Genetic characterization, breeding strategies and pond management for enhancement of the Malaysian giant prawn, Macrobrachium rosenbergii production / Mohamed Omer Elsheikh Siddeeg

The giant Malaysian prawn, (Macrobrachium rosenbergii de Man, 1879, 2n=59), is an important species for aquaculture in the tropics and subtropics. Currently, it has been introduced into more than forty countries for this purpose. In the past half a century an accumulation of a reasonable amount of literature that definitely aided in the success of farming of this species was achieved. But after the decades extending from 1960s to this date unit per area production is approaching a plateau; this is attributed to the exhaustion of management improvement opportunities that typically contribute to crop increases only during the first few decades that follow the start of farming an undomesticated species. As a result, its aquaculture in Malaysia and other countries in Southeast Asia faced challenges that lead to decline in production. This research was conducted in order to dig reasons and find solutions for these challenges. So, investigations were conducted through genetic and management studies. Pond management investigations were conducted through an in-depth interviewing and visiting of GMP farmers at their farms in Negeri Sembilan States. Results of this portion of the study showed that many farmers are facing problems in obtaining seeds. In addition, feed cost was also found to increase tremendously. Moreover, farmers were found to ignore important steps such as proper pond bank repairing, grading, fertilization and some even do not discern the life cycle of the species, and consequently do not know the conditions required for its reproduction. Grow-out data for conventional genetic improvement study and tissue samples for molecular genetic study were collected from a farm owned by Department of Fisheries, Kg. Pulau Sayak at Tapah village. DNA extraction and molecular genetic analysis were conducted at the Animal Genetics and Genomics Laboratory, Division of genetics and Molecular biology, Institute of Biological Sciences, Faculty of Science, University of Malaya. Regarding economically important characters, Kedah population showed significant (P<.05) superiority over the other populations for harvest weight, total length, carapace length and tail length. Moreover, heritability estimates for these characters range from high to moderate. So, using selection methods is recommended for future improvement of stocks. Harvest weight directly reflects product amount, therefore, multiple linear regression approach was applied to predict it through information of the rest of growth related traits. This model is more accurate than simple relations models. The predictors were significant (P<.05) factors for the multiple regression equations drawn. Significant differences between the equations according to age and sex was found. In studying the genetic diversity of these populations, the COI gene was sequenced for samples of the studied populations and their progenies. Forty three haplotypes were generated from 117 sequences of the parental populations; most which were unique. Genetic diversity for studied populations fall within the range of moderate to high (0.6575-0.9206) but nucleotide diversity was low (0.2511-1.1942%) showing subtle variation among them (Amova 5.45%, p<.00006). Networking the haplotypes and constructing a phylogenetic tree for only the unique ones revealed significant genetic structuring of these populations. Cyclical mating was found to be successful in securing genetic diversity as the genetic variability of progeny groups was high (0.7381 - 0.9412). Unique haplotypes may be useful in identifying breeding families and help in aquaculture improvement programs. Tajima’s neutrality test indicated significant (p<.027) departure of Negeri Sembilan population from mutation- drift equilibrium; meaning that it may have been losing variability. Consequently, seasonal band of fishing to replenish the species populations in rivers of South Malay Peninsular is recommended