Lightweight rowers, start adjusting your diet in the fall rather than shocking your body come spring. Eat balanced meals and watch your fat intake. Open weight rowers need to increase your intake of complex carbohydrates. This is doubly important for those tall skinny guys that have difficulty gaining weight. Make sure you are getting enough protein.
Protein builds muscle mass.
During the fall we will be lifting weights extensively. I expect all of my open weights to gain 5-10 of muscle. This will not happen though with a diet low in protein. Try adding a can of tuna a day to your diet. It is cheap.