From what I have read (definitely not from what I "know") the most likely "natural" cross is RES male x GSF female. It appears the GSF females are more likely to be flusies than the RES females.
The opposite cross can be done in controlled environment but usually requires human intervention. That is my understanding so I assume (dangerous) that my RES crosses are that direction.
As far as turbidity, yes there have been changes. Early on in this ponds life there was a lot of clay around and every rain made it turbid. So for the first year or two there were periods of turbidity mostly dependent on rain patterns. I lined most of the pond with crushed limestone so as the pond developed and got a good algae bloom it was much less turbid and any turbidity was because of algae instead of suspended clay. So that could explain the unusually high number of hybrids produced earlier in the ponds life. I get lots of hybrids produced in my sediment pond also and it suffers from seasonal turbidity because of agricultural runoff and sediment. So in my opinion, turbidity does play an important role.
One other interesting thing that may affect hybrid production going forward. My daughter is in the process of building a small house 30 feet from my forage pond. In that process we have dug up a lot of clay for septic lines, water line and electric line. Now that pond just the other day again became very turbid because of this runoff from a recent rain and probably will continue to be affected through next spring after rainfall events. So it will be interesting to see if I start seeing more hybrids again as the RES do their late season spawn this fall and into the spawn next spring.
