Citizen Science for the Critically Endangered


The critically endangered european eel, Anguilla anguilla, is a mysterious animal whose life history is of great curiosity. Larvae are spawned in the Sargasso Sea, particular for it’s clear calm waters, before drifting towards Europe. Across the course they develop into glass eels approximately 7cm long, entering river estuaries.

U.S. Fish and Wildlife Service

U.S. Fish and Wildlife Service

Strong enough to battle upstream, the eels then develop into elvers, resembling small adults, approximately 14cm long. Up to 20 years later in the fresh water, eels sexually mature into silver eels, before beginning the long migration back to the Sargasso Sea.

During the commute upstream, the eels meet barriers in the river system, imposed by anthropogenic intervention, preventing eels reaching mating grounds. River weirs, dams, and other blockages are all examples of these.

Citizen science projects, charities, and NGOs have been coming together to assist the eel migration over recent years. Groups are setting up eel traps to enable young glass eels to swim up stream. A small ramp enables the eels to climb into a temporary holding box, where they may be measured and weighed for monitoring purposes, before being released upstream to continue their migration unabated.

Eel trap

Eel trap

Releasing elvers upstream

Releasing elvers upstream

Sadly, the eels are subject to a number of threats besides these river boundaries, including overfishing, parasites, and pollution. ‘Jellied eel’ remains a British delicacy, whilst fishermen are catching young eels to use as bait for bigger fish. Eels are also sold internationally, with high demands from countries such as China.

By JanesDaddy (Ensglish User) (English Wikipedia - [1]) [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC-BY-SA-2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/2.5-2.0-1.0)], via Wikimedia Commons

By JanesDaddy (Ensglish User) (English Wikipedia – [1]) [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC-BY-SA-2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/2.5-2.0-1.0)%5D, via Wikimedia Commons

The complex understudied life history of the eel complicates conservation efforts and remains a limiting factor in the long term improvement of population numbers. It is hoped that efforts to ease migration routes will assure a future for the European eel. Although this year has experienced an unexpected increase in migrating glass eels, it is thought this is an anomalous result caused by changing currents.Perhaps increasing demand for sustainable energy sources, such as hydroelectric plants, may prohibit progress; interrupting river ecosystems may have additional knock on effects.

 

 

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