Genetic diversity in wild stocks of the giant freshwater prawn (Macrobrachium rosenbergii): implications for aquaculture and conservation

The giant freshwater prawn (Macrobrachium rosenbergii) is cultured widely around the world but little is known about the levels and patterns of genetic diversity in either wild or cultured stocks. Studies have suggested that genetic diversity may be relatively low in some cultured stocks due to the history of how they were founded and subsequent exposure to repeated population bottlenecks in hatcheries. In contrast, wild stocks have an extensive distribution that extends from Southern Asia across Southeast (SE) Asia to the Pacific region. Therefore, wild stocks could be an important resource for genetic improvement of culture stocks in the future. Understanding the extent and patterns of genetic diversity in wild giant freshwater prawn stocks will assist decisions about the direction future breeding programs may take. Wild stock genetic diversity was examined using a 472 base-pair segment of the 16S rRNA gene in 18 wild populations collected from across the natural range of the species. Two major clades ("eastern" and "western") were identifi ed either side of Huxley’s line, with a minimum divergence of 6.2 per cent, which implies separation since the Miocene period (5-10 MYA). While divergence estimates within major clades was small (maximum 0.9 per cent), evidence was also found for population structuring at a lower spatial scale. This will be examined more intensively with a faster evolving mtDNA gene in the future.

Baseline biochemical and genetic profiles of four fishes from the River Nile

Six enzyme systems coding for 10 loci and 6 proteins were examined in the blood of Polypterus senegalus, Clarias lazera, Tilapia nilotica and Protopterus annectens, using electrophoresis. Six loci were polymorphic in all the four species, three polymorphic in three species and one polymorphic in T. nilotica. Four protein loci were monomorphic in all the four species with variants in P. senegalus and T. nilotica. Haemoglobin can be used as a species-specific marker. Polymorphism was 53-56 per cent and average heterozygosity was 0.1-0.15.

Marine fisheries, genetic effects and biodiversity

Preservation of marine biodiversity deserves serious consideration as almost 65% of the earth's organisms (excluding insects) are marine. There is little knowledge at present on the status of marine biodiversity. However, the seas are an important source of protein for human consumption and genetic diversity is a key factor in ecosystem functioning, stability and resilience. Overfishing and destructive practices may have unalterable impact on marine biodiversity. This paper discusses measures that can be adopted to protect the most productive areas of the marine ecosystem.

Down to earth thoughts on conserving aquatic genetic diversity

A discussion is presented on the topic of maintaining genetic diversity in aquatic ecosystems, considering the various threats caused by irreversible damage or loss to the environment. The current situation in aquaculture and future prospects regarding the conservation and protection of endangered species are outlined, describing the case of tilapias in Africa as one particular example of fish conservation.