Transcript Abiotic factors and fish

Environmental Factors and Fish Ecology
Environmental factors
affecting organisms and
local assemblages
•Many factors
•High complexity
•Abiotic
•Large, long
•Geological strata
•Climate change
•Small, short
•Micro-hydraulics
•Temperature
•Biotic
•Competition
•Predation
From Matthews 1998
Important Abiotic Environmental Variables
Affecting Organisms in Streams
•
•
•
•
Current velocity/Discharge
Substrate
Temperature
Dissolved oxygen
Relationships between
environmental
variables can be very
important
Organism Adaptations to Flow
• Streamlined shape
– Fusiform shape
– Reduced fins and fin
location
• Suckers
• Benthic habit
– Enlarged pectoral fins
– Dorsal eyes
– Loss of swim bladder
Effect of Current Velocity and Discharge on
Substrate
Effect of Current Velocity on Fish
• Position maintenance
– Swimming ability
• Species, size, life stage
– Energy use
• Food availability
– Drift feeders
• Bioenergetically
– Cost/benefit relationship
Hill and Grossman 1993
Effect of Substrate on Current Velocity and Flow
• Eddies
• Wake interference
• Quasi-smooth flow
Boston Mountains
•Higher gradient
•Bedrock-cobble
•High flow variation
Ozark Highlands
•Lower gradient
•Cobble-gravel
•Spring influence
Research Questions
• Does fish morphology predict fish swimming ability
and refuge use?
Five Common Arkansas Stream Fish
Central stoneroller
Campostoma anomalum
Cardinal shiner
Notropis cardinalis
Orangethroat darter
Etheostoma spectabile
Green sunfish
Lepomis cyanellus
Longear sunfish
Lepomis megalotis
Pictures by W. N. Roston, from ‘Fishes of Arkansas’
Two substrate types:
1. Complex (w/ rocks)
2. Smooth plexiglas
Velocity increased by
10 cm/s every 15 min
until fish exhaustion
Results
Mean CSS in cm/sec (SE)
Low complexity
High complexity
Central stoneroller
35.51 (2.52)
37.40 (8.40)
Cardinal shiner
31.70 (2.38)
26.48 (4.59)
Orangethroat darter
22.49 (3.02)
17.25 (4.49)
Longear sunfish
14.40 (0.18)
15.74 (3.67)
Green sunfish
13.89 (0.59)
11.41 (5.77)
Relative Velocity
Low complexity
Low complexity
Half-CSS speed
CSS speed
1.4
1.4
1.2
1
1.2
1
0.8
0.6
0.8
0.6
0.4
0.2
0
0.4
0.2
0
CDS CSR
GSF
LES
OTD
1.4
1.4
1.2
1
1.2
1
0.8
0.6
0.4
0.2
0
0.8
0.6
0.4
0.2
0
CDS CSR
GSF
LES
OTD
CDS CSR
GSF
LES
OTD
CDS CSR
GSF
LES
OTD
High complexity
High complexity
Half-CSS speed
CSS speed
• Mean, max and min
temps.
– Survival
– Growth
– Reproduction
• Cumulative temperature
–
–
–
–
–
Degree-days
Latitude
Stream size
Groundwater influence
Elevation
Temperature
Effect of Temperature on Egg Hatching
Temp and DO in Lakes and Rivers
Allan 1995
Organisms Vary With Abiotic Variables
Longitudinal pattern in streams
• Rivers generally increase in size as one proceeds
downstream
– Velocity (U) varies with gradient, depth, and substrate texture
• Average velocity usually increases downstream!
– Gradient decreases, but depth increases and friction
decreases
Gradient
Fish species and
numbers are
related to these
changes in
stream abiotic
variables.
Depth
Velocity
Friction
Distance from headwater
Size (Spatial and Temporal Scale) Matters
• Relationship between
environmental variables
and organisms is scale
dependent
Questions
• How do crayfish species-environmental
relationships change with spatial scale?
• How do lotic crayfish species relationships
change with spatial scale?
Study Design
• Balanced,
hierarchical
design.
• Replicate units
contained within
a particular
level.
• Each level
represents a
different level
Sub-wat ershed
n=7
St ream
n=21
St ream Sect ion
n=6 3
Run
n=18 9
Sample
n=56 7
Study Site
• Drainage area of
3, 926 km2
• Streams 2nd or 3rd
order.
• Stream sections at least
500 m apart defined as
3 consecutive runs
separated by riffle or
pool habitats.
Spring River
Watershed
Field Methods
• Measurements of substrate composition, stream
width, current velocity, and depth measured at
each sample location.
• Water temperature, pH, and conductivity
measured in each stream section.
• Crayfish collected identified to species, sexed,
and carapace length measured.
Contribution to Species-Environment Relationships
Effect
Variance
%explained
Sub-watershed
0.033
27.0
Stream
0.029
23.8
Stream section
0.026
21.3
Run
0.018
14.8
Sample
0.016
13.1
TSS
0.122
Importance of Environmental Variables with Scale
Variable
Watershed
Stream
**
**
**
**
**
**
*
N. S.
N. S.
N. S.
N. S.
**
N. S.
N. S.
N. S.
*
**
N. S.
**
N. S.
N. S.
N. S.
%Cobble
Depth
%Pebble
Conductivity
Temperature
Width
pH
%Gravel
%Boulder
Velocity
%Bedrock
** < 0.005
* < 0.05
S. = Not Significant
Stream
Section
*
*
N. S.
N. S.
N. S.
N. S.
N. S.
**
N. S.
N. S.
N. S.
N.
Contribution to Crayfish Species Relationships
Effect
Sub-watershed
Stream
Stream section
Run
Sample (RSS)
TSS
SS %variance
explained
0.189
0.123
0.158
0.195
0.335
1.00
18.9
12.3
15.8
19.5
33.5
F
p
21.7
6.95
3.59
1.74
-
0.002
0.002
0.002
0.005
-
Conclusions
• Importance of environmental variables differed among
levels of scale.
• Largest scale (sub-watersheds) explained most variation
in species-environmental relationships (27.0%) and this
decreased with decreasing spatial scale.
• Greatest amount of variation in crayfish species
relationships explained (33.5%) attributed to differences
at the microhabitat (sample) level.