ELSEVIER Fisheries Research 24 (1995) 321-329 Age and growth of a Himalayan teleost Schizothorax richardsonii (Gray) from the Garhwal Hills (India) Deepak Singh, Ramesh C. Sharrna” Department ofZoology, H.N.B. Carhwal University, P.O. Box 67, Srinagar Garhwal - 246 174, U.P.. India Accepted 26 January 1995 Abstract Scales from 3 13 specimens of a Himalayan teleost Schizothorux richnrdsonii from the Alaknanda hillstream in the Garhwal Himalayas were read for age determination and calculation of growth parameters. There was a strong linear relationship between fish length and lateral scale radius. Annuli formation occurred in August-September coinciding with spawning and the frequent flash floods in Garhwal. The growth constant parameter indicated that the fish enter ‘old age’in the fifth year of life. Growth rate decreases successively at higher ages. Keywords: Schizothorax richardsonii; Growth, fish; Age determination 1. Introduction Sclzizothorax richurdsonii (Gray), commonly known as ‘snow-trout’ is one of the most common cyprinids inhabiting coldwater (8.5-20°C) hillstreams and lakes of Himalayan and sub-Himalayan regions of the Indian sub-continent, Afghanistan and China. Snow-trout attain a maximum length of 45-55 cm and generally contribute an estimated 55-70s to the total annual fish catch in hillstreams of the Garhwal Himalayas (Badola and Singh, 1981; Sharma, 1988). The management and development of the snow-trout fishery in the Garhwal Himalayas (India) is therefore of economic importance for local inhabitants. The age and growth of fish have been extensively studied using marks on scales, otoliths, opercular bones, vertebrae, fin spines and cleithrum. The importance of growth rings on scales and otoliths has been well documented. In many cases these rings have been shown to be annual, probably formed due to seasonal fluctuations in growth. Studies on scales for age and growth determination of India fishes include Kagwade, 1971; Hanumantha Rao, * Corresponding author. 0165-7836/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDIO165-7836(95)00376-2
Transcript
ELSEVIER Fisheries Research 24 (1995) 321-329
Age and growth of a Himalayan teleost Schizothorax richardsonii (Gray) from the Garhwal Hills (India)
Deepak Singh, Ramesh C. Sharrna” Department ofZoology, H.N.B. Carhwal University, P.O. Box 67, Srinagar Garhwal - 246 174, U.P.. India
Accepted 26 January 1995
Abstract
Scales from 3 13 specimens of a Himalayan teleost Schizothorux richnrdsonii from the Alaknanda hillstream in the Garhwal Himalayas were read for age determination and calculation of growth parameters. There was a strong linear relationship between fish length and lateral scale radius. Annuli formation occurred in August-September coinciding with spawning and the frequent flash floods in Garhwal. The growth constant parameter indicated that the fish enter ‘old age’ in the fifth year of life. Growth rate decreases successively at higher ages.
Keywords: Schizothorax richardsonii; Growth, fish; Age determination
1. Introduction
Sclzizothorax richurdsonii (Gray), commonly known as ‘snow-trout’ is one of the most common cyprinids inhabiting coldwater (8.5-20°C) hillstreams and lakes of Himalayan and sub-Himalayan regions of the Indian sub-continent, Afghanistan and China. Snow-trout attain a maximum length of 45-55 cm and generally contribute an estimated 55-70s to the total annual fish catch in hillstreams of the Garhwal Himalayas (Badola and Singh, 1981; Sharma, 1988). The management and development of the snow-trout fishery in the Garhwal Himalayas (India) is therefore of economic importance for local inhabitants.
The age and growth of fish have been extensively studied using marks on scales, otoliths, opercular bones, vertebrae, fin spines and cleithrum. The importance of growth rings on scales and otoliths has been well documented. In many cases these rings have been shown to be annual, probably formed due to seasonal fluctuations in growth. Studies on scales for age and growth determination of India fishes include Kagwade, 1971; Hanumantha Rao,
* Corresponding author.
0165-7836/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDIO165-7836(95)00376-2
322 D. Sin& R.C. Shanna / Fisheries Research 24 (1995) 321-329
1974; Panthani, 1981; Tandon and Johal, 1983, 1993; Johal and Tandon, 1987; Herrera et al., 1988; Tandon et al., 1989, 1993; Desai and Srivastava, 1990.
With the exception of a preliminary report on Tar putitora (Hamilton) from Garhwal (Nautiyal, 1990) there are no studies on the age and growth of fishes dwelling in Garhwal streams. The purpose of this investigation is to study age and growth parameters of the snow-trout to help in the development and management of its fishery by the local inhabitants.
2. Materials and methods
Specimens of snow-trout were sampled from the Alaknanda River (Fig. 1) using various fishing methods, i.e. gill nets, cast nets, angling and seine nets. Seine nets of different mesh sizes have been used to catch fish of different size groups during day and night. Monthly collections were made at the Alaknanda River from October 1991 to September 1992. To study age and growth, scales were dissected from each fish from just above the pectoral fin and below the lateral line, washed in 5% KOH, and rinsed in distilled water. These scales were then bound tightly between two slides with Sellotape and marked with the details of the fish. The slides were observed under a compound microscope to determine the nature
Fig. 1. The map of the study area depicting the general range of distribution of Schizothorar richardsonii and collection area.
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of the rings: seasonal, larval or annual. The complete and bright lines were identified as annuli. The true annuli were characterised by light bands in the form of grooves extending to all sides of scales, while irregular and incomplete rings were identified as false. These annuli were counted and the age of the fish in years was determined.
Fish growth was also computed from scale observations. The total scale radius from the focus (centre) of the scale to the edge was measured to establish the relationship between the fish length and the total scale radius. The distance between the focus of the scale and each annulus was measured for back calculation and growth rate analysis. Back calculation was done following the modified formula given by Lee ( 1920):
La=c+S (l-c)
where Ln, calculated intermediate length; 1, observed total length at the time of capture; Sn, length of the scale focus to annulus ‘n’; S, length of the total scale radius; c, correction factor.
As the body and scale growth demonstrate a straight-line relationship, but not passing through zero, so the fish would have attained a certain length before the formation of the scale. This length is subtracted as a correction factor (c) in back calculation.
Age determination with scales was confirmed with Peterson’s length-frequency method (Bagenal and Tesch, 1978). By this method, fish of different sizes collected at each sampling site were pooled and arranged into size-groups with a class interval of 5 cm. The lengths of fish of one age tend to form a normal distribution. Age was then determined by counting the peaks.
Statistical treatment of data (standard deviation, correlation coefficient, regression) was also made using standard statistical methods.
3. Results
The scales of S. richardsonii are cycloid and can be distinguished into four portions, (i) the anterior embedded field, (ii), the posterior exposed and pigmented portion, and (iii) the two lateral portions which were overlapped by other scales. The focus which represents the origin of growth in scales, was located near the anterior field. The ridge-like structures (radii) radiate from the nucleus towards the periphery, and the radii were radiating from the focus as well as from other portions of the scales (Fig. 2). The highest percentage of scales with minimum width in the terminal zone occurred in August to September. These months were considered to be the months of ring formation. The number of observations by month on the cycloid scales of snow-trout are shown in Table 1.
3.1. Growth rate
Growth rate of individual fish was assessed by back-calculation. The first growth ring was laid down at an average length of 10.22 _+ 0.76 cm, the second at 20.47 f 1.45 cm, the third at 29.62 + 1.86 cm, the fourth at 39.14 + 1.43 cm, and the fifth growth ring 47.99 cm.
324 D. Singh, R.C. Sharma / Fisheries Research 24 (1995) 321-329
Fig. 2. Scale of S. richardsonii showing four annuli.
The annual increment in length was calculated to be 10.22 cm, 10.25 cm, 9.15 cm, 9.52 cm, and 8.85 cm for lst, 2nd, 3rd, 4th and 5th age groups, respectively. The average increments in weight were 5.77 g, 59.74 g, 173.35 g, 394.57 g and 659.43 g for lst, 2nd, 3rd, 4th and 5th age groups. The 4th age group showed the highest growth rate over its previous age group. The phenomenon is referred to as growth compensation (Table 2).
The total fish length and the lateral scale radius relationships were calculated, giving a linear relationship. The regression equation is as follows:
Y=a+bX
Y=O.4654+0.0015X
r= 0.9686
c=25 mm
n=25
P > 0.01
Table 1
Percentage of scales of S. richdsonii with minimum width in the terminal zone during different months of the yeas
Months October November December January February March April May June July August September
Total no. of scales 75 52 52 56 56 56 54 56 52 52 48 44
examined
No. of scales with 25 15 19 11 12 16 09 16 la 20 32 25
313 31.94 10.22 20.47 29.62 39.14 47.99 *SD f0.76 f 1.45 f 1.86 f 1.43 f 0.00
Annual increment in length (cm) 10.22 10.25 9.15 9.52” 8.85 Annual increment in weight (g) 5.71 59.74 173.35 394.57 659.43
“Growth compensation, N, number of specimens in each age class.
A curvilinear length-weight relationship was obtained, while a linear relationship was found between the log length and log weight. The length-weight relationship was used to calculate the weight of fish for back-calculation. The length-weight relationship was cal- culated as follows:
Log W= 0.0043 + 1.5864 log L
W= - 2.36653 15 L’.5864
The length-frequency distribution (Peterson’s method) was used to calculate the age classes and growth. Monthly distribution of different size groups is shown in Table 3.
Table 3 Length-frequency distribution of Schizofhorux richardsonii (Gray) in Alaknanda River
Size group Frequency
(cm) October November December January February March April May June July August September
326 D. Singh. R.C. Shanna / Fisheries Research 24 (1995) 321-329
m
m Aug. Sep.
Nov.
Fig. 3. Length-frequency distribution of S. richardsonii.
Histograms of length and frequency indicate that the peaks at age groups 1 + to 5 + were at an average length of 12.5 cm, 25.00 cm, 41 .OO cm and 50.00 cm, respectively (Fig. 3).
D. Singh, R.C. Sharrna / Fisheries Research 24 (1995) 321-329 327
4. Discussion
This study is principally concerned with the annual marks on the scales of fish. The growth of a fish is not uniform either throughout a year or throughout its total life span; it shows alternating fast and slow rates of growth depending on favourable or adverse eco- logical conditions. The rings on scales and other hard parts are not necessarily annual, and may be associated with external factors such as the dry season, non-availability of food, disease, water temperature variation and loss of condition.
For the study of age and growth using scales, it is essential to select the location from where the scales occur in regular order, with little variation in size and with a minimum of regenerated scales. Keeping in view the scales are taken from just above the pectoral fin and that below the lateral line where the scales were first formed. The scales were taken from the same place for each individual fish. Ideally at the start of a study, the fish age should be determined by more than one method since two methods do not always agree (Messieh and Tibbo, 1970). Therefore, in the present study two methods (the length- frequency distribution method and scale method) were used.
The length-weight relationship of several species of Indian fishes has been studied by Narashimhan ( 1970), Majumdar ( 1971), La1 (1980), Tandonet al. (1993). They all noted the curvilinear or parabolic relationship between the length and weight of fish. Kulshreshtha et al. ( 1993) observed the length-weight relationship of an Indian major carp Cutla cutEa from the water bodies of Bhopal, so as to get a comparative picture of the growth of fishes and observed a parabolic relationship. In the present study, a curvilinear relationship was observed while a straight line was found between the log length and log fish weight (r=0.874982).
In the present study a fish length plot against the total scale radius produced a straight line relationship. Pathani ( 198 I), and Nautiyal ( 1990) recorded a straight line relationship between the scale radius and fish length of Cirrhina mrigala (Hamilton) and Torputitoru (Hamilton), respectively. Tandon et al, ( 1989) found a straight line relationship between the fish length and scale radius of L.ubeo calbasu from Rajasthan. Dobriyal and Singh ( 1990) and Tandon et al. ( 1993) also reported a linear relationship between the fish length and scale radius of Barilius bendelisis and Torputitora, respectively.
In the present study five annual rings were observed in S. richardsonii. Various authors have discussed several causes for the ring formation or appearance of annuli on the scales or hard parts of the fishes. Fage and Veillet (1938) showed that maturation of gonads accompanied by decreased feeding activity was followed by decrease in growth rate. Natra- jan and Jhingran ( 1963) noted that the annuli formation was related to the spawning or was an indicator of non-availability of food.
Sunder and Subla ( 1987) considered that feeding had no direct relation to ring formation of Schizothorax curuifrons from Kashmir. They suggested temperature as the most important factor in annulus formation. Rounsefell and Everhart ( 1953) suggested winter rings in fish scales were possibly due to low temperature coupled with low feeding. Similar findings were recorded by Pathani ( 198 1) in the case of Kumaun mahseers.
Some authors believe that the physiological stress caused by cumulative effect of high temperature, non-availability of sufficient food, maturation of gonad and breeding activity of fish resulted in ring formation (Hanumantha Rao, 1974; Rammohan Rao, 1974). Johal
328 D. Singh, R.C. Shartna / Fisheries Research 24 (1995) 321-329
and Tandon (1981, 1992) reported that the spawning period coincided with the ring for- mation.
In the present study the maximum percentage of scales with minimum width in the terminal zone coincided with the spawning period of S. richardsonii. The spawning period extends from August to September in the Alaknanda River of Garhwal Himalaya. Therefore, it can be suggested that during the spawning period, under physiological stress and sluggish feeding activity followed by destruction of food resources in their habitat due to frequent flash floods in the critical period, the annual marks on the scales are laid down.
The annuli formation was also found to be associated with the temperature (Deshmukh, 1973). Snow-trout being coldwater fish, the fluctuations in the temperature may trigger the formation of false rings in Alaknanda fishes.
Dhar ( 1967) analysed the age of ‘snow-trout’ (Schizothorax esocinus, S. plagiosfomus) from the water bodies of Kashmir and found specimens up to only 4 + age group. He estimated the length attained at age groups 1 f ,2 + ,3 + and 4 + years as 22.00,27.00 cm, 34.50 cm and 54.50 cm in 5. esocinus compared with 17.5 cm, 26.5 cm, 30.00 cm and 33.00 cm in S. plagiostomus.
Sunder and Subla (1987) studied the age and growth of S. curuijrons, and recorded lengths of 13.55 cm, 19.65 cm, 25.79 cm, 31.55 cm, 36.67 cm and 41.49 cm attained after the age from l-6 years.
In the present study specimens of snow-trout (5. richardsonii) in the age groups from l-5 years were found and attained average lengths of 10.22 cm, 20.47 cm, 29.62 cm, 39.14 cm and 47.99 cm, respectively using the correction factor of 25.00 mm.
Growth rate declined successively in higher age-classes. The fish specimens of the first year group showed the highest growth rates. Growth compensation has been reported in 5. richardsonii. Similar findings have been reported by Johal and Tandon ( 1992); Tandon and Johal ( 1993) and Tandon et al. ( 1993) on Catla catla (Hamilton), Lube0 rohita (Hamilton) and Z’or putitora (Hamilton), respectively. Abbas and Siddiqui ( 1987) also reported that the specific growth rate decreased with the increasing age and size of fish.
Acknowledgements
The authors wish to thank H.R. Singh and M.S. Johal for reviewing early drafts on the manuscript.
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