CHAPTER 3: FISH BIOLOGY

Transcription

1 65 CHAPTER 3: FISH BIOLOGY INTRODUCTION Esomus danricus and Parluciosoma (Rasbora) daniconius are commonly known as Indian flying barb and stripped Rasbora respectively. Both the species are small fresh water fish, belonging to the family Cyprinidae widely distributed in India, Pakistan, Bangladesh, Nepal, Afghanistan and Sri Lanka (Talwar & Jhingran, 1991). They are also found in brackish water, drains, paddy field, wetlands and river (Talwar & Jhingran, 1991 and Gupta & Gupta, 2006). The maximum length for Esomus danricus and Rasbora daniconius attained upto 6.8 cm and 8 cm respectively. They are very active species and are able to jump to a considerable height. It is therefore necessary to have a well fitting lid on the tank or aquarium. Members of the genus (Esomus) can easily be recognized by the very long barbles on a 1.5 cm fish. In Esomus dandricus (Ham.), 4 pairs of gills are present with secondary lamellae having a thin lamellar epithelium. The space, which is present in between the proximal margin of gill filaments and branchial septum, forms the so-called water channels to distribute water along the length of the gill filaments, (Bhattacharya & Subba, 2003). Morphological features, specifically those related to the capture and intake of prey, evolved to maximize feeding performance, and have been strongly correlated

2 66 with diet (Gatz, 1979; Wikramanayake, 1990; Piet, 1998; Hugueny & Pouilly, 1999). Individual species are adapted not only to feed on a specific component of the broader resource base, but also on food particles of a particular size. Matthews et al. (1982) showed a strong direct relationship between mouth width and prey size. Food is a major axis along which co-existing fish species are segregated (Ross, 1986). Differences in trophic adaptations among species have the effect of physical feeding segregation while differences in diet by coexisting species reflect underlying morphological diversities. Therefore, variation in morphology leads to variation in feeding success on food resources, thereby influencing diet (Wainwright & Richard, 1995). Fish like any other organisms depends on the energy received from its food to perform its biological processes such as growth, development, reproduction and other metabolic activities. Food is the main source of energy and plays an important role in determining the population levels, rate of growth and condition of fishes (Begum et al., 2008). Studies on the growth performance in fishes in relation to feeding period are useful information for successful application in the management and exploitation of the resources. Growth rate is different in animal to animal pretending to sexual maturity (Asdell, 1946). Study of food and feeding habits of fishes have manifold importance in fishery biology. For successful fish farming, a thorough knowledge about the food and feeding habit is necessary. As the nature of food depends to a great extent upon the nature of environment, the problem is interesting from species point,

3 67 as well as ecological point of view (Bhuiyan et al., 2006). Feeding is one of the main concerns of fishes, where in they devote large portion of its energy searching for food. Detailed data on the diet, feeding ecology and trophic inter-relationship of fishes is fundamental for better understanding of fish life history including growth, breeding, migration (Bal & Rao, 1984) and the functional role of the different fishes within aquatic ecosystem (Blaber, 1997; Wootton, 1998; Hajisamae et al., 2003). Fishes have become adapted to a wide variety of food. Feeding is usually a part of the daily routine. Sometimes rate of feeding has a bearing on the spawning of the fish. The nature of food composition of fish will also throw light on the possible habitats it frequents. Availability of natural food has great effect on the distribution, abundance and growth of fish species, knowledge of the food of fish and its feeding behaviour can help in understanding ecological relationship and therefore useful in the fish management. Food of an animal may differ at different stages of life and also vary from place to place and from season to season. It also differs according to abundance and availability of the food organisms (Gaikwad et al., 2009). Fish food consumption might be influenced by many environmental factors such as water temperature, food concentration, stocking density, fish size and fish behaviour (Huolihan et al., 2001). Thus food and feeding habits of fishes have a great significance in aquacultural practices.

4 68 According to LeCren (1951), knowledge of the length-weight relationship of a fish is essential, since various important biological aspects, viz., general well being of fish, appearance of first maturity, onset of spawning, etc., can be assessed with the help of condition factor, a derivative of this relationship. Moreover, the length-weight relationship of fish is an important fishery management tool because they allow the estimation of the average weight of the fish of a given length group by establishing a mathematical relationship between the two (Beyer, 1987). As length and weight of fish are among the important morphometric character, they can be used for taxonomy and ultimately in fish stock assessment. In fishery science, the condition factor or K- factor is used in order to compare the condition, fatness or well being of fish and it is based on the hypothesis that heavier fish of a given length are in better condition (Bagenal & Tesch,1978a). Condition factor is also a useful index for the monitoring of feeding intensity, age and growth rates in fish (Oni et al., 1983). Condition factor has been used as an index of growth and feeding intensity (Fagade, 1979). While attempting a study of the biology of a fish, it is usual to analyze the mathematical relationship between its length and weight. This analysis will reveal the extent to which the two variables, length and weight are related to each other and thereby help one to calculate with ease one variable when the other is known (Chandrika & Balasubramonian, 1986). The study of length-weight relationship of fishes have two objectives, (i) to determine the type of mathematical relationship between two variables so that if one variable is known the other could be computed

5 69 and (ii) to know the well being of fish and also type of growth i.e. whether isometric or allometric (Kumar et al., 2005). Sex ratio and size structure constitute information basic in assessing reproductive potential and estimating stock size populations (Vazzoler, 1996). The study of sex determination in fish is important for several reasons. The biology and ecology of fish is sufficiently diverse to provide unique examples of sex-determination mechanisms, yet they possess many of the same processes and pathways that are used in other vertebrate systems. Because they are amenable to artificial culture and experimental investigation, in many cases fish also provide unique opportunities to investigate and test theoretical concepts of sex determination, ranging from evolutionary mechanisms to biochemical processes (Devlin & Nagahama, 2002). An understanding of the reproductive biology of any species is important for the purpose of stock assessment (Schaefer, 1996; 1998). In order to achieve success in fish culture, it is important to assess the yearly breeding cycle of culturable fishes. Spawning of fish occurs during a particular phase of the reproductive cycle. Some of them breed once a year, while some oth at regular intervals throughout the year. Information of gonadal development and the spawning season of a species make subsequent studies on spawning frequency of its population easier, which is important for its management.

6 70 Knowledge about fecundity of a fish is essential for evaluating the commercial potentialities of its stocks, life histories, practical culture and actual management of the fishery (Lagler, 1956; Doha & Hye, 1970; Karim & Hossain, 1972; Shafi & Mustafa, 1976; Islam & Hossain, 1984; Bhuiyan & Rahman, 1984). Knowledge of fecundity and length at first maturity are important in the estimation of abundance and reproductive potential. In recent years fecundity studies have been considered useful in tracing the different stocks or populations of the same species of fish in different areas. Further fecundity of fish is an important aspect of fish biology and ecology due to its direct relation to fish production and fisheries (Pathani, 1981). Itano & Williams (1992) studied that the reproductive parameters of the fish over a broad area must be accurately correlated to data on fishing methodology, school aggregation, feeding behavior and environmental conditions at the time and area of capture. Links between spawning activity, temporal and areal spawning distributions and vulnerability need to be examined. Life history or other ecological information essential in conserving rare species is often lacking or incomplete (Tear et al., 1995). This information is necessary to insure that habitat and community composition is appropriate at sites where reintroductions are planned.

7 REVIEW OF LITERATURE Since their first description by Hamilton (1822), the distributional range of E. danricus and P. daniconius was reported by many authors. A comparative study of the yolk nucleus in the oocytes from E. danricus has been reported by Nayyar (1964). Earlier studies have clearly indicated that there exists a close relationship between the structures of gills with their function (Gray 1954; Hughes & Morgan 1973; Laurent & Dunel 1976; Hughes 1980). Bhattacharya & Subba (2003) also recorded the E. danricus from Nepal. Utayopas (2001) studied on the meristic characters and morphometric characters of E. metallicus. Fang Fang (2003) suggested that the genus Esomus is the most closely related genus to the Danios, closer even than the Devario genus. Again, Prasad (1986) observed the oxygen uptake during early life in the fresh water fish, Esomus danricus (Ham). The relationship exists at various levels of the gill sieve system. Different workers in the fishes from different habitats have observed modification in the architectural plan of the gills. Bhattacharya & Subba (2003) studied on structure of respiratory organs of E. dandricus in Nepal. Gupta & Gupta (2006) discussed the body description, bionomics and distribution of E. danricus and Rasbora daniconius. Again, Vutukuru et al. (2006) also studied on acute effects of copper on superoxide dismutase, catalase and lipid peroxidation in the freshwater teleost fish, E. danricus. On the other hand, Vutukuru et al. (2005 & 2007) reported the architectural changes in the gill morphology of E. danricus as potential biomarkers of copper toxicity using automated video tracking system. Literature on fish gill morphology has been

8 72 provided by Moon (1995); Fernandez & Perna (1995); Laurent et al. (1996); Munshi (1996); Subba (1999). While, Kalvati & Narasimhamurti (1984) also described a new myxosporidan parasite from Esomus sp. Kottelat (2005) describes a new species Rasbora notura from the eastern slope of northern Peninsular Malaysia and Ward- Campbell et al. (2005) discussed morphological characteristics and intestinal content of Rasbora caudimaculata. While, Ruber et al. (2007) reported on the evolution of miniaturization and the phylogenetic position of paedocypris of cyprinids fish including Rasbora and Esomus species and Roos et al. (2007) analyzed the Vitamin A, Calcium, Iron, Zinc and other nutrient contents in Esomus and Rasbora. Further, Das & Gupta (2009) worked on the biometrics and growth features of E. danricus, from Barak valley, south Assam and Liao et al. (2009) reported phylogenetic analysis and morphometric of the genus Rasbora. Also, Donsakul et al. (2009) examined the karyotypes of five cyprinid fishes, including Rasbora agilis, R. dorsiocellata, R. rubrodorsalis, Boraras maculate and B. urophthalmoides from Thailand while, Pathan et al. (2009) observed the histochemical changes in the liver of Rasbora daniconius, exposed to paper mill effluent. Recently, Pasco-Viel et al. (2010) examined the evolutionary trends of the pharyngeal dentition in cypriniformes family including Esomus and Rasbora species. As far as length-weight relationship of the two cyprinids fish is concerned, Kumar et al. (2005) studied on the length-weight relationship of Rasbora daniconius from Saravathi reservoir of Karnataka while Balescu (2005) reported the external morphology of cyprinid species, Rasbora argyrotaenia. Again, Gaikwad et al. (2009)

9 73 also studied on the length and weight relationship and morphometric of Rasbora daniconius. Mustafa (1976) investigated on the length-weight relationship and condition factor of common minnow, Esomus danricus (Ham.) from different freshwater environments. Available information on the food and feeding habit of these two cyprinid weed fish is very limited. Mustafa (1976) reported the selective feeding behaviour of the common carp Esomus danricus (Ham.) in its natural habitat while Kumar & John (1985) investigated on the feeding ecology of the allochthonous feeder Rasbora daniconius. Similarly, Weliange & Amarasinghe (2007) also studied on the food and feeding habit of Rasbora daniconius. Again, Mustafa, (2008) examined the selective feeding behaviour of the common carp Esomus danricus, in its natural habitat. Recently, Gaikwad et al. (2009) studied on the feeding habit and growth patterns of Rasbora daniconius. Dutta (1989); Serajuddin & Mustafa (1994); Serajuddin et al. (1998); Ochi et al. (1999); Serajuddin & Ali (2005) studied on food and feeding habit of Mastacembelus fish species. Introduction on the different aspects of biology of both the species are very scanty. A few literatures on the reproductive biology of the two species have been marked in the last three decade. Nagendran et al. (1981) studied on the fecundity of the cyprinid Rasbora daniconius whereas Randy (1991) reported on the spawning of Rasbora species in controlled condition. Various aspects of biology in Rasbora and

10 74 Esomus species have been carried out by several workers. Bhargava & Raizada (1973) reported on the seasonal changes of pituitary gland in R. daniconius whereas Krishnamurty et al. (1972) observed chemical composition of oocytes and fate of yolk vesicles of the same species. Again, Tewari (1978) studied on the development of myodomes and the position of the eye muscles in R. daniconius. Similarly, Khangarot & Rajbanshi (1979) also examined the toxicity of zinc to a freshwater Teleost, R. daniconius (Ham.) in Udaipur while Elizabeth et al. (1981) studied on the effect of alkaline and acidic fractions of individual effluents on some lymphoid cells of the fish R. daniconius. In the earlier, both the E. danricus and R. daniconius species were use for mosquito control (Sen, 1937; WHO 2003) in West Indies, America and Eastern Mediterranean Region and Bhattacharya & Subba (2003) studied on the structure of respiratory organs of E. danricus (Ham.). Again, Pathan et al. (2009) deals with the toxicity and behavioural changes in R. daniconius exposed to lethal concentration of paper mill effluent in Aurangabad.Recently, Jha (2010) analyzed the comparative study of aggressive behaviour in transgenic and wild type flying barb E. danricus (Hamilton), and their susceptibility to predation by the snakehead Channa striatus (Bloch). Recently, Muchlisin et al. (2010) studied on the certain reproductive biology like sex ratio, GSI, gonadal development and spawning season of Rasbora tawarensis (Pisces: Cyprinidae) in Lake Laut Tawar, Aceh Province, Indonesia.

11 MATERIALS AND METHODS Feeding and reproductive biology: Total 500 specimens of E.danricus out of which 383 males and 117 females while for P.daniconius a total of 475 specimens containing 345males and 130 females had been had been studied for certain aspects of fish biology following the standard methods given below: Relative length of gut (RLG): All the specimens were measured for total length (TL) and body weight to the nearest millimeter (mm) and milligram (mg) respectively. The ratio between the gut length and total length has been estimated by adopting the following of Al-Hussainy, (1949), GL RLG = TL Where, GL = Total length of the gut and TL = Total length of the fish Gastrosomatic index (GSI): It has been used to estimate the feeding intensity of Esomus danricus and Rasbora daniconius. This can be calculated as follows (Desai, 1970, and Khan et al., 1988), Weight of the gut GSI = X 100 Total weight of the fish

12 Fullness of Gut: It is represented visually by recording the amount of food content in the gut. The fullness was designated as empty, ¼ full, 1/2 full, 3/4 full and full as per methodology of Abdelghany (1993) and Bhuiyan et al. (2006) Length-weight relationship and condition factor: The length-weight relationship is expressed as allometric growth equation: W=aL n (LeCren, 1951). Converting it into logarithmic form, the equation is Log W = Log a + b Log L Where, W = Weight of fishes L = Length of fishes a = Initial growth index of fish and in a constant b = Equilibrium constant or growth co-efficient. Condition factor has been calculated by using formula of Beckman (1948) & Wootton (1992) W x 10 5 K = L 3 Where, K=condition factor; W= weight of the fish in gm; L = length of the fish in mm is a factor that brings the K factor close to unity Sexual dimorphism and Sex ratio: Sexual dimorphism of fish species was studied by visual (under microscope) inspection and later confirmed by the description of Jayaram (1981) and Talwar & Jhingran (1991). The sex ratio was expressed as the proportion of males to the total number of the fish sampled. Sex ratio of the fish was

13 77 studied using Chi-square test (X 2 ), following the equation of Fisher (1970), assuming that the ratio of male to female in the population to be 1: Gonadosomatic ratio (GSR): The gonadosomatic ratio or mature index has been used for estimating spawning season of a species. The GSR as proposed by Nikolsky (1963) has been calculated month-wise and sex-wise. For estimation of GSR, samples have been weighed whole to the nearest 0.5 g and gonads are then weighed separately to the nearest 0.1 mg in an electronic balance. The ratios were calculated as suggested by Hopkins (1979) and Biswas, (1993): Weight of the gonad GSR = x 100 Total body weight Ova diameter: For measurement of the diameter of ova, formalin preserved materials were taken. In the preliminary study it was observed that within (anterior, middle and posterior part of individual ovary) and among individuals of the paired ovary, there was no significant difference, either in relative number or in the mean ova-diameter. Consequently, random sub-samples were taken and determined through visual and microscopically examination as described by Clarke (1934) and Hickling & Rutenberg (1936) Fecundity: Ovaries from mature specimens collected just before breeding were only used for fecundity studies. First, the ovaries were removed from the preserved gravid females of the species of known length and weight. Sub sample by weight method has been employed and fecundity has been calculated from the counts of

14 78 mature ova in two random sub samples of the ovary of known weight after drying off the excess moisture with the help of a blotting paper. The following formula is now employed to calculate the absolute fecundity as of Bagenal, (1957) NG F = g Where, F = fecundity; N = No. of eggs in the sub sample; G = Weight of the ovaries; g = Weight of the sub-sample Relative fecundity: Relative fecundity was calculated according to the following formula (Hardisty, 1964; Das, 1964). Egg number Relative fecundity = Body weight Maturity stage or gonadal cycle: Routine assessment of maturity stages is normally done by assessing individuals to stages by characters which can be differentiated with the naked eye. Periodical, microscopically examinations of gonads were done as per methods of Qasim (1957); Kesteven (1960) and Crossland (1977) Length at first maturity and M 50 : The length at first maturity for females was determined directly by plotting the percentage of mature fish against their length. The length at which 50% of the males and females were mature was considered as the length at first maturity. The maturity was also determined by the colour, size of gonads, gonadosomatic index (GSI) and the size and microscopic appearance of translucent ova. It has been determined following standard methods of Hodkiss & Mann (1978).

15 RESULTS Relative length of the gut (RLG): RLG values in E. danricus showed little variation among different size groups. The lowest value was found as 1.24 (±0.52) in > 5 cm group whereas the highest values as 1.6 (±0.7) in 4-5 cm group (Table 3A). In case of P. daniconius, RLG was found to be lowest (0.76 ± 0.19) in the size group of cm and highest (1.12 ± 0.4) in the size group cm (Table 3B). The results reveal that RLG value was higher in younger size groups in both the specimens. Table 3A: RLG values in different size group of E.danricus Size group R L G ± ± 0.7 > ± 0.52 Table 3B: RLG values in different size group of P.daniconius Size group R L G ± ± ± ± ± 0.19

16 Gastrosomatic index (GSI): GSI in relation to months and seasonal variation for both sexes: Table 3.1A shows the average monthly gastro somatic index (GSI) of E. danricus was ranged from ± (Jan) to ±2.690 (Apr) for males and that of female, from ± (Dec) to ± (Apr). As whole, lowest GSI for both the males (2.6 ± 0.9) and females (2.53 ± 0.62) of E. danricus were observed during winter (Dec-Feb) and that of higher GSI were observed for males (4.5 ± 1.49) and for females (4.4 ± 1.43) during pre-monsoon (Jun-Aug) and post-monsoon (Sep-Nov). Table 3.1A: Monthly mean variations of GSI in E. danricus Month Males Females Jan ± ± Feb ± ±0.459 Mar ± ± Apr ± ± May ± ± Jun ± ± Jul ± ± 1.78 Aug ± ± Sep ± ± Oct ± ± 2.38 Nov ± ± Dec ± ± 0.389

17 81 In case of P. daniconius, the gastro somatic index (GSI) was ranged from 1.8 ± (May) to 5.93 ± 2.44 (Aug) for males while in case of female it was varied from 2.5 ± 0.42 (Dec) to 5.9 ± 1.9 (Jul) (Table 3.1B). The maximum GSI value for both the male (4.41 ± 2.2) and female (4.93 ± 2.04) was observed during monsoon (June- August) while that of lowest for male (3.07 ± 0.69) and female (2.9 ± 0.61) were recorded during winter (Dec-Feb). The intensity of feeding was found to be moderate during pre-monsoon (Mar-May) for both the sexes. Table 3.1B: Monthly mean variations of GSI in P. daniconius Month Males Females Jan 2.87 ± ± 0.77 Feb 3.22 ± ± 0.65 March 4.86 ± ± 1.64 Apr 3.07 ± ± 1.75 May 1.8 ± ± 2.35 June 5.1 ± ± 2.5 July 2.2 ± ± 1.9 Aug 5.93 ± ± Sep 3.1 ± ± 0.89 Oct 2.86 ± ± 1.58 Nov 4.62 ± ± 1.1 Dec 3.13 ± ± 0.42

18 GSI in relation to maturity stages: In male E.danricus, the minimum GSI (3.31 ± 1.7) was observed in immature stage and that of maximum (5.14 ± 1.04) in mature stage whereas in case of female, minimum (2.4 ± 1.1) and maximum (4.55 ± 1.3) values were recorded in maturing and ripe stage respectively (Table 3.2A). Similarly, in P. daniconius, highest GSI (5.2 ± 0.98) was recorded in immature stage and lowest GSI (3.01 ± 1.4) in spent males while it was found to be lowest (3.2 ± 1.2) in maturing and highest (4.8 ± 1.36) in mature females (Table 3.2B). Table 3.2A: GSI of E.danricus at different maturity stages Maturity Males Females stages Immature 3.31 ± ± 1.5 Maturing 4.9 ± ± 1.1 Mature 5.14 ± ± 1.21 Ripe 5.13 ± ± 1.3 Spent 3.53 ± ± 1.3 Table 3.2B: GSI of P.daniconius at different maturity stages Maturity stages Males Females Immature 5.2 ± ± 1.34 Maturing 4.7± ± 1.2 Mature 3.5 ± ± 1.36 Ripe 3.3 ± ± 1.2 Spent 3.01 ± ± 1.05

19 Fullness of gut: In E.danricus, the active feeding (full and 3/4 full) was recorded in November (66.7%), moderate feeding in May (61.8%), while poor feeding was observed in August (48.6%). Empty stomach was also recorded throughout the year (Table 3.3A). In case of P.daniconius, the active feeding was mostly encounter during April (59.44%) and December (52.3%), moderate feeding was also recorded in September (66%) and November (62.8%) while the highest percentage of poor feeding (48.57%) was noted in June. More empty stomach (28.26%) was recorded during February (Table 3.3B). As far as fullness of gut in relation to the maturity stage is concerned, the highest active feeding (41.1%) was recorded in ripe species, moderate (47.4%) and poor feeding (25%) were recorded in mature and immature stage respectively while the highest percentage of the empty stomach (25%) was observed in immature of E.danricus (Table 3.3C). In case of P. daniconius, active feeding (47.3%) was found in mature, moderate feeding (50.44%) and poor feeding (36.8%) were recorded in immature stage. Empty stomach (21.1%) was also observed in immature stage (Table 3.3D).

20 84 Table 3.3A: Monthly variations of fullness of gut in E.danricus Monthly No. of specimen examined Active feeding Moderate feeding Poor feeding Full ¾ full ½ full ¼ full Empty Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Overall Table 3.3B: Monthly variations of fullness of gut in P.daniconius Months No. of specimen examined Active feeding Moderate feeding Poor feeding Full ¾ full ½ full ¼ full Empty Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Overall

21 85 Table 3.3C: Percentage of fullness of gut of E.danricus at different maturity stage Maturity No. of specimen Full ¾ full ½ full ¼ Empty stages examined full Immature Maturing Mature Ripe Spent Table 3.3D: Percentage of fullness of gut of P.daniconius in different maturity stages Maturity No. of Full ¾ full ½ full ¼ full Empty stages specimen examined Immature Maturing Mature Ripe Spent

22 Length-weight relationship of E. danricus & P. daniconius in different size group E. danricus: In E. danricus, the co-efficient of regression (b) was in juvenile; 1.01 in male and in case of female. As a whole, E.danricus did not follow the cube law (b=3). Again the result reveals that females have better growth than males and juvenile. The b value was slightly over 1 in all the cases except in female in > 5 cm group (Table 3.4A). The finding indicates that both the sexes show allometric growth. Higher values of b were observed in older length groups in both the sexes. Co-efficient of correlation (r) of E. danricus shows more or less similar trend in all length groups irrespective of both males and females. The length and weight were positively correlated in both sexes. The lowest r value was found in the 4-5 cm length group; moderate was recorded in the 3-4 cm length group and highest recorded in the > 5 cm length group (Table 3.4A). Condition factor K was found to be highest (1.0198) in the length group of 3-4 cm and that of lowest (0.8141) in the >5 cm length group. Juvenile: Y= X (r = 0.690) Male: Y= X (r = 0.844) Female: Y= X (r =0.893)

23 87 Table 3.4A: Length- weight relationship of E.danricus in different size group Length r b a K Regression equation Group Sex ( Y=a + bx) 3-4 Male Y= X Female Y= X 4-5 Male Y= X Female Y= X > 5 Male Y= X Female Y= X P. daniconius: In P. daniconius, the co-efficient of regression b value was in juvenile; in male and in case of female, it was P. daniconius also did not follow the cube law (b=3). However, the b value indicated that females had better growth than males and juveniles. The highest value (2.427) was recorded in female (3-4cm). The result indicates that both the sexes shows allometric growth as well as higher length groups was better growth rate (b) than lower length group in both the sexes (Table 3.4B). The value of coefficient of correlation (r) of P. daniconius shows similar in trend in all length groups of both the males and females. The value of r for males and females were positively correlated in the entire length group. The lowest r value was found in the 3-4 cm (for males) and 7-8 cm length group (for females) and highest for males and females was recorded in the 7-8 cm and 5-6 cm length group respectively

24 88 (Table 3.4B). Condition factor K was ranged from to in the length group of 3-4 cm and 6-7 cm length group respectively. Juvenile: Y= X (r = 0.509) Male: Y= X (r = 0.853) Female: Y= X (r =0.601) Table 3.4B: Length- weight relationship of P. daniconius in different size group Length Group Sex r b a K Regression equation ( Y=a + bx ) 3-4 Male Y= X Female Y= X 4-5 Male Y= X Female Y= X 5-6 Male Y= X Female Y= X 6-7 Male Y= X Female Y= X 7-8 Male Y= X Female Y= X

25 Length-weight relationship of E. danricus & P. daniconius in different seasons The regression coefficient (b) of male Esomus, was found to be highest (1.038) in monsoon while lowest (1.004) in pre-monsoon. In case of females, it varied between (post-monsoon) and (pre-monsoon). In different season too, E. danricus did not follow the cube law (b=3) and both sexes showed allometric growth (Table 3.5A). The highest co-efficient of correlation (r) for males in E. danricus ranged from (post-monsoon) to (pre-monsoon) while in females, the r value was varied from 0.86 to during winter and pre-monsoon respectively. The value of r for both males and females were strongly positive correlated in different season. Condition factor K for male was found to be highest (1.344) in pre-monsoon and that of lowest (0.951) in winter whereas females K value fluctuated from to during post-monsoon and pre-monsoon. Table 3.5A: Length- weight relationship of E.danricus in different season Season Sex r b a K Regression equation ( Y=a + b X ) Winter Male Y= X Female Y= X Premonsoon Male Y= X Female Y= X Monsoon Male Y= X Female Y= X Postmonsoon Male Y= X Female Y= X

26 90 Length-weight relationship of P.daniconius in different season has been shown in Table 3.5B. The b value of male was found to be highest (1.051) in monsoon while lowest (1.004) in post-monsoon. In case of female it varied between (monsoon) and (pre-monsoon). In different season too, of P. daniconius did not follow the cube law (b=3) and reveals that both sexes showed allometric growth. Highest co-efficient of correlation (r) were ranged from (pre-monsoon) to (monsoon) for males while it was varied from to during premonsoon and monsoon respectively for females. The value of r for both sexes were strongly positive correlated in different season. Condition factor K for males was found to be highest (1.242) in post-monsoon and that of lowest (1.019) in winter whereas in females K value fluctuated from to during post-monsoon and pre-monsoon respectively. Table 3.5B: Length- weight relationship of P. daniconius in different season Season Sex r b a K Regression equation (Y= a + bx) Winter Male Y= X Female Y= X Premonsoon Male Y= X Female Y= X Monsoon Male Y= X Female Y= X Postmonsoon Male Y= X Female Y= X

27 Reproductive biology Sexual dimorphism and sex ratio: It is difficult to identify the sex when specimens are very young. In adults, only visible difference is the bulging belly of female during breeding season. In ripe males milt oozes out when gentle press is applied. Generally males are having brighter coloration in both the specimens. The monthly sex ratio of E.danricus and P.daniconius has been given in Table 3.6A & 3.6B which shows that M:F of E.danricus varied from 1:0.07 (November) to 1:3.8 (June). In case of P. daniconius, it ranged from 1:0.023 (December) to 1:1.2 (May). The sex ratio of M: F was significant at 5% level mostly during postmonsoon and winter. Table 3.6A: Monthly variation in sex ratio of E.danricus Months Males Females Sex ratio Chi-square Jan : * Feb : * Mar : * Apr : May : Jun : * Jul : Aug : Sep : Oct : * Nov : * Dec : * Total : * *significant at 5% level

28 92 Table 3.6B: Monthly variation in sex ratio of P.daniconius Months Males Females Sex ratio Chi-square Jan : * Feb : * Mar : Apr :0.7 1 May : Jun :0.7 1 Jul : Aug : Sep : Oct : * Nov : * Dec : * Total : * *significant at 5% level Maturity stage: Five stages of maturity for both the specimens have been identified (Table 3.6C). The percentage occurrence of E. danricus in different stages has been given in Table 3.6D. Females were mostly immature (53.35%) and maturing stage (40.57%) from March to May. Mature (26.51%) and ripe (63.94%) individuals occur in between May and August. Spent specimens (85.19%) were appeared from September onwardswhile immature male (22.39%) appeared from February till April, maturing (28.01%) were recorded from March to June, ripe (48%) were observed from June to September whereas spent stages (65.43%) were mostly available from October to January.

29 93 In case of P.daniconius, the monthly maturity stages of males and females are given in (Table 3.6E).Immature stages (52.38%) appeared between February and April in females while maturing stages (30.64%) and mature stages (43.43%) were observed from March to June/July. The ripe stages (42.66%) females being active from July till September while spent stages (90%) were mostly encountered from October onwards till January. Immature (33.4%) and maturing (27.29%) males were dominated from January to April/May, while mature stages (43.14%) and ripe (47.81%) appeared from May till August/September. The spent stages (66.2%) were recorded from October to February. Maturity stages Stage I (Immature) Stage II (Maturing) Stage III (Mature) Stage IV (Ripe) Stage V (Spent) Table 3.6C: Morphology of gonads at various maturity stages of E.danricus and P.daniconius Testes Testes are very small thread-like, strings and contained within a transparent membrane. Testes uniformly ribbon-like, surface of testes appears smooth and uniformly textured. It occupies ½ of the total body cavities. Mature testes large & highly convoluted; occupies ¾ of total cavities. Sperm cannot be extruded. It occupies entire of the body cavity. Testes creamy, soft milk and freely or extrude sperm when compressed slightly. Spent testes are flat, flaccid and pale whitish colour. Ovary Immature ovaries small, flat, tapered, & transparent. It occupies ¼ th of total length of body cavity and hardly visible with naked eyes. Forming two distinct, transparent lobes with well-developed blood vessels. A few individual ova present and fill up to ½ of the body cavity, with distinctly visible opaque, orange eggs. Mature ovaries fill more than ½ of the cavity & contain distinctly visible eggs, eggs are not extruded when ovaries are compressed. Most eggs are opaque, rounded & orange in colour. Ovaries large, filling the total body cavity. Most eggs are transparent though some opaque eggs may remain. Eggs are extruded from the body under slight pressure & easily separated from each other. Spent ovaries are shrunken, but flaccid, watery, and generally reddish. Scattered unspawned eggs can be seen and begins to develop the ovary into the Early Developing.

30 94 Table 3.6D: Percentage occurrence of E.danricus in different stages of maturity Mont Maturity stages (Males) Maturity stages (Females) h I II III IV V Total exam ined I II III IV V Total examin ed Jan Feb Marc h 7 3 April May June July Aug Sep Oct Nov Dec

31 95 Table 3.6E: Percentage occurrence of P.daniconius in different stages of maturity Mont Maturity stages (Males) Maturity stages (Females) h I II III IV V Tota l exa mine d I II III IV V Total exami ned Jan Feb Marc h 5 5 April May June July Aug Sep Oct Nov Dec

32 Maturity index or Gonadosomatic ratio (GSR): Monthly mean variation of GSR in E. danricus and P. daniconius has been given in the (Table 3.6F & G). In E. danricus, the highest value (10.6 ± 3.2) was recorded in August and that of lowest (1.1 ± 0.56) in February for males; whereas the maximum GSR value (3.45± 3.73) was observed during August and the minimum (0.64 ± 0.43) was observed during November for females. In case of P. daniconius, the highest (9.39 ±1.59) and lowest (1.35 ± 0.64) G.S.R for males were observed during August and February respectively; while the maximum (11.85 ± 1.85) and minimum (1.16 ± 0.47) G.S.R for females were recorded during August and November respectively. Table 3.6F: Mean gonadosomatic ratio (GSR) in E. danricus Month Males Females Jan 1.2 ± ± 0.40 Feb 1.1 ± ± Mar 1.13 ± ± 0.18 Apr 6.13 ± ± 2.51 May 9.24 ± ± 2.33 Jun 9.16 ± ± 2.37 Jul 10.4 ± ± 3.7 Aug 10.6 ± ± 3.73 Sep 1.17 ± ± 0.91 Oct 1.84 ± ± 0.09 Nov 1.12 ± ± 0.43 Dec 1.67 ± ± 0.27

33 97 Table 3.6G: Mean gonadosomatic ratio (GSR) in P. daniconius Month Males Females Jan 1.45 ± ± 0.23 Feb 1.35 ± ± 0.21 Mar 2.61 ± ± 1.81 Apr 6.55 ± ± 2.94 May 7.4 ± ± 2.84 Jun 6.05 ± ± 2.2 July 7.36 ± ± 2.42 Aug 9.39 ± ± 1.85 Sep 1.44 ± ± 0.05 Oct 2.58 ± ± 0.97 Nov ± ± 0.47 Dec 1.4 ± ± 0.2 As far as GSR in relation to different maturity stage, the lowest GSR value of the male Esomus danricus (1.6 ± 0.88) and females (1.9± 0.34) was found in spent and immature specimen while highest GSR of male (9.8 ± 4.62) and female (11.5 ± 4.32) were observed in ripe specimens (Table 3.6H). Again in P. daniconius, the maximum GSR value for both the males (5.6 ±1.44) and females (10.56 ±5.54) was observed in ripe (gravid) stage whereas the minimum (1.72 ± 0.51) in males and female (1.63 ± 0.48) was recorded in immature individuals (Table 3.6I).

34 98 Table 3.6H: GSR at different maturity stages of E. danricus Maturity stages Males Females Immature 1.7 ± ± 0.34 Maturing 4.9 ± ± 1.41 Mature 7.2 ± ± 4.09 Ripe 9.8 ± ± 4.32 Spent 1.6 ± ± 0.93 Table 3.6I: GSR at different maturity stages of P. daniconius Maturity stages Males Females Immature 1.72 ± ± 0.48 Maturing 2.13 ± ± 0.85 Mature 4.29 ± ± 6.41 Ripe 5.6 ± ± 5.54 Spent 1.98 ± ± Ova diameter: The ova diameter was found to range from 0.1 to 0.6 mm in E.danricus during March and in August (Table 3.6J). In case of P.daniconius it was ranged between 0.2 (February) and 0.74 (August) (Table 3.6K). In relation to the different maturity stage, the ova diameter of E.danricus was varied from 0.1mm (immature) to 0.49mm (ripe) whereas the ova diameter of P.daniconius ranged from 0.2mm (immature) to 0.6mm (ripe).

35 99 Table 3.6J: Monthly progression of mean ova diameter of E. danricus Month Range of OD(mm) Mean OD Jan - - Feb - - Mar ± Apr ± May ± 0.05 Jun ± 0.08 Jul ± 0.05 Aug ± 0.07 Sep ± 0.07 Oct - - Nov - - Dec - - Table 3.6K: Monthly progression of mean ova diameter of P.daniconius Month Range of OD(mm) Mean OD Jan - - Feb ± 0.09 Mar ± 0.09 Apr ± 0.12 May ± 0.06 Jun ± 0.05 Jul ± 0.06 Aug ± 0.08 Sep ±0.05 Oct - - Nov - - Dec - -

36 Fecundity: In E.danricus the lowest (576.47±100.29) and highest (709.6 ± 88.4) absolute fecundity were recorded during April and August respectively (Table 3.6L), whereas in P.daniconius the minimum ( ± ) and maximum ( ± ) were observed during February and May respectively (Table 3.6M). The highest ( ± 120.7) relative fecundity of E.danricus was recorded in August and lowest (249.7 ± 94.01) in May. In case of P.daniconius the maximum ( ± ) and minimum ( ± 85.24) relative fecundity were recorded during August and February respectively. Table 3.6L: Monthly variations in fecundity of E.danricus Months Mean body length (cm) Mean body weight (g) Mean ovary weight (g) Mean absolute fecundity Mean relative fecundity Jan 5.4± ± ±0.01 Spent - Feb 4.6± ± ±0.1 Spent - Mar 4.5± ± ±0.01 Spent - Apr 4.9± ± ± ± ±62.6 May 5.34± ± ± ± ±94.01 Jun 4.98± ± ± ± ±218.5 Jul 4.34± ± ± ± ±313.6 Aug 4.6± ± ± ± ±120.7 Sep 4.6± ± ±0.05 Spent - Oct 4.98± ± ±0.01 Spent - Nov 5± ± ±0.01 Spent - Dec 4.6± ± ±0.01 Spent -

37 101 Table 3.6M: Monthly variations in fecundity of P. daniconius Months Mean body Mean body weight (g) Mean ovary Mean absolute fecundity Mean relative fecundity length (cm) weight (g) Jan 7.13± ± ±0.02 Spent - Feb 6.13± ± ± ± ±85.24 Mar 6.81± ± ± ± ± Apr 6.54± ± ± ± ± May 6.64± ± ± ± ±80.08 Jun 6.72± ± ± ± ±45.12 Jul 6.1± ± ± ± ± Aug 5.68± ± ± ± ± Sep 5.76± ± ± ± ± Oct 5.79± ± ±0.02 Spent - Nov 5.7± ± ±0.01 Spent - Dec 6.1± ± ±0.01 Spent Size at first maturity (M 50 ): In E. danricus, the percentage for both the immature males (65.7) and females (67.9) appeared in the length group of 3-4 cm. Again the 50% or above of mature/ripe males (52.78) and females (59.1) were recorded in the length group of 4-5 cm and this length may be considered at which M 50 maturity for both the sexes attained. The highest percentage of maturity for both the males (89.96) and females (95) were observed in the > 5 cm length group (Table

38 N).In P. daniconius, immature males (72) were recorded mostly in < 3 cm length. The 50% of the mature specimens, males (52.1) and females (50.5) were found in the length group of 4-5 cm. Hence, this length group may be considered at which 50% maturity for both the sexes attained. The 100% of maturity in both the sexes of mature/ ripe were attained in the length group of 7-8 cm (Table 3.6O). Table 3.6N: Percentage of maturity in different length groups in E. danricus (M 50 ) Size group (cm) Sex Immature% (Stage I) Maturing% (Stage II) Mature/Ripe% (Stage III/ IV) 3-4 Male Female Male Female > 5 Male Female Table 3.6O: Percentage of maturity in different length groups in P. daniconius (M 50 ) Size group (cm) Sex Immature (Stage I) Maturing (Stage II) Mature/Ripe (Stage III/IV) 3-4 Male Female Male Female Male Female Male Female Male Female

39 DISCUSSION Gupta & Gupta (2006) described the morphological features of Esomos danricus as follows: Lip absent, eye diameter in HL, 1.0 in snout and in the interorbital width and 2 pairs of barbels. In Rasbora daniconius, lower jaw with one central and two lateral prominences fitting into corresponding emarginations in the upper jaw, lips thick, eye diameter in HL, 1.0 in snout and in the interorbital width and barbels absent (Gupta & Gupta, 2006). In the present study also there is practically no variation observed in the morphological description for the two species (Fig A & 3.1.1B). RLG values reveal that both the specimens are having slight variations in all the length groups (Fig A & 3.1.2B, Anex.I). Further it is evident that the minimum value of RLG was found in the older size groups and that of maximum was found in the younger size groups. The results reveal both the specimens were fall in the carniomnivorous category. It seemed that the specimens may be choosing its food depending on the prevalence of materials in the habitat and can subsist on a wide range of food items. The RGL appears to decrease with increase in body length in R. daniconius (Wejegoonawardana, 1990), and it does not seem to change much with increase in body length in D. aequipinnatus (De Silva et al., 1980) B. titteya (De Silva et al., 1977) and B. sarana (Wejegoonawardana, 1990). The RGL has been shown to

40 104 (A) Alimentary tract (B) Fig A: Alimentary tract of E. danricus B: Alimentary tract of P.daniconius

41 105 be related to the body length in several cyprinid species. An increase in RGL with body length was observed in Acrossocheilus hexagonolepis (Dasgupta, 1988), B. bimaculatus (De Silva et al., 1977), B. amphibius and B. dorsalis (De Silva et al., 1980), Amblypharyngodon melettinus, B. chaola, B. dorsalis and B. filamentosus (Wejegoonawardana, 1990). Al-Husaainy (1949) stated that if RLG is < 1, the fish is a carnivore. In herbivorous fishes such as Labeo rohita and L. gonius the R.L.G values were about 12 and 9.5 respectively (Das & Moitra, 1956). In omnivorous fishes the R.L.G values were lower in Puntius conchonius had 3.3 and Barbous hexastichus had 2.3 (Das & Nath, 1965). In carnivorous fishes R.L.G values were generally low, as in Bagarius bagarius (0.8) and Notopterus chitala (0.4) as reported by Das & Moitra (1956). Parameswaran et al., (1970) found that food and feeding habits of N.nandus changes as they grow into adult. It is evident that R.L.G value has a close relationship with the nature of food of the fish (Dasgupta et al., 2008). Interestingly, this variation was noticed in both young and adult fish, thus ruling out any substantial change in diet. In view of the consistency in the gut length/body length ratio over the entire size range of the fish inclusive of both juveniles and adults. In teleosts, it has been shown that the length of gut is very much related to the food habit (Kapoor et al., 1975).The relative importance of different food items differs in different species, even among those species that live together in the same habitat

42 106 This would obviously reduce the intensity of competition for the same food item and would play an important part in niche segregation. For instance, De Silva et al. (1980) showed that, among the co-habiting Barbus amphibius, B. dorsalis, Danio aequipinnatus and Rasbora daniconius, the latter three species are omnivorous. B. amphibius was found to feed almost exclusively on plant material (Kumar et al., 1986) GSI in relation to months and seasonal variation for both sexes The gastrosomatic index of fish is generally used as a reflexion of the intensity of feeding (De Silva & Wijeyaratne, 1977). The lowest gastro somatic index (GSI) of E. danricus was found in January (for males) and in December (females) while the highest was recorded in April (both males and females). In gastro somatic index (GSI) of E. danricus, lowest GSI for both the males and females were observed during winter and that of highest GSI were observed for males and for females during premonsoon and post-monsoon (Fig.3.1.3A). In case of P. daniconius, the gastro somatic index (GSI) was minimum in May and maximum in August for males where as for female it was maximum in July and minimum in December. In case of P. daniconius, the maximum GSI value for both the males and females was observed during monsoon while that of minimum for males and females were recorded during winter (Fig.3.1.3B). The intensity of feeding was found to be moderate during pre-monsoon for both the sexes.

43 GSI of E.danricus GSI value Female Male 0 Winter Pre-monsoon Monsoon Post-monsoon Season Fig A : Seasonal GSI of E.danricus 12 GSI of P.daniconius GSI value Female Male 0 Winter Pre-monsoon Monsoon Post-monsoon Season Fig B: Seasonal GSI of P.daniconius

44 108 The value of gastro-somatic index for various months showed intense feeding activity during March-April, June-August and declined from December onwards. Low feeding in winter months is because fish being poikilothermous, they are unable to ingest sufficient food due to low metabolic rate. A similar result was also made by Choudhury (2004) in Channa barca. This kind of feeding habit may be an optimal strategy for habitats where food sources are subject to seasonal fluctuations (Welcome, 1979). The variation in high and low values of feeding intensity was found much more in the case of females as compared to males because of the fact that ovaries occupy more space as compared to testes (Prakash & Agarwal,1989). However, the results was quite contrast to the finding of Rao et al. (1998) in Catla catla who reported that the feeding intensity remained high during winter months (non spawning period) and reduced during summer months (pre-spawning period). They also added that generally during spawning season, feeding rate would be relatively lower and it increases immediately after spawning as the organisms feed voraciously to recover from fast (Rao et al., 1998). Earlier, Quayyum & Quasim (1964) recorded a cessation of feeding activity in fishes during winter season. In the present observations also, a low rate of feeding was found to occur during the colder month. Some of the reported differences in the feeding habits of these fishes are perhaps due to the variations in the abundance and availability of food items in the water bodies studied. Further feeding intensity was

45 109 found to decrease with increase in the size of the Himalayan mahseer (Kumar et al., 2009) GSI in relation to maturity stages: In relation to maturity stages of E. danricus, the minimum and maximum for male GSI was recorded in immature and mature stage respectively while in case of female, minimum and maximum values were recorded in maturing and ripe stage respectively (Fig.3.1.4A, Anex.I). Similarly, in P. daniconius, the lowest and highest GSI were found in spent and immature males while it was found to be lowest in maturing and highest in mature females (Fig.3.1.4B, Anex.I). The low feeding activities in case of spent fishes coincides with the spawnning season. In the present study suggested that feeding was never discontinued and even during spawning. There was no cessation of feeding. The feeding intensity of fish is related to its stage of maturity, reproductive state and the availability of food items in the environment (Ricker, 1969). Khan et al. (1988) and Serajuddin et al. (1998) also reported same type of feeding intensity in relation to the stage of maturity in Mystus numerous and Mastacembelus armatus respectively. The occurrence of low feeding in other fishes coincide with their peak breeding was reported by several workers such as Jhingran, (1961), Desai (1970), Bhatnagar & Karamchandani (1970), Fatima & Khan, 1993 and Serajuddin et al. (1998).Serajuddin et al., (1998) recorded high feeding intensity in spiny eel (M. armatus) in early maturity and was relatively lower in ripening of the gonad.

46 Fullness of gut: In E.danricus, the active feeding was found in November, moderate feeding in May, while poor feeding was observed in August. Few empty stomachs were also noted throughout the year in both the species. In case of P.daniconius, the active feeding was mostly encounter during April and December, moderate feeding recorded during September and November while the highest percentage of poor feeding was noted in June. Most of the empty stomachs were recorded in February. Further feeding intensity was generally low during August- October in both the species. This might may be due to regurgitation while removing from deeper waters (Job, 1940) or be due to the faster digestive rates of carnivores (Qasim, 1972). Seasonal variation occurs in the composition of the diet of the both the species because availability of food organisms are often cyclic due to factors of their life histories or to climate, or other environmental conditions. The result of the higher fullness of stomach during the period (March-May), more so, the availability of food material may be the reason for higher percentage of full stomach. The result is in line with the findings of Shinkafi & Ipinjolu (2001) on the occurrence higher percentage of Synodontis clarias. Again in relation to the maturity stage of E. danricus, the highest active feeding was recorded in ripe specimen and followed by moderate feeding and poor feeding were observed in mature and immature stage respectively, while the highest percentage of the empty stomach was observed in immature stage (Fig.3.1.5A Anex.I). In P. daniconius, too the trend was found almost identical (Fig.3.1.5B Anex.I).

47 % of fullness Full Nearly full ¾ ½ ¼ Nearly empty Winter Pre-monsoon Monsoon Post-monsoon Fullness of gut Fig C: Percentage of fullness of gut of E.danricus at different season % of fullness Full Nearly full ¾ ½ ¼ Nearly empty Winter Pre-monsoon Monsoon Post-monsoon Fullness of gut Fig D: Percentage of fullness of gut of P.daniconius at different season

48 112 The variations in the feeding intensity of both sexes of the E.danricus and P.daniconius were observed to be in the same pattern. A maximum number of empty guts were found during spawning and during the winter season (Fig C & D). Khan (1972) & Chatterjee (1974) also reported than fluctuation in feeding intensity in the fishes took place due to maturation of their gonads. The diet and feeding intensity can vary even during the diurnal cycle Keast & Welsh (1968), Elliot (1970), Ikusemiju (1975a). The seasonal variation in the feeding habits of fish resulting from climatic changes has been reported by Moriarty & Moriarty (1973), Ikusemiju (1975b), Tudorancea et al. (1988). This may suggest earlier stoning of the fish samples immediately after capture and active fishing methods employed. Similarly higher occurrence of non-empty stomach was due to good feeding strategy of species and food abundance in most part of the year (Fagade, 1978). Feeding was better in males throughout the year than in the females. Intraspecific competition is reduced because different size classes rely on different food categories (Mayekiso & Hecht, 1990). The exponent value (b) of both the specimens is significantly different from cube law and this indicates negative allometric growth. The slope (b) values slightly over 1, except in adult female (> 5cm) of E. danricus and P. daniconius (3-4 cm) group obtained of the fish specimens in this study shows that the growth of the species is allometric. The correlation coefficient (r) for LWR was high for E. danricus and P. daniconius, indicating increase in weight with increase in every unit of length. A positive correlation was found in the length group as well as in various seasons. These

49 113 agreed with earlier studies on length and weight in other fish species (Tesch, 1971; Fagade & Olaniyan, 1972; Fagade, 1983; Merella et al., 1997; Ruiz-Ramirez et al., 1997; Laleye, 2006; Singh, 2011; and Paswan et al.; 2012). The variation in the exponential value (b) is supposed to be under the influence of numerous factor viz, seasonal fluctuation, physiological condition of the fish at the time of collection, sex, gonadal development and nutritive condition of the environment of the fishes as reported by LeCren (1951). Significant variations in (b) values were found in case of juvenile, males and females of E.danricus and P.daniconius. The (b) values for juvenile, males and females of both the species were found to be lower than 3; indicating allometric growth. Lal & Dwivedi (1965), Sekheran (1968) and Dasgupta (1988) have also observed an intraspecific difference in the power function (b) of length in relation to body weight in Rita rita, Sardinella albella, S. gibbosa and Acrossocheilus hexagonolepis respectively at different stages of their growth. However, Beverton & Holt (1957) suggested the departure of the b value from 3 is rare in adult fishes. Pathak (1975) reported a b value of less than 3 for Labeo calbasu from Soni River and Harish Kumar et al. (2006) reported values less than 3 for the males and females of Rasbora daniconius from Karnataka. The mean K value for both the specimens is found greater than one, and this shows that both the studied fish specimens are in good condition. The variation in mean K values was higher during pre-monsoon and monsoon season, related to the breeding activities of the fish due to depletion of reserves during rainy season.

50 114 Condition factor has also been closely linked with reproductive cycle for fishes in other water bodies (Salzen, 1958; Fagade & Olaniyan, 1972; Ugwumba, 1990; Wade, 1992; Aboaba, 1993 and Saliu, 1997). In the present study, the females of E. danricus showed better growth rate than male and juvenile but in case of P. daniconius juvenile had more growth rate than male and female (Fig A-F). The relative condition factor (Kn) is an indicator of general well-being of the fish, its relative robustness, suitability of habitat and to some extent the size at first maturity and peak period of spawning. Kn values greater than 1 is an indicative of general well being of the fish good. Shrivastava & Pandey (1981) reported that in IMC, feeding influenced the condition factor, while the sexual cycle had no direct influence. Both the species display considerable changes in average condition, reflecting normal seasonal fluctuations in their metabolic balance and in the pattern of maturation and subsequent release of reproductive products. Even fullness of the alimentary canal; may influence K factor (Wheatherley, 1972). Month wise and size group fluctuation of K factor shows no specific trend. Variations in the condition factor may be attributed to different factors, such as environmental condition, food availability and the gonadal maturity as has been suggested by many workers (LeCren, 1951; Jhingran, 1972; Bashirullah, 1975). According to Rizvi et al. (2002) the value of b is generally closely to 3 and may vary between 2.5 and 4.0 and Bagenal & Tesch (1978b) and Goncalves et al. (1997) the b value may change seasonally and even daily and also between habitats.

51 115 Weight (g) y = 1.007x R² = Length (cm) Fig A: Length-weight relationship of E.danricus (Juveniles) Weight (g) y = x R² = weight Linear (weight) Length (cm) Fig B: Length-weight relationship of E.danricus (Males) Weight (g) y = x R² = Length (cm) Fig C: Length-weight relationship of E.danricus (Females)

52 116 Weight (g) y = x R² = Length (cm) Fig D: Length-weight relationship of P.daniconius (Juveniles) Weight (g) y = x R² = Length (cm) Fig E: Length-weight relationship of P.daniconius (Females) Weight (g) y = x R² = Length (cm) Fig F: Length-weight relationship of P.daniconius (Males)

53 Sex ratio: A comprehensive knowledge of sexuality in fishes is considered vital for the understanding of behaviour patterns, breeding periodicity, growth rates, body colour and shape or sexual dimorphism (Yamazaki, 1983). Information on sex development has also been applied in fish culture to either initiate sexual change or to improve growth of a particular sex (Yamazaki, 1983; Nakamura et al., 1989). In both the specimens, males were comparatively brighter than the females and females are always bigger in size as well as more weight than their male counterpart. Females were lighter in colour and larger in size. In case of mature females, the abdomen was soft and swollen, pelvic fins were smooth and caudal fin was deeply forked. During the spawning season their distended abdomen easily recognized mature females (Plate 3.1.7). Sexual dimorphism based on the occurrence of contact organs and colouration during the breeding season was observed and the former may be used to distinguish between the sexes in larger fish (Mayekiso & Hecht, 1990).

54 118 PLATE 3.1.7: SEXUAL DIMORPHISM Fig. A: Male (E. danricus) Fig. B: Female (E.danricus) Fig. C: Male (P. daniconius) Fig. D: Female (P. daniconius)

55 119 The sex ratio observed for both the specimens was slightly different from the expected ratio of 1:1 (male: female). The chi-square test showed that there was significant variation in the sex ratio of the fish from the expected ratio of 1:1 when the males outnumbered females in the population. The lowest M : F of both the specimen was found in winter and that of highest was in monsoon season. In the present study, the overall sex ratio of the 500 investigated of E. danricus was 1:0.31 and of the 475 P. daniconius, the ratio was 1:0.4. Males were mostly encountered round the year except May and August (Fig E & F, Annex.I). The 1:1 ratio might also be affected by differential fishing factors related to seasons and schooling in feeding and spawning grounds (Sarojini, 1957; Silva & De Silva, 1981; Lasiak,1982). This happens because of differential behaviour of sexes, environmental conditions and fishing pressure (Bal & Rao, 1984). The monthly distribution of two specimens did not show a significant difference in the distribution of sexes when males were dominance over females. Similar observation was also reported by Naama et al. (1986), Varadi & Horvath (1993), Unlu et al. (2000), Vicentini & Araujo (2003), Singh (2011) in other fish species. High sex ratio in favour of males during the spawning period was reported in species like Elops lacerta (Ugwumba, 1984; Lawson & Aguda, 2010). However, this is contradictory to that of Cek et al. (2001) in Puntius conchonius, Sarma (2008) in Puntius gelius and Muchlisin et al. (2010) in Rasbora tawarensis where females dominated over their male counter part.

56 120 The variation of sex ratio may be due to different fishing methods and coinciding to the breeding period of the specimens. Another factor that could influence sex ratio is food availability. Nikolsky (1963) reported that when it is abundant, females predominate, with the situation inverting in regions where food is limited. Feeding activity, in this case, would be influencing metabolism through hormonal activity, resulting in changes in production of individuals of a given sex. It is now clearly shown that sex ratios of various freshwater species, from temperate or tropical habitats can be influenced by some environmental factors. Among them, temperature seems to be the main environmental determinant of sex (Baroiller & Cotta, 2001). It has been also suggested that females require better environmental conditions than males, suffering in their development when environmental conditions deteriorate (Vicentini & Araujo, 2003). Furthermore, the seasonal variation in the sex ratio observed was probably because once fertilization of eggs was completed, male possibly emigrates from spawning area towards feeding ground located in the shallow areas (Offem et al., 2007) Gonadosomatic ratio The GSR increases with the maturation of fish, being maximum during the period of peak maturity and declining abruptly thereafter, when the fish become spent (Le Cren,1951). De Vlaming et al. (1982) discussed the utility of GSR as an indicator of the reproductive activity of a stock. The GSR is usually established for males and females alike, although the development of gametes is not reflected in this index in an

57 121 identical way in both sexes. The monthly change of GSR reflects the ovarian activity of fish. Monthly GSR of E.danricus increases from April onwards and it gradually decrease from August. The highest value of GSR in E. danricus was recorded in monsoon and that of lowest in winter for both the sexes (Fig.3.1.8A). Again, the monthly GSR of P. daniconius was observed from April till August and gradually decrease the highest GSR and lowest for males were observed during monsoon and winter respectively in female highest observed during monsoon and lowest during post-monsoon (Fig.3.1.8B). Gonado-somatic ratio (GSR) is usually established for males and females alike, although the development of gametes is not reflected by this index in an identical way in both sexes. Like other species, the lowest GSR value of male and female for E. danricus were recorded in spent and immature specimen and that of highest GSR were observed in ripe specimen (Fig C, Annex.I). In P. daniconius, the higher GSR value for both the males and females were observed in ripe (gravid) stage whereas the lowest were recorded in immature individual (Fig.3.1.8D, Annex.I). The GSR values gradually increased from pre-monsoon to monsoon season but abruptly dropped down during post-monsoon indicating the culmination of spawning activities. Sexually mature fish had high GSR value and in females, the value was much as six times greater than in males (Chellappa et al., 2003). The maturity stage in both the species indicated that female had their peak spawning time in May-June however spawning continued till August. The monthly change of GSR reflects the ovarian

58 122 Mean GSR Males Females 0 Winter Pre-monsoon Monsoon Post-monsoon Season Fig A: GSR of E.danricus seasonally Mean GSR Males Females 0 Winter Pre-monsoon Monsoon Post-monsoon Season Fig B: GSR of P.daniconius seasonally

59 123 activity of fish. GSI of P. sarana is highest during July when the fish is found to be mature (Chakraborty, 2008). It reveals that both the specimens have prolonged and spawn once during the spawning season. The GSR values of both the specimens with peaks in May, June, July and August, presumably the likely onset of the spawning seasons largely coincided with the rainy seasons. After September onwards the GSR gradually fall down and indicating spawning was over when the fish become spent. GSR values in females of both the specimens were consistently higher than in males. The GSI had been used to describe the development of gonads in Pike, Esox lucius (Danilenko, 1983). Mohammed ( 2010) also noted that GSI increases progressively with increased percentage of the ripe individuals towards the spawning seasons The most common practice for determination of determination of a species spawning season is the establishment of its GSR and the histological examination of the gonads (El-Greisy, 2000; Assem, 2000 & 2003; Honji et al., 2006). It has further been observed that seasonal peaks in the GSR values coincided with the peaks in the percentage of occurrence of matured individuals. The result on GSR indicates that both the males and females mature at the same time of the year, the peak breeding period being July and August Ova diameter: The ova diameter variation is probably one of the important pieces of evidence used in determination of fish reproductive strategy (Tomasini et al., 1996). The ova diameter of E. danricus was found gradually progressed from March to

60 124 August. In case of P.daniconius, the minimum ova diameter was found in February and that of maximum in July-August. The diameter of the ova was significantly higher in July-August which indicated that the diameter of the ova attained its highest in the peak spawning season. The results coincide with those obtained from the study of monthly variation in maturity stages and gonadosomatic index of the specimens. The differences in the ova diameter as well as the age and size of the female brooder (Bagenal, 1967) are mainly determined by the genotype of parental fish (Springate & Bromage, 1985). Variation in egg diameter has been reported for other tropical fish species (Awachie & Ezenwaji, 1981). The availability of food also affects egg size (Springate & Bromage, 1984). The diameter of ova from representative ovaries of the five maturity stages were measured and found to be spherical and uniform in diameter. Similiar finding were also reported by Nabi & Hussain (1996) and Singh (2011).The development of egg(ova diameter) was found to be in full agreement with that of gonado-somatic index. Higher value of mean ova diameter and gonado-somatic index from June- August indicate that the peak breeding take place during this period. Again in both the specimens, the lowest and highest ova diameter were recorded in immature and ripe (Fig A & B). The specimens which have prolonged breeding season are those in which the ovaries include several batches of eggs destined to be matured and shed periodically (Qasim, 1957 ). The reproductive

61 125 mean OD Mean OD 0 Immature Maturing Mature Ripe Maturity stages Fig A: Mean ova diameter of E. danricus in different maturity stages Mean OD Immature Maturing Mature Ripe Maturity stages Mean OD Fig B: Mean ova diameter of P. daniconius in different maturity stages

62 126 potential of a population is one of the basic exigencies to designate the individuals of that population in respect to their gonadal conditions (Jhingran & Verma, 1972) Fecundity In E.danricus the minimum and maximum fecundity were recorded during premonsoon and monsoon while in P.daniconius the minimum and maximum were observed during winter and pre-monsoon respectively. The food consumed by the fish especially the parent population, determinates not only the fecundity but also the quality of the sexual products and the viability of the off springs (Nikolaev, 1958; Nikolsky, 1961 a & b). Fecundity of fish is also affected by environmental factors and supply of food (Bagenal, 1957& Bromage et al., 1992). The variation in the result obtained on fecundity of E. danricus and P. daniconius in the present study may be due to environmental factors in a different geographical location. The high fecundity of C. gariepinus, obtained could be explained by the non-parental care of the species (Viveen et al., 1985). The fecundity of a species is also dependent on egg size. High fecundity is often correlated with small egg size (Rath, 2000). The high fecundity, therefore, might be an attempt by this species to ensure that some young ones survive from season to season to perpetuate the generations of the species (Egwui et al., 2007). Very low GSR value in females also supports low fecundity of the species (Baruah & Borah 2008). Fecundity of fish is found to vary from species to species, depending on age, length, weight and environmental condition (Nasar & Biswas, 1982). Many workers

63 127 have worked on the fecundity of different fish as for example Bhuiyan et al. (1993), Kuddus et al. (1996), Alam et al. (1994), Bhuiyan & Parveen (1998), Bhuiyan et al. (2000) & Dobriyal et al. (2000), Kiran & Puttaiah (2003). Clarke (1934) reported that the fecundity of a species increases in proportion to the square of its length. Swarup (1962), Singh et al. (1982) reported a direct relationship between fecundity and length of fish. In all the fish s number of eggs increased with the increase with their length (Dewan & Doha, 1979). Furthermore, the fecundity increases with the increase in length and weight of the spiny eel (Singh, 2011). But it was just reversed in the present observation. In the present study, both the specimens it reveals that larger weights and ovary weights of the specimens obtain maximum fecundity. Similar observation was also made by Sarkar et al. (2002). This finding gives additional support to the same conclusion for M. tengra (Khan et al., 1992).However it was reported that fecundity increases towards the end of the spawning season (Van Damme et al., 2005). Fecundity of both the specimens is highly variable. Hossain et al. (1997) reported that the fishes of the same size might show great variation in their fecundity due to the multi-spawning pattern of the small species. However, in the present study, higher fecundity was found in younger individuals than larger one. It may be concluded that fecundity increased with increase in fish weight in both the specimens and have a moderate fecund in both the specimens.

64 Maturity stages and spawning period: Five maturity stages were identified in the studied fish specimens. It was observed from April to mid September as indicated by the presence of an appreciable number of females berried condition. Some of these became fully ripe; on the other hand the others remained under mature condition. During the entire period of study except from October to February, maturing as well as mature individuals were observed. In both the species, immature & maturing stage (Plate3.1A, Fig. C-F) were observed maximum from October to April/May and altogether absent from May onwards. Thus, it can be stated that the females breeding period varies from April to September/October. From October onwards, all the individuals were found to be spent and indicating that spawning was over. It can thus be presumed that the period from November to February is the resting period for male individuals. The time and duration of spawning in both specimens are practically the same, the breeding seasons last for about 4 months during May and August/September. There is a regular seasonal cycle in the gonads, it appears that each individual spawns once only. The results of the maturity studies in both the specimens indicate that the male and female mature at same length group and as they were having prolong spawning season (April-September). It has been observed that the seasonal peak in the mean GSR coincided with the peak in the percentage of the mature individuals; hence GSR can be used as an index of gonadal development. Similar observation was also reported by Ahmed (1948); Dasgupta et al. (2008); Singh (2011) in Neolissocheilus

65 129 hexagonolepis and spiny eels. According to Mazzoni & Caramashi (1995) the size at first maturity has an important role in understanding life history of a species during its evolution. Such a case has also been reported by Kakuda & Nakai (1981). Gonado somatic ratio (GSR) or maturity index is another indicator to determine the spawning periodicity in fish. Biswas et al. (1984) and Dasgupta (1994) reported that the GSR is an indicator of fish spawning and this is well documented both in temperate and tropical fishes. Monthly gonadal progression in both the specimens revealed that during the initial stages of development, the testis was very delicate and fine structure, hardly traceable with naked eye. The fully mature testis was yellowish white, elongated structure with wavy edge extending to about th 3/4 of the body. The fully mature ovary was an elongated transparent sack-like structure filled with mature eggs extending to about th ¾ of the body. The ripe eggs were bright yellow, soft and round structure with mm in diameter for both the specimens (Fig A & B). In fully mature female, yolk-laden eggs oozed out upon gentle pressure on the genital region. Fishes are well known for their high biotic potentiality with most species releasing thousand to millions eggs annually (Bond, 1979). The value of the ova diameter gradually increased as the fish approached to gravid stage. Spawning in rising water is an adaptation of lotic fishes to increase reproductive success. Single spawners spawn during floods (Schubart 1954; Godinho & Kynard 2006) and, at any given river, floods may happen many times during the spawning season Therefore, a single spawner

66 130 individual may have many opportunities to spawn during the same spawning season but spawns only once, although its population may spawn many times (Godinho et al., 2007). The morphological changes in the gonads, progression of the size of the ova and above all, the rise and fall in GSR values are indicator of spawning season. The gonads in both the specimens were suddenly reduced in size and completely shrinked from October onwards indicating that spawning was over. In some tropical fish, the capacity to build up fat reserves allows the time of spawning to be independent of the time of food abundance (De Alvarenga et al., 2006). The observation of females with the increase in gonadal volume from April onwards, and subsequent increase of gonad weight on pre-monsoon months indicated that resources are being stored during dry months to be invested later in reproduction as reported by Torres & Ramírez (2008). From the observed data it may be inferred that the E.danricus and P.daniconius has a prolonged breeding season which started from April and continued up to September and both the species spawn once in a year with single spawning peak. It is well known that fishes exhibit various types of spawning, which are closely related to the development and distribution of eggs (Prabhu, 1956). According to the gonadosomatic indices, mean oocyte diameters and histological analyses obtained, the spawning of yellowfin tuna in the western Pacific Ocean occurred all the year around with a peak season from February to June (Sun et al., 2005)Increased water temperature is another important factor recorded with maturation of gonads. As the temperature gradually

67 131 starts rising from March onwards, gonads starts to mature and become ripe(plate 3.1B, Fig. G-J) in both male and female. This is an indication that the species is an annual breeder as also observed by Itano & Williams (1992) Length at first maturity and determination of M 50 There is a close relationship between maturity and the length of the fish (Chimitz, 1955; Pongsuwana, 1956; Mironova, 1969). Size at first gonadal maturity is a very sensitive parameter in the life cycle of animals and the considerable influence of the genetic component on the delimitation of this parameter suggests that it may be an important adaptive character (Schaffer, 1974). Wootton (1998) observed that maturity at earlier stage is a survival mechanism for fish to get extinct. The size of first gonadal maturation is a variable reproductive tactics, because it is closely related to growth, presenting spatial-temporal intraspecific variation related to biotic and abiotic conditions of the occupied area or period that the population is submitted to these factors (Vazzoler, 1996). The result indicated that in the 3-4 cm length group of E. danricus, immature males and females were recorded. Again the 50% or above of mature/ripe males and females were recorded in the length group of 4-5 cm and this length may be considered at which M 50 maturity for both the sexes attained (Fig K). In P. daniconius, immature males were recorded in the length group of 3-4 cm. The 50% of the mature males and females were found in the length group of 4-5 cm. Hence, this length group may be considered at which 50%

68 132 PLATE 3.1A:GONADS OF BOTH THE SPECIMENS C C Fig. C : Immature testis (I) of Esomus danricus D D Fig.D : Immature ovary (I) of Esomus danricus E E Fig. E: Immature testis (I) of P. daniconius F Fig. F: Maturing Ovary (II) of P. daniconius F

69 133 PLATE 3.1B:GONADS OF BOTH THE SPECIMENS G G Fig. G: Ripe testis (IV) of E.danricus H H Fig. H : Ripe ovary (IV) of E.danricus I I Fig. I: Ripe Testis (IV) of P. daniconius J Fig. J: Ripe Ovary (IV) of P. daniconius J