Genetic assessment of philippine milkfish (Chanos chanos) stocks based on novel microsatellites for markeraided broodstock management
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Reports on genetic diversity within/among milkfish populations using DNA markers are sparse. Earlier work dealt with evolutionary relationships among wild populations to define management units in the Indo-Pacific region where milkfish naturally abound. However, application of milkfish genetic markers in broodstock development and management remains to be investigated. Here, nine novel microsatellites developed by NGS were utilized to (a) describe the genetic structure of Philippine wild and hatchery-bred milkfish; (b) monitor the impact of domestication selection and inbreeding; and (c) formulate marker-aided broodstock management methods, a prerequisite to genetic improvement. Milkfish samples from three wild populations: Claveria (CLA), Currimao (CUR), Camiguin (CAM); eleven local hatchery stocks: SEAFDEC Integrated Hatchery (SIH), SEAFDEC Big Hatchery-Igang batches 1 and 2 (SBH-I1 and SBH-I2), SEAFDEC Big Hatchery-Dumangas (SBH-D), Hautea Hatchery (HH), Sual Pangasinan Hatchery (SPH), BFAR Dagupan Hatchery (BDH), BFAR Bohol Hatchery (BoH), BFAR Palawan Hatchery (PAL), Zambales Hatchery-P0 (ZH-P0), Zambales Hatchery-F1 (ZH-F1); and a hatchery stock from West Java in Indonesia (WJH), were examined. An Indonesian stock was included since in the Philippines, Indonesian milkfish fingerlings are imported and farmed for having purportedly better production traits. Genetic diversity indices such as expected heterozygosity (He) and allele frequency (A) ranged from 0.655 to 0.697 and 9.2 to 11.1, respectively. AMOVA showed significant but low genetic differentiation among the milkfish populations (FST = 0.013; P=0.000,) since much of the variation is attributed to intrapopulation differences (98.6%). The oldest hatchery stock SIH (30-35 years) had relatively moderate genetic variability (He = 0.66, A = 10.6), which is lower than that of 5-year old SBH-I1 (He= 0.687, A= 11.5) considering that both stocks originally came from the same source in the wild. A reduction in genetic diversity was seen when a local hatchery stock (ZH-P0;He = 0.66 and A= 10.8) was monitored after one generation (ZH-F1; He = 0.65, A=9.3). Finally, the Indonesian stock WJH had genetic variability levels (He= 0.66; A= 10.5) comparable with local stocks. Results of genetic analyses are herein discussed in the context of promoting effective milkfish broodstock management practices for the production of good quality seed stock.
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milkfish microsatellites broodstock management genetic variability inbreeding selective breedingDescription
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Romana-Eguia, M. R. R., Santos, B. S., Ikeda, M., Basiao, Z. U., de Jesus-Ayson, E. G. T., & Kijima, A. (2017). Genetic assessment of philippine milkfish (Chanos chanos) stocks based on novel microsatellites for markeraided broodstock management. Aquaculture , 472(Supplement 1), 136. https://doi.org/10.1016/j.aquaculture.2017.03.032
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Genetic assessment of milkfish (Chanos chanos Forsskal) stocks based on novel short tandem repeats for marker-aided broodstock management
Romana-Eguia, Maria Rowena R.
; ; ; ; (John Wiley and Sons, 2018)
Milkfish hatchery broodstock are either from on-grown wild-caught or hatchery-produced fry/juveniles. To determine if a marker-assisted management scheme can be formulated for improved milkfish hatchery production, milkfish stocks were genetically characterized using nine novel short tandem repeats or microsatellites. Eight wild-bred Philippine stocks (CLA, CUR, CAM, SIH, SBH-I1, HH, PAL and ZH-P0), four hatchery-bred stocks (SBH-I2, SBH-D, BoH and ZH-F1), two farm stocks of known mixed lineages (SPH and BDH) and one Indonesian hatchery-bred stock (WJH) were assessed. WJH was included since milkfish fingerlings from Indonesia reared in Philippine farms could be developed into future broodstock. Mean allelic richness (Ar) was highest in wild-bred stocks (9.5) and lowest in hatchery-bred spawners (9.1). Mean expected heterozygosities (He) were relatively similar in all stocks with wild-bred stocks slightly higher (0.67) than the others. An analysis of molecular variance indicated significant yet low genetic differentiation among stocks (FST = 0.013; p = .000) where variation (98.6%) was explained by intra-stock differences. In some of the domesticated stocks, reductions in mean allelic richness were observed in first generation hatchery broodstock (e.g. ZH-F1; Ar = 8.3), compared with their founder stock (e.g. ZH-P0; Ar = 9.4). The Indonesian stock was similar to local wild-bred stocks based on genetic variability indices; thus, it might be likely that the local stocks’ fitness traits could be comparable with the imported milkfish stock which has been perceived to be better. The quality of locally available farmed milkfish and prospects of formulating a broodstock management scheme for the production of good quality milkfish seedstock are herewith discussed. -
[The Philippines recommends for milkfish:] Fry production
(DOST-PCAARRD, 2016) -
Research on marine and freshwater fishes
(Aquaculture Department, Southeast Asian Fisheries Development Center, 1995)Most of the fish research at SEAFDEC AQD in 1992-1994 was on milkfish. Studies were conducted on year-round spawning through hormonal or environmental manipulation; optimum lipid and protein levels and ration size for captive broodstock; and the influence of spawner age on reproductive performance. The economics of hatchery operations, alone or integrated with broodstock as a commercial enterprise, was assessed. Mass production of larvae was refined with the use of commercial or SEAFDEC-formulated larval diets. Alternative rearing schemes in large tanks and ponds were tried. Hatcheryproduced and wild-caught larvae were compared in terms of growth and production in experimental nursery and grow-out ponds. Supplemental diets for brackishwater grow-out culture were formulated. Studies on broodstock management of grouper Epinephelus spp. included lipid enrichment of the diet and hormonal induction of sex inversion. Seed production techniques were developed but survival rates were low. Grouper culture was found economically feasible in experimental ponds with 'trash' fish as feed. The mangrove red snapper Lutjanus argentimaculatus was successfully induced to spawn with injection of human chorionic gonadotropin. Initial larval rearing trials were successful but survival rates must be improved. Hormonal manipulation of spawning of the Asian sea bass Lates calcarifer allows seed production during most of the year. Photoperiod manipulation leads to maturation of females, but not males, beyond the natural breeding season (April-November). Nursery rearing of 9 mm juveniles is feasible in floating net cages with night lights that attract food zooplankton. The requirements of sea bass for lipid, protein, carbohydrates, and essential amino acids were determined. In the rabbitfish Siganus guttatus, weekly injections of luteinizing hormone releasing hormone analogue (LHRHa) sustains milt production for three weeks. Thyroid hormones injected into broodstocks improved the growth of larvae to day 7. Induced spawning techniques for the Asian catfish Clarias macrocephalus were refined by determining the seasonal responsiveness to LHRHa and pimozide injections and testing for pheromonal induction of spontaneous spawning. The optimum insemination rate was determined and egg hatchability was enhanced by removal of the adhesive coat before incubation. Several practical diets for catfish during grow-out culture were tested against 'trash' fish. The broodstock management for bighead carp Aristichthys nobilis was studied. Cage-reared juveniles from cage-reared broodstock showed the best growth. To improve the reproductive performance, the broodstock diets were supplemented with vitamins A, C, and E. Research on tilapias focused on genetics and strain selection. Several strain testing procedures for Nile tilapia were evaluated in their efficiency to detect economically important strain differences. Reference lines were developed from two existing red tilapia strains to measure and reduce the effects of uncontrolled nongenetic variables in strain evaluation experiments with Nile tilapia. The tolerance of two Nile tilapia strains to heavy metals was similar when gauged by the 24-hour and 96-hour lethal concentration and by fish growth, survival, and reproductive performance. In a separate study, four strains of red tilapia showed generally higher seed production when reared in tanks than in cages. Improvements in the feed and feeding management for Nile tilapia were also studied. Intensive tilapia farming and feeding have led to oxygen depletion and fish kills in Sampaloc Lake. To rehabilitate the lake, it is imperative to reduce the farming area from 30 to 6 hectares; stop the use of commercial feeds; and remove the water hyacinths and other debris. Fish kills in Laguna de Bay have also become serious in recent years, and a review of the occurrences, losses, and possible causes is currently being conducted. Studies on the epizootic ulcerative syndrome of snakeheads in Laguna de Bay have yet to pinpoint the pathogen. Skin lesions in tilapias in several ponds and lakes in the country were found to be due to bacteria.
