Aeromonas load and species composition in the rearing water, sediment, gills and intestines of healthy tilapia Oreochromis niloticus collected every 2 weeks from Days 30 to 120 after stocking in six earthen ponds in the Philippines were determined. Presumptive Aeromonas counts (PACs) in the water and sediment ranged from 10¹–10³ c.f.u./ml and 10¹–10³ c.f.u./g while in the gills and intestines, PACs ranged from 10⁴–10⁷ c.f.u./g and 10²–10⁵ c.f.u./g, respectively. Presumptive Aeromonas counts in the water, sediment, and gills of tilapia varied among days of culture while in the intestines of tilapia, PACs markedly dropped by approximately 2 logs at Day 75 and either remained in the same level or decreased by another 1 log at Day 120 of grow‐out culture. Aeromonas hydrophila predominantly constituted 94% of all presumptive Aeromonas spp. examined (n = 343), followed by A. sobria (4%) and A. salmonicida (2%). Taken together, current data provide some putative threshold levels of tilapia reared in earthen ponds to Aeromonas spp. The dominance of A. hydrophila together with negligible population of A. salmonicida and A. sobria indicate that Aeromonas are common commensal bacteria in tilapia and their environment which under conditions of stress could instigate disease epizootics.

This publication contains results from the research project “Development of Genetically Improved Strain of Macrobrachium” covered by the Program on the Promotion of Sustainable Aquaculture in the ASEAN Region (previously known as Integrated Rural Aquaculture Program). It specifically includes activities from the inception of the project in 2002 up to 2005 under the Special Five-year Program on Sustainable Fisheries for Food Security in the ASEAN Region as well as research updates from 2006 to date. Project activities from 2006 to 2010 have been placed under the ASEAN-SEAFDEC Fisheries Consultative Group (FCG) collaborative mechanism with financial support from the Government of Japan Trust Fund. Dr. Koichi Okuzawa, AQD's Deputy Chief from 2005-2007, was project leader at the time the studies started until early 2007.

The history of M. rosenbergii hatchery operations in Northern Mindanao can be traced from minor activities in different locations by several institutions. Earlier attempts to produce freshwater prawn postlarvae in hatcheries by Mindanao State University (MSU) faculty/researchers were conducted in the MSU-Marawi College of Fisheries (COF) and in commercial hatchery facilities for the tiger shrimp at MSU-Naawan. Early efforts to produce freshwater prawn seedstock were done by an MSU-Marawi COF faculty member and his staff in the 1970s. Breeders were collected from Kapay, 30 m from the oceanic waters of Iligan Bay. However the group failed to rear larvae successfully to the postlarval stage. In Naawan, several larval rearing trials were conducted in the late 1970s and early 1980s as part of a project that included a study on the biology and ecology of the species in known prawn spawning grounds in Tambulig and Siay, Zamboanga del Sur. Live berried females from the two study sites were transported to Naawan and held in tanks until hatchlings were obtained. Larvae were reared in brackish and greenwater medium and fed Brachionus, Artemia and strained fish flesh. Unfortunately, not one larval rearing trial was successful. Hatchery trials were also conducted in 1994 at the Multi-species Hatchery of the Dipolog School of Fisheries in Zamboanga del Norte. Few postlarvae were produced within one year and eventually the school discontinued the activity.

Freshwater prawn thrives in inland waters like rivers, lakes, swamps, irrigation canals, estuaries and even in rivers upstream. A recent survey in Luzon Island, Philippines identified 12 species of freshwater prawn found in the island (Agasen, unpublished). The country’s interest on freshwater prawn fishery started in 1914 as explained by Cowles (1914), when the freshwater prawn was recognized as one of the important fisheries during that time. In late 1976, trials were made to culture the freshwater prawn, however, the efforts were not sustained. These trials were conducted in Misamis Oriental, Mindanao between 1976-1979 by Dejarme et al., with the collection of wild spawners and the subsequent rearing of M. rosenbergii hatchlings. In 1981, a local banker-industrialist established a 100-hectare commercial Macrobrachium farm in Sta. Rosa, Nueva Ecija and a hatchery in Bulacan. Services of experts from Israel were tapped for the project. Marketable prawns were sold live in Metro Manila utilizing in-house retail outlets. After a few years, the company diversified their operations to include tilapia culture. However, even the diversification attempt failed to save the first venture of commercial Macrobrachium rosenbergii production in the Philippines.

Molecular technology at enzyme/protein level known as “allozyme marker” is a widely accepted powerful technique to study genetic variation (Ward and Grewe, 1995) as well as intraspecific population studies (Sodsuk, 1996; Sodsuk and Sodsuk, 1998a & 1998b; Sodsuk et al., 2001). Since the allozyme technique can be readily applied, it has become a basic tool for the evaluation of genetic variation in aquaculture stocks. This study aims to: (1) evaluate genetic variation (measured as as per locus averages of observable heterozygosities and number of alleles) of nine crosses from three Macrobrachium rosenbergii stocks (genetically improved AAGRDI, WILD, FARM); (2) apply polymorphic allozyme markers in the evaluation; (3) compare genetic variation among the nine crosses to determine genetic stock differences; and (4) use genetic variability and performance evaluation information in choosing the best cross for the conduct of a selective breeding program in specific farm environments.

Three stocks of Macrobrachium rosenbergii namely, “AAGRDI” (Aquatic Animal Genetic Research and Development Institute), “FARM” (Petchaburi Farm) and “WILD” stocks were used for the selective breeding program. Generally, a good base population for genetic improvement should have high genetic variability and the stock should have traits that make them adaptable in each local environment. Therefore, all possible crosses of these three stocks should be evaluated on both performance traits and genetic diversity before selective breeding takes place. Hence, the proposed genetic improvement program was divided into two parts: (1) evaluation of growth performance of the three stocks and their reciprocal crosses in four environments; and (2) the establishment of improved economic traits in the best cross using a suitable selection procedure. The four environments used were: 20 m2 concrete pond located at the Aquatic Genetic Research and Development Research Center (AAGRDI), Pathumtani Province; and in 5 x 5 x 1.5 m2 net cages at the three Fisheries Test and Research Centers in Chumphon, Buriram and Uttaradit Provinces. The “AAGRDI” stock was the M. rosenbergii selected for improved growth rate for two generations in the AAGRDI environment (Uraiwan et al., 2003). The “FARM” stock originally came from a private hatchery in Petchaburi Province in 2002, which was also reared at the AAGRDI for one generation. The “WILD” stock was collected from the river in Chantaburi Province in 2002. This “WILD” stock has been domesticated under hatchery conditions at the AAGRDI for one generation. This experiment deals with the growth performance comparison and the genetic variations of these stocks conducted simultaneously by Sodsuk et al. (2005).

The giant freshwater prawn (Macrobrachium rosenbergii) is a widely distributed indigenous species in Indonesia. The giant freshwater prawn from Pangkalanbun-Kalimantan has a big head, long claws and is yellow-green in color. On the other hand, those from Kuala Tungkal-Jambi has a small head, short claws and is gold in color (Sabar and Ali, 2001). The giant freshwater prawn is an important commodity that has been successfully fanned in Indonesia. It has been produced in several areas in West Java, i.e. Ciamis (Tambaksari, Parigi, Rancah and Pasir Nagara) and Tasikmalaya. Some commercial hatcheries (a local government hatchery, and seven private hatcheries) are found in Jogjakarta in East Java, freshwater prawns are cultured in brackishwater ponds. Freshwater prawn culture has also spread to some areas in the island of Bali, e.g. Gianyar, Klungkung, Buleleng and Tabanan, and in Riau, South Sulawesi and South Sumatera. Several natural populations of freshwater prawns are unique to Indonesia. To date, about 19 species are found in almost all of the islands in the archipelago (Holthuis, 1980). However, this potential genetic resource has not yet been fully used in freshwater aquaculture. Moreover, inspite the fact that the freshwater prawn culture technology has been developed and adopted in Indonesia, some problems are still plaguing the industry. To solve the problems of poor growth rate, disease susceptibility and small meat yield or edible portion, the Research Institute for Freshwater Aquaculture (formerly RIFF) started numerous research programs since 1996 to improve growth rate and the size of the edible portion of cultured prawns. The GI Macro, a selected strain of the giant freshwater prawn was developed by RIFA and has been distributed to farmers in Java. Varying results were obtained from growth trials conducted in different locations, hence another phase of selection is necessary to construct a wider and more improved base population using additional wild stocks. An assessment of the genetic background of the wild stocks is an important pre-requisite before the new selection program is initiated. Genetic variation is an important parameter to consider to enable the evaluation of individual fitness of the stock in the short term and their survival in the long term (Ferguson et al., 1995). In this study, genetic variation of giant freshwater prawns collected from Sulawesi, Kalimantan, Sumatera and Java were analyzed using molecular markers.

A selective breeding program was conducted to improve freshwater prawns with the use of a synthetic population formed from numerous breeders collected from Tanjung Air (Bekasi), Kalipucang (Ciamis) and Musi (Palembang). The stock from Tanjung Air was collected in February 1995 with an average body weight of 70 g/pc. Individual selection was applied to this stock to increase its edible portion. The stock from Kalipucang was collected in June 1996 with an average weight of 72g. Index selection was used in this stock to improve growth rate and edible portion. After two steps of selection, the synthetic population was constructed from these two stocks and incorporated to the stock from Musi (ABW=75g, collected in May 1997). Family selection was then applied to the synthetic population. Thus, in 2001, a new breed of freshwater prawn has been developed and released to the farmers. This strain was the GI Macro or the Genetically Improved Macrobrachium rosenbergii (Emmawati et al., 2001). This study was conducted to evaluate the capability or performance of GI Macro in different locations/environments. Growth of the GI Macro was evaluated in three different locations : low (<10 m), moderate (150-250 m) and higher (>250 m) than the sea surface level.