Long-term shifts in faunal assemblages in Eastern North

America

Introduction to the ERF Special Session SCI 050

Chairs: Rodney Rountree (Marine Technology and Ecology Applications, Inc.)

Francis Juanes (Dept. Natural Resources Conservation, UMass Amherst)

Long-term Shifts in Faunal Assemblages in Narragansett

Bay, Rhode Island

With Joachim Gröger, Institute for Sea Fisheries, Hamburg, Germany

Analysis Based on RIDEM Seasonal Trawl Survey

MassachusettsRhodeIs.

<20 ft

>20 ft

1300 tows 1979-2001

20 minutes at 2.5 knots

Two depth strata

effort proportional to strata area

Benthic fishesPelagic fishes

79-8384-88

94-98 89-93

99-01

72%

15%

Assemblage shift in Narragansett Bay

Narragansett Bay Trend Suggests Eutrophication Effects

But….

… Similar Shifts have been observed on Georges Bank and attributed to fishing effects

M. Fogarty, NMFS, NEFSC

1963 1967 1971 1975 1979 1983 1987 1991 1995 1999 2003

Year

0

20

40

60

80

100

120

140

Bio

ma

s s I

nd

ex

(kg

/to

w)

0

2

4

6

8

10

12

Pelagic B

iomass (M

illion MT

)

other

groundfish

pelagic

elasmobranch

Shift between benthic and pelagic mid-1980’s

Possible causes of observed assemblage shift

1) Regional warming and the invasion of warm water fishes such as scup

2) The release of limited food resources to transient species due to the decline of winter flounder

3) Overfishing of key species

4) Eutrophication

5) Habitat loss

6) Other human impacts (local and regional)

7) “Natural” cycles

0.0

25.0

50.0

75.0

100.0

1 2 3 4 5

Normalized Mean CPUE in Narragansett Bay

Urophycis chuss

Declining

Urophycis regia

IncreasingNo change

Raja spp.

79

16

0

4

8

12

16

No change Decline Increase

Number of species exhibiting significant temporal changes

Can’t see the forest for the trees

So look at how similar trees cluster together.

Cold water benthic –scavenger?

Pelagic - planktivores

increasing

Piscivores (benthic and pelagic)or warmwater demersal

Increasing/no change

Benthic feeding fishes – warm and cold decreasing

Species type category

Species

Percent hauls Habitat Temp Exploited Feeding Spawning

Linear trend

P. americanus 84 benthic coldwater over benthic estuarine decline

S. aquosus 62 benthic temperate non benthic shelf decline

S. chrysops 49 demersal warmwater over benthic shelf increase

L. pealeii 48 pelagic temperate over zoo-plankton

shelf increase

H. americanus 48 benthic coldwater over benthic shelf increase

M. canis 5 benthic temperate non benthic estuarine none

Characterize 32 species type and annual trend

Ben

thic

Pis

civo

re

Zoop

lank

ton

DeclineIncrease

NC

0102030405060708090

Comparison of Temporal Trend by Food Type

Planktivores - tend to increase

Benthic feeders - tend to decline

Piscivores - increase or decline

Co

ld

Te

mp

era

te

Wa

rm

DeclineIncrease

NC

0

10

20

30

40

50

60

Comparison of Temporal Trends by Temperature Preference

Cold water fish – tend to decline

Warm water fish – increase or decline

Ben

thic

Dem

ersa

l

Pel

agic

DeclineIncrease

NC

01020

304050

60

70

80

Comparison of Temporal Trend by Habitat Preference

Benthic fish – tend to decline

Demersal – no change or decline

Pelagic – tend to increase

-0.6

-0.6

0.6

0.60.4

0.4

-0.4

-0.4

0.2

0.2

-0.2

-0.2

0.0

0.0 Decline

Increase

No change

Freshwater spawner

Estuarine spawner

Shelf spawner

Under exploited

Over exploited

Demersal habitat

Pelagic habitat

Benthic habitat

Temperate

Warm water

Coldwater

Piscivore

Zooplanktivore

Benthic feeder

ConclusionsMultivariate analysis of Narragansett Bay fish community change suggests:

Strongest patterns are related to trophic source

- fishes depending on benthos for food are most likely to decline

- fishes depending on plankton for food, or piscivores indirectly depending on plankton, tend to increase

Secondarily, estuarine spawning fishes tend to decline, while freshwater or shelf spawners are increasing or not changing

Thirdly, cold (northern) water fish tend to decline, while southern fish tend to increase

Benoit and Swain. Gulf of St. Lawrence (Fish & Inverts)

Able and Sullivan. Little Egg Inlet, NJ (Ichthyoplankton)

Allen, Ogburn-Mathews and Tracy. North Inlet, SC (Zooplankton and nekton)

Mitchell, Buckel, Taylor, Bathand Shertzer. Beaufort Inlet, NC (Ichthyoplankton)

Keenan, Matheson, Switzer,Greenwood and McMichael. Tampa Bay, FL (Nekton)

Broad-scale Studies:

Hale. Coastal Delaware to Maine. (Benthic Inverts) *poster

Chmura, Van Guelpen and Pohle. Coastal marine Florida to Canada (Modeling)

Four Southern New England Studies:

Rountree and Juanes. Narragansett Bay (Fish)

Lynch and Lee. (poster) Narragansett Bay (Fish)

Danila and Landers. Millstone, Long Island Sound (Fish & inverts)

Whitlatch and Osman. Southern New England. (Benthic inverts)

O’Connor and Juanes. Hudson River (Fish) *Student

Chant. New York Bight (Oceanography)

Five Chesapeake Studies:

Ruck*, Kraus, Chris and Kelso. Potomac River. (Fish) *StudentAguilar, Hines, Kramer and Goodison. Rhode River, Upper Ches. (Fish)Wingate and Secor. Mesohaline Ches. (Fish) *PosterBreitburg and Cottingham. Chesapeake Bay. (Stressors)Kimmel and Newell. Ches. Bay. (Oysters) *Poster

Can we use similar methods to compare temporal patterns among a wide range of geographic areas and taxa to determine the most likely major causes of observed assemblage shifts?

Acknowledgements

Woods Hole Sea Grant College Program for travel support

Thank you!

Http://www.fishecology.org

Spatial ComparisonMassachusettsRhode

Is. Mt. Hope Bay

31

2

45

6

7

8

9

3

1

2

4

5

6

7

8

9

Mt. Hope Bay

Greenwich BayUpper Narragansett

Middle West PassageMiddle East PassageUpper SakonnetWest PassageEast PassageLower Sakonnet

0

0.5

1

1.5

No change trend

Mustelus canis

050

100150200250300350

Increasing trend

Peprilus triacanthus

0

40

80

120

160

Decreasing trend

Pseudopleuronectes americanus