Estimates of entanglement risk for lobster fishing off the coast of Maine Chris Brehme, Keene State...
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Estimates of entanglement risk for lobster fishing off the coast of Maine Chris Brehme, Keene State College Hauke Kite-Powell, Woods Hole Oceanographic
Estimates of entanglement risk for lobster fishing off the
coast of Maine Chris Brehme, Keene State College Hauke Kite-Powell,
Woods Hole Oceanographic Institution Scott Kraus, Kerry Lagueux,
and Brooke Wikgren, New England Aquarium Patrice McCarron and
Heather Tetreault, Maine Lobstermens Association 2013 Northeast
Regional Sea Grant Meeting New Bedford, 19 November 2013
Slide 2
Approach: Estimate the expected number of whale/fishing gear
encounters per year this will depend on: fishing effort vertical
line density trap string configuration whale activity density
behavior (transiting, feeding, etc.) topography water depth bottom
characteristics Consider adjustments to fishing effort (time,
location, gear configuration) to reduce risk.
Slide 3
Vertical Line Risk Probability of whale- line encounter = f
(lines/km 2 whale track/km 2 [whale size] )
Slide 4
Ground Line Risk Probability of whale-line encounter = f (h
line length/km 2 whale track/km 2 [whale size] water depth whale
diving )
Slide 5
Model Polygons and Fishing Zones
Slide 6
Fishing Activity Data 5.9 million VL-months Exempt state: 70.6%
Non-ex. state:22.7% 3-6 miles: 3.2% 6-12 miles: 1.4% 12-40 miles:
2.1%
Slide 7
Fishing Gear in the Water
Slide 8
Whale Activity Data
Slide 9
SPUE from on-effort survey only
Slide 10
Modeled Whale Activity Interpolation approach based on: E.
Bellier and Monestiez P., 2008. Model based block kriging to
estimate spatial abundance of wildlife populations from count data.
In Proceedings of the Eighth International Geostatistics Congress.
Julian Ortiz & Xavier Emery (Eds.). GECAMIN. pp 119-128.
ISBN:978-956-8504-18-2.
Slide 11
Whale Activity
Slide 12
Whale Activity by Zone FTWEs: Dec, Jan:52.5 Feb, Mar: 3.6 Apr,
May: 5.7 Jun, Jul: 9.0 Aug, Sep:16.2 Oct, Nov:28.6 511,500 km whale
track
Sensitivity Analysis Both fishing effort and whale activity
data sets incorporate assumptions Fishing effort: total number of
active traps, and allocation of traps to areas designated by
fishermen as rarely/sometimes/always fished Whale activity: whale
activity level in nearshore waters where there is little systematic
survey work Question: do risk hot spots predicted by the model
depend on these assumptions?
Slide 19
Sensitivity Scenarios: Fishing Effort Five vertical line
models: 5/35/60 allocation of traps to rarely/sometimes/often
fished areas (base case) 0.5/9.5/90 shifts more traps to often
fished 25/35/40 shifts traps to rarely/sometimes fished 5/ +1 conf
is 5/35/60 with more traps active 5/ -1 conf is 5/35/60 with fewer
traps active Moderate uncertainty; +/- 35% (median)
Slide 20
Sensitivity Scenarios: Whale Activity Three whale activity
models: Predicted WA: assumes some degree of whale activity (0.5 x
standard error) in all polygons with at least one sighting (base
case) Low WA: Predicted WA minus 2 x standard error (truncated at
zero); represents lower than predicted nearshore whale activity
High WA: Predicted WA plus 2 x standard error; represents higher
than predicted nearshore whale activity High uncertainty, esp.
inshore; +/- 90% (median)
Slide 21
Sensitivity Analysis: Base case hot spots Base case risk hot
spots (63%): A-3 (Aug, Sep) 32% A-40 (Jun Nov) 8% C-40 (Oct Jan) 9%
D-3 (Jun Sep) 5% F-40 (Nov Jan) 4% G-40 (Dec, Jan) 5% Share of risk
in these hot spots is insensitive to fishing effort assumptions and
Predicted/Low WA But decreases to 30% with High WA
Slide 22
Sensitivity Analysis continued Base case has 50-60% of risk in
state waters (more than half of this in A3 Aug, Sep), and 30% in
12-40 nm. With half of base case near shore whale activity, state
waters risk drops to less than 20%, and 12-40 nm risk rises to 60%.
(Plausible.) With 10% of whale activity in state waters, state
waters risk rises to 90%. (Conceivable but not likely.)
Slide 23
Model Application Examples (Note: Area 1 Maine only) Effect of
Sinking Ground Line (rule in place) NMFS NE Proposal (2011)
Offshore Trawl-up (12-40nm)
Slide 24
Sinking Ground Line (rule in place) 347 avoided
encounters/year; 12% reduction in total pre-rule encounter risk
Risk would rise 14% if all zones went back to floating ground line,
mainly from: A non-exempt (Aug, Sep) A40 (Aug, Sep) C non-exempt
(Jun, Jul) C40 (Dec, Jan) D40 (Dec, Jan) E40 (Nov Jan) F40 (Nov
Jan) G non-exempt (Oct, Nov) G40 (Nov-Jan)
Slide 25
NMFS NE Proposal (2011)
Slide 26
Results: NMFS NE Proposal (2011) expected encounters/year: VL
1,987 (-167) GL 342 total 2,329 7% reduction from baseline ~80% of
this from: C40 (Dec, Jan) D non-ex (Jun Sep) F40 (Nov Jan) G40
(Dec, Jan)
Slide 27
Offshore Trawl-ups Most significant months for 12-40 trawl up
risk reduction: Zone A: Aug, Sep, Oct, Nov Zone B: Oct, Nov Zone C:
Oct, Nov, Dec, Jan Zone D: Dec, Jan Zone E: Dec, Jan Zone F: Nov,
Dec, Jan Zone G: Dec, Jan Risk reduction: from 12% (min 20) to 25%
(min 30) VL-month reduction: from 46,000 (min 20) to 72,000 (min
30) DMR2012: 70,000 NMFS NE: 456,000 (8%)
Slide 28
Summary Highest resolution fishing effort & more complete
representation of Right Whale activity to date Model is operational
(spreadsheet implementation), can easily reflect alternate
management measures and assumptions about fishing & whale
activity Spatial distribution of risk is sensitive to assumptions
about inshore whale activity Assuming inshore activity = 0 is a
sure way to NOT address significant percentage of total risk Risk
is concentrated in temporal/spatial hot spots Danger: blanket
measures that miss hot spots are unlikely to reduce risk
significantly (though they may reduce VLs) Opportunity: targeted
management measures can reduce risk with minimal disruption of
fishing (but may be harder to enforce)
Slide 29
Acknowledgements Collaborators: Chris Brehme, Keene State
College Tara Hetz, WHOI Summer Student Fellow Scott Kraus, New
England Aquarium Kerry Lagueux, New England Aquarium Cris Lutazzi,
WHOI Summer Student Fellow Patrice McCarron, Maine Lobstermens
Association Heather Tetreault, Maine Lobstermens Association Sophia
Weinman, WHOI Guest Student Brooke Wikgren, New England Aquarium
Funding provided by the WHOI and Maine Sea Grant Programs and:
