Frustrating Reporting (or, the Eelevator!)

[makattak]

Press release from Cornell about a project they've been a part of:

http://news.cornell.edu/stories/2017/06/eelevator-project-gives-american-eels-lift

Interesting means of getting natural migrators around man-made blocks (dams).

What is frustrating is this is the only paragraph about what I wanted to know and it fails to address it:

Migrating eels seeking a way above the dam can climb a short ramp lined with old netting and kept wet by hoses from above. These eels – most often about 3 to 6 inches in length and in the “elver” stage of development – enter a bucket of circulating water that is checked twice weekly by volunteers. Sizes are recorded, and the eels are released above the dam to continue their life’s journey.

That's really interesting how it functions, but why do they eels go into the bucket in the first place? It's not like they read a sign that says "Going up?"

Now, apparently it works as they claim to have moved 500K+ eels since they started in 2008, but they are really vague on the how which is the part I'd be interested in. (Not enough to go searching, just enough to complain about it, though.)

[Fly320s]

Speculation:  The eels go up the ladder because of instinct.  Somewhere along that ladder the eels fall into or are trapped by the bucket so they can be counted.

[Pb]

Dams have really damaged aquatic wildlife in my state.