To know the direction of change they need to monitor the water quality, elaborate forecasts, and performing a risk mitigation strategy.
a.) They do not have enough water for their fish, they need to farm something else or choose an entirely different source of income.
b.) The water quality or volume change for the worse, they can use other fish species. If it is feasible, they can manage the water (cleaning, proper airflow, etc.).
c.) If the water is turning better for fish farming (higher value species or higher yield), the adaptation is easier, they only need to recognize the opportunity.
The adaptation measures to be followed the fish farmers due to climate change in their fish ponds may be to compensate the water temperature by the compensation of the dissolved oxygen content either through mechanical or through chemical application methods.