1. Influence of habitat additions on growth, condition, and survival of extensively-reared juvenile muskellunge
Daniel Dembkowski1, Steven Fajfer2, and David Ewald3
1Fish Propagation Science Center, Wisconsin Cooperative Fishery Research Unit, College of Natural Resources, University of Wisconsin-Stevens Point, Stevens Point, WI 54481; 2Wild Rose State Fish
Hatchery, Wisconsin Department of Natural Resources, Wild Rose, WI 54984; 3Fishiding Reclaimed Artificial Fish Habitat, Wonder Lake, IL 60097
INTRODUCTION
• The influence of natural littoral structures such as coarse
woody material on fish populations is well documented.
• In general, coarse woody material and other natural littoral
structures have been associated with increased growth,
survival, and production of a variety of fishes.
• Increased growth, survival, and production are often goals of
fish propagation facilities, but the extensive rearing process
typically occurs in earthen or lined ponds devoid of structure.
• Fish population responses to structural habitat observed in
natural settings have prompted fish propagation facility
managers to consider integration of structural habitat in the
extensive fish rearing process.
• Therefore, our objective was to determine the influence of
structural habitat additions on fish population characteristics
in an extensive fish production setting.
• Specifically, we compared growth, body condition, and
relative survival of age-1 Great Lakes spotted muskellunge
Esox masquinongy between rearing ponds with and without
structural habitat additions.
HABITAT ADDITIONS
• Artificial structures were constructed of reclaimed rigid PVC
cemented into a corrugated plastic base.
• Structures are easily manipulated into a variety of shapes and
can be easily disinfected.
METHODS
• Age-0 Great Lakes spotted muskellunge were transferred
from the Michigan DNR to Wild Rose State Fish Hatchery
(WRFH) in fall 2014.
• Approximately equal numbers of age-0 muskellunge were
stocked into each of four 0.2-ha rearing ponds; two randomly
selected ponds contained habitat additions and two remained
devoid of structure.
• Muskellunge were grouped into ponds according to genetic
relatedness; all ponds were fed at a similar rate and water
quality parameters were measured daily.
• Muskellunge were reared at WRFH until July 2015, at which
point ponds were harvested for stocking into locations around
Green Bay.
• At harvest, all muskellunge were implanted with passive
integrated transponders (PITs) and counted; a random
subsample of 50 fish per pond were measured for total length
(mm) and weight (g).
• Growth was indexed as the mean total length at harvest,
body condition as mean relative condition factor (Kn) at
harvest, and relative survival as the ratio of the number of
age-1 fish at harvest compared to the number of age-0 fish
stocked into each pond.
• Growth, body condition, and relative survival were
qualitatively compared between ponds with and without
habitat additions; a lack of spatial and temporal replicates
precluded more detailed statistical analyses.
RESULTS
• Growth, body condition, and relative survival varied across
rearing ponds and treatments, but were qualitatively greater
in ponds with habitat additions compared to those without.
• Although results are preliminary and represent only a single
year of data collection with limited spatial replication, our
findings suggest a positive influence of habitat additions on
Great Lakes spotted muskellunge growth, body condition,
and relative survival.
• Therefore, the use of artificial structures may be a viable
strategy in terms of meeting goals of increase growth,
survival, and production in a fish propagation context.
• Comparisons of growth, condition, and relative survival
between rearing ponds with and without habitat additions will
continue for several years, eventually enabling more detailed
statistical analyses.
• Additionally, we anticipate obtaining data relative to the
influence of habitat additions on long-term growth and
survival via encounters of PIT-tagged muskellunge from each
treatment in Green Bay.
DISCUSSION
Habitat Bare
Total length 366 mm
(310-412 mm)
355 mm
(304-391 mm)
Relative condition 103
(90-141)
97
(76-120)
Relative survival 78%
(78-79%)
73%
(73-75%)
ACKNOWLEDGMENTS
We thank the staff at Wild Rose State Fish Hatchery, especially Rich Klett and Jake Seifert,
and the Winnebagoland Musky Club. Funds associated with the habitat structures were
provided by the Primising family in memory of WDNR fish biologist Mike Primising.