Which method can enhance feed efficiency in aquaculture?

Using genetically modified organisms (GMOs) can significantly enhance feed efficiency in aquaculture. This is primarily because GMOs can be designed to have specific traits that allow them to utilize feed nutrients more efficiently, improve growth rates, and reduce feed conversion ratios. By enhancing these traits, GMOs can lead to fish that grow more quickly and require less feed for the same amount of growth, which is a crucial factor in aquaculture as feed costs can be a major expense.

The other methods mentioned do not directly enhance feed efficiency in the same way. For example, stocking more species can potentially lead to increased competition for food resources rather than improved efficiency. Reducing water temperature can slow down metabolic rates, impacting growth and feed utilization negatively. Increasing salinity levels can alter the physiological processes in fish and might lead to stress, which again may not improve feed efficiency. Thus, the use of genetically modified organisms stands out as a targeted approach to enhance feed efficiency in aquaculture settings.