Floating mats of seaweed — known in southern California as “kelp paddies” — are havens for offshore game fish. Baitfish use them for cover in vast stretches of open water, and in turn, cruising tuna, yellowtail and dorado stop by for an easy meal. This phenomenon isn’t exclusive to the Pacific. Mats of sargassum are prized by East Coast anglers in search of dolphinfish. Use these three tips to score in offshore weeds.