Genetic selection of shrimp has been ongoing since the late 1990’s during which time the principal focus has been on either faster growth or greater resistance to disease. This is reflected in the different approaches taken by genetics providers in Asia and the Americas. In Asia, the focus has been on using the SPF (Specific Pathogen Free) approach to breed faster growing lines while in the Americas breeding programmes used survivors of natural disease outbreaks to develop SPR (Specific Pathogen Resistant) lines.
The antagonistic relationship between growth and resistance resulted in a clear divergence over time with Asian lines showing faster growth but lower resistance and lines from the Americas having more resistance with slow growth. This has led to some market differentiation with some markets opting for higher resistance and others for faster growth.
A third option, pioneered by SyAqua, was the “balance line” approach. As shrimp are grown in a wide range of environments, with multiple and changing disease threats and varying stresses, both the growth and resistance lines would have relatively limited application across the industry. The balance line approach, which uses a “selection index” to select families over multiple factors, allows us to select the best families that share multiple traits. Incorporating both fast growth and resistance in the index allows us to select those families that both grow faster and have higher resistance, meeting the objectives of a wider range of farmers.
In the early days, SyAqua’s balance line approach was perceived skeptically by farmers who were accustomed to "pure" growth and resistance lines. However, continued application of the selection index approach was seen to give better and more consistent return on investment and now successfully attains performance levels comparable to “pure” lines across a broader range of farming conditions.
The Balance Line approach provides more flexibility since the selection index can be used to develop shrimp that are resistant, robust and with optimal growth while allowing the inclusion of other economically valuable traits without losing performance in other traits. This allows us to tailor the selection of traits that address the needs of specific markets and ever-changing environmental conditions.