Ken,
I would think brush would probably help with winter survival ... at least it is an arguable outcome. In the what I have read, brush and plants were not discussed as cover for the shrimp but rather as substrate providing additional attachment surface that winds up providing more food for shrimp relative to the control.
The most production I have seen cited was with brush in combination with fertilization. In the treatments where fertilization and brush were used, the production of PK shrimp was 1044 lbs/acre. What is remarkable about that number is that the shrimp were stocked with 1500 2" BG/acre which produced 210 lbs/acre of BG. All this in the space of 6 months.
Stocked without brush in fertilized ponds and as a monoculture, the PK shrimp only produced 566 lbs/acre. When fertilized ponds without brush were stocked with 1500 BG/acre they produced about 93 lbs/acre of PK shrimp and 209.5 lbs/acre of BG.
So the interesting part is that the brush didn't make a difference in the GAIN of 1500 BG/acre. Apparently, the BG ate as much as they were able to in both treatments. The difference for the PK shrimp is that there was much more food and habitat for them because of the brush. In so much as the brush produces more shrimp, brush must also help more of them overwinter even if it were to provide no meaningful cover for shrimp.
Grass shrimp have a few things going for them with respect to survival. They reproduce, they can eat a wide variety of foods including detritus, and they have adapted to be difficult to see. All these things help them survive predation and establish populations.
***Bump***
PK shrimp are not native to Virginia but
P. Paludosus is and depending on your location may be better than kadiakensis.
