An eel ladder is type of fish ladder designed to help eels swim past barriers, such as dams and weirs or even natural barriers, to reach upriver feeding grounds. (Many eels are catadromous, living in fresh water but spawning at sea.) The basic design of an eel ladder has the eel swim over the barrier using an eel ascending ramp, which provides the eels a climbing substrate to "push against" while slithering upstream. For some higher barriers, elevator-style systems are also used. Pool-and-weir fish ladder at Bonneville Dam on the Columbia River Fishways, most commonly referred to as fish ladders but also known as fish passes, are structures placed on or around man-made barriers (such as dams and weirs) to assist the natural migration of diadromous fishes. ... Families Suborder Anguilloidei Anguillidae (freshwater eels) Heterenchelyidae Moringuidae (worm eels) Xenocongridae (false morays) Muraenidae (moray eels) Myrocongridae Suborder Nemichthyoidei Nemichthyidae (snipe eels) Serrivomeridae (sawtooth snipe eels) Cyemidae (bobtail snipe eels) Suborder Congroidei Congridae (congers) Muraenesocidae (conger pikes) Nettastomatidae (witch eels) Nessorhamphidae (duckbilled eels) Derichthyidae (neck eels) Ophichthidae (snake eels) Macrocephenchelyidae... Scrivener Dam, in Canberra, Australia, was engineered to withstand a once-in-5000-years flood event A dam is a barrier across flowing water that obstructs, directs or retards the flow, often creating a reservoir, lake or impoundment. ... The bridge and weir mechanism at Sturminster Newton on the River Stour, Dorset. ... Many types of fish undertake migrations on a regular basis, on time scales ranging from daily to annual, and with distances ranging from a few meters to thousands of kilometers. ... This article is about biological spawning. ... A modern elevator has buttons to allow passengers to select the desired floor. ...

An eel ladder typically consists of four parts: an eel ascending ramp, a supporting structure, a water-feeding system, and a side gutter. The side gutter provides an attraction flow to draw eels toward the ladder, the water-feeding system ensures the proper flow of water to the gutter and the ramp, and the supporting structure mounts the ladder to the barrier.

The eel ascending ramp can be a fairly simple constructions, such as a hollowed out tree filled with recycled fishing net, or a more complex structure designed to accommodate specific species or ages of eels. For example, the Canadian company Milieu Inc. manufactures eel ascending ramps made of moulded ABS with undulating side walls and staggered studs throughout the length of the ramp. These studs form the substrate the eels push against during the climb over the barrier.   The international symbol for recycling. ... Fishing with a net. ... Monomers in ABS polymer Acrylonitrile butadiene styrene, or ABS, (chemical formula ) is a common thermoplastic used to make light, rigid, molded products such as pipes, golf club heads (used for its good shock absorbance), automotive body parts, enclosures and toys including LEGO bricks. ...

See also

• Fish ladder
• Fish migration
• Eel story

Pool-and-weir fish ladder at Bonneville Dam on the Columbia River Fishways, most commonly referred to as fish ladders but also known as fish passes, are structures placed on or around man-made barriers (such as dams and weirs) to assist the natural migration of diadromous fishes. ... Many types of fish undertake migrations on a regular basis, on time scales ranging from daily to annual, and with distances ranging from a few meters to thousands of kilometers. ... Juvenile eels Leptocephalus larvae of an ocean eel The story of the eel was a mystery for a long time and many questions still remain. ...

External links

• Milieu Inc. eel ladder at the St. Ours Dam (Richelieu River, Québec)
• Fish-Pass sarl eel ladder and elevator systems
• Dwight St. Dam Eelway project (Chicopee River, Massachusetts)