Embryo Survival, Substrate Composition, and Dissolved Oxygen in Redds of Wild Brook Trout
File(s)
Date
1981-06Author
Hollender, Bruce A.
Publisher
University of Wisconsin-Stevens Point, College of Natural Resources
Metadata
Show full item recordAbstract
Survival of brook trout (Salvelinus fontinalis) embryos and alevins
in redds and factors affecting their survival were studied in two undisturbed
headwater streams, supporting natural reproduction of brook trout,
on Pennsylvania's Allegheny Plateau. Both study streams supported
relatively high numbers of trout but average size of trout was small.
Estimated population was 6,067 fish/hectare and 58 kg/hectare in one
stream and 4,507 fish/hectare and 60 kg/hectare in the other.
Redds were often located immediately upstream of a small pool or a
buried log. Egg pockets were about 5-10 cm below the gravel surface and
were sometimes located in a gap between two large stones. Diameter of
wild brook trout eggs averaged 4.6 mm. Mean intragravel dissolved oxygen
concentration in 36 redds ranged from 3.7 to 10.5 mg/liter but usually
exceeded 6 mg/liter. Intragravel and surface water temperatures were
similar. Geometric mean particle size of redds ranged from 0.6-mm coarse
sand to 14.2-mm gravel with a grand average of 3.3 mm.
Estimates of survival to eyed egg, corrected for decay and loss of
dead embryos, ranged from 0 to 100% and averaged 69%. Survival was
related directly to mean dissolved oxygen concentration and inversely to
substrate particle size. Based on the total number of eyed embryos
recovered and the estimated number of eggs deposited in redds, survival
to eyed egg was 39%. Emergence success from 10 artificial redds stocked
with eyed eggs averaged 34% and ranged from 5 to 92%. Fry began emerging
in February but peak emergence was in March and early April. Emergent
fry averaged 22.5 mm long and 0.067 g in weight. In both streams,
estimated egg deposition was about 53,000 eggs/hectare and an average
of 1,593 young-of-the-year/hectare were present. Thus, survival from
egg deposition to fall fingerling was approximately 3%. Survival from
egg deposition to emergence was estimated to be 23%. Survival in redds
was apparently adequate to sustain these brook trout populations at
relatively high densities.