Post on 12-Jan-2016
Do hypoxia- and temperature-induced changes in habitat use affect fish abundance and quality?
Kevin L. Pangle (Central Michigan University), Paul J. Hurtado (MBI; OSU), Yuan Lou (OSU), Elizabeth A. Marschall (OSU), Daniel K. Rucinski (LimnoTech),
Dmitry Beletsky (University of Michigan), Stuart A. Ludsin (OSU)
GoalExplore the population consequences of
how thermal stratification & hypoxia affect growth & survival of pelagic fishes.
Thermal Stratification
Rabalais, Turner & Wiseman (2002)
creates environmental heterogeneity drives vertical distributions & habitat use.
How?
Thermal stratification hypoxia
Vanderploeg et al (2009)
Temp
DO
ZP
Fish
Nutrients(N, P)
Phytoplankton
Bacteria
Hypoxia
Excess Nutrients Hypoxia
Coutant (1987)
Study System: Lake ErieCanada
USA
Warm epilimnion
West
CentralEast
Cool
Low oxygen
Cool hypolimnion(becomes hypoxic)
Vanderploeg et al (2009)
ZooplanktonBenthic Macroinverts.
Walleye(www.buckeyeangler.com)
PlanktivorousFish
BenthivorousFish
Emerald shiner(www.cnr.vt.edu)
Rainbow smelt(nas.er.usgs.gov)
Yellow Perch(©Shedd Aquarium)
White Perch(www.cnr.vt.edu)
PiscivorousFish
Brandt et al.
Central Lake Erie Food Web
– Direct mortality• Sessile benthic organisms more affected than mobile organisms• Mobile pelagic species can be susceptible
– Sub-lethal effects → more likely for mobile species• Caused by reduced access to optimal temperature, prey or refugia
Atlantic Menhaden(Narragansett Bay)(www.geo.brown.edu)
Gulf Menhaden(N. Gulf of Mexico)
(www.leeric.lsu.edu)
An “island” ofdead menhaden
Hypoxia effects on fish?
Modeling ApproachMechanistic Model: behavior/movement, physiology, ecology.
Growth Survival
Physical Environment(Temperature, Dissolved Oxygen)
Sub-lethal consequences: growth (fish mass; w) Direct consequences: survival (# of fish; N)
Movement
# of fish
Nfish mass
w
Physical Environment (1987-2005)
Rucinski et al, 2010
“Bad”
Annual Variation (1987-2005)
o
Modeling ApproachMechanistic Model: behavior/movement, physiology, ecology.
Growth Survival
Physical Environment(Temperature, Dissolved Oxygen)
Sub-lethal consequences: growth (fish mass; w) Direct consequences: survival (# of fish; N)
Movement
# of fish
Nfish mass
w
Q1
Q2
Q3
Q…
Q24
Movement ModelWater column divided into 24 “patches” each roughly 1 meter deep.
Qi = quality of patch i Ni = # fish in patch i
N1
N2
N3
N…
N24
Leave based on“patch” quality
N1
N2
N3
N…
N24
Redistribute
Movement Rule:Quality = GRP x Survival
Qi = (Gi-Gmin) x (1/μi)
• Predation, low DO, high Temperatures, “other”:
Mortality Rate (μ)
Dissolved Oxygen (ppm) Temperature (⁰C)
General Model
Growth Survival
Physical Environment(Temperature, Dissolved Oxygen)
Movement
# of fish
Nfish mass
w
Cool Warm
Cool Warm
Results: 1987-2005 (Aug-Oct)Population Size
Results: 1987-2005 (Aug-Oct)Growth Rate
Results: 1987-2005 (Aug-Oct)Mortality Rate
1994
Results: 1987-2005 (Aug-Oct)RefugiaLow Mortality High Mortality
Concluding RemarksSummary
Warming and hypoxia negatively impact pelagic fish:↓Survival (direct)↓ growth (indirect)↑ aggregation/density
Model captures key interactions affecting growth & survivalAllows us to quantify contributions from many factorsDirectly explore causal relationshipsApplicable to other species
Concluding RemarksManagement Implications
Meso-scale (~1m) environmental factors may have big effects!Refugia during hypoxic events – hard to measure/predict
Information gaps? Mortality model, movement rules, refugia
Next steps Horizontal movement? Sources of mortality? Fish with other natural histories? Thermal preferences? Feedback via trophic interactions? Disease risk?
Questions?