay coast. Murty (1983) reported ‘b’ values of 2.4302 and 2.9568 for males and females of N. japonicas of Kakinada.

Vinci and Nair (1974) reported ‘b’ values of 2.8376 and 2.8689 in males and females of N. japonicas collected from Kerala coast and according to them the length-weight relationship of N. japonicas showed no change in the form of the relationship when classified according to maturity and sex. Hence in the present study a common regression estimate was made for both males and females. The specimens of N.japonicus collected from the south west coast of India during the present study reveal a ‘b’ value of 1.56103 which shows its allometric growth rate. The present results deviated from the findings of Vinci and Nair (1974), thus showed intraspecific variation.

REFERENCES:

1. Azad JS. and Udupa KS. Length-weight relationship of the Indian mackerel of Mangalore. Indian J. Anim. Sci: 59 (1); 1989: 202-206

2. Brody S. Bioenergetics and growth. Reinold Publishing Corporation, Newyork. 1945: 1023

3. Brown ME. Experimental studies on growth. In: The physiology of fishes, (M.E. Brown,ed.), Academic Press, Newyork.1957: pp. 361-400

4. Bwathondi POJ. and Pratap HB. The length-weight relationship of fishes of Kunduchi Creek. J.msr.biol.Ass. India, 23(1&2)1981: 161-165

5. Cinco E. Length-weight relationships of fishes. In: Small scale fisheries of San Miguel Bay, Philippines: biology and Stock assessment. ICLARM Tech. Rep7 1982: 124

6. Dalzell PJ. and Wankowski JW. The biology, population dynamics and fisheries dynamics of exploited stocks of three bait fish species. Stolephorus heterolobus, S. devisi and Spratelloides gracilis in Ysabel passage, New Ireland Province. PNG Department of Primary Industry (Port Moresby) Res. Bull.1980: pp. 22:124

7. Ganapati PN. and Rao KS. On the bionomics of Sardinella gibbosa (Bller) off Waltair Coast. J. Zool.Soc, India, 9 (2); 1957: 62-82

8. Gopakumar G., Gopalakrishna Pillai and Omana TA. The fishery characteristics and biology of mackerel at Vizhinjam. J.mar. boil.Ass. India, 33(142); 1991: 107-114

9. Hamsa Ameer KMS. Mohammed Kasumi H. and Arumugam G. The fishery, biology and stock assessment of Nemipterus delagoae (Smith) off Tuticorin. Gulf of Mannar. Bull. Cent.Mar. Fish. Res.Inst., 47; 1994:112-120

10. Hoda SMS. Length- weight and volume relationship in the thread fin bream Nemipterus japonicus from the Pakisthan Coast. J.Mar. biol. Ass. India 18; 1981: 421-430

11. Krishnamoorthi B. Biology of the thread fin bream Nemipterus japonicas (Bloch). Indian J.Fish, 18; 1971:1-21

12. Kumar K. and Balasubramanyan K. Fishery and Biology of oil sardine Sardinella longiceps (val.) from coastal waters of Parangipettai. CMFRI Bullettin, 44;1989: Part I

13. Lagler KG. Freshwater Fishery Biology, Wm. C. Brown Company, Dubuqu, Lowa:1952

14. Le –Cren KD. The length-weight relationship and seasonal cycle in gonad weight and condition in the Perch (Perca fluviatilis). J.Anim.Ecol., 20 (2); 1951: 201-219

15. Luther, G. 1973. Indian J. Fish, 20 (2): 701-715

16. Mohan M. and Velayudhan AK. A few observations on the taxonomy and biology of Nemipterus delagoae (Smith) from Vizhinjam. Indian J. Fish., 31(1); 1984:113

17. Murty V. Observations on the fisheries of thread fin breams (Nemipterridae) and on the biology of Nemipterus japonicas (Bloch) from Kakinada. Indian J. Fish., 31 (1); 1983: 1-18

18. Nalluchinnappan I. and Jeyabaskaran Y. Observations on the biology of Thryssa mystax off Tuticorin coast,Gulf of Mannar. J.man.biol.Ass.India 33(1&2); 1991: 49-54

19. Natarajan AV. Desai VR. Misra DN. and Srivastava NP. Some new light on population ecology of the Gangetic major carp Catla catla (Ham.) from Richand reservoir, UP, India. Matsya, 3; 1977: 46-59

20. Pradhan LB. Mackerel fishery of Karwar. Indian. J. Fish. 3; 1956:141-182

21. Rao T. Appa. On some aspects of fishery and biology of sardines of Waltair area. Indian J. Fish, 29 (142); 1981: 96-103

22. Rao. KVN. Observations on the bionomics of the Indian mackerel Rastrelliger kanagurata (c), caught in the Lawson’s Bay, near Waltair, Andhra Coast. Proc. Symp. Scomb. Fishes, Part III: 1962; pp. 574-585

23. Rounsefell GA. and Everhart WH. Fishery Science: Its methods and application, John Wiley and Sonas Inc., Newyork. 1953: 444

24. Safran Patrick 1992. The theoretical analysis of the weight- length relationship in fish juveniles. Mar. biol., 112: 545-551

25. Sekharan KV. On the mackerel fishery of the Mandapam area. Indian J. Fish., 9 (2):1962

26. Sekharan KV. Length-weight relationship in Sardinella albella (Val.) and S. gibbosa (Bleek). Indian J. Fish., 15 (1&2); 1968: 68-80

27. Seshappa G. Length-weight relationships in three species of flat fishes at Calicut. J. mar.biol.Ass. India, 23(1&2); 1981:141-150

28. Syda Rao G. Biology of Stolephorus devisi (Whitley) from Mangalore area, Dakshina Kannada. J. mar.biol.Ass. India, 30 (1&2); 1988a: 28-37

29. Tampubolon GH. Growth and mortality estimation of Indian mackerel R. kanagurata in the Malacca strait, Indonesia. FAO Fis. Rep, 389; 1986: 372-384

30. Udupa KS. and Krishna Bhat CH. Length-weight relationship of Indian mackerels caught off Mangalore , Gangoli and Karwar by Purse Sciences. Indian J. Fish., 30(1); 1983: 155-157

31. Venkataraman G. Studies on some aspects of the biology of the common aehoy, Thrissocles mystax. Indian J. Fish 3;1956: 311-333

32. Vinci GK. and Kesavan Nair AK. Length-weight relationship on the thread fin bream Nemipterus japonicas along the Kerala Coast. Indian J. Fish., 21(1); 1974: 299-302

33. Yohannan TM. Indian J.Fish., 24; 1977:113-123

Received on 21.04.2016 Modified on 23.05.2016

Research J. Pharm. and Tech. 2017; 10(2): 367-370.

DOI: 10.5958/0974-360X.2017.00074.9