Page 74 - Engineering in Nature

Engineering in Nature

There were two clues. One, the box with a grill lid, opening into
the channel used to empty excess water from the pool, was found bro-
ken. Could the fish have entered the channel in order to return to its
birthplace and then have entered the pool by breaking the metal lid?

It seemed incredible that the salmon could have made the long
journey from the ocean to the pool. Yet there was no other explana-
tion.
In order for the salmon to return to the farm, it must have begun its
journey from the point where Redwood Creek joined the ocean. The
fish would then have to have swum 5 kilometers (3 miles) against the
current before reaching the first fork; then have made the correct
choice and turned north, before coming to a more difficult parting of
the ways. At this point, from the salmon's point of view, there were
two very similar signals. The farm where the salmon was born was lo-

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