A fishing sinker or knoch is a weight

Weight

In science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:...

 used in conjunction with a fishing lure

Fishing lure

A fishing lure is an object attached to the end of a fishing line which is designed to resemble and move like the prey of a fish. The purpose of the lure is to use movement, vibration, and colour to catch the fish's attention so it bites the hook...

 or hook to increase its rate of sink, anchoring ability, and/or casting distance. Fishing sinkers may be as small as 1/32 of an ounce for applications in shallow water, and even smaller for fly fishing

Fly fishing

Fly fishing is an angling method in which an artificial 'fly' is used to catch fish. The fly is cast using a fly rod, reel, and specialized weighted line. Casting a nearly weightless fly or 'lure' requires casting techniques significantly different from other forms of casting...

 applications, or as large as several pounds or considerably more for deep sea fishing. They are formed into nearly innumerable shapes for diverse fishing applications. Environmental concerns surround the usage of lead

Lead

Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

 and other materials in fishing sinkers.

Types

A large variety of sinkers exist which are used depending on the fish being pursued, the environment, the current and personal preference.

Pyramid sinkers

Pyramid

Pyramid

A pyramid is a structure whose outer surfaces are triangular and converge at a single point. The base of a pyramid can be trilateral, quadrilateral, or any polygon shape, meaning that a pyramid has at least three triangular surfaces...

 sinkers are shaped like a pyramid and are used when it is desirable to anchor on the bottom of water bodies. They are attached to the terminal end of fishing line by loops of brass

Brass

Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...

.

Barrel or egg sinkers

Barrel

Barrel

A barrel or cask is a hollow cylindrical container, traditionally made of vertical wooden staves and bound by wooden or metal hoops. Traditionally, the barrel was a standard size of measure referring to a set capacity or weight of a given commodity. A small barrel is called a keg.For example, a...

 or egg

Oval

An oval is any curve resembling an egg or an ellipse, such as a Cassini oval. The term does not have a precise mathematical definition except in one area oval , but it may also refer to:* A sporting arena of oval shape** a cricket field...

 sinkers are rounded and often bead

Bead

A bead is a small, decorative object that is usually pierced for threading or stringing. Beads range in size from under to over in diameter. A pair of beads made from Nassarius sea snail shells, approximately 100,000 years old, are thought to be the earliest known examples of jewellery. Beadwork...

-like with a narrow hole through which fishing line is threaded. These sinkers are desirable on rock

Rock (geology)

In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

 or debris

Debris

Debris is rubble, wreckage, ruins, litter and discarded garbage/refuse/trash, scattered remains of something destroyed, or, in geology, large rock fragments left by a melting glacier etc. The singular form of debris is debris...

 covered substrates.

Split-shot sinkers

Split-shot

Lead shot

Lead shot is a collective term for small balls of lead. These were the original projectiles for muskets and early rifles, but today lead shot is fired primarily from shotguns. It is also used for a variety of other purposes...

 sinkers are small and round with a split cutting halfway through the sinker. The split can be placed on a piece of fishing line and then crimped closed. This feature makes adding and removing the weights easy and quick.

Bullet sinkers

Bullet sinkers are bullet

Bullet

A bullet is a projectile propelled by a firearm, sling, or air gun. Bullets do not normally contain explosives, but damage the intended target by impact and penetration...

-shaped and used widely in largemouth bass

Largemouth bass

The largemouth bass is a species of black bass in the sunfish family native to North America . It is also known as widemouth bass, bigmouth, black bass, bucketmouth, Potter's fish, Florida bass, Florida largemouth, green bass, green trout, linesides, Oswego bass, southern largemouth...

 fishing for rigging plastic worms "Texas-style"

Texas Rig

The Texas rig is a technique used for fishing with soft plastic lures. It involves a bullet-shaped weight being threaded onto the fishing line first followed by an optional glass or plastic bead, and then the line is secured to a hook, usually an offset worm hook.The hook is then inserted into the...

.

Dipsey

Dipsey sinkers are ovate or egg-shaped and are attached to the fishing line with a loop of brass wire embedded in the sinker.

Bank sinker

Bank sinkers are long and ovate and have a small hole at the top for the fishing line to thread through.

Materials

Today, an ideal material for a fishing sinker is environmentally nontoxic, cheap and dense. Density is desirable as weights must be as small as possible, in order to minimize visual cues which could drive fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 away from a fishing operation.

In ancient times as well as sometimes today, fishing sinkers consisted of materials found ordinarily in the natural environment, such as stones, rocks, or bone. Later, lead became the material of choice for sinkers due to its low cost, ease of production and casting

Casting

In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process...

, chemical inertness (resistance to corrosion), and density

Density

The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...

. However, lead is known to cause lead poisoning

Lead poisoning

Lead poisoning is a medical condition caused by increased levels of the heavy metal lead in the body. Lead interferes with a variety of body processes and is toxic to many organs and tissues including the heart, bones, intestines, kidneys, and reproductive and nervous systems...

 and enter the environment as a result of the inevitable occasional loss of fishing sinkers during routine fishing. Thus, most lead-based fishing sinkers have been outlawed in the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, and some states in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. Lead based fishing sinkers are banned in all of US and Canadian National Parks. These bans have motivated the use of various other materials in sinkers.

Steel

Steel

Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

, brass

Brass

Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...

, and bismuth

Bismuth

Bismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead...

 sinkers have been marketed, but fishermen have not widely adopted them due to their lower density and higher cost compared to lead. Tungsten

Tungsten

Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...

 is now in use, especially among largemouth bass

Largemouth bass

The largemouth bass is a species of black bass in the sunfish family native to North America . It is also known as widemouth bass, bigmouth, black bass, bucketmouth, Potter's fish, Florida bass, Florida largemouth, green bass, green trout, linesides, Oswego bass, southern largemouth...

 fishermen. Although several times costlier than lead, tungsten is just under twice as dense as lead and thus found desirable. The environmental effects of tungsten, however, are essentially unknown. Sandsinker

Sandsinker

Sandsinkers are lead-free fishing sinkers made of fabric and filled with sand. Although they do not cast as easily or as far for surf fishing, they are a healthy alternative to lead for fishing from jetties or any situation where casting distance is not a prime consideration.-External links:*...

s have also been developed, using sand as weight. However, sand has a comparably low density to that of lead and makes a poor replacement.

External links

• Do lead fishing sinkers threaten the environment? (from The Straight Dope)
• Toxic Tackle (article by Aquarium Monsters Australia)
• Let's get the lead out
• Stone plummets discovered in Canada