Food And Feeding Habits Of Three Fresh Water Fishes


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INDRODUCTION

Fishes are the most fascinating and remarkable form of animal life in the world. They dominate the water of the world through a marvelous variety of morphological, physiological and behavioural adaptations. The success of fishes in terms of their diversity and number is to a large extent the measure of their success in finding adequate food, sometimes in the most unlikely situations. The magnitude of fishes stocks in a region is a function of its food potentialities. Food is an important factor in the biology of fishes to the extend of governing their growth, feeding and migratory movements. The basic function of an organism is its growth, development and reproduction and it takes place at the expense of energy which enters the organism in the form of its food.

The first stage in the life cycle of a fish is completed at the expense of food reserves contained in yolk in the egg. These resources however sustain it only for a short period which is subject to some variations depending on the quantity of yolk stored and conditions under which the eggs develop. After the complete utilization of the yolk, the young fishes commences feeding from its habitat. During the process of development of the fish, changes takes place in its food which are connected with changes in the structure of the feeding and digestive organs.

Fishes have became adapted to a wide variety of food. The importance of the knowledge of food and feeding habits of fish in understanding its fishery biology has been well established. 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. Variation in the seasonal and diurnal abundance of the favorite food organisms of different species of fish in any region may influence the horizontal and vertical movements of the fish stocks. Hence the correct knowledge of the relationship between the fishes and food organism is essential for the production and exploitation of the fish stocks. An objective study of these relationship should be properly integrated in the orientation of a commercially exploited fishery, taking into account, the diversity of the component species constituting the total fishery of the region.

Fishes are well designed, especially well for food gathering. Feeding in some species may require extended periods of time. The amount of food ingested per day and the times of day that feeding is performed depends on many factor. Active predators with their high metabolic rates require more food energy than do sluggish fishes. Daily and seasonal temperature fluctuations affect food intake in most fishes. Some species feed mainly by sight and are active by day although peaks of feeding actively occur in mourning and evening. Other fishes that depend more on chemical sense can feed effectively in the absence of light or at night. So they may be most active in early morning and late evening.

The result of many studies on feeding of various fishes however show that small individuals consume more per day in relation to their body weight, than large individuals. Though fishes are either herbivorous or carnivorous or omnivorous, they are mostly and highly adaptable in their feeding habits. Fresh water fishes can be divided in to four feeding types, herbivorous, omnivorous, carnivorous and plankton feeders.

Herbivorous fishes:-

A number of fresh water fishes feed mainly on unicellular algae, filamentous algae, and portion of higher aquatic plants along with some sand or mud. Plant material of the food is 75% or more of total gut content, hence considered herbivorous in habit.

Omnivorous fishes:-

A large number of fishes feed on unicellular and filamentous algae and portion of higher aquatic plants, Rotifers, insects and their larvae, crustaceans, mud and sand. They are thus regarded as omnivorous in habit.

Carnivorous fishes:-

A number of fishes feed on high percentage of animals such as crustaceans – mainly copepods, water bugs, beetles, dragonfly larvae etc. small fishes, tadpoles etc are also taken.

Plankton feeders:-

They feed on phytoplankton and zooplankton which they obtain by filtering the water through their gill rakers. Nikolsky (1963) states that in the majority of fishes, in the early stage of development when they feed on plankton, the eyes and the organ of lateral line play the major part in orientation towards food.

In the present study, an attempt has been made to understand. The feeding habits of 3 varieties of fresh water fishes collected from the ponds of valanchery. The fishes are Anabas, Ophiocephalus and Etroplus.







MATERIALS AND METHOD

Three varieties of fishes – Anabas, ophicephalus and Etroplus were collected from the ponds of Valanchery. Soon after, they were killed and preserved in 5% formalin for further study.

In the laboratory, the fishes were wiped off and each specimen was weighed accurately. Then the stomach was dissected out, fixed in 5% formalin and noted the degree of fullness of stomach – heavy, good, moderate, poor or empty. Fish with heavy and good stomach were categorized as actively fed, those with moderate stomach as moderately fed. And with poor stomach is poorly fed. The stomach was dried between shuts of filter paper and cut opened. It was rinsed with water in a Petridish.

The contents were made up to 5ml by adding 5% formalin. After stirring well, a sample of 1ml was taken with a graduated pipette and evently spread over a counting chamber. The contents were examined under a stereomicroscope and numerical percentage of small food items was found. The food items were identified as far as possible, depending upto the extend of digestion. The number of various food items consumed was also noted. The gastro somatic index was determined by the following method

Gastro somatic index(GSI) = Weight of stomach contents x 100
Weight of fish







OBSERVATIONS

Gut contents of each fish was observed in each month from September to January. The intensity of feeding was good in September, October and November. During this period when the ponds were highly productive, the intensity of feeding was also high. In low productive season, i.e in December and January, the feeding intensity of observed fishes was poor and high percentage of sand and mud was found in the stomach contents.

FOOD COMPOSITION OF FISH

1. ANABAS
The various components present in the gut contents of Anabas are given below
Worms
Plankton
Egg mass
Plant matter
Sand and mud
2. OPHIOCEPHALUS
The major food constituents of ophiocephalus are:-
Egg mass
Spirogyra
Plant matter
Worms
Sand and mud



3. Etroplus
The gut content of Etroplus include:-

Green algae
Spirogyra
Diatoms
Plant matter
Sand and mud.






















RESULTS AND DISCUSSION

Examination of the stomach contents of Anabas revealed that the food contained both plants materials and animal matter. So it is an omnivorous fish. Occasionally fish scales and diatoms were seen. About 50% and more of the food constituents were animal matter. Usually plankton and small organisms are seen. Stomach contents include 23. 84% worms, 32.11% plankton, 5% egg mass, 23.98% plant material and 15.07% sand (Table I, Figure I).

In the case of Ophiocephalus, the stomach contains both plant materials and animal matter. So it is also an omnivorous fish. When the stomach contents of this fish were examined, filamentous algae seen regularly. The stomach contents include 17.41% egg mass, 34.87% spirogyra, 5.49% plant matter, 32.08 % worms and 10.14% sand and mud ( Table II, Figure II). The major part of the food content of Etroplus is green algae and filamentous algae. The stomach contents include 33.09% green algae, 27.41% filamenrous algae, 12.06% worms, 6.68% plant matter and 20.63% sand and mud. (Table III and figure III)

Quayyum and Quasin (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. The fishes do not seen to restrict themselves only to some particular varieties. This is proved by the fact that most of the items present in the habitat that fall within the ingestible size range were represented in their guts as well. This would suggest that there is little selection on the part of the fish. Some of the reported difference 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.

The fact that these fishes can subsit on a wide variety of food material as revealed by the present study, as well as the earlier studies carried out by others, indicates that the species can adapt itself and if necessary even change its preference to certain food items, depending on the availability of such items in a particular environment. This aspect seems to be important in so far as the culture of this species in fresh water pond is concerned. Moreover the preliminary observations have revealed that these fishes accept artificial feed also. These advantage often give a wide scope for successful culture of these fishes in fresh water ponds either separately or in combination with other compatible species of fishes.










FEEDING INTENSITY OF ANABAS




Month

Weight of fish

Weight of gut content

GSI
Percentage of gut content
Worms Plankton Egg mass Plant matter Sand
September 31.5gm 500mgm 1.58 18.00 30.00 8.6 18.00 25.4
October 33gm 540mgm 1.6 18.5 30.00 4.6 29 17.9
November 30.25gm 520mgm 1.7 20.5 35.5 6.5 18.5 19
December 35gm 400mgm 1 30.5 40 2 22.5 5
January 38.5gm 300mgm 0.7 31.7 25.5 3.3 31.9 8.5
Average Percentage of gut content 23.84 32.11 5 23.98 15.07






















FEEDING INTENSITY OF OPHIOCEPHALUS




Month

Weight of fish

Weight of gut content

GSI Percentage of gut content
Egg mass Spirogyra Plant matter
Worms
sand
September 158gm 2.32gm 1.46 8.5 39 6 29 17.5
October 160gm 5.25gm 3.28 11 48 5 24 12
November 175gm 4gm 2.28 12 32 5 40 11
December 155.5gm 1.75gm 1.12 23.5 30.6 8.05 29.3 9
January 152.3gm 1.25gm 0.82 32.52 24.78 3.4 38.1 1.2

Average Percentage of gut contents 17.41 34.87 5.49 32.08 10.14
















FEEDING INTENSITY OF ETROPLUS






Month

Weight of fish

Weight of gut content


GSI
Percentage of gut content

Green Algae
Spirogyra
Worms
Plant Matter
sand
September 182gm 2.8gm 1.54 33 39.62 12.8 7.8 6.78
October 180.5gm 3.5gm 1.94 35 34 13.3 11.2 6.5
November 178 gm 3gm 1.7 39.48 31.02 14.2 10.2 5.1
December 185.5gm 1.9gm 1.02 42 28 20 3 7
January 184gm 1.25gm 0.68 16.9 4.93 0 1.2 77.78

Average Percentage of gut contents 33.09 27.51 12.06 6.68 20.63

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