This sequence of three frames of the same fish shows how it can change from largely silver to striped to solid orange-red, a transformation that occurs in a matter of seconds.

They fish by it, because the silver-flicking mackerel come there in dense shoals, feeding on the funeral weeds that hang among the girders.

Bighead and silver carp - both native to Asia - have been migrating toward the lakes since escaping from Deep South fish ponds and sewage treatment plants in the 1970s.