Science • Analysis Indian Journal of Science, Volume 10, Number 24, May 14, 2014

IndianANALYSIS • ZOOLOGY Journal of Science • Analysis Indian Journal of Science, Volume 10, Number 24, May 14, 2014

49 77 Indian Journal of

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EISSN 2319

30 ci e nce 77 S –

ISSN 2319 Length-Weight Relationship and Condition Factor of Hill Stream Fish, Devario aequipinnatus (McClelland)

Dey S1, Ramanujam SN2҉

1. Research Scholar, Fish Biology Laboratory, Department of Zoology, North Eastern Hill, University, Shillong - 793022, India 2. Professor, Fish Biology Laboratory, Department of Zoology, North Eastern Hill University, Shillong - 793022, India

҉Corresponding author: Fish Biology Laboratory, Department of Zoology, School of Life, Sciences, North Eastern Hill University, Shillong - 793022, India, e-mail: [email protected]

Publication History Received: 05 March 2014 Accepted: 28 April 2014 Published: 14 May 2014

Citation Dey S, Ramanujam SN. Length-Weight Relationship and Condition Factor of Hill Stream Fish, Devario aequipinnatus (McClelland). Indian Journal of Science, 2014, 10(24), 47-52

ABSTRACT Length-weight relationship (LWR) and condition factor (K) in ornamental hill stream fish Devario aequipinnatus were investigated from Mamulu hill stream in Sohra, Meghalaya. The analysis of this fish species was based on 769 specimens (males 48% and females 52%) ranging in size from 4.7 cm to 11.2 cm and weight from 0.66 gm to 12.1 gm collected from March 2012 to February 2013. The value of the exponent ‘b’ in the LWR varied between 2.14 and 2.95. This shows that the species exhibit negative allometric growth pattern in their natural habitat. Studies on seasonal changes in K have shown that it is highest during monsoon with values of 0.954, 0.956 and 0.955 in male, female and pooled sexes (male and female) respectively. Males recorded least value of K in winter with 0.863, whereas female and pooled sexes in autumn with a value of 0.84 and 0.868 respectively. Monthly changes of K in both male and female showed its first peak in June indicating the beginning of the spawning season and least in September indicating the end of the spawning season. The present study will help to establish baseline data on LWR and K of D. aequipinnatus which may be utilized both in basic and applied research.

Keywords: Length-weight, condition factor, Devario aequipinnatus, ornamental

Dey et al. Page Length-Weight Relationship and Condition Factor of Hill Stream Fish, Devario aequipinnatus (McClelland), Indian Journal of Science, 2014, 10(24), 47-52, www.discovery.org.in http://www.discovery.org.in/ijs.htm © 2014 Discovery Publication. All Rights Reserved

1. INTRODUCTION Devario aequipinnatus belongs to family Cyprinidae, is an active and brightly striped hill stream fish and has a great value as an ornamental fish in the global market. This fish is commonly called giant danio. It is a native of India and widely distributed in Asia, Nepal and Sri Lanka (Vishwanath, 2010). It inhabits hill streams up to an elevation of 300 Figure 1 m and does not grow more than 15 cm (Talwar and Jhingran, 1991). It Devario aequipinnatus is found in shaded, mid-hill clear waters with pebble or gravel substrates (Pethiyagoda, 1994) and occurs in schools at the surface in small high-gradient upland streams (Rainboth, 1996). It mainly feeds on exogenous insects (Rainboth, 1996) and also on worms and crustaceans (Mills and Vevers, 1989). This fish is not found in local markets, but popular in aquarium trade (Rainboth, 1996; Arunachalam et al., 2000). It has got 4 or 5 horizontal stripes, P, P+1, P-1, P-2 and P+2 present; four interstripes I+1, I-1, I+2 and I-2, P stripe broader and distinct than other stripes (Vishwanath et al., 2007). Many species that were formerly within the Danio genus, such as the giant danio, have now been reclassified as Devario (Fang, 2003). There are currently approximately 44 danionin species (Fang, 2001) distributed throughout South and Southeast Asia, their highest species diversity in north-eastern India, Bangladesh and Myanmar (Barman, 1991). Length-weight relationship is of great importance in fishery assessments (Goncalves et al., 1997). Length and weight measurements can give information on the stock composition, life span, mortality, growth and production (Bolger and Connoly, 1989; King, 1996; Moutopoulos and Stergiou, 2002). Pitcher and Hart (1982) reported length-weight relationship has both applied and basic uses. LWRs were originally used to provide information on the condition of fish and may help determine whether somatic growth is isometric (b=3) or allometric (negative allometric: b<3 or positive allometric: b>3) (Ricker, 1973; Spiegel, 1991). Condition factor refers to the well- being of a certain species and its degree of fatness, which depends on the weight of the fish sampled (Pauly, 1983; Fafioye and Oluajo, 2005). Different values of K of a fish indicate the state of sexual maturity, the degree of food sources availability, age and sex of some species (Williams, 2000) and the system of environment (Dhakal and Subba, 2003). The condition of a fish reflects recent physical and biological circumstances and fluctuates by interaction among feeding conditions, parasitic infections and physiological factors (Le Cren, Figure 2 1951). Map showing the study site (Mamulu hill stream, Sohra, Presently, very limited studies are available on the ecology of Meghalaya). freshwater fishes of Meghalaya in relation to the length-weight relationship and condition factor (Manorama and Ramanujam, 2011). There is no previous report on length-weight relationship and condition factor of D. aequipinnatus and the present study will thus further contribute to comprehensive baseline data on freshwater fishes of the region.

2. MATERIALS AND METHODS

2.1. Study site

Mamulu hill stream in Sohra, Meghalaya was selected for the present study which is a fast flowing hill stream and natural habitat of D. aequipinnatus (Figure 1). The site of collection is located in the region of 25°15'47.61" N latitude and 91°42'45.72" E longitude at an altitude of 1292 msl (Figure 2).

2.2. Collection of fish and analysis

A total of 769 specimens (males 48% and females 52%) ranging in size from 4.7 cm to 11.2 cm and weight from 0.66 48 gm to 12.1 gm were collected every month from March 2012 to February 2013. The data collected were analyzed Dey et al. Page Length-Weight Relationship and Condition Factor of Hill Stream Fish, Devario aequipinnatus (McClelland), Indian Journal of Science, 2014, 10(24), 47-52, www.discovery.org.in http://www.discovery.org.in/ijs.htm © 2014 Discovery Publication. All Rights Reserved

Figure 3 Logarithmic relationship between length and weight of male (a) and female (b) D. aequipinnatus.

under four seasons representing pre-monsoon (Mar.- May), monsoon (Jun.-Aug.), autumn (Sept.-Nov.) and winter (Dec.-Feb.). Collection of fish was done using cage net and other locally made traps. Collected samples were kept immediately in an ice box and brought to the laboratory for further examinations. Total length (cm) of individual fish was taken from the tip of the snout to the extended tip of the caudal fin using Vernier calipers. Body weight (gm) of each fish was taken to the nearest gram using a top Mark Electronic Balance after blot-drying excess water from the body surfaces. Sexes could be differentiated only in mature specimen. The sexes of the young specimens were determined by dissecting the gonads.

2.3. Length-weight relationship The relationship between the length and weight was estimated by using the equation W = aLb (Ricker, 1973), where, W= Total weight of fish (gm), L= Total length of fish (cm), a is the intercept in the y-axis, and Figure 4 the regression coefficient b is an exponent indicating Monthly condition factor male and female D. aequipinnatus isometric growth when close to three. The statistical significance level of r2 (determination coefficient) was estimated and the parameters a and b estimated by linear regression on the transformed equation, log W = log a + b log L. To test for significance differences in both slope and intercept, the analysis of covariance was followed. All statistical analysis was considered significant at P < 0.05.

2.4. Condition factor Condition factor was calculated using the equation given by Fulton (1904) as K = 100 (W/L3), where W is the body weight, and L is the total length.

3. RESULTS AND DISCUSSION 49 3.1. Length-weight relationship

Table 1 Seasonal descriptive statistics and estimated parameters of the length-weight relationship for male, female and pooled sexes of D. aequipinnatus in the Mamulu hill stream, Sohra, Meghalaya

From a total of 769 specimens of D. aequipinnatus collected during the study period, 48% were males and 52% were females. The LWR was calculated for different seasons to study the seasonal fluctuations on the relationship. Four seasons viz, pre-monsoon (Mar.-May), monsoon (Jun.-Aug.), autumn (Sept.-Nov.) and winter (Dec.-Feb.) were taken into consideration. The sample size, the minimum and maximum length, the parameters a and b of length weight 2 relationship, 95% confidence range for b, coefficient of determination (r ) and condition factor (K) are given in Table 1. The value of the exponent ‘b’ obtained for male, female and pooled sexes of the length-weight data varied between 2.14 and 2.95 in all the four seasons and was found to be lower compared to the cube law (b=3), indicating a negative allometric growth in their natural habitat, suggesting that they tend to become thinner as they grow larger, which may be a morphological adaptation for hill stream habitat of the fish as observed in P. shalynius (Manorama and Ramanujam, 2011). According to Shukor et al. (2008), fast ﬂowing stream environment could lower b value (and vice versa) as recorded in R. sumatrana from Peninsular Malaysia. According to Bagenal and Tesch (1978) and Goncalves et al. (1997), the ‘b’ value may change seasonally, and even daily and also between habitats. Analysis of covariance revealed significant differences between sexes and seasons for the slopes (b) of the regression lines (P < 0.05). The LWR in males ranged between 4.7 - 11.2 cm in total length and 1.05-12.1 gm in total weight and it was 2 expressed with the regression equation Log W = -1.626+2.503 Log L (r =0.901) shown in Fig. 3a; whereas in females ranged between 5.1 - 10.7 cm in total length and 1.2 - 11.46 gm in total weight and it was expressed with the 2 regression equation Log W= - 1.74+2.644 Log L (r =0.868), shown in Fig. 3b. The intercept ‘a’ of all the seasonal was 2 negative which indicates a perfect linear relationship between the variables. The determination coefficient (r ) varied from 0.867 to 0.949, which indicate that there is positive correlation between length and weight in all the seasons. Length-weight relationships may present spatial and temporal variations due to water temperature, food availability and reproductive activities (Weatherley and Gill, 1987; Wootton, 1990). Therefore, it can be suggested that the

parameters of length weight relationships are affected by several factors such as season, habitat, gonad maturity, sex, diet and stomach fullness, health and preservation techniques. 50

3.2. Condition factor Condition factor recorded highest for male and female (0.954 and 0.956) during the monsoon and least for male (0.863) in winter, female (0.84) and pooled sexes (0.868) in autumn. The values of the condition factor vary according to seasons and are influenced by environmental conditions, food availability and the gonadal maturity has also been suggested by many workers (Jhingran, 1972; Bashirullah, 1975; Braga, 1986). Monthly changes of Fulton’s condition factor (K) of both male and female is shown in Figure 4 with a first peak in June at the beginning of the spawning season and a second peak in October for males and November for females, following the spawning season. Williams (2000) and Froese (2006) concluded that variation in condition factors of fish is primarily due to maturity state, degree of nourishment, food availability, spawning, age as well as sex of fish. This trend in alteration of K resembles a general pattern of increase towards the spawning season, a sharp decline after spawning, and a second increase after spawning (Le Cren, 1951; Rao, 1968; Froese, 2006). A perusal of present data revealed that in case of D. aequipinnatus, highest values of K during monsoon was attributable to gonadal development.

4. CONCLUSION In conclusion, this study provides basic information on the length-weight relationship and condition factor of ornamental hill stream fish, D. aequipinnatus which may be useful for a sustainable management of this fish in the hill stream environment.

ACKNOWLEDGEMENTS The authors are thankful to Ministry of Environment and Forest, New Delhi and UPE scheme of UGC to Life Sciences, North Eastern Hill University, Shillong for financial support. We would like to pay our sincere thanks to the Head of Department of Zoology for the encouragement and support and. Dr. T. K. Sinha (Computer Centre, NEHU, Shillong) for helping with the statistical analysis.

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