A fishing line is a cord used or made for fishing. Important parameters of a fishing line are its length, material, and weight (thicker, sturdier lines are more visible to fish). Factors that may determine what line an angler chooses for a given fishing environment include breaking strength, knot strength, UV resistance, castability, limpness, stretch, abrasion resistance, and visibility.

Terminology

Fish are caught with a fishing line by encouraging a fish to bite on a fish hook. A fish hook will pierce the mouthparts of a fish and may be barbed to make escape less likely. Another method is to use a gorge, which is buried in the bait such that it would be swallowed end first. The tightening of the line would fix it cross-wise in the quarry's stomach or gullet and so the capture would be assured.

Fishing with a hook and line is called angling. In addition to the use of the hook and line used to catch a fish, a heavy fish may be landed by using a landing net or a hooked pole called a gaff.

Trolling is a technique in which a fishing lure on a line is drawn through the water. Trolling from a moving boat is a technique of big-game fishing and is used when fishing from boats to catch large open-water species such as tuna and marlin. Trolling is also a freshwater angling technique most often used to catch trout. Trolling is also an effective way to catch northern pike in the great lakes. It's also good for muskellunge in deeper lake using large baits also known as crankbaits or other big baits using strong line. This technique allows anglers to cover a large body of water in a short time.

Long-line fishing is a commercial fishing technique that uses hundreds or even thousands of baited hooks hanging from a single line.

Snagging is a technique where the object is to hook the fish in the body. Generally, a large treble hook with a heavy sinker is cast into a river containing a large amount of fish, such as a Salmon, and is quickly jerked and reeled in. Due to the often illegal nature of this method some practitioners have added methods to disguise the practice, such as adding bait or reducing the jerking motion.

Early developments

Fishing lines were often constructed from horse hair or silk thread, with catgut leaders. From the 1850s, modern industrial machinery was employed to fashion fishing lines in quantity. Most of these lines were made from linen, silk, and more rarely cotton or flax , sometimes with a waterproofing compound added during line manufacture.

Modern lines

Modern fishing lines intended for spinning, spin cast, or bait casting reels are almost entirely made from artificial substances, including nylon, polyethylene, Dacron and Dyneema (UHMWPE). The most common type is monofilament, made of a single strand. Fishermen often use monofilament because of its buoyant characteristics and its ability to stretch under load. Recently, other alternatives to standard nylon monofilament lines have been introduced made of copolymers or fluorocarbon, or a combination of the two materials. Fluorocarbon in particular is well regarded for its refractive index, which is similar to that of water and as a result less visible to fish. Fluorocarbon is also a more dense material, and therefore, is not nearly as buoyant as monofilament. Anglers often utilize fluorocarbon when they need their baits to stay closer to the bottom without the use of heavy sinkers. There are also braided fishing lines, cofilament and thermally fused lines, also known as 'superlines' for their small diameter, lack of stretch, and great strength relative to standard nylon monofilament lines. Both braided and thermally fused 'superlines' are now readily available.