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?