Flounder are saltwater fish that typically weigh up to 4 pounds for winter flounder--or blackback flounder--and up to 15 pounds for summer flounder, or fluke. You can identify a flounder by its shape (flat) and eyes, both of which are on one side of its head. Because flounder swim in schools or venture off individually at the bottom of the water, it's best to cover more area by fishing different lines (trolling) and changing your location frequently.
A 12-pound test monofilament line is best for shoreline fishing, which is where small flounder generally are found. Water disturbance is less severe near the shoreline, so a 12-pound test monofilament line is sufficient for inshore currents. Use 12-pound test monofilament line only with light tackle. Check the breaking strength of the line if you are uncertain. You can find the breaking strength of the test line on the package.
Boat anglers fishing offshore, but not along extremely strong currents, must use a strong line. A 15-pound monofilament test line is thin enough to go undetected by fish, but strong enough to hold flounder and other large fish that take the bait. Use a clinch knot to tie the line to the eye of the weight.
Thread a standard flounder rig with 30-pound test monofilament leader. A 30-pound test monofilament leader features extreme shock strength, abrasion resistance and the knot strength to hold terminal tackle. Leader is available in wheels and coils. Tie the leader to a trolling sinker and then tie the sinker to the line. A 30-pound test monofilament leader is durable enough for extreme water agitation and is the best line for dragging tackle across the bottom of a lake for flounder. Deep-sea anglers must always use a 30-pound test monofilament line to compensate for the large fish found in deeper waters.