The Importance of Pelagic Processes in determining Habitat in the Sea

SeaScape MeetingSandy Hook

March 2, 2012Donald B. Olson

With major input from Jerry Ault, Ashley McCrea-Strub, Jing-Gang Luo, and William Harford

Regional Oceanography

Bathymetry & Currents Sea Surface Temperature1 June 2011

Bottom topography and SST

Retrograde fronts: Density surfaces are perpendicular to the bottom topography

Examples: Mid-Atlantic Bight

Prograde fronts: Density surfaces parallel to bottom topography.

Examples: Gulf Stream along U.S. coast or Kuroshio off China

See Mooers et al. 1978 or Olson 2001

Hudson River Plume Front

Ecosystem organization and fronts:

Olson (2006)

Behavioral concentration in fronts under photo- or geo-taxis. (Olson and Backus, 1985, Olson, 2001, 2007)

Drifter trajectories on Georges Bank

Frontal Sweeping of Fish:

Olson (2007)

• Small boney fish.•Oily•High protein •Detrital diet is rich in terrestrial nutrients

Americas First and Foremost Fishery: Menhaden or Mossbunker• Early visitors to America came for cod; but the

early colonists were not fishermen per see.• Capt. John Smith noted on his first trip to

Virginia that a small fish formed massive shoals in the shallow bays.

• Squanto (Tisquantum) taught the Pilgrims to place these small fish in mounds of corn to act as fertilizer.

The Menhaden Industry

• Early Long Island and New England fishery involved groups of farmers covering their fields with fish.

• In 1850s this gave way to industrial trying and processing oil and meal separately.

• Meal becomes easily shipped fertilizer and later animal feed.

• Oil becomes prime replacement for whale oil following the fall of the whale fishery after the early 1860s.

Conflicts with other resources:

Other species that cross habitats:

Tracing large scale flows using salinity and oxygen isotopes. The water entering high latitudes is lighter, has less O18 and more O16, since the latter evaporates more easily.

Drowned river valleys: Also partially mixed estuaries except at high flow.

Shallow well mixed systems

Conditions in an estuary and the nature of drainage basins.

Olson (2007)

What factors determine the maximum flux, Qr, that a linear riverine plume can take?

What happens if this flux is exceeded?

A succession of river plumes

Gulf Stream

Shortfin mako - Bluefish Interactions in the Western North Atlantic Ocean

• A large fraction (>80%) of mako diet consists of bluefish during part of the year;

• Food web model developed using Ecopath with Ecosim;

• Emphasis on indirect effects of fishing.

Shortfin mako Bluefish

Fishery FisheryIndirect Effects

William Harford

Multispecies Yield Surfaces

• Resource-driven control by bluefish was strongly evident;

• Mako fishery had little effect on bluefish (right), whereas bluefish fishery had notable effect on mako (left);

• Suggestive of competition for shared bluefish prey between mako & fisheries.

Olson (2009)

Model spatial grid resolution:5.5 km x 5.0 km in south5.5 km x 3.8 km in north< 3000 m; 136083 cells

Atlantic Coast Ecosystem Simulation Model

Atlantic Coast Ecosystem Simulation (ACES) Model

McCrea-Strub (2009)

Chlorophyll a

Sea Surface Temperature

Small prey (Spring)< 200 mm

Small prey (Fall)

Prey Abundance

Factors affecting fish “spatial growth rate potential”

Wdt

dWcomponents of “essential habitat”.

max

)(

cos1),(~

)( max

maxt

b etaVX

max

)(

sin1),(~

)( max

maxt

b etaVY

AugustAge 0 Menhaden

AugustAge 4 Menhaden

n

(X,Y)

tX /

tY /

Bluefish

October 1

Transport and Movements of Predator & Prey

April 15

ACES Model simulationsMenhaden Biomass Bluefish Biomass

Warm core ring: Age 2 mos

Olson(2001)

Olson (2001)

Modeling Schooling with turbulence: (Flierl et al., 1999)

Spatial Ecosystem Models to Assess Multispecies Fisheries Risks from Exploitation and Environmental ChangesSpatial Ecosystem Models to Assess Multispecies Fisheries Risks from Exploitation and Environmental Changes

What are the effects of schooling affinities?

• Bakun’s Red fish/Blue fish hypothesis: Obligations to remain in schools shift fish populations towards different geographic locations based on metapopulation density within schools. Selection and genetics?

• The MacCall hypothesis: Fish make use of their ability to migrate as schools to exploit changes in mesoscale habitat linked to larger scale climate variations.

Olson (2009)

Simple Conceptual Model

N1

N2 N3 F

K Olson, Cosner, Cantrell and Hastings (2005)

The process of predation:

• Predator/Prey encounters

• Handling times (satiation included)

• Explicit inclusion of schooling dynamics (Cosner et al., 1999)

McCrea-Strub (2009)

McCrea-Strub (2009)

Olson (2009)

Fisheries yield and yield vs costs

N₂

N₁

Cost

N₂

Olson et al. (In prep)

Summary

• Fisheries habitat is at the highest level set by the physical factors: Climatological postions of front and circulations and their dynamics; seasonal progression of S, T,…

• Trophic interactions between species and the adaptation to each other and the environment.

• The use of habitat by fishermen is a crucial factor in terms of understanding fisheries.