Potential of cowpea (Vigna unguiculata L.) meal as an alternative protein source in diets for giant freshwater prawn (Macrobrachium rosenbergii, de Man 1879)

Growth trials were conducted to evaluate cowpea Vigna unguiculata (L.) meal as a potential protein source in diets for giant freshwater prawn, Macrobrachium rosenbergii (de Man 1879), reared in tank and lake-based cages. Five isonitrogenous (approximately 37% crude protein) and isocaloric diets were formulated where fish meal (FM) protein was replaced with 0%, 15%, 30%, 45% and 60% cowpea meal protein (or CP0, CP15, CP30, CP45, and CP60, respectively). Results of an 8-week tank trial showed that the final body weight (FBW), percent weight gain, specific growth rate (SGR) and survival of prawns were not significantly influenced by dietary treatments (P > 0.05), although the highest values, except for survival, were observed with CP45. In a lakebased cage trial that lasted for 16 weeks, prawns fed CP30 and CP45 had significantly higher FBW (13.1 and 14.4 g, respectively) compared to other treatment groups (P < 0.05). SGR (4.52 5.00%/ day), survival rates (53-77%), yield (98.5-116.5 g m-2) and feed conversion ratio (FCR; 2.0-2.7) were not affected by increasing levels of cowpea meal in the diets. Based on these results, cowpea meal can be considered as an alternative protein source in diets for M. rosenbergii

Freshwater prawn research at SEAFDEC/AQD

The Philippines lags behind Thailand and Indonesia as far as research and commercial production of the freshwater prawn, Macrobrachium sp., are concerned. Although studies on Macrobrachium sp. (or ulang as it is locally known), started at the Binangonan Freshwater Station of SEAFDEC/AQD in the mid-1980’s, research efforts were discontinued soon thereafter because of a) inadequate technical skills; b) problems with larval rearing and the domestication of wild stocks; and among others, c) the Macrobrachium sp. being considered in the Philippines as a low priority species in contrast to commercially important freshwater commodities like tilapia and milkfish. This was two decades ago and in retrospect, had researches continued, the freshwater prawn in the Philippines could have been successfully domesticated and current problems concerning limited aquaculture production of genetically depauperate non-indigenous stocks could have been resolved. With the renewed interest in the culture of alternative species like the freshwater prawn, researchers at the Binangonan Freshwater Station started to conduct some studies on the refinement of breeding, larval rearing and culture of Macrobrachium rosenbergii in late 2003. These studies are briefly described here

Nursery culture of tropical anguillid eels in the Philippines

This technical publication focused on nursery production of anguillid eels from glass eels to elver using data gathered from eel farm surveys and rearing trials conducted by SEAFDEC/AQD as part of the JAIF (Japan-ASEAN Integration Fund) project on Enhancing Sustainable Utilization and Management Scheme for Tropical Anguillid Eel Resources in Southeast Asia

Genetic characterization, domestication and improvement of Macrobrachium rosenbergii in the Philippines

Extensive studies in the Philippines and in adjacent countries revealed that 528 caridean prawn species are found in this region alone (Chan, 1998). Of all the known species, the giant freshwater prawn is considered the most commercially important. Except for the Philippines, culture of the giant freshwater prawn, Macrobrachium rosenbergii, has already made substantial contributions to the local aquaculture production in Southeast Asia, i.e. in Thailand, Malaysia and Indonesia. However, efforts are now being made to improve the aquaculture production of Macrobrachium rosenbergii in the Philippines, thus, optimal methods for the culture and propagation of this high value freshwater aquaculture species are being developed by the Philippine Government fishery agencies as well as other research and academic institutions. The Integrated Rural Aquaculture Program under the ASEAN-SEAFDEC Special Five-Year Program or what is presently known as the Program on the Promotion of Sustainable Aquaculture in the ASEAN Region enabled the Bureau of Fisheries and Aquatic Resources, the Mindanao State University and the Aquaculture Department of SEAFDEC to jointly conduct studies on the genetic characterization, domestication and improvement of Macrobrachium rosenbergii stocks in the Philippines in order to improve the aquaculture production of the giant freshwater prawn. Under the collaborative project which started in late 2004, specific research activities under were conducted, and an update on their results are summarized

Microcystins from the cyanobacteria Microcystis aeruginosa in Laguna de Bay, Philippines

Laguna de Bay, the largest freshwater lake in the Philippines, experiences periodic blooms of the cyanobacteria Microcystis aeruginosa. The results of analysis for the presence of the hepatotoxin microcystins in bloom samples of this cyanobacteria from 1996, 1998, 1999 and laboratory cultures from 1997 isolates, based on the studies conducted at Binangonan Freshwater Station of SEAFDEC/AQD are presented. Twenty structural variants of the toxin have been isolated with microcystin LR (MC-LR) being the most abundant form. MC-LR contribution ranged from 22% to almost 100% of the total microcystins in the samples. Microcystis bloom in 1998 had MC-RR as the most dominant form of the toxin with almost 38% followed closely by MC-WR (23%) and MC-LR (22%). The harvest from 1996 had the highest total toxin concentration (4048 µg g-1). Laboratory-cultured M. aeruginosa had even higher total toxin concentrations ranging from 11,472 to 12,160 µg g-1. The presence of high microcystins concentrations in M. aeruginosa from Laguna de Bay has far reaching implications in terms of the use of this resource for fishery and domestic water supply

Fish biodiversity and incidence of invasive fish species in an aquaculture and non-aquaculture site in Laguna de Bay, Philippines

Laguna de Bay is the Philippines' largest inland water with 900 km2 surface area. The lake has been assessed as hypereutrophic (Rohani and Roblo, 1984) to dystrophic (Barril and Tumlos, 2002). To make use of the lake's natural productivity a pilot aquaculture project started in 1971 (del Mendo and Gedney, 1979). The aquaculture industry in the lake rapidly developed, mainly using species not native to the lake. Since then, the lake has become a major source of fish in Metro Manila and the adjacent provinces. An assessment of the impact of aquaculture in the lake showed increased total finfish biomass in the lake; ecotrophic efficiency of phytoplankton increased; and the calculated total net primary production decreased by a factor of two compared to the pre-aquaculture period (de los Reyes, 1993). The dominant species cultured in Laguna de Bay are introduced species. After more than 40 years the lake is now populated with non-native species including species that are considered invasive and nuisance. Many of these species were deliberately introduced for aquaculture and there are those that were considered accidental introductions like ornamental fish cultured in ponds within the lake's watershed. To assess the impact of aquaculture in localized areas in the lake, a study was conducted to monitor diversity in the fisheries resources of the lake at two adjacent, but distinctly different sites: the West Cove (WC), an open fishery area, with no aquaculture and the East Cove (EC) which is an aquaculture site with cages for Nile tilapia, bighead carp, giant freshwater prawn

Embryonic development of the Caridean prawn Macrobrachium mammillodactylus (Crustacea: Decapoda: Palaemonidae)

The freshwater knob-tooth prawn Macrobrachium mammillodactylus is a commercially exploited species in the Philippines. To study the biology of this species, broodstock from the wild was collected, transported to the laboratory and kept in pairs in indoor polyethylene tanks for breeding. Eggs from berried females were sampled to follow the stages of embryonic development until hatching to zoea larva. It took 18.0 ± 2.1 days for the eggs to hatch at ambient water temperature between 25 and 28 °C. The morphological landmarks of development at the different stages (pre-cleavage, cleavage, blastula, pre-nauplius, post-nauplius and pre-hatching) of the live embryos are described. Incremental percentage staging was adopted from 0% at fertilization to 100% at hatching and were matched with corresponding morphological development. Egg volume increased significantly toward the mid-to-later stages of development. The eye index also showed a significant increase as the egg developed. The colour of the egg mass changed from light olive green to grey as the eggs progressed in development. The general pattern of development was comparable to other members of the genus Macrobrachium.This work was supported by a grant from the Department of Science and Technology’s National Research Council of the Philippines (DOST-NRCP) under Project Code E-211

Mercury levels in the sediment, water, and selected finfishes of Laguna Lake, the Philippines

Monthly samples of sediment, water and commercially important species of fish, primarily Oreochromis niloticus and Chanos chanos , plus a few other species, were collected from the West Bay area of Laguna Lake, The Philippines from January to December 1987. Mercury levels were determined in all samples by cold vapor atomic absorption spectrophotometry. Results showed that sediment samples contained mercury levels ranging from 26.7 to 117 ppb. Mercury levels in water samples were low, ranging from below detectable to 0.5670 ppb. The mercury levels in the water were negatively correlated with conductivity and dissolved oxygen and positively correlated with turbidity. The mercury burden of the fish species samples was below the maximum permissible level set by the WHO and USFDA of 0.05 ppm. No direct correlation was observed between mercury levels in sediment and water, water and fish and sediment and fish

Resistance to a heavy metal mixture in Oreochromis niloticus progenies from parents chronically exposed to the same metals

Poster presented at the Fifth International Symposium on Genetics in Aquaculture, June 19–25, 1994, Halifax, Nova Scotia, Canada.Adult Oreochromis niloticus were mass spawned in concrete tanks. The one-month old progenies (F1) were exposed for two months to a mixture of 0.01 mg L−1 Hg, 0.1 mg L−1 Cd and 1.0 mg L−1 Zn. The survivors were grown to sexual maturity in a natural environment (lake). The fish were spawned and the progenies (F2) of the exposed F1 (EF1) were exposed to another mixture of the three metals: 3.0 mg L−1 Zn, 0.30 mg L−1 Cd and 0.01 mg L−1 Hg, both in a static and static-renewal system. Another group of F2 from unexposed F1 (UF1) received the same treatment. Results showed that in both exposure systems, survival of the F2 of EF1 was significantly higher (P&lt;0.05) than those from UF1. The medial lethal time (LT50) of the F2's were estimated from the time-response curve following regression analysis: 5.16 days (F2 of UF1) and 9.03 days (F2 of EF1) in the static exposure experiment; 3.34 days (F2 of UF1) and 5.52 days (F2 of EF1) in the static-renewal run. Exposure of the parental stock resulted in the culling out of individuals which were more susceptible to the heavy metals. The more resistant members of the population (survivors) which have the ability to adapt to the toxicants were able to pass on the resistance to their offspring. The results are supported by other studies in the field which demonstrate high resistance in populations of organisms living in contaminated sites

Cage culture of the giant freshwater prawn (Macrobrachium rosenbergii)

An extension manual describing biology, site requirement, grow-out operations, health management, harvest, post harvest handling and processing, and economic analysis