purpose : stocking density, walleye survival, and zooplankton communities at baldhill national fish...
TRANSCRIPT
Purpose:
Stocking Density, Walleye Survival, and Zooplankton Communities at Baldhill National Fish HatcheryAmy Doll 1, Casey Williams 1, Kurt Eversman 2, David Demuth3; 1Department of Science, Valley City State University, Valley City, ND 58072; 2US Fish and Wildlife Service Valley City National Fish Hatchery, Valley City, ND 58072, 3 Great
Plains STEM Education and Research Center, Valley City State University, Valley City, ND 58072
Methods:
Results:
WalleyeFry were stocked in six ponds (Figure 1) at three
stocking rates on June 3, 2013200,000 fish/surface acre (FPSA) – Ponds 2 and 5250,000 fish/surface acre – Ponds 6 and 9300,000 fish/surface acre – Ponds 13 and 14
Harvested between June 24th and June 26thPercent survival of walleye stocking densities were
arcsine transformed and analyzed with 1 Factor Analysis of Variance (ANOVA; α = 0.05). Tukey’s test (α = 0.05) were used for pairwise comparisons.
Ponds were normally fertilized twice a week.Zooplankton
Sampled on Mondays and Thursdays during June.Split into manageable sample size using a Folsom
plankton splitterCounted and identified using a Ward Counting
Wheel. Categorized into five groups: rotifers, cyclopoids,
calanoids, nauplii, and cladocerans
This study was conducted to examine juvenile walleye Sander vitreus fry survivorship at three stocking densities in ponds at Baldhill National Fish Hatchery.
Walleye survival rates were correlated with temporal patterns in zooplankton populations to examine possible interspecific regulation of walleye abundance and survival.
Compared to higher stocking rates, stocking walleye fry at 200,000 fish per surface acre results in the highest survivorship; thus, the lower stocking density should be used to maximize walleye production at Baldhill National Fish Hatchery (Figure 4).
Current fertilization rates appear to promote adequate zooplankton communities to support walleye production at Baldhill National Fish Hatchery.
Figure 3. Temporal plankton density in Baldhill National Fish Hatchery ponds stocked with walleye fry at three stocking densities.Figure 1. Aerial view of Baldhill National Fish Hatchery
1
4
8
12
23
5
9
13
6
15
16
710
1114 17
18
1920
Figure 2. Percent survivorship for three stocking rates of walleye fry at Baldhill National Fish Hatchery. Letter designations (A, B) represent statistical significance (α = 0.05) between stocking rates.
Rotifers
X Data
8 16 53 106 53 99
Den
sity
(#/
Lite
r)
0
100
200
300
400
Cyclopods
X Data
8 16 53 106 53 99
02468
10121416
Calanoids
X Data
8 16 53 106 53 99
0.0
0.5
1.0
1.5
2.0
Cladocerans
Sampling Date
6/3 6/6 6/10 6/13 6/17 6/19
0
5
10
15
Pond 2Pond 5Pond 6Pond 9Pond 13Pond 14
} 200,000 FPSA
} 250,000 FPSA
} 300,000 FPSA
Stocking Rate (#/surface acre in thousands)200 250 300
Per
cent
Sur
vivo
rshi
p (%
)
10
20
30
40
50 A
ABB
Conclusion:
Walleye percent survivorship was significantly higher (P < 0.05) when stocked at 200,000 FPSA (mean = 47.5%, SD =0.7) than 300,000 FPSA (mean = 25.5%, SD =6.4; Figure 2).
Although not statistically significant (P >0.05), walleye survivorship was higher when stocked at 200,000 FPSA than when stocked at 250,000 FPSA (mean = 33%, SD = 1.4).
Similar trends in zooplankton abundance across ponds suggests zooplankton abundance is not a limiting factor between different stocking rates (Figure 3).
Stocking Density (in thousands)
200 250 300
# F
ish
Pro
duce
d (in
tho
usan
ds)
70
80
90
Figure 4. Mean number of fish produced per surface acre for three stocking densities at Baldhill National Fish Hatchery.