Fish eggs

Following a brief description of lake-based hatcheries and nurseries for tilapias, the advantages as compared to land-based systems are discussed, indicating also some of the disadvantages.

This study was carried out in order to understand the technical and economic characteristics of different Egyptian Nile tilapia (Oreochromis niloticus) hatchery systems. Hatchery operators at fifty tilapia hatcheries in four governorates were interviewed and four focus group discussions were held with 61 participants in March 2012.

Despite the success in fertilization and hatching of fish eggs with cryopreserved sperm, report on growth and survival of larvae produced from frozen-thawed sperm is inadequate. This study evaluates the applicability of cryopreserved sperm for mass seed production by comparing the growth and survival of a popular food-fish olive barb, Puntius sarana (Hamilton 1822) larvae produced from cryopreserved and fresh sperm.

Results of the studies undertaken for breeding and nursing Nile tilapia (Oreochromis niloticus) in ricefields in Thai Binh province in Vietnam during the years 1995-96 are briefly presented in this paper.

The study assesses the relative profitability of stocking eggs versus hatchlings of common carp (Cyprinus carpio) in the rice-fish systems in Bangladesh. Results showed that although stocking eggs-covered water hyacinths directly into rice fields is a simple low cost option, the yields and profits are much higher from incubating eggs in cloth hapas and nursing hatchlings before stocking them into rice fields.

A cheap method of propagating the African catfish, Clarias gariepinus, by incubating the fertilized eggs in a cage placed directly in a flowing river is described. Hatching ranged between 39 and 70%. This is not significantly different from the commonly used water recirculating flow through system. The economic advantages of the river hatching method are discussed with special emphasis on the rural fish farmers.

A computer program was developed for the identification of the teleost fish eggs that may be found in the pelagic zone of the Black Sea. The program identifies eggs of 70 species, using up to 28 descriptive characters, and may be adapted for use outside of the Black Sea.

A major new international research program of importance to fisheries is likely to be adopted later this year. Ocean Sciences in Relation to Living Resources, sponsored by FAO and IOC, a proposal concerning the relationship between ocean variability and fish variability has been developed by a special group, as well as suggestions for incremental development of a broader program on the relationship of ocean science and living resources.

The high demand for the stinging catfish (Heteropneustes fossilis) and declining wild stocks led the Centre for Aquaculture Research and Extension of India to look for methods for the culture of the species. This paper presents a low-cost, simple breeding technique developed and tested by the Centre that can be easily adopted by rural farmers.

The success of induced spawning for the production of fish seed depends on many factors which affect hatchery conditions. This paper discusses the results of an investigation on the effects of six different levels of salinity on the fertilization and hatching of Heterobranchus bidorsalis eggs. The results indicate that spermatozoa of H. bidorsalis can survive under a wide range of saline concentrations, with survival increasing with an increase in salinity from 0 to 0.4% and then decreasing as the level of salinity increases. Survival was optimum of 0.4% saline concentration.