Transcript Will The TMDL Result in Increased Benefits from

Will The TMDL Result in Increased
Benefits from Recreational Fishing?
Doug Lipton
Department of Agricultural & Resource Economics
University of Maryland College Park
EPA Workshop
October 31, 2011
Motivation
• Recreational demand modeling was sophisticated in
developing values for quality (i.e., catch rate) changes, but
naïve in linking these changes to environmental factors
(e.g., including nitrogen directly)
• Spatial ecological modeling, particularly the work of Brandt
et al. utilizing bioenergetic approaches for striped bass
– Spatial temperature-oxygen squeeze in Bay
– Differential impacts of temp/oxygen on predator and prey
locations
• One could take the Chesapeake Bay model run outputs and
assign a probability of catching striped bass based on the
predicted DO, temperature, and location of prey species to
every output cell
Ecosystem States & Recreational Fishing
Water Quality Change
Expected Catch Rate Change
Random Utility Model
Benefit Change
Basic Premise
• Fishermen (correcting for skill – avidity, age, etc.)
would expect (historical catch rate) to catch striped
bass at a certain location during a certain period.
• Through communication among recreational fishermen
(fishing reports, radio communication, tackle shops,
online forums, etc.) they modify those expectations
and travel to different sites. Those modifications to
historical expectations are underlain by unobserved
water quality that change observed catch rates
• Thus fishermen choose to travel to alternative sites
where catch rate expectations are higher (better water
quality)
Expected Catch Rate is a
Function of Ecosystem State
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Variable
Constant
Historic catch rate
LN(Hours)
Years Fished
Days Fished (12)
Surface Temp
Bottom Temp
Surface Oxygen
Bottom Oxygen
Oxygen2
Coefficient
-5.897
0.631
0.344
0.019
0.001
-0.255
0.323
0.259
0.225
-0.017
t-test
-6.592*
11.396*
3.337*
6.073*
1.474
-2.596*
2.838*
4.414*
1.953*
-2.023*
Asset Values From Striped Bass RUM – 5%
Discount Rate
• Total (Access Value) Current
• Increased Catch Rate
• Lower Water Quality (DO)
– <= 5 mg/l
– <= 4 mg/l
– <= 3 mg/l
$1.071 Billion
$81.4 Million
-$ 98.5 Million
-$122.9 Million
-$145.3 Million
Other Issues
• No a priori expectations that water quality would result
in decreased welfare. Could have concentrated fish in
areas closer to where fishermen were located
• For a given population of fish, so didn’t capture stock
dynamics as dealt with in Massey and Newbold for
flounder.
• Focused on striped bass based on Breitburg trawl
survey data linked to oxygen – other species not as
sensitive
• What about Breitburg work suggesting decreasing
fisheries productivity with reduced nutrient loads?
Data Issues
• Assigning anglers from
intercept sites to fishing
location
• Using water quality
station data or
interpolated data (see
Mason M.S. thesis
2008)
Challenges
• Still don’t know where people actually fish
adds error
• DO and temperature move fish around
directly and indirectly – i.e., availability of
prey. Wanted to capture, but lacked spatial
distribution of prey species. Tried using
Chlorophyll a as indicator of abundance of
prey species (e.g., menhaden, bay anchovy,
etc.)
Additional Work with Bricker (NOAA)
on Human Use Indicators of
Eutrophication
• Gulf of Maine
– Exploration of approach to different species,
estuaries
• Barnegat Bay
– Summer flounder
• Mason Thesis
– Interpolated versus point data for water quality
– No difference
Statistical Results of Developing
Eutrophication Indicators (Bricker et al.)