21:02 Sep 11, 2011 

I think I would go for re-stocking generally, , but possibly call it release of eel fry or elvers to avoid too much repetition in a short passage.

Some 40-50 years ago, my husband and his relatives used to fish enthusiastically in the Gudenå and its subsidiaries, and caught a lot of eel. Since then the numbers of fish have dropped dramatically and eel have almost completely disappeared.

Considerable efforts are now being made (as your text perhaps explains) to improve conditions in the rivers and re-establish the fish populations. It is hoped that this will help to save rare species from extinction.

If the plans succeed, the fish and eel will replenish themselves naturally, and repeated releases of fry or restocking will not be necessary.
In the case of eel this depends on a lot of factors beyond the control of the Danish aquaculturalists, but they are making sure that their link in the chain is not the weak one.

15:42 Sep 11, 2011 

I'd use stocking, unless a prior stocking was involved here that went awry. Then it would be restocking, of course. (Not knowing the intricacies of Danish eel management offhand, I'm unclear whether this is a species that is actually stocked regularly.) I know that "release" is used for intentional restoration and/or replenishment as well. But "release" seems inadequate to describe the scope of what's contemplated here. Surely there are expenses reflected here to raise and transport the young'uns before they're dumped into a cold, cruel world to eat or be eaten.