Dr. Rafael D. Guerrero III: the Father of Tilapia Sex-Reversal

by

Melchor F. Cichon
July 18, 2006

Among the Filipino fisheries scientists tilapias have always been linked with Dr. Rafael D. Guerrero III.
Why is this so?

He observed that one of the most prominent problems in tilapia culture is overpopulation. Tilapia matures after two to three months from its fry stage and can produce as much as 5,000 eggs every three months depending on its size.

When he took his doctorate degree in Auburn University in the early 1970s, he focused his dissertation on  the production of monosex tilapia into male using synthetic androgens.

When he returned to the Philippines, he continued his experiment on tilapia sex reversal at the Central Luzon State University in Muñoz, Nueva Ecija where he served as the first dean of its college of fisheries.
And he was successful.

Now, the technology he developed has been adopted not only by Filipino fish farmers but by other fish farmers in other parts of the globe.

This can be seen from the awards he has been receiving here and abroad.
Dr. Guerrero was born in Manila on August 7, 1944. His parents are Rafael Guerrero, Jr. and Rizalina Guerrero.
He took his B.S. (Zoology) at the University of the Philippines in Diliman, Quezon City in 1964 and finished his M.S. (Applied Zoology) from U.P. Los Baños, Laguna in 1970. In 1974, he received his PhD degree in Fisheries Management from Auburn University, USA as a recipient of the NEDA-USAID Postgraduate Scholarship Award.

Two years after that, he became the Dean of the College of Inland Fisheries of Central Luzon State University from 1976 to 1981. Then he worked as Director for Training and Extension of the Southeast Asian Fisheries Development Center's Aquaculture Department in 1983.

The year before that, he and his wife, Luzviminda, co-founded the Aquatic Biosystems, an aquaculture consulting firm in 1982.

At present (2006), Dr. Guerrero is the Executive Director of Philippine Council for Aquatic and Marine Research and Development (PCAMRD).

Dr. Guerrero has published a lot of works related to tilapias.

Here are some of his publications, this writer has captured:

Guerrero, R. D. III. 1973. Cage culture of male and female Tilapia mossambicus with and without supplementary feeding in a fertilized pond. Central Luzon State University Science Journal 9:18-20

Guerrero, R. D. and W. L. Shelton. 1974. An aceto-carmine squash method for sexing juvenile fishes. Prog. Fish-Cult. 36-56.

Guerrero, R. D. III. 1974. The use of synthetic androgens for production of monosex male Tilapia aurea (Steindachner). PhD Dissertation, auburn University, Auburn Alabama. 97p.

Guerrero, R. D. III. 1974. Culture of monosex male Tilapia mossambica and Ophiocephalus striatus in fertilized ponds with supplementary feeding. Philippine Journal of Fisheries 12(1-2):64-74.

Guerrero, R. D. 1975. Use of androgens for the production of all-male Tilapia aurea (Steinfachner). Trans. Am. Fish. Soc. 104: 342-348

Guerrero, R. D. III and L. A. Guerrero. 1975. Monosex culture of male and female Tilapia mossambica in ponds at three stocking rates. Kalikasan, Philipp. J. Biol. 4:129-134.

Guerrero, R. D. III and L. A. Guerrero. 1975. Use of androgens for the production of all-male Tilapia aurea (Steindachner). Trans. Am. Fish. Soc. 104:342-348.

Guerrero, R. D. 1976. Culture of Tilapia nilotica at two densities with fertilization and supplemental feeding. Fish Res. J. Philipp. 1(1):39-43

Guerrero, R. D. and T. A. Abella. 1976. Induced sex-reversal of Tilapia nilotica with methyltestosterone. Fish. Res. J. Philipp. 1(2):46-49.

Guerrero, R. D. 1976. Tilapia mossambica and T. zillii treated with ethynyltestosterone for sex-reversal. Kalikasan, Philipp. J. Biol 5:187-192.

Guerrero, R. D. III. Culture of male Tilapia mossambica produced through artificial sex reversal. Proc. FAO Tech. Conf. On Aquaculture, Kyoto, Japan, FAO:AQ/Conf./76/E.15 3p.

Guerrero, R. D. III and L. A. Guerrero. 1976. Culture of Tilapia nilotica and Macrobrachium species separately and in combionation in fertilized freshwater fishponds. Phil J. Fish. 14(2):232-235

Guerrero, R. D. 1977. Production of tilapia fry in floating net enclosures. FAO Aquaculture Bulletin 8(3/4):4

Guerrero, R. D. 1979. Culture of male Tilapia mossambica produced through artificial sex reversal, p. 166-168. In T. V. R. Pillay and W.A. Dill (eds.). Advances in aquaculture. Fishing News Books Ltd., Farnham, Surrey, England.

Guerrero, R. D. 1979. Cage culture of tilapia in the Philippines. Asian Aquaculture 2(11);6

Guerrero, R. D. 1979. Use of hormonal steroids for artificial sex reversal of tilapia. Proc. Indian Nat. ?Sci. Acad 45B;512-514.

Guerrero, R. D. and E. P. Villanueva. 1979. Polyculture of Cristaria plicata (leach) at two densities with Tilapia nilotica and Cyprinus carpio in fertilized ponds. Fish. Res. J. Phil 4(2):13-17.

Guerrero, R. D. III. 1980. Studies on the feeding of Tilapia nilotica in floating cages. Aquaculture 20:169-175.

Guerrero, R. D. 1980. How to produce fingerlings of Nile tilapia. Modern Agriculture and Industry—Asia 3(2):4-5

Guerrero, R. D. III, A. G. Cagauan and T. A. Abella. 1980. Pond cultivation of three tilapia hybrids. CLSU Sci. J 1(1):15-18.

Guerrero, R. D. 1981. Bay town cashes in on tilapia bonanza. Asian Farms and Gardens (Feruary):14.

Guerrero, R. D. 1981. Introduction to fish culture in the Philippines. TRC Series. Technology Resources Center, Manila.

Guerrero, R. D. III. 1981. Recent developments in the cage culture of tilapia in the Philippines. Paper presented at the IFS General Assembly Meeting, 12 November 1981, Chiang Mai, Thailand.

Guerrero, R. D. 1982. Control of Tilapia reproduction. , pp. 309-316. In R.S.V. Pullin and R. H. Lowe-McConnell (eds). The biology and culture of tilapias. ICLARM Conference Proceedings 7. International Center for Living Aquatic Resources Management, Manila, Philippines.

Guerrero, R. D. 1982. An overview of tilapia culture in the country. Philippine Farmer’s Journal 24(3):28-29,331,35.

Guerrero, R. D. III., R. C. Sevilleja and A. M. Tolentino. 1982. Studies on the cage culture of Tilapia nilotica in Aya Reservoir and Laguna de Bay, Philippines. Paper presented at the Regional Workshop on Limnology and Water Management in Developing Countries of Asia and the Pacific, Kuala Lumpur, Malaysia.

Guerrero, R. D. and A. M. Garcia. 1983. Studies on the fry production of Sarotherodon niloticus in a lake-based hatchery, p. 388-393. In L. Fishelson and Z. Yaron (comps) Proceedings of the International Symposium on Tilapia in Aquaculture. Tel Aviv University, Tell Aviv, Israel.

Guerrero, R. D. III. 1983. A comparative study on the cage culture of Tilapia nilotica and male T. nilotica x female T. aurea hybrid in Laguna de Bay. Paper presented at the 5th Annual Meeting of the Nations Science Technical Authority, Bicutan, Metro Manila. 6p.

Guerrero, R. D. III and L.A. Guerrero. 1985. Effect of breeder size on fry production of Nile tilapia in concrete pools. Trans. Nat. Acad. Sci. Tech. (Phils.) 7:63-66.

Guerrero, R. D. III and L.A. Guerrero. 1985. Further observations on the fry production of Oreochromis niloticus in concrete tanks. Aquaculture 47:257-261.

Guerrero, R. D. III and L.A. Guerrero. 1985. Outdoor treatment of Nile tilapia fry for artificial sex reversal. Paper presented at the Asian Symposium on Freshwater Fish Culture, Beijing, China, 10-15 October 1985. 6p.

Guerrero, R. D. III. 1985. Tilapia farming in the Philippines: practices, problems and prospects, p. 3-13. In I.R. Smith, E, B. Torres and E. O. Tan (eds.). Philippine tilapia economics. ICLARM conference Proceedings 12, 261p. Philippine Council for Agriculture and Resources Research and Development, Los Baños, Laguna and ICLARM, Manila Philippines.

Guerrero, R, D. 1986. Commercial production of tilapia in freshwater ponds and cages in the Philippines. Paper presented at the First National Symposium and Workshop on Tilapia Farming, PCARRD,Los Baños, Laguna, Philippines, 24-26 November 1986. 12p.

Guerrero, R. D. III. 1987. Tilapia farming in the Philippines. Technology and Livelihood Resource Center and National Book Store, Manila, Philippines. 84p.

Guerrero, R. D. III and L.A. Guerrero. 1988. Feasibility of commercial production of sex-reversed Bile tilapia fingerlings in the Philippines, p. 183-186. In R.S. V. Pullin , T. Bhukaswan, K. Tonguthai and J. L. Maclean (eds.) The Second International Symposium on Tilapia in Aquaculture. ICLARM Conference Proceedings 15, 623. Department of Fisheries, Bangkok, Thailand, and ICLARM, Manila, Philippines.

Guerrero, R. D. III. 1999. Seaweed farming in Batangas. Agriculture 111(10):18-19.

Dr. Guerrero has been a consultant for aquaculture of various government and private corporations such as the Technology and Livelihood Resource Center, San Miguel Corporation and the Meralco Foundation, Inc.
He also served as president of the Fisheries Research Society of the Philippines; Team Leader for Aquaculture Research of the Philippine Council for Agriculture and Resource Research, and served as Director of the Fisheries Research Department, Philippine Council for Aquaculture and Resources Research and Development. He was a Visiting Professor of Aquaculture Management of the CDFM, UPLB and Scientific Adviser for aquaculture of the International Foundation for Science.

For his distinguished career as a researcher, consultant and administrator, Dr. Guerrero received several awards both here and abroad. Among these are the following:

1978--Ten Outstanding Young Men (TOYM) Award for Aquaculture and Fisheries conferred by the Philippine Jaycees.

1980--Ten Outstanding Young Scientists (TOYS) Award given by the National Science and Development Board (NSDB)

1987--IBM Science and Technology Award

1992--Elected Academician by the National Academy of Science and Technology in recognition of his scientific and technological contribution to the development of sex reversal and hatchery technique that led to the commercial production of high yielding market-size tilapia in the Philippines and other countries.

2005-- Mgr. Dr. Jan D.F. Heine Memorial Award by the International "Je Dois Faire" Assembly "in recognition of his outstanding efforts to stimulate sustained improvement of world wide human living standards." And for his pioneering work on tilapia sex reversal technology that contributed significantly to world aquaculture. The award was conferred to Dr. Guerrero by Heine and World Aquaculture Society president Keven Fitzsimmons during the 6th International Symposium on Tilapia in Aquaculture in Manila.

The Mgr. Dr. Jan D.F. Heine Memorial Award is conferred to internationally recognized individual who has worked for the advancement of tilapia science and has also made an impact on the lives of people in developing countries dependent on fish as a major source of animal protein.

Tilapia was once considered as a fishpond culture pest. Today this is called the chicken of the pond.

And its production in 2001 was 106.7 metric tons amounting to PhP12,999,000, second only to milkfish (bangus).

And Dr. Guerrero III has been a part of this development.