In various countries, pond breeding species are generally preferred for fish culture as they do not involve the difficulties in the collection and transportation of young fish. But the widely cultured species of carps reputed for their very fast growth and culture conditions do not ordinarily breed in ponds and as such their young ones have necessarily to be collected mainly from the flooded rivers where these carps spawn annually during-the short monsoon season. Indian major carps ordinarily breed in flooded rivers during the south-west monsoon months of June to August. They also breed in reservoirs, tanks and irrigation dams. In the confined waters of ponds they do mature but do not breed. If these matured breeders are transferred from confined waters to semi-confined rain-fed ponds, where the pond bottom is of muddy nature, the fish breeds whenever there is a good rainfall and a drop in temperature of water. This indicates that the few factors which are responsible for breeding may not be found in the ponds. The semi-confined rain-fed seasonal water bodies have more dissolved oxygen, light, waves, water current and turbidity, and less temperature, which stimulate ovulation. Based on the above factors, the places where excess of rain water is used in creating riverine conditions, which stimulate ovulation in fishes, are known as bundhs. The bundhs are suitable places in producing fish seed.
Types of bundhs
The bundhs are of two types viz. wet and dry bundhs.
These are also known as perennial bundhs. The wet bundh is a perennial pond located on the slope of a vast catchment area of undulating terrain with proper embankments having an inlet facing towards the upland and an outlet towards the opposite lower ends. During summer, only the deeper portion of the pond retains water containing breeders. The remaining portion is dry and is used for agriculture.
After a heavy rain a major portion of the bundh gets submerged with water flowing in the form of streamlets from the catchment area and excess water flows out through the outlet. The fish starts spawning in such a stimulated natural condition in the shallow areas of a bundh.
The outlet is protected by fencing to prevent the escape of breeders. The wet bundhs are comparatively much bigger in size than the dry bundhs. These are also known as perennial bundhs.
A dry bundh is a shallow depression enclosed by an earthen wall, which is locally known as a bundh. on three sides, and an extensive catchment area on the fourth. Bundhs get flooded during the monsoon, but remain completely dry for a considerable period during the remaining part of the year. These are seasonal rainfed water bodies, and are also known as seasonal bundhs. The topography of the land has a great role to play in the location and distribution of the dry bundhs. It is preferred to have undulated land because it provides a large catchment area and facilitates quick filling of the bundh even with a less rain, at the same time quick and easy drainage due to gravitation. In West Bengal, a catchment area of more than five times the bundh area is considered most suitable (Saha, 1977), whereas in Madhya Pradesh a ratio of 1:2.5 is considered essential (Dubey and Tuli, 1961). In Bankura district of West Bengal, most of the dry bundhs are fed with water from storage tanks, constructed in the upland area.
Bundh breeding being practiced since a century, has been given a greater importance. Since last three decades particularly after it has been reviewed in Madhya Pradesh, it has gained importance to such an extent that in some of the states like West Bengal, Rajasthan and Andhra Pradesh, besides rivers, the contribution of spawn production from bundhs is quite significant, particularly the spawn from dry bundhs as this source yields 100% pure spawn. It is known for its simplicity and mass production at one time.
The efficiency of the bundhs depends on many factors. The following criteria may be kept in mind when designing bundhs for fish breeding.
1. Extensive upland area from where, with heavy rains, considerable amount of rain water carrying soil and detritus enters the main pond.
2. The pond should have extensive shallow marginal areas which serve as ideal spawning grounds.
3. The soil should be of gritty nature which is considered to be the most suitable for the breeding of fishes.
4. Increase in oxygen contents of water which is due to the vast and shallow area of the pond.
The land should provide a place where a good sized pond can be made with a small dam. The place with a flat area surrounded on three sides by steep slopes should be selected. The fourth side, where the area drains out, should be as narrow as possible. The side slopes should constrict to shorten this up the construction area or axis of the dam.
A water shed with more than fifteen hectares of hard land for every hectare of water surface in the pond is considered essential. If the soil is retentive in nature, then forty hectares of watershed for each hectare of surface water is a better proposition. The fields must not erode. If the water shed is found either too big or too small even then it may be possible to correct the situation by using diversion terraces. .If water is more, excess watershed may often be cut off and the water disposed off elsewhere. If more water is needed, a diversion terrace will increase the effective water shed.
The embankment must be constructed at the low level side. The slopes must be built on each side of the dam. On the lower side the slope should be 20%, i.e., two feet on horizontal distance for each foot of vertical rise. The upper or pond side slope requires more attention. If the fill material has a very high proportion of clay, it may safely be built to the 2 to 1 dimension. If it is loamy or silty or with any sand or gravel in it. this slope should be broadened out to 3 to 1. For one hectare pond, a minimum of 4 feet width is desired at the top and a free board of 2 feet is essential.
A spillway and sluice are a must in the bundhs also. The spillway or flood outlet is a surface drainage way that will carry surplus water during heavy rains. Without this, the whole dam may be lost by overlapping in some sudden monsoon cloudburst. It must be placed around one end of the dam in hard ground. When required the pond can be emptied completely with the help of sluice gates. Spillway and sluice should be provided with strong iron netting, so that the fishes may not escape from the breeding bundh.
Factors responsible for spawning
Hora (1945) stated that heavy monsoon and flood are the primary factors responsible for spawning of Indian major carps. The strong current is necessary to influence the breeding intensity of carps. Mookherjee (1945a) observed that a low depth of water is quite sufficient for fish breeding. Das and Dasgupta (1945) believed that the molecular pressure of water particles and silt on the body of natural breeders has a stimulating effect for spawning in conjunction with rising temperature. Dasan (1945) reported that monsoon floods from the hills, having a peculiar smell, specific chemicals and physical properties, were responsible for breeding of fishes in the bundhs. The availability of shallow ground was also considered to be a factor for spawning (Khan, 1947). According to Saha (1957), temperature has no specific influence on spawning, but cloudy days accompanied by thunder storm and rain seems to influence the spawning. Mookherji (1945) stated that pH and oxygen content of water do not influence spawning in fishes. Bundhs having highly turbid waters with a distinct red colour, low pH between 6.2-7.6, 5-8 ppm of dissolved oxygen, low total alkalinity and 27-290 C temperature provide favourable conditions for spawning in bundhs.
Fish breeding techniques
Rohu, catla, mrigal, common carp, silver carp and grass carps are used to breed in bundhs. 100% pure seed can be produced in bundhs. Besides, more seed can be produced at a time. Once the bundhs are constructed, they can be used for many years to get more profits.
The brooders are collected in May and stocked in storage tanks where they are kept sex wise till the first monsoon showers. As soon as water accumulates in the bundhs, a selected number of these breeders are introduced into these bundhs and a constant vigil is maintained. In the olden days no importance was given to maturity, sex ratio, etc. The techniques were improved later and the breeding was done with a better understanding of sex, ratio and number of breeders. Fully ripe females and males 1:2 in number and of 1:1 weight were introduced into the bundhs on rainy days. Successive spawning could also be achieved as many as 5 times in one season.
In the modern techniques few pairs of females and males are being injected with either pituitary, or HCG or ovaprim extract and are released in the bundhs. This process, “sympathetic breeding in dry bundhs” has been used in West Bengal. By this method of partial hypophysation all the limiting factors for spawning like rain, thunder, storm and current of water can be bypassed. It is reported that about 160-200 million spawn of major carps has been produced.
Recently at Mogra, the farmers have created a cement pond of about 75* x 25′. The bottom of the pond is pucca, but divided into two portions possessing a gradual slope. When water is filled into the pond, the first part possesses about one meter depth of water an4 lower one has about 2 meters depth. The owners called it as West Bengal bundhs. The bottom is filled with 6″ of fine river sand. Before releasing them into the pond, the male and female breeders are partially hypophysed. It is reported that 160-200 million spawn of major carps has been produced here.
Fish in bundhs generally commence to breed during the early hours of the morning and continue to breed throughout the day. Catla prefer deeper waters, when compared to rohu or mrigal, which breed in shallow waters varying in depth from 0.5-1 metre. In wet bundhs, the brooder stock may be maintained throughout the year or replenished prior to the monsoons. The brooders are generally not injected with pituitary extracts but are stimulated to breed due to the current of rainwater from the catchment area, like in the case of dry bundh breeding,
Collection and handling of eggs
As soon as breeding commences, arrangements for collection and hatching of eggs are made. The eggs are collected by pieces of nylon net or mosquito netting, cloth or gamcha after lowering the water level and hatched in the double walled hatching hapas, ordinarily fixed in the bundhs. Collection of all the eggs is impossible, especially in case of wet bundhs, due to its larger areas. About 70% of eggs can be collected .from the bundhs. In Madhya Pradesh, the hatching of eggs is carried out either in double-walled hatching hapas fixed in the bundh itself or in rectangular cement hatcheries measuring 2.4 x 1.2 xO.3 m. However, in West Bengal, the eggs are kept for hatching in specially dug out small earthen pits with mud plastered walls. The hatchlings are lifted from the pits by dragging muslin cloth pieces after 12 hours of hatching and are transferred to similarly prepared bigger earthen pits. The survival rate is about 35-40% in the hapas. It can be increased to 97% by using modern hatcheries.
Improved features of dry bundhs
The dry bundhs can be improved keeping in view the following points:
- Selecting shallow sloping depressions and undulating terrain of sandy soils with maximum catchment areas
- Constructing a small earthen bundh at the far end of the depression opposite to the catchment area so that water could be retained for a certain period. A maximum depth of 2 meters of water is maintained in the bundhs and a fine meshed wire netting protects any overflow water.
- Since major carps generally breed almost at any place in the shallow bundhs, it may be advantageous to prepare spawning grounds at different levels so as to get them flooded at different water levels in the bundh. But, it is necessary to have the spawning ground away from the direction of the current.
- A few storage tanks, cement cisternae or earthen ponds can also be provftfed adjacent to the bundhs to store the breeders temporarily prior to their introduction in the bundh.
- Constructing a battery of 10-20 rectangular cement hatcheries measuring 2.4 x 2 x0.3m.
- Constructing a small double storied building which could serve as an observation tower cum store cum shelter.