Notes on the maturity and spawning of Opisthopterus tardoore (Cuvier)

The present study on the biology of Opisthopterus tardoore (Cuvier) was initiated in 1955 as part of the comprehensive investigation of the biology of the common clupeoids of North Kanara. Little is known about the fishes belonging to the genus Opisthopterus, excepting the post larval stages of Opisthoperus tardoore which have been described by John (1951). In view of this a detailed study of various aspects of the biology of this species was undertaken, and the present paper relates to notes on maturity and spawning of Opisthopterus tardoore, and incorporates the results of investigations carried out in the inshore regions at Karwar

A Ray-Tracing Model of the Vela Pulsar

In the relativistic plasma surrounding a pulsar, a subluminal ordinary-mode electromagnetic wave will propagate along a magnetic field line. After some distance, it can break free of the field line and escape the magnetosphere to reach an observer. We describe a simple model of pulsar radio emission based on this scenario and find that applying this model to the case of the Vela pulsar reproduces qualitative characteristics of the observed Vela pulse profile.Comment: 23 pages, 9 figures, accepted for publication in Ap

Artificial spawning by stripping in Dussumieria acuta, a marine pelagic fish and studies on its early development

Artificial spawning was successfully conducted in Dussumieria acuta Valenciennes (Family: Dussumieriidae), a marine pelagic fish, by stripping the fully ripe female and male. The experiment was conducted on board a privately owned shrimp trawler operated in the Palk Bay, by participating in one of its night fishing trips, on 2nd March, 1973. The stripped eggs and milt were mixed in filtered sea water. Majority of the eggs were fertilized. Detailed microscopic studies were conducted the next day in the laboratory. The first larva hatched out 24 hours after fertilization. The larvae could be reared only upto 48 hours after hatching. The developmental stages of the embryo and the larva are described and discussed. It is suggested that the technique of artificial spawning by stripping and early ranching of the embryos into the sea, if arried out by the fishermen in a variety of commercially important species which it is possible on board the fishing vessels on a large scale, can increse the natural production