Genetic assessment of milkfish (Chanos chanos Forsskal) stocks based on novel short tandem repeats for marker-aided broodstock management
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Abstract
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.
Suggested Citation
Romana-Eguia, M. R. R., Santos, B. S., Ikeda, M., Basiao, Z. U., & Kijima, A. (2018). Genetic assessment of milkfish (Chanos chanos Forsskal) stocks based on novel short tandem repeats for marker-aided broodstock management. Aquaculture Research , 49(4), 1557-1568. https://doi.org/10.1111/are.13610
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ArticleISSN
1355-557X; 1365-2109Koleksi
- Journal Articles [1266]
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Genetic assessment of philippine milkfish (Chanos chanos) stocks based on novel microsatellites for markeraided broodstock management
Romana-Eguia, Maria Rowena R.
; ; ; ; ; (Elsevier, 2017)
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. -
Systematics, distribution, genetics and life history of milkfish, Chanos chanos
Bagarinao, Teodora (Springer Verlag, 1994)
Chanos chanos belongs to a monotypic gonorynchiform family and is most closely related to the freshwater Ostariophysi. The earliest gonorynchiforms occurred in the Cretaceous of Brazil and west Africa. Chanos occurred in the freshwater Eocene deposits of Europe and North America, and probably invaded the circumtropical Tethys Sea during transgression episodes. At present, milkfish occurs near continental shelves and around oceanic islands throughout the tropical Indo-Pacific. Milkfish populations throughout the range show high genetic variation but low genetic divergence, similar to many other commercially important teleosts. The natural life history of milkfish is one of continual migration. Adults are relatively large (to 1.5 m or 15 kg), long-lived (to 15 years), pelagic and schooling. They spawn offshore near coral reefs or small islands. The eggs, embryos and larvae are pelagic and relatively larger than those of most marine species. Larvae ≥ 10 mm long and 2–3 weeks old move inshore via a combination of passive advection and active migration. Passing shore waters and surf zones, they settle in shallow-water depositional habitats such as mangrove swamps and coral lagoons, where they metamorphose and spend a few months as juveniles. Some juveniles may enter freshwater lakes where they grow into sub-adults but do not mature. Both small juveniles and large sub-adults go back to sea when they reach the size limit supportable by the habitat. Little else is known of the dynamics of wild populations of milkfish. A fishery on inshore larvae supports the centuries-old aquaculture of milkfish in southeast Asia. During the past ten years, milkfish have matured and spawned under various conditions of captivity, and hatcheries have produced larvae to supply the culture ponds. Much remains to be learned concerning the milkfish, particularly its ecology and physiology. -
Meristic variations in milkfish Chanos chanos from Philippine waters
(Springer Verlag, 1988)Variations in meristic characters occur within and between samples of milkfish Chanos chanos (Forsskal) collected on June 1977 from five localities in Philippine waters. The unbranched anal and ventral fin rays are the most plastic, and vertebral number is the most stable of nine meristic characters examined. The number of ventral fin rays is the only meristic feature which differed consistently enough to suggest distinct population groups: South China Sea, comprising samples from Ilocos and Panay Island; Pacific Ocean from Bicol; and Celebes Sea, from Zamboanga and Davao. A discriminant analysis which incorporated generalized distance (Mahanalobis D2) and percent overlap of a reduced set of characters indicated several morphometric subgroups of milkfish in Philippine waters, although geographic subgroups were not clearly demonstrated.
