Milkfish R&D in the Philippines

Culture of milkfish in brackish water ponds has been practiced for many years in the Philippines and recently its culture has expanded to fish cages in marine waters. Following the spontaneous spawning of milkfish in floating net cages in 1979, protocols for its seed production were developed. Studies to determine sustainable culture techniques in ponds and cages were conducted. Studies on nutritional requirements of milkfish at different developmental stages were done to reduce dependence on live prey organisms during hatchery operations and optimize feed formulations for nursery and grow-out cultures. In recent years, research geared towards the environmental impact of milkfish culture and ways to mitigate the negative effects of intensive farming practices. Prospects for the milkfish industry are discussed in light of the recent advances in milkfish R&D and Philippine government initiatives to increase fish production by mariculture

Milkfish hatchery and nursery production in the Philippines

Milkfish is the most important farmed fish species in the Philippines. In the last 5 years, milkfish production has been increasing. Culture of milkfish in brackishwater ponds still contributes most to milkfish production, although production from marine cages has been on the rise, recently. To sustain milkfish production, a reliable supply of good quality seeds is imperative. Following the spontaneous spawning of milkfish in floating net cages in 1979, protocols for broodstock management, breeding and seed production were developed and these have been continuously refined over the years. Compared to Indonesia and Taiwan, however, commercialization of milkfish seed production in the Philippines, took a long time to take off. Currently, there are a number of government-run and private milkfish hatcheries in operation. In contrast, milkfish fingerling production in brackishwater ponds has long been practiced in the Philippines and is an industry in itself. Traditionally, milkfish fry were from catch from the wild. Recently, more and more come from local hatcheries as well as fry imported from neighboring countries like Indonesia and Taiwan. Prospects for the milkfish hatchery and nursery industries are discussed in light of the Philippine government initiatives to increase fish production, including milkfish, through mariculture as well as by improving production efficiency in other traditional culture systems

mRNA expression patterns for GH, PRL, SL, IGF-I and IGF-II during altered feeding status in rabbitfish, Siganus guttatus.

Feeding time is a major synchronizer of many physiological rhythms in many organisms. Alteration in the nutritional status, specifically fasting, also affects the secretion rhythms of growth hormone (GH) and insulin-like growth factor-I (IGF-I). In this study, we investigated whether the expression patterns for the mRNAs of GH, prolactin (PRL) and somatolactin (SL) in the pituitary gland, and insulin-like growth factor I and II (IGF-I and IGF-II) in the liver of juvenile rabbitfish (Siganus guttatus) follow a rhythm according to feeding time and whether these hormone rhythms changes with starvation. Hormone mRNA levels were determined by real time PCR. The daily expression pattern for the mRNAs of GH, PRL and SL was not altered whether food was given in the morning (10:00 h) or in the afternoon (15:00 h). The daily GH mRNA expression pattern, however, was affected when food was not available for 3 days. In contrast, the daily expression pattern for IGF-I mRNA reaches its peak at roughly 5–6 h after feeding. This pattern, however, was not observed with IGF-II mRNA. During 15-day starvation, GH mRNA levels in starved fish were significantly higher than the control fish starting on the 9th day of starvation until day 15. The levels returned to normal after re-feeding. In contrast to GH, PRL mRNA levels in starved fish were significantly lower than the control group starting on the 6th day of starvation until 3 days after re-feeding. SL mRNA levels were not significantly different between the control and starved group at anytime during the experiment. Both IGF-I and IGF-II mRNA levels in starved group were significantly higher than the control fish on the 3rd and 6th day of starvation. mRNA levels of both IGF-I and II in the starved fish decreased starting on the 9th day of starvation. While IGF-I mRNA levels in the starved group continued to decrease as starvation progressed, IGF-II mRNA levels were not significantly different from the control during the rest of the starvation period. The results indicate that aside from GH and IGF-I, PRL and IGF-II are likewise involved in starvation in rabbitfish

Ration reduction, integrated multitrophic aquaculture (milkfish-seaweed-sea cucumber) and value-added products to improve incomes and reduce the ecological footprint of milkfish culture in the Philippines

In the Philippines, cage culture of milkfish in marine environments is increasing. The practice uses high stocking densities, with significantly greater inputs of artificial feeds which more often than not, have led to excessive feeding and consequently excessive nutrient loading in receiving waters, exacerbating problems with pollution. These could have contributed to occurrence of periodic fish kills in areas of marine milkfish culture clusters. In marine cage culture, about 80% of variable expenses are attributable to feed costs. Experiments were conducted to compare production characteristics of milkfish fed on alternate days versus those raised on daily feeding in marine cage culture. Fish were fed either daily or every other day using a reduced feed ration at 7.5% of fish biomass at the start of culture down to 3% of fish biomass towards harvest. We showed this ration level was as effective as the industry standard that begins at a rate of 10% average body weight. Morevover, we had previously found that milkfish reared in brackishwater ponds on an alternate day feeding scheme using the reduced ration level produced a 56% cost savings in feed with little impact on total yield relative to fish raised on a daily feeding protocol. In the present study, survival rates (~ 90%) were comparable between the control fish fed daily and groups fed on alternate days in marine cages. Similarly, total harvested biomass of fish in the alternate day and daily feeding groups was similar as was the harvest value, although fish on the alternate day feeding scheme grew slightly less. The amount of feed and the corresponding cost of feeds consumed were significantly lower in stocks that were fed on alternate days compared with those fed daily (P < 0.05). Feed conversion ratio (FCR) was lower in the alternate-day fed group (FCR = 2.46) relative to stocks fed daily (FCR = 3.59). Overall, the results demonstrate that feed costs can be reduced by around 32% in stocks fed on alternate days, which yields an estimated 20-25% improvement in production efficiency relative to raising animals on a daily feeding protocol. Hence, a significant costs savings with reduced impact of nutrient loading in the environment is likely to be realized for farmers who adopt an alternate day feeding scheme in raising milkfish in marine cages

Alternative feeding strategies to improve milkfish production efficiency in the Philippines

In the Philippines, cage culture of milkfish in marine environments is increasing. The practice uses high stocking densities, with significantly greater inputs of artificial feeds which more often than not, has led to excessive feeding and consequently excessive nutrient loading in receiving waters, exacerbating problems with pollution. These could have contributed to occurrence of periodic fish kills in areas of marine milkfish culture clusters. Sixty percent of milkfish farming expenses are attributable to feed costs. A series of experiments were conducted in an attempt to develop alternative feeding strategies that will reduce feed inputs without compromising growth and resulting production. In the first experiment, growth was compared in milkfish fed daily, on alternate days and on alternate 2-week or 4-week starvation and refeeding cycles in a tank environment provided with flow-through water system. Results show, that milkfish fed on alternate days do not grow as well as milkfish that are fed daily. Feed restriction for 2 weeks followed by 2 weeks of refeeding elicited a compensatory growth response such that average body weight (ABW) of fish was not significantly different from ABW of fish fed daily. Another experiment compared growth of fish given a ration equivalent to 10% of BW (usual practice) or 7.5% of BW. Results show no significant effect on growth or final ABW or biomass in fish fed daily or on 2-week cycles of feed restriction and refeeding. Thus, a lower feeding ration can be given to milkfish without compromising yield. Results of the tank experiments were verified in actual marine cage and brackishwater pond production systems using an initial feeding rate of 7.5% rather than 10% ABW. In the experiment in cages, survival rates between the control fish and the groups subjected to cycles of 2-week starvation followed by 2 weeks of normal feeding were comparable, except for one replicate of the starved-refed group where survival rate was very low (38.78%). After 3 cycles of starvation and refeeding, weight gain in the starved-refed groups were generally lower than in the control groups, which may suggest that small-sized fish cannot adapt very well to periodic starvation. In brackishwater ponds, growth, survival and total biomass at harvest was comparable between milkfish fed daily and those fed on alternate days. Hence, FCR was lower in the milkfish fed on alternate days compared to fish fed daily. On the other hand, survival was very low in fish subjected to 2 cycles of 2 weeks starvation followed by 4 weeks of normal feeding. These results suggest that as in tilapia, alternate day feeding can be adopted to milkfish culture in brackishwater ponds without compromising production while at the same time lowering production cost and environmental impact. Overall, these studies provide two practical strategies, reduced ration size and alternate day feeding, to improve production efficiency of milkfish, the largest finfish aquaculture industry in the Philippines

Seed production of rabbitfish Siganus guttatus

This manual is mainly intended to serve as a practical guide to fishfarmers and other stakeholders interested to venture in operating a rabbitfish hatchery. It details site selection, hatchery design & layout, and protocols in broodstock management, spawning, larval rearing, and harvest & transport. It has also a section on natural food production for rabbitfish larvae

2010 and beyond: better seeds for sustainable aquatic food production in Asia.

Asia is a major contributor to world aquaculture production. Most Asian countries have maintained their rank in the ten top aquatic food producing nations after developing refined techniques for major commercially important aquaculture species and promoting an increased awareness on the merits of using quality seeds (genetically enhanced or otherwise) as supplied in sufficient quantities. Quality seedstock simply means fit, clean , uniformly-sized seeds which could be eggs, fry, fingerling, juveniles and/or plantlets (for seaweeds) that subsequently express good performance attributes during culture. Beneficial traits refer to good color, shape, growth, efficient feed conversion, high reproduction, tolerance and survival when exposed to stressors (e.g. diseases, poor and/or extreme environmental conditions). Such traits are mostly heritable, hence, quality seeds are usually assumed as produced only by mating stocks perceived or proven to be genetically superior. Some bloodstocks may be genetically mediocre but if bred and manage properly through efficient farm protocols (suitable hatchery, nursery feeding and water management methods), may also produce good quality seeds. Success in the sustainable production of aquatic species for human consumption depends primarily on the availability of seedstock and adoption of optimal husbandry techniques among others. With the intensification of aquaculture systems and the environmental challenges such as those resulting from climate change, it is wise to continue considering both factors -- genetic quality and culture management as equally important in ensuring a steady production of good quality seeds and later, marketable products from aquaculture. Views on what, how and why better quality aquaculture seeds should be produced evolve as times change. To understand these concerns, this paper will cover: (a) the present state of fish seed production in Asia, (b) recent and current seedstock production issues that require attention, and (c) recommendations on how to further enhance aquaculture production in the region in the next decade through better quality seedstock

Cloning of mangrove red snapper (Lutjanus argentimaculatus) growth hormone cDNA and mRNA expression during early development

Growth hormone regulates growth and development in vertebrates. As a first step to understand the role of growth hormone in the regulation of growth and development of the mangrove red snapper Lutjanus argentimaculatus, the red snapper growth hormone (sGH) cDNA was cloned using reverse transcription - polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends. The expression of sGH mRNA in embryos and larvae was examined also by RT-PCR. Excluding the poly-A tail, the full-length red snapper GH cDNA is 945 base pairs (bp) long. It contains untranslated regions of 99 bp and 234 bp in the 5’ and 3’ ends, respectively. It has an open reading frame of 612 bp coding for a signal peptide of 17 amino acids and a mature hormone of 187 amino acid residues. Red snapper GH contains 4 cysteine residues and the typical polyadenylation site 16 bp upstream of the poly-A tail. Based on the amino acid sequence of the mature hormone, sGH shows higher sequence identity (>75%) to GHs of perciforms like grouper, seabass, tilapia and rabbitfish than to GHs of salmonids and carps. Semi-quantitative RT-PCR showed that expression of sGH mRNA commenced two days after hatching

Vibrio load and percentage composition of sucrose‐fermenting vibrios in Nile tilapia (Oreochromis niloticus) cultured in brackish water earthen ponds and biocontrol potential of recycled tilapia‐conditioned greenwater against population growth of V. parahaemolyticus and non‐sucrose‐fermenting vibrios in the grow‐out culture of white leg shrimp (Litopenaeus vannamei)

Vibrio are known opportunistic pathogens of pond-cultured fish and shrimp. This study determined the presumptive Vibrio count (PVC) and percentage composition of “beneficial” sucrose-fermenting vibrios (SFVs) and “pathogenic” non-SFVs in the water, sediment, gills and intestines of healthy tilapia Oreochromis niloticus collected every 2 weeks from Days 30 to 120 post-stocking in brackish water earthen ponds. PVCs in water and sediment ranged from 102–104 CFU/ml/CFU/g while in tilapias' gills and intestines, PVCs ranged from 103–106 CFU/g and 102–106 CFU/g, respectively, with SFVs dominating in water, sediment, gills (≥50%), and intestines (≥80%) of tilapia. Because use of tilapia-conditioned green water (TCGW) for shrimp's grow-out culture has been reported effective against acute hepatopancreatic necrosis disease outbreaks caused by V. parahaemolyticus, PVC, SFVs/non-SFVs (%), and V. parahaemolyticus count (VPC) in the recycled TCGW and Litopenaeus vannamei's hepatopancreas were also examined from stocking until 105 days of culture (DOC) in earthen ponds. PVCs ranging from 102–103 CFU/ml and 103–104 CFU/g were noted in water and shrimp's hepatopancreas, respectively. While non-SFVs population in water varied, a downward trend typified by an abrupt 50% reduction was noted in hepatopancreas at DOC 42, and remained or further dropped until DOC 105. VPCs in water likewise varied (undetectable–102 CFU/ml) while in hepatopancreas, counts dropped to undetectable level from DOC 70 onwards. Current data illustrate that remarkable shift of SFVs' dominance in the water and concomitantly in shrimp's hepatopancreas, plays a pivotal role in regulating non-SFVs proliferation in shrimp's hepatopancreas via competitive exclusion.This study was funded by SEAFDEC AQD (study code: FH02-F2013-T) and in part by the Department of Science and Technology-National Research Council of the Philippines (DOST-NRCP) (NRCP Project No. E-225)

Changes in mRNA expression of grouper (Epinephelus coioides) growth hormone and insulin-like growth factor I in response to nutritional status

Growth hormone (GH) and insulin-like growth factor-I (IGF-I) are key links to nutritional condition and growth regulation in teleost. To understand the endocrine mechanism of growth regulation in grouper, we cloned the cDNAs for grouper GH and IGF-I and examined their mRNA expression during different nutritional status. Grouper GH cDNA is 936 base pairs (bp) long excluding the poly-A tail. It contained untranslated regions of 85 and 231bp in the 5'- and 3'-ends, respectively. It has an open reading frame of 612bp coding for a signal peptide of 17 amino acids (aa) and a mature hormone of 187aa residues. Based on the aa sequence of the mature hormone, grouper GH shows higher sequence identity (>76%) to GHs of perciforms than to GHs of cyprinids and salmonids (53-69%). Grouper preproIGF-I cDNA consisted of 558bp, which codes for 186aa. This is composed of 44aa for the signal peptide, 68aa for the mature peptide comprising B, C, A, and D domains, and 74aa for the E domain. Mature grouper IGF-I shows very high sequence identity to IGF-I of teleost fishes (84-97%) compared to advanced groups of vertebrates such as chicken, pig, and human (=<80%). Using DNA primers specific for grouper GH and IGF-I, the changes in mRNA levels of pituitary GH and hepatic IGF-I in response to starvation and refeeding were examined by a semi-quantitative RT-PCR. Significant elevation of GH mRNA level was observed after 2 weeks of food deprivation, and increased further after 3 and 4 weeks of starvation. GH mRNA level in fed-controls did not change significantly during the same period. Hepatic IGF-I mRNA level decreased significantly starting after 1 week of starvation until the 4th week. There was no significant change in IGF-I mRNA levels in fed-controls. One week of refeeding can restore the GH and IGF-I mRNA back to its normal levels. Deprivation of food for 1-4 weeks also resulted in cessation of growth and decrease in condition factor.We thank Jossette Bangcaya and Josephine Nocillado for providing us degenerate IGF-I reverse primer, Mr. Roman Sanares for the statistical analyses, Dr. Ebonia Seraspe for her valuable advice and help. This study was funded by SEAFDEC AQD to EGT de Jesus-Ayson (Nr-01-F2001T) and by a grant from USAID to FG Ayson (Grant No. TA-MOU-99-C19-001, Program in US-Israel Cooperative Development Research, Economic Growth)