Bighorn River Float 2001 Environmental Studies – John Miller Bio II – George Grover

What is a redd? When the female trout finds a spawning site, she builds the nest, or “redd”. The gravel and stones that will hold the eggs must be rather large – one to 10 inches in diameter, the water must be between 40 and 55 o, and there must be an upwelling of ground water directly beneath the nest or a current.

She nestles against the stream bed and anchors herself with her caudal fin. She swishes back and forth wildly so that her movements create a shallow in the gravel and stir up a cloud of debris. The particles of sediment, organic matter and insects get swept away by the current. A clean nest enables oxygenated water to bathe the eggs after spawning.

The spawn is complete when the female releases her eggs and the male discharges a dose of milt (sperm). The female completes the redd by using her fins to shovel a load of clean gravel atop the fertilized eggs.

Educational activities: Students sampled water temperature several times during the day and made field notes on the aquatic activity. Macro-invertebrates were collected from kick nets and saved for lab work in the classroom.

Sketching and painting materials were provided for those wanting to record artistic impressions. Bird identification was made from field notes. Underwater camera and digital camera provided photographs. Redds and fisherman proximity were counted.

Information collected from the Bighorn River float is being used by Environmental Studies students to create educational posters about the redds for the Montana Department of Fish Wildlife and Parks.