Aquaculture CRSP

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Selection of a New Nile Tilapia Genetic Line to Provide Broodstock for Southeastern Mexico

Reproduction Control Research 2 (10RCR2)/Experiment/Mexico

Collaborating Institutions
Universidad Juárez Autónoma de Tabasco, Mexico
     Wilfrido Contreras-Sánchez
     Mario Fernández Perez
     Gabriel Márquez Couturier

Oregon State University
     Guillermo R. Giannico
     Carl B. Schreck

Objectives
1) Evaluate the performance of wild and introduced stocks of Nile tilapia based on traditional genetic selection.

2) Provide tilapia fry farms in Southeastern Mexico with a good quality broodstock.

3) Provide farmers and institutions with a protocol for breeding strategies for the maintenance of the broodstock quality and for tilapia genetic enhancement.

Significance
Tilapia (Oreochromis spp.) culture has been the principal aquacultural activity in Southeastern Mexico since the 1960s – 1970s (Fitzsimmons, 2000). With the introduction of tilapias to Mexico, the different institutions responsible of fish production created remarkable expectations among Mexican farmers and investors. Unfortunately, several problems have resulted in these expectations being unrealized. The loss of the lineages introduced, the lack of effective genetic selection programs, and poor management decisions have created disappointment and uncertainty around tilapia culture in Mexico. Meanwhile, other countries in Central and South America have demonstrated that tilapia culture can be a remarkable investment for both business and social projects.

Because of its geographic and hydrological components, the Southeastern region of Mexico has been considered as one of the top areas in Mexico for aquaculture and especially for tilapia culture. Currently there are 6 main tilapia hatcheries in the Mexican states of Tabasco and Chiapas that provide fry to more than 5,000 small tilapia farmers. However, the quality and quantity of the fry provided has been a constant criticism from the farmers to the hatchery managers. In 1993, Contreras-Sánchez and Fernández documented in an internal report for the State's Office for Development (Secretaría del Desarrollo) the need for establishing a new tilapia line appropriate for meeting the needs and conditions of the Central American tropics. This document also suggested the need to establish broodstock selection programs and the formation of high quality broodstock lots in the fry production facilities. To date, all hatcheries in Tabasco and Chiapas are buying fry from the Mexican States of Veracruz, Oaxaca, and Guerrero to partially fulfill the demand. However, the quality of the fry is still low. We propose to develop a program for acquiring local and foreign tilapia broodstocks, conduct a selection program following Bhujel's (2000) recommendations for broodstock management strategies, and create a broodstock selection program that avoids risk by following elements in a risk assessment analysis for determining the genetic vulnerability of the broodstock outlined by Currens and Busack (1995).

We have identified a stock of wild Nile tilapia in the Usumacinta River that shows good phenotypic traits (small head, small tail, large body, and uniform color). In the present study we proposed to select a group of adult fish that will be used for progeny testing and traditional genetic selection. Another group of fish from a region that shares similar climatic conditions with Tabasco will be obtained from a tilapia-breeding center (ideally GIFT tilapia from the Philippines) and both local and introduced lines will be managed under the same breeding protocol. The quality of the fry of both stocks will be contrasted (condition factor, growth, conversion factor) and traditional selection will be used for genetic enhancement. Quality of the fry produced will be estimated using growth, fertility, survival, and feed utilization as indicators.

The establishment of good quality broodstock treatments, their distribution to local hatcheries, and the implementation of intensive masculinization programs are basic steps for sustainable aquaculture. These actions can improve significantly the production of good quality fingerlings and have a favorable impact on more than 5,000 subsistence farmers and medium-scale producers.

Extension workshops and outreach activities and materials that help increase the awareness of farmers and producers about the importance of maintaining broodstock quality over time will be prepared and offered through a variety of selected public information and training institutions.

Well-supported aquacultural practices can help secure good quality food products in the near future. Especially in the proposed site of study where a large population of extremely poor campesinos characterizes the rural social structure.

Research Design
Site: Acclimation of adult fish and progeny testing will be conducted at the Laboratory of Aquaculture at UJAT, Tabasco, México.

Activities: Capture of wild adult Nile tilapia from Jonuta, Tabasco; acquisition of GIFT tilapia from the Philippines; acclimation of fish to laboratory conditions; genetic selection using phenotypic traits

Laboratory and Pond Facility: Universidad Juárez Autónoma de Tabasco (DACB); 20 aquaria (50 l), 3 reproduction concrete tanks (8 m2), 50 net cages (1 m3) for grow-out, 3 grow-out ponds (200 m3), a total of 10 females and 30 males for production of fry. Universidad Juárez Autónoma de Tabasco (DACA); 2 reproduction concrete ponds (50 m2), 2 grow-out ponds (50 m2). 20 net cages (1 m3) for grow-out.

Stocking Density for Spawning: 3 females:1 male/m2

Stocking Density for Grow-Out: 100 fish/m2 (first 2 months); 50 fish/m2 (2 months); 20 fish/m2 (last 2 months)

Culture Period: 6 months (three cycles)

Test Species: Nile tilapia (Oreochromis niloticus)

Nutrient Inputs: None

Water Management: Flow through 10% water exchange/day

Sampling Schedule: Total length, fork length, weight, total height, total width, and head and tail size of the tilapias will be measured once a month.

Statistical Methods and Hypothesis: H01: Fish with the highest condition factors show no decrease in food conversion. To select the most valuable traits, multifactor anovas and discriminant analysis will be performed using the morphometric factors as the independent variables and food conversion rate as the discriminant factor. Fish with the highest condition factor will be selected using Multivariate Analysis.

Schedule
Data collection, 7/01 to 2/03; Technical report, 3/30/03

Literature Cited
Bhujel, R.C., 2000. A review of strategies for the management of Nile tilapia (Oreochromis niloticus) broodfish in seed production systems, specially hapa-based systems. Aquaculture, 181:37­59.

Contreras-Sánchez, Fernández-Perez, and Márquez Couturier, 1992. Reporte técnico de las condiciones y propuesta técnica para el mejoramiento de la Piscifactoría Mariano Matamoros, de Teapa, Tabasco, México.

Currens, K.P. and C.A. Busack, 1995. A framework for assessing genetic vulnerability. Fisheries, 20:24­31.

Fitzsimmons, K., 2000. Tilapia aquaculture in Mexico. In: B.A. Costa-Pierce and J.E. Rakocy (Editors), Tilapia Aquaculture in the Americas, Vol 2. The World Aquaculture Society, Baton Rouge, Louisiana.

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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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