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LENGTH WEIGHT RELATIONSHIP OF HIPPOCAMPUS KUDA (BLEEKER, 1852) (FAMILY: SYNGNATHIDAE), OFF THOOTHUKUDI WATERS, SOUTHEAST COAST OF INDIA T. Vaitheeswaran1 and V.K. Venkataramani2 Directorate of Fisheries Extension and Research (Fisheries), Fisheries College and Research Institute Campus, Thoothukudi - 628 008 ABSTRACT Length-Weight relationship was studied in Hippocampus kuda collected from the reef islands of Gulf of Mannar by SCUBA diving for a period of six months from January 2004 to June 2004. The slope value (b) estimated for H. kuda male was found to be 2.4259 and for females 1.7260. The regression equations calculated for female was Log W = 2.7044 + 1.7260 Log L and for male was Log W = -4.1805 + 2.4795 Log L. The correlations coefficient was found to be significant (P<0.01). The significant difference between sexes of the species 'F' value was at 1% level. The b value differed from the ideal cube law of '3' as is with the case of length-weight relationship studied in this species else where. The slope value was compared here could be very useful for comparison with the marine ornamental species in other geographical locations. Keywords: Hippocampus kuda - length-weight relationship - regression analysis- Population dynamics Gulf of Mannar - Southeast coast of India. INTRODUCTION The Gulf of Mannar biosphere Reserve there are 21 reef islands extending between 08 47'N 78 12'E and 09 15'N 79 14'E from Tuticorin to Pamban, Southeast coast of India. Among finfishes, this marine province harbours 115 marine ornamental species which finds a good place in domestic aquarium and also for export (Venkataramani et.al., 2004 a). The study of length-weight relationship of H. kuda is having vital importance to fisheries biologists as it serves three purposes. First, it establishes the mathematical relationship between the two variables, length and weight so that the unknown variable can be readily calculated from the known variables in practical fisheries problem. Secondly, the relative condition can be estimated to assess the general well being of the animals. Finally, it is used in the estimation of potential yield per recruit in the study of their population dynamics. The actual relationship between length and weight may part from the cubic value 3 and this may be due Corresponding author1: E.mail: [email protected] Senior Research Fellow, Directorate of Fisheries Extension and Research (Fisheries), Fisheries College and Research Institute Campus, Thoothukudi-628 008. 2. Dean, Fisheries College and Research Institute Campus, Thoothukudi-628 008. Tamilnadu J. Veterinary & Animal Sciences 8 (3) 119-125, May - June, 2012 119 Vaitheeswaran and Venkataramani to environmental condition in which the animal lives and also due to the physiological condition of the animal. Global trade in marine ornamental fish was estimated to include more than 1,200 species from 54 countries (Bruckner, 2001). Estimates value the global trade at US$ 28 to US$ 44 million annually (Wood, 2001). Hippocampus kuda commonly called as spotted seahorse coral fishes occur in good numbers in the reef islands of Gulf of Mannar. Seahorses (Genus: Hippocampus) are members of the family Syngnathidae, which also includes pipe fishes, pipe horses and seadragons. They are found in-shallow, coastal, tropical and temperate waters from about 450 S to 450 N (Louire et.al., 1999). Heather and Keith (2009) have reported 46 species of Hippocampus species (seahorse) from different geographical areas and world oceans. Of the 46 species, H. kuda occurs in large numbers in the reef islands of Gulf of Mannar, Southeast coast of India. The precious of ornamental fishes such as clown fish, butterfly fish, wrasse, damsel fish, rabbit fish, scorpion fish and leather jackets were recorded in large quantities in coral reef islands of Gulf of Mannar. In 1995, it was conservatively estimated that at least 20 million seahorses (more than 56 metric tonnes) were caught for the traditional medicine market. In response to a significant increase in international demand, a target fishery for seahorses along the southeast coast of India in the Gulf of Mannar was started in 1992 (Lipton, 1998). Along Ramnadu coast in TamilNadu, dried sea horse is used as a medicine to arrest whooping cough in children (Marichamy et.al., 1993). Seahorses are exploited both as an incidental catch (by-catch in trawl nets) and target catch, for export. It is estimated that the global trade in dried seahorses exceeded 70 tonnes in 2000. This would amount to at least 24.5 million seahorses, using an average of 350 seahorses per kilogram. The large importers are Philippines, Thailand, China and Hong Kong, while largest exporters are India. (Annual sales 120 at least 1.3 million seahorses or 3000 kg). India is one of the largest exporters of dried seahorses globally, exporting at least 3.6 tonnes (1.3 million seahorses) annually (Vincent, 1996), and contributes to about 30% of the global seahorse trade. The global trade involves at least 20 million seahorses a year. Presently, the commercial exploitation of seahorses is being carried out from TamilNadu and Kerala coasts (Anil et.al., 1999). The value of the seahorses is quite high; the price of dried seahorses in Hong Kong markets ranges from Rs.11,500 to 45,000 (US $ 275 to 1200) per kg depending on the species, quality and size. The estimation of yield per recruit in prediction models, and in the estimation of biomass from length observations. Though the biodiversity of ornamental finfishes are high in reef islands of Gulf of Mannar, limited studies have been made on population dynamics. The species is non-migratory and has been recorded at a depth 10-15 meters in the reef islands. As no work has been done on this species thereafter from Thoothukudi coast, in the present study, an attempt has been made to study the length-weight relationship in H. kuda from the reef islands of Gulf of Mannar, Southeast coast of India. Distribution and Habitat Seahorses are exclusively marine generally living in coastal habitats in shallow temperate and tropical waters. They are distributed from C 500 north to 500 south, while the highest diversity of species occurs in the Indo-Pacific region (Lourie et.al., 1999). While individuals of most seahorse species were found in shallow waters (<30 m depth), many have been found between depths of 40 and 100 m; Hippocampus kelloggi were reported to depths of 90 m in Malaysian waters (Choo & Liew, 2003), and Hippocampus minotaur and H. histrix were reported from trawls at 100 m in Australia (Gomon, 1997). Overall, the most commonly reported seahorse habitat was seagrass, and mangroves were the least reported (Lourie et.al, 1999). Temperate species Tamilnadu J. Veterinary & Animal Sciences 8 (3) 119-125, May - June, 2012 Length weight..... predominantly inhabited algae, while tropical species were primarily found among coral reefs. Some estuarine species, such as H. abdominalis, H. capensis, H. kuda and H. reidi (Rosa et.al., 2002), appear to tolerate fluctuating salinities, although they could experience high rates of mortality during freshwater flooding (Russell, 1994; Bell et.al., 2003). employed to find out whether the regression coefficients differed significantly between males and females. The significance of difference in the estimate of 'b' in pooled data of sexes from the expected value of 3 (isometric growth) was tested by the't' test as given by the formula. t = b-3/ Sb MATERIALAND METHODS b = regression coefficient of log transformed data. Length-weight relationship study was carried out in 173 specimens of Hippocampus kuda (Fig 1) ranging from 86 to 135 mm in total length. A total of 173 specimens were measured for the lengthweight relationship studies, which include 86 females and 87 males. The length of females ranged from 93 to 135 mm and weight 4 - 10g. The males were recorded in the length range of 86- 130 mm and the weight ranged from 4 - 10g. The specimens were collected from Van island and Kaswari islands 08º 50'N 78º 15'E and 08º 52'N 78º 15'E of Thoothukudi coast by undertaking SCUBA diving. The diving was made for six months (thrice in a month - once in 10 days) from January 2004 to June 2004. Seahorse measurements were most commonly given as height (ht) or standard length (SL). Height was measured from the top of the coronet to the tip of the straightened tail, while SL was measured as head, trunk and tail length (Lourie et.al., 1999). The total-length (TL) cannot be measured in seahorses because they lack a caudal fin; researchers who claimed to have measured TL had probably recorded height. For the purposes of this study, all SL measurements were converted to Ht using metric conversions provided by researchers and weight was recorded to the nearest 0.1 gm. Specimen where the tails are broken are rejected. The length-weight relationship was calculated by the method of least squares using the equation of LeCren (1951): W= a. Lb , where W= weight in fish, L total length of fish and 'a' and 'b' are the exponents. The same in the logarithmic form can be written as log W = log a + b log L. Analysis of covariance (Snedecor and Cochran, 1967) was RESULTS AND DISCUSSION The maximum length recorded for this species in the Kaswari islands of Gulf of Mannar was 13.0 cm. The reported maximum length for this species is 30 cm (Myers, 1991). The linear equation was also fitted separately for males and females. The correlation coefficient derived for the lengthweight relationship for males and females are given in Table.1. The regression equations derived for both the sexes are presented below Table.2. Female Log W = -2.7044 + 1.7260 Log L Male Log W = -4.1805 + 2.4259 Log L The results showed significant between sexes of the species and the 'F' values were found to be significant at 1% level (Table.3). The observed total length plotted against total weight males and females are presented in Figure 2 & 3. In fishes, generally the growth pattern follows the cube law (Lagler Karl, 1952). Beverton and Holt (1957) stated that major deviations from isometric growth are rare. Such cubic relationship for fishes will be valid when fish grows isometrically. But in reality, the actual relationship between the variables, length and weight, may depart from this, either due to environmental conditions or condition of fish (Le Cren, 1951). According to Martin (1949) the value of the exponent 'b' in the parabolic equations usually lies between 2.5 and 4. Depending upon the deviation of 'b' values from '3' fishes can be classified into three groups (i) b= 3 where the Tamilnadu J. Veterinary & Animal Sciences 8 (3) 60-67, 119-125, 2012 121 Vaitheeswaran and Venkataramani body form of fish remains constant at different lengths (isometric) (Allen, 1938), (ii) b<3 when fish becomes more slender as the length increases and (iii) b>3 (allometric) when fish grows more stouter with increase of length (Growner et.al., 1976). In majority of the fishes the shape and density change with increasing age, which often causes the regression coefficient of weight of length, depart from 3. The present observation is also in agreement with the above view and it can be concluded that the cube formula W = al3 will not be a proper representation of the length-weight relationship for H. kuda as the't' value is significantly different and the growth is not isometric. Recently, the Ministry of Environment and Forests, Government of India through a Gazette Notification has included all Syngnathids in Schedule I of the Wild Life (Protection) Act, 1972. The Statistical analysis revealed that the length weight relationship of the fish when compared between the two stations differed significantly. species, it could be concluded that the slope value is less than 3 for the both sexes of H. kuda. Beverton and Holt (1975) suggest that the value of 'n' is almost always near to 3. Several theories have been advanced by a number of workers as to what governs or influences the value of 'n' is dependent and governed by the feeding behavior of fish. Also the size of type of food consumed by the fish seems to have influence on the value of 'n'. for example, planktonivores, herbivores and predators have different ranges for the value of 'n' H. kuda are undergoing progressive changes in shape and condition as they grow and consequently affecting the regression of the log of weight and log of length. Choo, C.K., and Liew, H. C. (2003). Spatial distribution, substate assemblages and size composition of seahorses (Family Syngnathidae) in the coastal waters of Penninsular Malaysia. Journal of Marine Biology Association., U.K. 83, 271-27 In fishes 'b' value is usually '3' in the lengthweight relationship, but during growth change in specific gravity of body contour, morphological changes due to age may also cause the coefficient of regression of logarithm on logarithm of length, to depart substantially from 3.0 (Rounsefell and Everhart, 1953). Thus, comparing the slope of Hippocampus kuda with other Syngnathidae Growner, H. John., Rogelio, O., and Juliano (1976). Length-weight relationship of pond raised milk fish in the Philippines. Aquaculture., 7, 339-346 122 REFERENCES Anil, M.K.; Kakati, V.S., Ganga, U., and Zacharia, S. (1999). Mar. Fish. Inf. Serv., T&E Ser., 162, 23-25 Bell, E.M., Lockyear., McPherson, J.F., Marsden, J.M., and Vincent, A.C.J. (2003). The first field studies of an endangered South African seahorse. Hippocampus capensis. Environmental Biology of Fishes., 67, 35-46 Beverton, R. J. R., and Holt, S.J. (1957). On the dynamics of exploited fish population. Fishery Invest. Lond Ser., 2 (19), 533 Bruckner Andrew, W. (2001). Tracking the trade in ornamental coral reef organisms: The importance of CITES and its limitations. Aquarium Sciences and Conservation., 3 (1-3), 79-94 Gomon, M.F. (1997). A remarkable new pygmy seahorse (Syngnathidae: Hippocampus) from Southeastern Australia, with a redescription of H. bargibanti whitley from New Caledonia. Memoirs of the Museum of Victoria., 56, 245-253 Heather J. Kolewey., Keith and M. Martin-Smith. (2009). A global review of seahorse aquaculture. Aquaculture., 302 (2010) - 131-152 Tamilnadu J. Veterinary & Animal Sciences 8 (3) 119-125, May - June, 2012 Length weight..... Laglar Karl F. (1952). Fresh Water Fishery Biology. Dubuque, IOWA. pp: 360 Le Cren E.D. (1951). Length-weight relationship and season cycle in gonad weight and condition in perch (Perca fluvitialis). J. Anim. Ecol., 20, 201-219 Lipton, A. R. (1998). In Proceedings of the First International Workshop on the Management and Culture of Marine Species used in Traditional Medicines, Project Sea Horse, Montreal, Canada, 1998, pp : 75-77 Lourie, S.A., A.C.J. Vincent., and Hall, H. J. (1999). Seahorses: an identification guide to the worlds species and their conservation. Project Seahorse, London. pp : 214 Marichamy, R.., Lipton, A. P., Ganapathy, A., and Ramalingam, J.R. (1993). Mar. Fish. Inf. Serv., T&E Ser., 119, 17-20 Martin, W.R. (1949). The mechanics of environmental of body form in fishes. Univ. Toronto Stud. Biol., 58 (Publ. Ont. Fish. Res. Lab.). 70, 1-91 Myers, R.F. (1991). Micronesian reef fishes. Second Ed. Coral Graphics, Barrigada, Guam., pp : 298 Ministry of Environment and Forests, Govt. of India, Gazette Notification, SO665 (E), 12 July 2001 Mohamed Kasim, H and Balasubramanian, T. S. (1990). Fishery, growth, yield per recruit and stock assessment of Sphyraena obsusata Cuvier off Tuticorin, Gulf of Mannar. Indian J. Fish., 37 (4): 281 - 288 Rounsefell, D. A. and W. H. EverHart. (1953). Fishery Science: Its method and application. John Wiley and Sons, Inc., N.Y. Rosa, I.L., Dias, and T.L., Baum, J.K. (2002). Threatened fishes of the world: Hippocampus reidi Ginsburg, 1933 (Syngnat hidae). Environmental biology of Fishes., 64, 738 Russell, I.A. (1994). Mass mortality of marine and estuarine fish in the Swartvlei and Wilderness Lake Systems, Southern Cape, South African Journal of Aquatic Sciences., 20, 93-96 Sendeor, G.W. and W. G. Cochran. (1967). Statistical Methods (6th Edn). Oxford and IBH publishing Co., New Delhi. pp: 250 Venkataramani, V.K., Jawahar., P, Santhanam R., and Vaitheeswaran, T. (2004 a). A monograph of Marine ornamental fishes of Gulf of Mannar. NATP/CGP publication. pp : 175 Vincent, A.C.J. (1996). The international trade in seahorses. TRAFFIC International., Cambridge, UK. 163 Wood Elizabeth. (2001). Global advances in conservation and management of marine ornamental resources. Aquarium Sciences and Conservation., 3 (1-3): 65 -77. Table 1 Statistics in the length-weight relationship of males and females of Hippocampus kuda Sex Male Female N SX2, SY2, SXY SX, SY N 87 86 = = = SX 178.7741 174.7733 SY 69.9825 69.0776 SX2 354.6052 355.3338 SY2 57.4341 56.6111 SXY 174.7434 140.6156 Number of fish Sum of squares and product Sum of logarithmic values of length and weight respectively. Tamilnadu J. Veterinary & Animal Sciences 8 (3) 119-125, May - June, 2012 123 Vaitheeswaran and Venkataramani Table 2 Regression data for the length-weight relationship of males and females of Hippocampus kuda Sum of Squares and Products Sex Male Female DF B SS 2 DF 87 86 X 354.6052 355.3338 XY 174.7434 140.6156 Y2 57.4341 56.6111 DF b 2.4259 1.7260 86 85 : Regression freedom : Regression Co-efficient : Sum of Squares Table 3 Test of Significance Source of Variation Deviation from individual with in sexes Difference between Regression Deviation from Total Regression DF 1 Sum of Square 412.0393 Mean Square 412.0393 171 411.9449 2.5437 172 823.9842 Observed F 161.9842 Significant at 1% level Figure 1 Hippocampus kuda 124 Tamilnadu J. Veterinary & Animal Sciences 8 (3) 119-125, May - June, 2012 LOG WEIGHT IN G Length weight..... LOG LENGTH IN CENTIMETER LOG WEIGHT IN G Figure 2 Logarithmic relationship between length and weight of male Hippocampus kuda (BLEEKER, 1852) LOG LENGTH IN CENTIMETER Figure 3 Logarithmic relationship between length and weight of female Hippocampus kuda (BLEEKER, 1852) Tamilnadu J. Veterinary & Animal Sciences 8 (3) 119-125, May - June, 2012 125