Estimates of strain additive and non-additive genetic effects for growth traits in a diallel cross of three strains of giant freshwater prawn (Macrobrachium rosenbergii) in Vietnam

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.

Annual report 2008/09

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.

Developments in the breeding of cultured fishes.

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.

Improving disease resistance of cultured fish through selective programs (an overview)

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.

Evaluation of the new fluorescent internal tag (soft visible implant alphanumeric tag) in the freshwater prawn, Macrobrachium rosenbergii

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.

Effects of relatedness and inbreeding on reproductive success of Nile tilapia (Oreochromis niloticus)

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).

Lessons from established breeding programs: terrestrial and aquatic animals

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.

Contamination of cultured Philippine Nile tilapia (Oreochromis niloticus) with O. mossambicus

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.

Choice of tilapia species for aquaculture

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.

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