The EA said: “The numbers of new, young eels arriving at our shores are now a tiny percentage of those that arrived in the 1960s and 1970s.”
It added the reasons for the sharp drop in numbers were “unclear but may be due to over-fishing, habitat loss and fragmentation, parasites or climate change”.
Peter Gray, EA fisheries team leader, said: “We are working hard to address the many struggles that eels face and are taking action to safeguard this critically endangered species.
“Over the coming months and years, we will closely monitor the released eels to see how they are surviving and growing. Eventually we want to discover whether this type of management produces more eels going out to sea to breed.”