Glass Eels Supplier | Anguilla Rostrata | Elvers for sale | Maine Elvers Supplier |Buy Glass eels in USA | American Elvers | Glass Eels Farm | Glass Eel Farmers Online | Premium Glass Eels
Elvers (Glass Eels) and Their Critical Role in Freshwater Ecosystems
Elvers, or glass eels (measuring between 5.5 to 7.0 cm), play a crucial role in the life cycle of eels, particularly the American eel. These juvenile eels arrive in freshwater during the spring months, with peak migration typically occurring in September and October, although they can be present from July to December depending on environmental conditions. This seasonal arrival is vital for both the elvers themselves and the ecosystems they inhabit.
Migration Patterns of Glass Eels (Elvers)
Glass eels enter freshwater systems in distinct pulses, with their migration patterns strongly influenced by tidal movements. Early in the season, they tend to enter rivers on the incoming (flood) tide, especially during spring tides around the new and full moons. At this stage, glass eels are more attracted to saltwater than freshwater and primarily migrate at night. However, as the season progresses, they begin to shift towards a stronger attraction to freshwater, often migrating on the outgoing tide.
Anguilla Rostrata Glass Eels
Once glass eels reach freshwater, they spend several days adjusting before migrating further upstream. During this phase, elvers demonstrate a strong tendency to swim against currents, making their way upstream both day and night. These migrations often occur in large schools, and this phase is crucial for eel conservation, as glass eels can be captured in large quantities during their movement to the limits of tidal zones before they continue their journey upstream in subsequent seasons.
Climbing Abilities of Juvenile Eels (Elvers)
An interesting feature of juvenile eels and some whitebait species like kōaro is their remarkable climbing ability. In fact, glass eels are known to climb damp, rocky surfaces, such as those found at locations like the Wairua Power Station on the Wairua River in Te Tai Tokerau. This climbing ability can be harnessed to design solutions that help elvers and other fish bypass natural barriers, such as dams and overhanging culverts, promoting their upstream migration.
Elvers’ Strong Olfactory Senses
Elvers have highly developed olfactory (smell) systems, allowing them to respond to various water odors. This sensitivity helps them choose suitable habitats for migration, with different species of glass eels, such as shortfin and longfin, possibly exhibiting different preferences for habitat types. Smaller eels tend to favor riffles and runs in freshwater streams where the substrate is coarse and the current is swift.
Global Decline in Glass Eel Recruitment
Recent studies suggest that the global population of glass eels has been declining in recent years. Several factors are believed to contribute to this troubling trend, including climate change, habitat loss, pollution, parasite infestations, overfishing, and migration barriers such as dams. The declining numbers of elvers pose a serious threat to the overall health of eel populations, making conservation efforts even more critical.
Key Takeaways:
- Elvers (glass eels) are juvenile eels that migrate from the ocean into freshwater systems, with their arrival typically occurring in September to October.
- Their migration patterns are influenced by tidal movements, and they show a preference for freshwater habitats as they move upstream.
- Glass eels possess remarkable climbing abilities, allowing them to navigate obstacles in rivers, which can be used in fish passage solutions.
- The global decline in glass eel populations is a major concern, driven by environmental and human-induced factors, highlighting the need for effective conservation measures.
By understanding the migration behaviors and challenges faced by elvers, we can better protect these vital creatures and ensure the health of freshwater ecosystems for future generations.
