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PD/A CRSP Nineteenth Annual Administrative Report |
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MOU No. RD009C
Staff
Oregon State University, Corvallis, Oregon
| Carl B. Schreck | US Principal Investigator, US Regional Coordinator |
| Wilfrido M. Contreras-Sánchez | Graduate Research Assistant (Mexico; through January 2001; CRSP funded) |
| Carisska Anthony | Undergraduate Student (through January 2001) |
| Janine Gonzalez | Undergraduate Student (through January 2001) |
| Damien Wycoff | Undergraduate Student (through January 2001) |
Universidad Juárez Autónoma de Tabasco, Villahermosa, Mexico
| Wilfrido M. Contreras-Sánchez | Host Country Principal Investigator |
| Gabriel Márquez Couturier | Host Country Principal Investigator |
| Alfredo Ramos Montero | Technician (from February 2001) |
| Heleodoro Reyes Reyes | Technician (from January 2001) |
| Alejandro MacDonald Vera | Technician Student (through June 2001; CRSP funded) |
| Guadalupe Morales Lara | Technician Student (partially CRSP funded) |
| Maria de Jesús Contreras Garcia | Undergraduate Student (from January 2001) |
| Luis Arturo Dorantes Lopez | Undergraduate Student |
| Thelma R. González Márquez | Undergraduate Student |
| Albaro Hernández Hernández | Undergraduate Student (from January 2001) |
| Sofia Carolina Santiago Ruiz | Undergraduate Student |
Cooperator
Oregon State University, Corvallis, Oregon
Martin Fitzpatrick
The PD/A CRSP has been active in Mexico since 1997. A Memorandum of Understanding (MOU) was signed between Oregon State University (OSU) and the Universidad Juárez Autónoma de Tabasco (UJAT) in June 1999. Until 2000, research conducted in Mexico was reported as either Reproduction Control Research or Effluents and Pollution Research. Beginning with last year's report, because of exclusive collaboration between OSU and UJAT, research conducted under the differing research themes was consolidated to form the Mexico Project. CRSP research in Mexico emphasizes reproduction control through the use of hormone immersion and examines the fate of masculinizing agents in effluents.
The following Ninth Work Plan investigation continued into the current reporting period:
This MOU was also awarded funding to conduct the following Ninth Work Plan investigations:
Note: The schedule for 9RCR5C was modified. The revised schedule appears in the Addendum to the Ninth Work Plan. 9RCR5D and 9ER2D were approved after the publication of the Addendum to the Ninth Work Plan. The work plans for these investigations will appear in the Second Addendum to the Ninth Work Plan.
Contreras-Sánchez met with Oceanol representative Silvia Wizar, director of development for the municipality of Centro, Tabasco, to initiate talks regarding collaboration between UJAT and the municipality on a proposal for the production of sex-reversed tilapia using clean technologies.
Formal collaboration between UJAT and the University of San Carlos, Guatemala, will take place in the form of a project that involves the use of activated charcoal filters for the elimination of MT from intensive fry production systems. UJAT also initiated contacts with the Office for Development in the municipality of Centro, which may participate in experiments with UJAT related to the study.
Allyse Ferrara (Clemson University), Reynaldo Patiño,
and Kevin Pope (both of Texas Tech University) contacted
the CRSP researchers to plan a visit to UJAT to develop
collaborative agreements to work with the native gar
Atractosteus tropicus. Since the alligator gar has been listed as a species
at risk in Texas, both Patiño and Pope are interested
in understanding how gar spawning and larval rearing
are performed at UJAT.
The laboratory of aquaculture at UJAT will provide 3,000 control fish (50% males) and 3,000 masculinized fish (95% males) to a group of tilapia producers from the Sánchez Magallanes, Cardenas. The farmers will conduct a short experiment in hapas where they will grow the fish and compare growth rates.
Márquez Couturier met with a producer at the Ejido Rio Playa, Comalcalco, Tabasco, which has recently built facilities for aquacultural purposes. UJAT will provide sex-reversed tilapia and training for initiating tilapia aquaculture.
Contreras was contacted by the nongovernmental organization Santo Tomás, a group that is interested in writing a proposal to work in collaboration with UJAT for developing the culture in hapas of masculinized mojarra castarrica (Cichlasoma urophthalmus), a native cichlid.
A group of producers from Huimanguillo requested information regarding the use of masculinized tilapia fry. UJAT will provide fry to start small production systems depending upon the producers' ability to form effective working groups.
The researchers received a request from Aqua Technics of Carlsborg, Washington, to analyze fish food for methyltestosterone, and the assays were conducted.
The UJAT laboratory is currently involved in training workshops for tilapia culture organized by Fideicomisos Instituidos en Relación con la Agricultura (FIRA). Candelario Bautista, a volunteer at UJATs laboratory, has already participated in two workshops, one of which was conducted in Sánchez Magallanes. The researchers are emphasizing the use of masculinized tilapia, and the laboratory is providing information for the workshop.
Contreras-Sánchez, W., 2001. Sex determination in Nile tilapia, Oreochromis niloticus: Gene expression, masculinization methods, and environmental effects. Ph.D. dissertation, Oregon State University, Corvallis, Oregon.
PD/A CRSP Annual Meeting at Orlando, Florida, 26 January 2001. (Contreras-Sánchez)
Schreck received the Excellence in Fisheries Education Award from the American Fisheries Society.
In a previous experiment in which Nile tilapia fry were successfully masculinized, we investigated how the concentration of trenbolone acetate (TA) in the immersion water changed before and after treatment. The results from that experiment indicated that the concentration of TA before and after treatment of Nile tilapia fry was highly variable and below the expected levels. Therefore, we decided to corroborate those results by running two experiments in which fry were not present and by testing different water sources. These new experiments confirmed our previous findings, indicating that independently of the source of water, the concentration of TA is highly variable and below the expected levels.
Preliminary studies in our laboratory showed that short immersions in the synthetic androgen trenbolone acetate (TA) constitute a good option for masculinizing Nile tilapia fry produced by a single female. This technique offers the potential to replace MT feeding for 28 days and avoid steroid accumulation in pond sediments. We investigated the effects of TA treatment on fry collected from a tank containing batches produced in multiple spawnings. Our results suggest that masculinization involving short-term immersions in TA results in significantly more males in the treated groups (55.9 and 61.6%) than in the controls (44.5 and 38.9%). However, the percentage of males produced is far below that recommended for aquacultural purposes. We further investigated the potential enhancing effects of elevated temperatures in combination with TA treatment during immersion time and found no significant effects of temperature on the proportion of males obtained.
The following study examined the persistence of 17a-methyltestosterone (MT) in the environment after its use for masculinizing Nile tilapia in nursery ponds located in the Universidad Juárez Autónoma de Tabasco, Mexico. Fry harvested from spawning ponds were treated with a masculinizing dose of MT (60 mg kg-1) for four weeks. Concentrations of MT were determined by radioimmunoassay. MT was not detectable in the water at any time. In the sediments, MT was not detectable during the first 10 days of treatment. Afterwards MT was detectable in all sampling points (mean = 146.7 pg g-1; SE = 21.3). MT values varied from not detectable to 368.9 pg g-1. Masculinizing efficiency was low in the first trial (87.4% males) but increased significantly afterwards, reaching 92.6% males in the second trial and 98.7% in the third trial.
Another outcome of this investigation is a manual on tilapia masculinization using synthetic steroids. This manual is intended to reach fry producers, extension agents and technicians; it contains a general description of the biology of the tilapias, traditional culture practices, masculinization methods, and a detailed section on safe handling of steroids.
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The Pond Dynamics/Aquaculture CRSP is funded under USAID Grant No. LAG-G-00-96-90015-00
and by
the participating US and Host Country institutions.
Questions for or about the Aquaculture CRSP? Comments about this site? Email ACRSP@oregonstate.edu.
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