Age and growth increment of Labeo calbasu (Hamilton 1822) from the Vindhyan region, Central India

Labeo calbasu is a medium size freshwater fi sh species belonging to the family Cyprinidae under the order Cypriniformes and is an ecologically signifi cant (example habitat restoration, manage keystone species and maintain food web) for both commercial and recreational fi sheries in tropical and sub-tropical waters. Labeo rohita, L. calbasu and L. bata species are very frequently appearing in the lotic ecosystem in the Indian subcontinent. The second most important of these is the L. calbasu which has a very wide distribution, formed choiceable fi shery and resistant to disease. L. calbasu supports an important commercial fi shery in the rivers (Example Ganga, Yamuna, Narmada, Godavari, Ken, Paisuni and Tons), wetlands, dams, lakes and reservoirs of India [1-6]. L. calbasu is a riverine fi sh especially in India, Pakistan, Bangladesh, Myanmar and Nepal but also well established in many large natural water bodies [7-10] and are able to tolerate a wide range of environmental conditions (example temperature, pollution). It is also culture with Indian major caps group fi shes (Catla catla, Labeo rohita and Cirrhinus mrigala) and also exotic major carp fi shes (Ctenopharyngodon idella, Hypophthalmichthys molitrix and Cyprinus carpio) in India, Bangladesh and Pakistan [11-13]. It is a bottom feeder in habit with harbivour. Accurate fi sh growth rates are important for growth analysis, age structure analysis and mortality rate estimation. The information of fi sh age and growth increment is also necessary to perceptive a species life history, reproductive biology, population dynamics, biomass and fi sheries sustainability [8,14-18].

Citation: Dwivedi  rivers. The scale method has been used for estimation of age and growth in the present investigations. The key scales were removed from the row above lateral line and below dorsal fi n region [23][24][25][26]. The scales were cleaned in 5% KOH solution to remove adhering-tissues and fi nally washed in distilled water. The scales were then pressed while drying in order to avoid their curling. The season with "minimum width in the terminal part of the anterior fi eld of the scale" was designated as the period of ring formation. Since this condition occurred only once a year, the ring was designated as annuli. The total length and growth rate were recorded as differences betweenat-age.

Result and discussion
The formation of growth ring occurred annually. The ring formation was closed with increasing of fi sh age in all fi shes (Plate 1). The fi shes of 1+ to 5+, 1+ to 6+ and 1+ to 7+ age groups were recorded in the Paisuni river, Ken river and Tons river, respectively (Table 1). Labeo calbasu is slow growing riverine fi sh. The key scales depicting different age are presented in Plate 2. The differences in growth may be observed when same species inhabit different rivers of the same ecoregion. The mean length was maximum in juvenile stage (1+ age group) in the Paisuni river compared to Tons and Ken rivers. The maximum growth rate was recorded in the Tons river in adult and old stock ( Table 1). The growth compensation was recorded in 6+ age class form Tons river fi shes. The growth rate was observed 19.2, 11.5, 7.7, 5.4, 3.4 and 2.3 cm for 1+ to 6+ age groups in the Ken river. The growth rate recorded for the Paisuni river was 21.3, 10.5, 7.7, 3.2 and 1.9 cm from 1+ to 5+ age groups. Similarly in the Tons river 20.9, 11.8, 7.5, 6.7, 4.5, 3.1 and 3.5 cm from 1+ to 7+ age was observed (Table 1). These growth rates indicated that the ecological condition of the Tons river was most suitable for the growth of L. calbasu.
The maximum growth percentage of L. calbasu was recorded in fi rst year in the Paisuni river (47.76%) compared to Ken river (38.79%) and Tons river (36.03%) (Figure 1). The growth percentage varied from age to age and river to river (Figure 1). The lowest growth percentage was recorded in 5+ age group (4.26%) from the Tons river. The growth compensation was estimated from the Tons river in 6+ age group and difference was 0.69% ( Figure 1). The growth rate of fi shes was not found in systematic order (increasing or decreasing order). The fl uctuations in fi sh length indicate the fi sh growth, compensation. It is very common in almost all natural stocks of fi shes (fresh water, brackish water and marine water).
In case of scales the study of annual growth is based on the fact that most temperate and the sub-arctic fi shes of Northern and Southern continents have their rate of metabolism and therefore growth strongly infl uenced by the seasonal variations. Summer is a period of activity resulting in brisk and fast or heavy growth and winter a period of slow or no growth resulting in differential growth and thus deposition of layers forming alternating growth zones, year after year [27]. It is for these reasons that the use of scales for age determination is most reliable for temperate fi shes. On the other hand, in tropics, temperature is uniform throughout the year, daylight is fairly constant and fi sh tend to spawn several times in a year, besides, the occurrence of wide fl uctuations in food composition and chemical composition of water due to the rains, organic load and fl oods. Thus, the fi sh inhabiting tropical regions show growth rings, which do not necessarily represent year marks. In the tropical regions, the annuli develop as result of cessation of growth during unfavourable periods such as poor availability of food caused by various factors like low water level or maturation of the gonads [28,29]. The productivity of aquatic ecosystems infl uences the age and growth, stock and size structure of the fi shes [19,[30][31] was Oreochromis niloticus) quality of the water (Example organic load, heavy metal concentration) and maturity [32][33][34][35][36][37][38][39][40].
Our fi ndings very clearly indicated that the age and growth increment of L. calbasu was different between habitats. Habitat variation in the age and growth of L. calbasu are generally reported.

Platec 2:
The key scale from the dorsal fin region depicting age of Labeo calbasu a-1+ age b-3+ age c-7+ age