Reproductive timing and use of redd sites by lake-spawning brook trout (Salvelinus fontinalis)

We provide a detailed description of a salmonine mating system based on daily observations of tagged individuals in a lake-spawning population of brook trout (Salvelinus fontinalis) throughout two breeding seasons. Actual spawning occurred over a period of similar to 50 d. Over 90% of spawning males were present soon after spawning commenced and outnumbered females for the duration of the spawning period. The amount of time males and females remained on the spawning grounds increased with body size; however, males were present over a longer period than females of equivalent size. A distinct seasonal peak in spawning activity (similar to 15 d) accounted for 58 and 84% (1994 and 1995) of all reproduction and was coincident with a decline in water temperature below 11 degrees C and increased rainfall. Selection of redd sites by female brook trout was determined by groundwater flow which was significantly greater than at nonspawning sites. A preference for certain redd sites was observed, with 50% of spawnings occurring at 11 sites. The construction of multiple redds and duration in spawning activity by females increased with body size. Extensive reuse of redd sites and rapid replacement of females during removal experiments indicate that redd sites are a limiting resource.