Transcript Methods Results Conclusions

Kriging in Linear Systems Population
dynamics and movements of shortnose
sturgeon in the
Ogeechee River, Georgia
Shannon E. Albeke & Daniel J. Farrae
Objectives
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Provide an introduction to Shortnose Sturgeon
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What are the issues with the Ogeechee River
Provide a brief review of Kriging
Why Kriging the Ogeechee seemed like a good idea
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Describe the two tools used to develop matrices
Display the R package…check to see if it is available on CRAN
Display results – I guess that I need to check if the two methods have similar results
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Linear referencing
Using euclidean distance and network distance
Can’t use one point in this case and had to improvise
Talk about the ‘real’ method by Erin Peterson
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Euclidean distance is incorrect
Needed to interpolate to areas beyond the sample extent
Talk about ‘poor-mans’ method
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The river is a continuous surface
How did we deal with temporal variability?
Issues with linear systems
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I need to have this first, talk about life history, mention old and new abundance measures, talk about tagging and telemetry,
then talk about why Ogeechee might suck for SNS because of habitat
Use slide for describing WQ thresholds
Spatially, where do they differ (must check the confluence areas, highest liklihood of bad math
How did this method help to describe the habitat use and availability for SNS
Introduction
Distribution
Introduction
Life History

maximum size ~ 1 m, range-wide

maximum age ~ 20 y in southern rivers

maturation: males 2-3 y, females 4-6 y

males spawn every 1-2 y, females 3-5 y

amphidromous

few studies on southern populations
Introduction
A History of Exploitation

sympatric with larger Atlantic sturgeon

harvested for flesh and caviar

listed as endangered in 1967

stocks remain depressed
Shortnose
Atlantic
Recovery Threats
Introduction

commercial fishery for American shad

anchored gill and drift nets

same that we use to catch sturgeon!

dams: block access to spawning areas

anthropogenic: habitat degradation

increased temperature

decreased dissolved oxygen

saltwater encroachment
Introduction
Ogeechee River

thought to be one of smallest populations

historic estimates
Introduction
Ogeechee River

thought to be one of smallest populations

historic estimates

signs of persistent recruitment failure

lack of juveniles

no direct evidence of spawning
Goals
Why has the Ogeechee River population of
Introduction
shortnose sturgeon not recovered?
1.
Analyze movements relative to habitat
2.
Compare kriging methods for our linear
system
Kriging Overview
Methods
Results
Conclusions
Study Area
Methods
Results
Conclusions
Sampling

daily, 1 June – 31 August 2007-2009

sites chose by random stratified design

anchored gill and trammel nets
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45 – 90 minutes during slack tide

perpendicular to channel
Methods
Results
Conclusions
Biological Data

measured TL (mm)

weighed (g)

PIT tagged

all fish released in good health
Methods
Results
Conclusions
Analysis – Model

closed capture robust design framework
Primary
Periods
(Summers)
Secondary
Periods
(Weeks)
2008
2007
1
2
13
1
2
2009
13
1
2
13
Downriver
(Atlantic Ocean)
Upriver
Fall, Winter, Spring
Results
Conclusions
Robust Design
Methods
Summer
Amphidromous!
Conclusions
Robust Design

Program MARK

data grouped by week

capture/recapture probabilities as constant,
Methods
Results
time-varying, and function of predictor variables

covariates: sampling effort (hrs), mean weekly
T, mean weekly DO
Methods
Results
Conclusions
Robust Design
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candidate set of models
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all combinations, additive and interactive
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exception: T and DO are autocorrelated
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AIC used to evaluate model likelihood

model-averaging used to account for
uncertainty in model selection
Methods
Results
Conclusions
Catch Statistics
Year
Total
Primary Period Unique
Captures Recaptures Individuals Net Hours
CPUE
2007
101
12
89
270
0.374
2008
86
12
61
170
0.506
2009
32
2
18
220
0.145
Results
Conclusions
Models
Model
AICc
AICc
Weight
Model
#
Likelihood Parameters
p=c (T * Effort); γ' = γ" (0)
94.30
0.35
1.0000
44
p=c (DO * Effort); γ' = γ" (0) 94.44
0.32
0.9312
44
p=c (T * Effort); γ' = γ" (.)
95.75
0.17
0.4842
45
p=c (DO * Effort); γ' = γ" (.)
95.96
0.15
0.4356
45
Methods
γ‘ : probability of remaining outside of study area between primary periods
γ“ : probability of migrating outside of study area between primary periods
Methods
Results
Conclusions
Model Estimates
Parameter
Estimate
SE
LCI
UCI
Survival: 2007-2008
0.737
0.328
0.092
0.987
Survival: 2008-2009
0.812
0.443
0.014
0.999
γ' and γ"
0.160
0.275
0.003
0.913
Abundance: 2007
404
117
175
633
Abundance: 2008
264
70
126
402
Abundance: 2009
203
124
32
446
Conclusions
Number Caught
Results
16
14
12
10
8
6
4
2
0
2007
16
14
12
10
8
6
4
2
0
2008
16
14
12
10
8
6
4
2
0
2009
1175
1125
1075
1025
975
925
875
825
775
725
675
625
575
525
450
400
350
Methods
Length - Frequency
Total Length
(mm)
Conclusions
Movements
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Methods
Results
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10 SNS moved from Altamaha to Ogeechee
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all tagged in Altamaha 2004-2006 as juveniles
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recaptured in Ogeechee 2007-2009
2 moved from Ogeechee to Altamaha
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all tagged in Ogeechee 2007
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recaptured in August 2008 and February 2009
Static Abundance
= 95% CI
600
Abundance Estimate
Methods
Results
Conclusions
700
500
400
300
200
100
0
\\
1993
1994
Weber et al.
2000
\\
Fleming et al.
2007
2008
Farrae
2009
Conclusions
Bottleneck?

lack of juveniles

persistent recruitment failure?

Methods
Results

no direct evidence of spawning
but abundance has remained static
Conclusions
Metapopulation

immigration from Altamaha
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Altamaha-Ogeechee shortnose are not
genetically distinct (Wirgin et al. 2005, 2009)
Methods
Results

others have suggested metapopulations
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large, source populations
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smaller, sink populations nearby
Results
Conclusions
Management
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currently based on individual rivers
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shift to discrete population segments
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dependent on genetic/field evidence
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Ogeechee-Altamaha is first to be supported
through both methods
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two systems should be managed as single unit
Methods


other source-sink populations?
but why can’t Ogeechee sustain population?
Chapter 3
Movements of the shortnose
sturgeon relative to habitat
quality of the Ogeechee River,
Georgia

objectives:

evaluate movements of shortnose sturgeon
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evaluate habitat suitability
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compare and contrast
Results
Conclusions
Chapter 3
Methods

fulfills a primary goal of NMFS Recovery Plan
Methods
Results
Conclusions
Movement

18 internal ultrasonic transmitters in adults
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15 males, 3 females
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weekly tracking throughout lower 65 rkm
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placement of CUB at upriver boundary to
monitor movements to potential spawning area
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telemetry: October 2007 – September 2009
Methods
Results
Conclusions
Habitat Quality

standardized and opportunistic sampling
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measured T, DO, salinity
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January 2008 – September 2009
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measured at discrete points
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need to “stretch” data to study area
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used kriging to interpolate values
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data grouped by month
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analysis performed using ArcGIS
Methods
Results
Conclusions
Kriging
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ordinary kriging uses Euclidean distance
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not accurate for river systems
Methods
Results
Conclusions
Kriging
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converted sinuous river to straight line data
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used in-stream distance as Euclidean
replicated points
Methods
Results
Conclusions
Kriging
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ordinary kriging performed to interpolate
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separately for T, DO, and salinity
Methods
Results
Conclusions
Kriging
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for sinuous display, points extracted and
converted to in-stream distances
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segments reclassifed for suitability
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thresholds literature based
Results
Conclusions
Reclassification
Methods

Variable
“Poor = 0”
“Good = 1”
Temperature
> 30 °C
< 30 °C
DO
< 4.0 mg/L
> 4.0 mg/L
Salinity
> 10 ppt
< 10 ppt
value for each variable added for segment

3 = suitable
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2 = marginal
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1 = unsuitable
Methods
Results
Conclusions
Telemetry

all surgeries successful
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492 total relocations

mean: 27 (range 1-56) per sturgeon
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mean T: 21.1 (7.4 – 31.1) °C

mean DO: 6.24 (2.91 – 10.92) mg/L

mean salinity: 1.0 (0.0 – 18.8) ppt

no signs of spawning runs
Methods
Results
Conclusions
Frequency Table
DO
T
Salinity
#
Locations
%
Locations
#
Segments
%
Segments
1
1
1
408
87.37
1848
75.86
0
1
1
32
6.85
146
5.99
1
0
1
24
5.14
34
1.40
1
1
0
3
0.64
369
15.15
1
0
0
0
0.00
22
0.90
0
1
0
0
0.00
16
0.66
0
0
1
0
0.00
1
0.04
Results
Conclusions
Movements

correlated with water quality
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concentrated during summer

limited to ~ 15 rkm at confluence
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intraspecific competition may limit survival

supports habitat “squeeze” theories

supports lab-derived physiological limits
Methods

salinity avoidance
July 2008
January 2009
July 2009
Methods
Results
Conclusions
Habitat Limitation
Does this translate to other systems?
Methods
Results
Conclusions
River Comparison
Altamaha
Ogeechee
Total length (rkm)
> 800
425
Mean discharge (m3/s)
240
59
Tidal freshwater (rkm)
30 – 40
0 – 25
Polyhaline zone (rkm)
0–8
5 – 25
SNS Abundance
~6300
~ 300
Methods
Results
Conclusions
Future

need to replicate on other systems

correlation between habitat availability and
abundance?

methods are effective and easily replicated

could be repeated for other species

results provide basis for better management
Shortnose Sturgeon
Final Conclusions


Ogeechee River is not unique population

lack of juveniles

persistent recruitment failure

poor summer habitat

genetically nondiscrete

immigration from Altamaha River
source-sink metapopulation with Altamaha
Acknowledgements
Advisor: Dr. Doug Peterson
Committee: Drs. Robert Bringolf, Nate Nibbelink
David Higginbotham
Drs. Cecil Jennings, Jim Peterson
Shannon Albeke
Joel Fleming
Technicians
Fellow students
Richmond Hill Fish Hatchery
PLEASE DON’T SQUEEZE STURGEON