Seafloor mapping for fisheries management: MSA requirementsand the NEFMC’s SASI model

Chad DemarestIntegrating Seafloor Mapping & Benthic Ecology Into

Fisheries ManagementPortland, ME

April 15, 2009

Objective

Describe the NEFMC’s use of seafloor maps and benthic ecology in meeting the MSA’s requirements to minimize to the extent practicable the adverse effects of fishing on EFH

The MSA requires FMP’s to:1. Describe and identify essential fish habitat

(EFH) for every fishery

2. Minimize to the extent practicable the adverse impacts of fishing on EFH

3. List the major prey species for the species in the FMU and discuss their location

4. Identify non-fishing activities that may adversely affect EFH

What is EFH?

“The term ‘essential fish habitat’ means those waters and substrate necessary to fish for spawning, breeding, feeding or growth to maturity.”

MSA, 2006

The Final Rule

“Adverse effect means any impact that reduces quality and/or quantity of EFH”

“Councils must act to prevent, mitigate, or minimize any adverse effects from fishing, to the extent practicable, if there is evidence that a fishing activity adversely affects EFH in a manner that is more than minimal and not temporary in nature.”

More Guidelines

“Loss of prey may be an adverse effect on EFH… Therefore, actions that reduce the availability of a major prey species, either through direct harm or capture, or through adverse impacts to the prey species’ habitat that are known to cause a reduction in the population of the prey species, may be considered adverse effects on EFH if such actions reduce the quality of EFH”

And yet more Guidelines

“Adverse effects may include direct or indirect physical, chemical, or biological alterations of the waters or substrate and loss of, or injury to, benthic organisms, prey species and their habitat, and other ecosystem components, if such modifications reduce the quality and/or quantity of EFH.”

“Adverse effects to EFH may result from actions occurring within EFH or outside of EFH and may include site specific or habitat-wide impacts, including individual, cumulative, or synergistic consequences of actions.”

NEFMC Objectives

• Identify all major fishing threats to the EFH of those species managed by the Council

• Identify and implement mechanisms to protect, conserve, and enhance the EFH of those species managed by the Council to the extent practicable.

• Define measurable thresholds for achieving the requirements to minimize adverse impacts to the extent practicable

• Integrate and optimize measures to minimize the adverse impacts to EFH across all Council managed FMPs

The SASI modelSASI (m2) = dt[(2∙wo∙co∙so ) + (2∙wc∙cc∙sc) + (ws∙cs∙ss)]

dt = distance towed in one tow (m) wo = effective width of an otter board (m), which equals otter board length

(m)∙sin (αo), where αo = angle of attack (ranging from 30o to 50 o) co = contact index, otter board so = sensitivity index, otter board wc = effective width of a ground cable (km), which equals ground cable length

(m)∙sin(αc), where αc = angle of attack (ranging from 10o to 20 o) cc = contact index, ground cables sc = sensitivity index, ground cables ws = effective width of sweep (m) cs = contact index, sweep ss = sensitivity index, sweep

Model components

1. Tow distance

2. Effective linear gear width

3. Gear component contact index

4. Gear component sensitivity index

• Tow distance and gear widths are modeled for nine primary gear types based on empirical data (observer, VTR, VMS)

• Contact indices are categorically defined

• Sensitivity indices are calculated as a function of habitat and gear-specific susceptibility and recovery values

Sensitivity is defined here as a combination of the effects of a fishing gear on the functional value provided by a unit of habitat (Susceptibility), and the recovery in functional value that unit of habitat will experience after the gear effect has passed (Recovery)

Sensitivity = ƒ (Susceptibility, Recovery)

where Susceptibility and Recovery are known to vary across:

– Habitats– Energy environments – Fishing gears

Sensitivity indices

1. Habitats Consistent with literature review of fishing gear

impactsSubstrate as primary impact surfaceInferred ‘features’ consistent with underlying

substrates

2. Energy environmentsClassified high or low based on:

• critical shear stress model• depth

3. Fishing gearsGear types and area swept based on spatially-

delineated commercial fisheries data

Assessment matrices

• All cells assessed (hypothetical interactions)

• Susceptibility independent of energy, but recovery not

Habitat component

Gear type

Feature Effects Susceptibility Recovery – high energy

Recovery – low energy

Studies considered

Feature_1 Effects 1 - x 0-3 0-3 0-3 #, #, #...

Feature_2 Effects 1 - x 0-3 0-3 0-3 #, #, #...

Feature_3 Effects 1 - x 0-3 0-3 0-3 #, #, #...

Gear type (9)1

Substrate (5)2

Energy (2)3

Region (2)4

Feature type Feature Gear effects

Susceptibility

Recovery

Studies considered

Geolo

gic

al

Featureless  x, y, z…  0-3  0-3  a, b, c…

Biogenic depressions  x, y, z…  0-3  0-3  a, b, c…

Biogenic burrows  x, y, z…  0-3  0-3  a, b, c…

Special-case biogenic burrows

 x, y, z…  0-3  0-3  a, b, c…

Scattered gravel  x, y, z…  0-3  0-3  a, b, c…

Gravel pavement  x, y, z…  0-3  0-3  a, b, c…

Gravel piles  x, y, z…  0-3  0-3  a, b, c…

Shell debris  x, y, z…  0-3  0-3  a, b, c…

Bio

log

ical

Sponges  x, y, z…  0-3  0-3  a, b, c…

Hydroids  x, y, z…  0-3  0-3  a, b, c…

Anemones  x, y, z…  0-3  0-3  a, b, c…

Anemones, burrowing  x, y, z…  0-3  0-3  a, b, c…

Soft corals and gorgonians  x, y, z…  0-3  0-3  a, b, c…

Sea pens  x, y, z…  0-3  0-3  a, b, c…

Hard corals  x, y, z…  0-3  0-3  a, b, c…

Colonial tube worms  x, y, z…  0-3  0-3  a, b, c…

Amphipods, tube building  x, y, z…  0-3  0-3  a, b, c…

Bivalves  x, y, z…  0-3  0-3  a, b, c…

Bryozoans  x, y, z…  0-3  0-3  a, b, c…

Brachiopods  x, y, z…  0-3  0-3  a, b, c…

Ascidians  x, y, z…  0-3  0-3  a, b, c…

Macroalgae  x, y, z…  0-3  0-3  a, b, c…

Sea grass  x, y, z…  0-3  0-3  a, b, c…

Mapping habitats for SASI

Data sources:

• usSEABED (extracted and parsed)

• SMAST video survey

• NOAA trawl survey hangs (codes 5 & 9)

Substrate class

Substrate subclass

Particle size range (mm)

Corresponding Wentworth class

MudClay-silt

< 0.0039 Clay

0.0039 – 0.0625 Silt

Muddy-sand < 0.0039 - 2 Clay to sand

Sand Sand/sand ripple 0.0625 – 2 Sand

Granule-pebble2-4 Gravel

4 – 64 Pebble

Cobble 64 – 256 Cobble

Boulder > 256 Boulder

Vorinoi tessellations allow the size of the unit area to vary in proportion to the density of data available, producing irregular shaped polygons of varying sizes

Unstructured grid

Area_km

05

101520253035404550556065707580859095

100

1 2,001 4,001 6,001 8,001 10,001 12,001 14,001 16,001 18,001

N 18,355Mean 32.04

Std Deviation 517.21

Quantile Estimate100% Max 43,389.43

99% 267.4895% 54.8690% 25.90

75% Q3 11.7850% Median 7.49

25% Q1 5.2110% 4.00

5% 3.541% 3.12

0% Min 3.00

Energy environments

Environments with different energy characteristics are created by the flow of water over habitats

These energy environments affect the:– nature of fishing gear impacts (i.e. loss of

functional value)– susceptibility of habitats to fishing gears– habitat recovery rates

Parameterization Condition Data source

High energy Low energy

Shear stress The max shear stress magnitude on the bottom in N∙m-2 derived

from the M2 and S2 tidal components only

High = sheer stress 0.194 N∙m-2 (critical sheer stress

sufficient to initiate motion in coarse sand)

Low = sheer stress < 0.194 N∙m-2

Depth Coastal Relief Model depth data High = depths ≤ 20m Low = depths > 20m

Area (km)

ENERGYHighLow 540,320

Area (km)

DOMINANT SUBSTRATE

BoulderCobble 1,489

Gravel 16,896

Mud 315,073

Sand 178,348

Area (km)

DATA SOURCECombined

NOAAHangs 76,150

SMAST 47,223

USSEABED 446,283

18,359

47,694

76,207

Applying the SASI model spatially

The model represents a quality-adjusted area of seabed impacted by NE gears per spatial unit (e.g. tms, 5k grid)

The Sensitivity Index (e.g., So, Sc, Ss) is derived from matrices specific to a combination of gear type / habitat / energy; they apply uniformly across gear components

Groundfish trawl Se

End products

1. Matrices summarizing the hypothetical sensitivity of habitat components to fishing gears

2. Maps depicting the realized vulnerability of habitat area units to fishing gears, as measured by quality-adjusted m2 and summed across all gears fishing in each area

3. Assessment of adverse effects based on pre-determined thresholds

Alternative impacts analysis

Matrices and SASI allow PDT to quantify and visualize changes in quality-adjusted seabed impacts, enabling analysis of:

• Area-based fishing restrictions (mapping hypothetical or re-directed fishing effort)

• Gear modifications (changing SASI contact and sensitivity indices)