Sex ratio of the false trevaly Lactarius lactarius (Bloch and Schneider)

The sex ratio in Lactarius lactarius at different months and years was studied. Sex ratio data show that males outnumber females in all months except in October. The insignificant difference in the number of individuals of both the sexes during spawning months (January, March, October and November) indicated that males and females congregate during the spawning season. Among the larger specimens, males constituted the minority.

Condition factor and length-weight relationship of Nemipterus japonicus (Bloch) off Bombay coast

Fluctuations in the K values of Nemipterus japonicus (Bloch) off Bombay coast were interpreted regarding sex, month and females maturity stage. These indicate differential growth rates in males and females. Males and females attain first maturity at 145 mm and 115 mm respectively, second maturity is attained by both the sexes at 195 mm. First spawning occurs when both are of 155 mm length and at second spawning males and females attain 215 and 205 mm of length respectively. The fish mature and breed at "O" year; the main spawning period is from August to November with peak spawning activities in October. It grows about 155 mm in first year at 12.91mm per month and about 215 mm in the second year at 5.0 mm per month on an average. Length-weight relationships for males and females are given. The rate of growth of females by weight was found to be slower below 150 mm, but faster than that of males above 150 mm specimens.

Some aspects of the biology of Trypauchen vagina Bloch and Schneider of Bombay coast

Morphometrics of 14 metric and 6 meristic characters of Trypauchen vagina of Bombay coast is presented. Number of spines and rays of dorsal, anal and pectoral fins differ with earlier studies. Sexual dimorphism in the length of caudal and anal fins was observed. Length weight relationship of males and females have been worked out to be W = 0.00000 687L super(2.8440) and W = 0.00000 2747L super(3.0274) respectively. The fish is a prolific breeder and peak breeding activity occurs in December. The growth rate was found to be 15.20 mm/month.

Studies on the feeding biology of an airbreathing fish Heteropneustes fossilis (Bloch)

The food and feeding habits of an air-breathing fish, Heteropneustes fossilis were studied from an eutrophic lake, Hussainsagar, Hyderabad, (Andhra Pradesh, India), during 1981-1983. The major preferred items of food were insect larvae, insects, ostracods, plant material and gastropods. Due to the mixed feeding habits of both plant and animal matter, this species is considered as an omnivorous feeder. Bryozoans were recorded for the first time in the diet of H. fossilis.

Anchorage of air bladder with the interspinous bone of the anal fin in Lactarius lactarius (Bloch and Schneider, 1801)

Specimens of the false trevally (Lactarius lactarius ), 127 to 221 mm in total length, were studied for the mode of anchorage of the air-bladder with the interspinous bone of the anal fin. The 1st and 2nd interspinous bones are fused together into a single piece (named here as the anchor bone) which pierces through the air-bladder, dividing it into two intercommunicating chambers at its upper end, and ultimately articulates with the 10th vertebral bone. The lower end of the bone is broad, fan like with one side affording articulation with the 1st and 2nd anal spines. This is an unique feature of great taxonomical importance to L. lactarius, the only species in the family Lactariidae. The anal fin counts (23-27) and vertebral counts (23) are also given.

Induced breeding, embryonic and larval development in Heteropneustes fossilis (Bloch) in the agro-climatic conditions of Maharashtra

Heteropneustes fossilis was induced bred for the first time in the agro-climatic conditions of Maharashtra, India. The embryonic development was completed within 16-18h after fertilisation. Head and tail ends were distinguishable after 3h and 11-12 somites were visible after 6-7h. The eggs started hatching after 14h of incubation. Average hatching time was 16-18h at 26 degrees C. In first day old pro-larva, notochord was deflected upwards, eyes were darkly pigmented and alimentary canal appeared. In fourth day old post-larva intestinal coiling could be seen and yolk was absorbed. Aerial respiration started by 8th day. The 10 day old post-larva was free swimming and fed voraciously attaining a length of 20 mm in 30 days.

Studies on maturity, spawning and fecundity of Nemipterus japonicus (Bloch) off Bombay coast

Studies indicated spawning season of Nemipterus japonicus off Bombay coast (Maharashtra, India), to be during July to December with peak breeding during November to December. Females attained first maturity at the length range 110-120 mm; 50% maturity and spawning occurred at 135 mm within one year of its age. Overall male: female ratio for the entire period of study was 1:1.01. Relationships of fecundity with total length of fish, total ovary weight and per g. fish weight were worked out as F=(-72674.33) L super(739.73); F =65.44 W super(807.33); F=3112.57 W super(22383.27) and F=467.85 W super(4.96) with coefficient of correlation values (r) 0.9090, 0.9443, 0.9911 and 0.8843 respectively.

Acute effect of sumithion on certain blood parameters and mortality rate of fish, Heteropneustes fossilis (Bloch)

The acute toxic effect of the toxicant sumithion (50% E.C.) on mortality rate (after 24, 48, 72, and 96 h), total RBC count and haemoglobin content (after 48 and 72 h) on Heteropneustes fossilis was investigated at four concentrations (9.7, 10.7 and 11.1 ppm). The sumithion treated fishes showed lower RBC and Hb levels than the untreated ones. A gradual decrease in the total RBC counts and Hb contents was recorded with increasing concentration of toxicant after 72 h but the blood showed fluctuating values after 48 h of treatment.

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.