Following domestication of shrimp in the 1990’s, pioneered by the Oceanic Institute as part of the US Marine Shrimp Farming Program, genetic selection has resulted in major improvements in shrimp productivity. Selection for growth resulted in farmed Penaeus vannamei reaching sizes similar to P. monodon within the same culture period. Together with development of Specific Pathogen Free (SPF) stocks, this has resulted in an almost complete shift in Asian shrimp production to P. vannamei .
In the Americas, successive outbreaks of disease led producers to select survivors from affected ponds as the basis of their breeding programs, the “Specific Pathogen Resistant” (SPR) approach. This resulted in shrimp lines that have better survival in the field than the SPF lines which were produced with no innate resistance but with a slower growth rate .
Because of the antagonistic relationship between growth and resistance, this led to a divergence between lines used in Asia (SPF, selected for faster growth) and lines from the Americas (SPR but with slower growth) . Subsequently, t his led to differentiation between markets opting for higher resistance or faster growth depending on local farming conditions.
This binary choice would seem to have relatively limited application across an industry where differences in management strategies, environmental conditions and disease threats affect the suitability and success of either the fast growth or resistant line approaches.
Since 2011, SyAqua has adopted a third option, the “balance line”, selecting for a combination of growth and resistance traits simultaneously. Simply crossing commercial fast growing and resistant lines typically results in highly variable populations with many slow growing and susceptible offspring. Using a carefully designed “Selection Index” allows us to choose families with the optimal combination of growth and resistance traits. This approach has led to shrimp exhibiting growth patterns similar to those of the best growth lines, while demonstrating heightened resilience to stressors and pathogens over time. Equally important, farmers can achieve better and more consistent returns on investment compared to “pure” lines as seasons, farming conditions and uncontrollable factors fluctuate.
The selection index approach can be adapted to include other economically valuable traits. This allows selection for more traits, addressing specific market needs and ever-changing environmental conditions without losing genetic variability or gains in growth and resistance.