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Fecundity of Spring‐ and Fall‐Run Steelhead from Two Western Lake Superior Tributaries
Author(s) -
Dubois Robert B.,
Plaster Scott D.,
Rasmussen Paul W.
Publication year - 1989
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1989)118<0311:fosafs>2.3.co;2
Subject(s) - tributary , fecundity , fishery , streams , salmo , shore , rainbow trout , spring (device) , geography , biology , fish <actinopterygii> , population , mechanical engineering , demography , cartography , sociology , engineering , computer network , computer science
We examined the relationship between egg number and body size for 70 steelhead Oncorhynchus mykiss (formerly Salmo gairdneri ) collected during 1985–1987 from the Bois Brule River and Pikes Creek, two Wisconsin tributaries to western Lake Superior. These data were compared with limited historical data from the Bois Brule River and nearby streams along the lakeˈs north shore in Minnesota. Within the Lake Superior basin, steelhead exhibited significant variation of fecundity among spawning runs in different rivers and among years but not between spring and fall (autumn) runs in the Bois Brule River in 1985. Steelhead that spawned in Wisconsin tributaries to Lake Superior during 1985–1987 were significantly more fecund at a given size than were steelhead collected from tributaries along the north shore in Minnesota 20–25 years ago. Steelhead from Wisconsin tributaries produced egg numbers (3,000–6,900/female) similar to numbers (1,200–6,900) produced by Pacific Ocean steelhead in the same size range. Both length and weight of steelhead were strongly correlated with egg number and egg size. Age was not a good predictor of egg number. A common slope of 2.02 adequately fit all available Lake Superior data of length‐fecundity relationships. The fecundity of steelhead for Wisconsin tributaries to Lake Superior can be estimated from the average equation for recent data from the two Wisconsin streams, log 10 y = –1.46 + 1.851og 10 x ( y = egg number; x = total length in millimeters).