First, figure out what's eating them.

Nets can stop birds, chicken wire can stop squirrels, neither can stop bugs or, more likely, slugs.

The netting is a must own for strawberry growers. Also, try sprinkling used coffee grounds around the plants, seems to deter slugs.

i had same issue. birds leave oblious markings and I have dogs that chase them off so I knew it was some sort of small insect. I have not seen any slugs. i sprayed my bed real good with Sevin (heavily diluted - 1 tablespoon in 1 gallon of water). Sprayed the ground underneath the berrys and underneath the leaves. Since then, my berries are getting fully red and very little damage.