Ok what about this then.

[Nebe]

Menhaden are essentially filter feeders, straining microscopic plankton, algae etc... when the water cools, less of this microscopic life exists, and the menhaden leave in search of richer waters. Visibility under water off the RI coast in february can be almost 80 feet, but when the water is warmer and full of life, its usually around 20 to 30....