ReviewIn order that survival of young be more than optimum, the timing of spawning by the mature adult fish is so adjusted that must be closely linked to the availability of maximum congenial environment added by increased food availability of food for the newly hatched young ones. The availability of food for the larvae and juveniles of most temperate and cold water fish species varies on a seasonal basis and following this fish are usually found to have a discrete and selective spawning season so perfectly timed that hatched out larvae will get readily available exogenous food from nature for their further development. Thus, in many temperate and cold water species, spawning is an annual event. Spawning culminates a series of preparatory events during which the gametes develop and the gonads increase in size. The annual cycle of fishesgenerally categorized into three major phases:A. Post Spawning phase: Period when the gonads are thin and slender and appear to be in a resting phase. B. Pre Spawning phase:Period in which the gonads begin production of gametes (gameto genesis) and incorporation of yolk into the oocytes (vitello genesis) which is accompanied by a process known as gonadal recrudescence i.e. gradual increase in gonad size. C.Spawning phase: Period involving final maturation and ripening of the gametes; this phase culminates in spawning act, with the release of egg and milt which ensures fertilization.Thus, gonadal development is considered to encompasses a series of interrelated phases, each requiring precise coordination and control if viable gametes are to be produced at the optimum time of the year for the subsequent survival of the young fish. The production of gametes involves the manufacture and incorporation of yolk into the developing oocytes (vitello genesis). During the early part of gonadal development, the oogonia, through the process of oogenesis produce mature eggs. Primarily, under the influence of GTHI, primary oogonium forms several primary follicles which ultimately develop into mature graffian follicle. It is within this graffwian follicle eggs mature and get associated with vitallogenin protein from liver known as yolk granule, acts as a readymade food for the growing embryo during development of larvae. Supported by this endogenous food gamete grow in size during post vitallogenic phase of development alin particular. In the salmonids, for example, the oocytes increase in diameter from about 50µm to 500-1000µm prior to the start of vitellogenesis. The incorporation of yolk that occurs during the vitellogenic phase leads to the diameter of the oocyte increasing to around 5000µm (5mm). Thus, there is an enormous increase in oocyte volume during post vitellogenic phase.This observation supports the view that in majority of fishesthe gametic development is dependent on endogenous hormone and the nutrient protein from liver and its subsequent incorporation into egg cytoplasm. The yolk is derived from vitellogenin, a lipophosphorotein-calcium complex with a molecular weight of approx...
Every year, between October and April, Gahirmatha beach in Odisha becomes the nesting ground for Olive Ridley Turtles. These beautiful creatures are an endangered species, and this area is the world's largest known rookery of the marine animals. Over 600,000 turtles come here together for nesting, but this area has not always been the safe haven for hatching the situation exists today. According to the International Union for Conservation of Nature and Natural Resources (IUCN), Olive Ridley Turtles are classed as a "vulnerable" marine species [1]. They derive their name from their heart-shaped, olive green-coloured shells. This mass nesting, popularly known as 'arribada' (a Spanish term used for en masse laying eggs by turtle species) is a yearly phenomenon. More than 4, 00,000 turtles arrive for nesting each year, each laying around 100-150 eggs in pits dug out instantly just before laying. The eggs, after an incubation period of 45-60 days, are hatched out yielding 60,000,000 hatchlings, which find their way to seas again. Only one in a thousand hatchlings survives. They take 25-30 years to reach maturity, and on attaining maturity, which usually takes 25-30 years the females then return to the same beach where they were born to lay their own eggs. The turtles migrate hundreds of kilometres for mating and nesting in this yearly breeding season, and every effort are initiated to ensure the mission successful. The Odisha government imposed a 7-month ban on fishing from November 2017 to protect the turtles following as the Orissa Marine Fishing Regulation Act, 1982, and Wildlife Protection Act, 1972. Nets are ensconced along the length of the beach to prevent the hatchlings from accidentally heading to the land instead of the sea. The Rushikulya Sea Turtle Protection Committee and The Orissa Marine Resources Conservation Consortium work towards conservation of the Olive Ridley Turtles proactively through formation of monitoring units at nesting sites, conduct regular beach patrols and training of guards and volunteers. They also publish and distribute educational material, conduct field trips and promote exhibitions during beach festivals to sensitize the public on the issue through sculptures and sand art. Many villagers are volunteers who are the go-to persons for fisheries, coast guards, forest departments, biologists, researchers and tourists. and are involved in turtle protection works for decades. They know exactly when the turtles will arrive, the best places to view them, where not to tread to avoid trampling the eggs incubating under the sand and when to expect the hatchlings. May 23, World Turtle Day is celebrated in these villages as 'Turtle ka Birthday,' a reminder of the millions of hatchlings that have made it safely to the water from these shores.
Ompok pabda, popularly known as "Butter cat fish", is a freshwater species native to India, Bangladesh, Pakistan, and Myanmar. This species is an indigenous catfish belongs to the family Siluridae of the order Siluriformes. It is listed as endangered fish species [1][2][3][4]. The fish has a wide geographical distribution covering Afghanistan, Bangladesh, Myanmar, the Indus plain and adjoining hill area of Pakistan, the North East States of India particularly in Bihar and West Bengal during the early 1970s. Due to rich lipo-protein content and soft bony structure this fish species is considered delicious and nutritious to the people of East India, North East India and Bangladesh as well [5][6][7][8].This species occurs in the lotic and fresh water ecosystem [1,9]. Also available in beels/mauns connected with rivers. In nature the fish breeds in rivers, reservoirs and water sheds, while in flooded condition during south west monsoon. However, in the early 1980s sharp decline in occurrence and abundance were observed [10,11]. Despite its greater economic value this species did not receive sufficient attention in aquaculture. Meager occurrence of live samples in nature and poor survival of the larvae are major constrains of the observations [12]. As a result of indiscriminate fishing during monsoon, application of pesticide in agriculture, soil erosion and siltation formation in river, contamination of habit due to sewage and industrial pollution etc. The population of this species is sharply reduced [13,14].The catfish belongs to the genus Ompok (La Cepede, 1803), mainly consists of medium-sized silurid fishes found in inland waters throughout South and Southeast Asia. The genus is traditionally diagnosed by the presence of a short dorsal fin with 4 rays, strongly forked caudal fin, subcutaneous eye, set immediately posterior to the mouth rectus and two patches of palatal teeth [15]. Born Busch showed that Ompok, as currently understood, is probably paraphyletic [16], distinguished by relatively short maxillary barbells (not extending beyond tip of pectoral fin) and 48-54 branched anal-fin rays. Males are slenderer and have strong serrations on the posterior edge of the pectoral spine (females lack these serrations). Ompok pabda is highly priced, delicious, good taste, fine flesh with soft meat texture and high nutritional value and well preferred fish as possess relatively few bones. This species is silvery in color with two one at distinguished spots, shoulder and another close to the base of tail; longitudinal stripes of dark color often present on the sides of the body. This species which attains a length of 24 cm is caught in fairly large numbers and as a nourishing food fish especially for invalids; it fetches a very high price. The price is above Rs. 300/-per kg (US $1= Rs.52/-). Captive breeding was conducted to compare the efficacy of CPE and Ovaprim on O. pabda and it was observed that both the inducing agents were quite effective. However, R 3 (CPE) dose (5 mg/kg bd.wt. to male and 16 mg/kg bd.wt. to fem...
to breeding seasons [4]. These fishes develop eggs but cannot shed them in captivity. To overcome the demerits of natural collection of spawn, the techniques of induced breeding otherwise known
A comparison of conservation measures directed towards terrestrial and aquatic environment revealed the magnitude of loss yielded by this sector only due to want of less attention from conservation biologists. For a considerable time frame, except marine mammals, the activities relating to preservation of aquatic biodiversity seem to be lagging far behind than that of the terrestrial component. Now at this space when a considerable number fishes and other important aquatic animals has disappeared and with the realization that fish is the only feed resources harvested from natural population, a growing concern has come up for proper management of this unique natural resources.
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