Additive genetic, heterotic and strain reciprocal effects were estimated using a diallel cross of two local wild strains of the giant freshwater prawn (Macrobrachium rosenbergii) in Vietnam (Dong Nai and Mekong) and a third domesticated Hawaiian strain, newly introduced to Vietnam. While some minor heterotic outcomes were detected in specific crosses, strain additive genetic and reciprocal effects were more significant sources of variation for all growth traits measured.
Along with a feature on our climate change work, this year’s Annual Report covers topics like fish breeding, coral reef work, post-cyclone rehabilitation, big numbers, and helping the most disadvantaged through aquaculture, to name just a few.
The controlled breeding of finfish for culture is reviewed with special refer-ence to recent developments and persistent problems. Freshwater species are at present cultured on a much larger scale than brackishwater and marine species which have potential for aquaculture in arid and semi-arid lands. A reliable supply of fish seed for freshwater farming can usually be produced from captive broodstock whereas coastal aquaculture still depends largely on collection of seed from the wild.
The sustainable development of aquaculture in Egypt needs the efforts coordinated of different sectors. Disease prevention is the most important aspect for protecting the success in the field of aquaculture. Egyptian farmers, like other farmers in other countries, use different chemicals and antibiotics to treat fish diseases. This approach is dangerous to aquaculture because of the residue in fish body and also for the development of drug resistant bacteria that not only affect fish but also induce harmful effect on humans and may have a deteriorative effect on the environment.
Common, Chinese and Indian major carps are cultured wherever traditional markets exist. However, their culture potential elsewhere is limited by market acceptability and lack of culture experience. This review considers cultured carp bionomics; regional and national statistics; research advances and likely technological developments.
The new version of the polyester visible implant alphanumeric tag (VI Alpha tag; Northwest Marine Technology Inc., Shaw Island, Washington, USA) was evaluated in the giant river prawn (Macrobrachium rosenbergii) under laboratory conditions. The new VI Alpha tag is soft and fluorescent with an alphanumeric code designed to identify individual specimens. Two tag sizes - standard (1.0 x 2.5 mm) and large (1.5 x 3.5 mm) - were tested on juveniles (standard size), subadults (standard size), and adults (large size) for 10 weeks.
It is well established that progeny of inbred matings are less fit than those of outbred matings, and that inbred individuals suffer from reduced viability and fertility. Inbreeding can be avoided by dispersal of progeny or by actively avoiding mating with kin (mate choice). We investigated the effects of sex ratio, relatedness (kinship coefficient) and level of inbreeding on the reproductive success in Nile tilapia under semi-natural mass spawning conditions in two net enclosures (hapas).
Some relevant components of selection program theory and implementation are reviewed. This includes pedigree recording, genetic evaluation, balancing genetic gains and genetic diversity and tactical integration of key issues. Lessons learned are briefly described – illustrating how existing method and tools can be useful when launching a program in a novel species, and yet highlighting the importance of proper understanding and custom application according to the biology and environments of that species.
Preliminary investigations of experimental and commercial stocks of Nile tilapia (Oreochromis niloticus) in the Philippines indicate contamination through interbreeding with wild O. mossambicus. Contamination was determined by polyacrylamide gel isoelectric focusing of skeletal muscle parvalbumins and starch gel electrophoresis of a wide variety of tissue enzymes, from which eye and heart phosphoglucose isomerases were selected as diagnostic markers.
The large body of information available on tilapia biology and culture presents a confusing picture to the prospective culturist. Further stock improvement and standardization of intensive culture methods are needed. Concentration on a few species - Oreochromis aureus, O. niloticus, their hybrids and the 'red' tilapias will facilitate progress. the macrophyte-feeder Tilapia rendalli may also have potential particularly for polyculture with microphagous tilapias. International cooperation is recommended for establishing research facilities and programs.