Control of crabs and snakes in freshwater fish seed farms

A design has been developed to adopt in freshwater fish seed farms for controlling crabs and snakes. The method is convenient and effective. It prevents the entry of crabs and snakes into the ponds.

Algae and water pollution in Mahi Estuary

Distribution of phytoplankton, chlorophyll A and phaeophytin was studied at different locations in the Mahi Estuary, Gujarat, India during 1982. The water quality at the discharge point was poor while the region away from it was relatively unpolluted. The results indicated a wide range of variation in phytoplankton population (7.68-5010, 96 x 10 super(4) cells/l, chl. a 2.22-58.22 mg/m super(3) and phaeophytin [0.20-10.21 mg/m super(3)]. The ratio of chl. a/phaeophytin were remarkably low at highly polluted stations. Higher abundance of the genera Oscillatoria and Nitzschia were recorded at polluted stations. The diversity of species at the unpolluted station was higher (1.56) as compared to the polluted station (1.07).

Karyotypic studies of freshwater prawn Machrobrachium rosenbergii

Chromosomal studies were conducted on Macrobrachium rosenbergii. On the basis of 50 metaphase plate counts, 38 metacentric, 14 sub metacentric and 66 telocentric chromosomes (2n = 118) were observed. The total length of the granomme was recorded to be 34.2 micron.

A note on the calorific values of a freshwater teleost, Labeo gonius (Hamilton)

Forty specimens of Labeo gonius (Ham) were analysed for protein, carbohydrate and fat values. The calorific value was calculated by multiplying the value of protein and carbohydrate with the energy factor 4.1 and for fat by 9.3. The average calorific values of fish for protein, carbohydrate and fat were 72.16, 9.55 and 11.90 cal/100 g respectively suggesting that the fishes are highly nutritious.

National issues raised by IIMA study on development and management of freshwater aquaculture in India: a review

An examination is made of various issues regarding freshwater aquaculture development raised by the IIMA study on inland fish marketing in India. The following topics are discussed: 1)fish production and the resources; 2)desirability for refined methodology for assessment of fish production; 3)pond resource under fish culture; 4)conflicting data and 5)observation on research input for freshwater.

Recent advances in tropical freshwater aquaculture

Several technological advances have been made in tropical freshwater aquaculture during the last three decades. Hatchery production of carp seed was achieved in India and China towards the late 1950's. Channel catfish farming in the U.S. has grown phenomenally. Development of the technology of high density culture using artificial aeration and nutritionally balanced diets has revolutionized freshwater aquaculture, particularly in Israel. Culture of fishes in cages, pens and running water have helped to achieve very high production levels. Considerable research work has been done on fish nutrition during recent years. Investigations on sex control reveal that it is possible to produce a single sex progeny which is more desirable for culture.

Limnological studies of a freshwater tropical impoundment : Powai Lake. 1: Morphometry and physical features

Powai Lake, an impoundment, came into existence in 1891 when the riverlet Dhanisar was dammed to conserve rainwater for drinking purpose. However, the water was found to be unpotable and the lake was leased out to the Angling Association, Bombay, exclusively for angling and sports. The lake is located about 27 km in the northeast of Bombay city at a height of 55m above MSL. It is rainfed with an average rainfall of 2,400 mm. The maximum waterspread area is 220 ha with a maximum capacity of 8.11 million m super(3) in the peak monsoon period when the water overflows the dam. There is no drawdown from the lake. Fluctuation in the water level is mainly due to evaporation and percolation. Transparency is low mainly due to suspended organic particles. There is hardly any difference in the water temperatures of surface and bottom, hence the annual heat budget is low at 2,818 cal m super(-2).

Breeding, age and growth of the freshwater shark Wallago attu (Bloch and Schneider) from the Dhir Beel of the Brahmaputra Basin, Assam, India

The Dhir Beel, one of the major live beels of the Brahmaputra Basin, Assam, has an area of 689 ha and situated in Dhubri district of Assam. The dominance of freshwater shark, Wallago attu (8.10%) in the beel is a striking feature. Restricted breeding of W. attu once a year from June to September was observed. The mean observed length was 37.5, 65.0, 84.5 and 99.0 cm in the 6th, 12th, 18th and 24th months of age respectively. The length growth coefficient (K), the asymptotic length (L infinity ), and the arbitrary origin of the growth curve (t omicron ), for W. attu were estimated to be 0.054484 per month, 136.16 cm and 0.0355 month respectively. The calculated life span (T infinity ) of the fish is 123.86 months (about 10 years). The weight growth parameters were estimated where the monthly growth coefficient (K), the asymptotic weight (W infinity) and the arbitrary origin of the growth curve (t omicron) were found to be 0.0743 per month, 7636.92 gram and 0.431908 month respectively. The length-weight relationship follows the cube law.

Tidal and sea level changes at Jeddah, Red Sea

Tidal and sea level changes during 1991 at a coastal station (Jeddah) in the central part of the Red Sea are investigated. Analysis shows higher sea levels in winter and lower in summer. The amplitude of change at Jeddah is above 50cm. Analysis of wind stress at Jeddah indicates an insignificant contribution of the cross-shore component, while a major part of the changes in the sea level can be accounted for by the long-shore component.

Acyclic diterpene alcohols isolated from four algae of Bryopsidophyceae and their toxicity

Three new acylic diterpenoids belonging to the class of phytol series have been isolated. They were obtained from the ethyl acetate soluble fractions of four siphonaceous green seaweeds, Bryopsis pennata Lamour., Caulerpa taxifolia (Vahl) C. Ag., Codium decorticatum (Woodw.) Howe and Valoniopsis pachynema (Mart.) Børg., collected from Karachi coast of Pakistan. Structures of these compounds were elucidated with the help of spectroscopic methods and confirmed by comparison with the known compounds. Even the known compounds are being reported for the first time from a green algal source. All the compounds were found to display a strong toxicity at all the three concentrations tested in the brine shrimp bioassay.

Studies on the biochemical composition of some freshwater fishes. Pt. 1. Muscle

Twenty five different species belonging to 16 genera of freshwater fishes were analysed for protein, fat, moisture, ash, carbohydrate, phosphorus, calcium and total iron content in their muscle. Calorific value for protein, fat and carbohydrate fractions and total calories for each species were also calculated.

Studies on the biochemical composition of some freshwater fishes. Pt. 2. Liver

Although considerable work has been done on the composition of fish liver oils, most of which includes the study of various vitamins and fatty acids, little attention has been paid towards the composition of fish liver as a whole.

Studies on the biochemical composition of some freshwater fishes. Pt. 3. Ovary

Biochemical composition of the spent ovaries of 23 different species of freshwater fishes showed a much lower value for protein and fat with higher moisture content than those of the ripe eggs, suggesting an inverse relationship between fat and moisture. Ovaries during the recovering phase showed fairly high values of phosphorus, but lower than those for the ripe eggs. Higher values of calcium and iron in spent ovaries than those in ripe eggs probably suggest that there is a greater requirement of calcium and iron during the spent phase of the gonads.

Studies on the biochemical composition of some freshwater fishes. Pt. 1. Muscle

Twenty five different species belonging to l6 genera of freshwater fishes were analyzed for protein, fat, moisture, ash, carbohydrate, phosphorus, calcium and total iron content in their muscle. Calorific value for protein, fat and carbohydrate actions and total calories for each species were also calculated.

Biochemical composition of the muscle of some freshwater fishes during the pre-maturity phase

Biochemical composition of the muscle of juveniles belonging to 18 different species of freshwater fishes showed that the protein percentage in juveniles was higher than the adults. The fat, on the other hand, was much lower. This suggests that the body fat increases with the onset of maturity. No clear inverse relationship was found between fat and protein in juveniles. Moisture percentage was very high in juveniles. This was probably because of low fat content. In most species the sum of fat and water contents (F + W) was found to be constant. The percentages of ash, calcium and phosphorus were higher in juveniles than those of adults. Dry matter percentage varied inversely with the moisture and in most species carbohydrate was generally low. In juveniles although the calorific value of protein-fraction was high the total calorific value was lower than the adults.