By the end of 1999, Fish and Game and CIFFI's Project Rainbow Trout built and installed a four-pen, trout rearing facility at the docks of Markley Cove Resort. Once in full operation, these pens hold tiny rainbow trout during the fall and winter months in an attempt to teach the fish how to feed and better survive the crucial winter months.

According to Dennis Lee, Senior Fisheries Biologist with the DFG at that time, the penned rainbows will get a growth jump on early season planters.  It is imperative for survival that these smaller fish

learn to feed on the lake's naturally developing minnows, baitfish, and aquatic insect life. The small fry will remain in the pens for approximately four to five months, being fed several times a day by volunteers from CIFFI and Markley Cove Resort. In this manner, the fry will thrive and grow and gain an understanding of what natural foods they can dine on as well. This knowledge will give them a distinct advantage over the rainbows planted in the lake each spring. Planter fish are fed pellets at hatcheries and, once they enter lakes, have a difficult time finding and feeding on enough food sources to build sufficient fat reserves to make it through the winter months. After 8 plus years of having these pens, these pen-raised fish have grow to a larger size by spring and are able to utilize the lake's huge population of natural food sources better than the smaller planter-sized fish.

Simply put, planter trout have mouths that are too small to attach and swallow the lake's minnows. Biological studies have proven that pen projects work and anticipation is high for a greater number of holdover sized fish in future years. This may offer anglers the trophy-sized trout that once prowled the waters of Berryessa.

The Lake Berryessa Pen Project has been extremely successful and there are no plans to end this great project.