How has trawling activity affected habitat How has trawling activity affected habitat and associated communities and associated communities

of the Norway lobster (of the Norway lobster (Nephrops norvegicusNephrops norvegicus) fisheries ) fisheries of the North Bay of of the North Bay of Biscay, NE Atlantic?Biscay, NE Atlantic?

François Le Loc’h1,2 & Christian Hily2

1 1 UR 070 RAP, Institut de Recherche pour le DUR 070 RAP, Institut de Recherche pour le DééveloppementveloppementCentre de Recherche Halieutique MCentre de Recherche Halieutique Mééditerranditerranééenne et Tropicale, SETE enne et Tropicale, SETE -- FRANCEFRANCE

22 UMR 6539 CNRS UMR 6539 CNRS –– LEMAR, Institut Universitaire EuropLEMAR, Institut Universitaire Europééen de la Meren de la MerUniversitUniversitéé de Bretagne Occidentale, BREST de Bretagne Occidentale, BREST -- FRANCEFRANCE

UR 070 RAPUR 070 RAP

8th International Conference on Shellfish Restoration

“Enhancement and sustainability of shellfish resources”

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How has trawling activity affected habitat and associated benthic communities of Norway lobster fisheries?

Trawling is one of the main disturbance sources

for the benthic communities on the continental shelf

Bay of Biscay Nephrops fishery = Grande Vasière (mud bank)

Marine ecosystems undergo important disturbances

How has trawling activity affected How has trawling activity affected

habitat and associated communities habitat and associated communities

of the Norway lobster fishery of the Bay of Biscay?of the Norway lobster fishery of the Bay of Biscay?

- 234 trawlers

- landings 3900 t/year

- 33.106 €/year- Each m² of the Grande Vasière is

trawled in average 6 time/year(Bourillet et al., 2005)

⇒ since the sixty’s no study has focused on

these benthic communities (Glémarec, 1969)

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Hamon grab(macrofauna)

2-m beam trawl(epifauna)

How has trawling activity affected habitat and associated benthic communities of Norway lobster fisheries?

AA1

AA2

AA3B2

B3

CC1

C1

C3

DD1

D1

D2E1

E2

E3

G3

G1G2

Stress 0,001

Multi-Dimensional Scaling

Species composition

Pure mudCirratulus filiformisNinoe armoricanaMicrospio cirriferaHyala vitrea

Biogenic medium sandDitrupa arietinaAponuphis bilineataAmpharete grubeiAmpelisca spinipes

Muddy sandTerebellides stroemiDasybranchus gajolaeCallianassa subterraneaNephtys caecaGlycera rouxiiAmpharete grubeiLumbrineris impatiens

Sampling strategy

Grande Vasière = Nephrops fishery

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Can we detect a fishing impact on the benthic communities of the Grande Vasière?

How has trawling activity affected habitat and associated benthic communities of Norway lobster fisheries?

Fishing efforts map

=> Comparison of the Terebellides muddy sand

community stations of the

central Grande Vasière

ACBD

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How has trawling activity affected habitat and associated benthic communities of Norway lobster fisheries?

ABC method (Abundance/Biomass Comparison)

When the cumulative percentage biomass curve is under the cumulative percentage abundance curve it reveals a disturbance

(Warwick et al., 1987)

Biomasse

Abondance

no disturbed

0

20

40

60

80

100

1 10 100log rank

Cum

ula

tive P

erc

enta

ge (%

)

low number of big species

0

20

40

60

80

100

1 10 100log rank

Cum

ula

tive P

erc

enta

ge (%

)

disturbed

high number of small species

Epifauna appears disturbed in the more trawled area

0

20

40

60

80

100

1 10 100log rank

Cum

ula

tive p

erc

enta

ge (%

)

0

20

40

60

80

100

1 10 100log rank

Cu

mu

lati

ve

pe

rce

nta

ge

(%

)

Endofauna

Area A

Area D

0

20

40

60

80

100

1 10 100

log rank

Cu

mu

lati

ve p

erc

en

tag

e

(%)

0

20

40

60

80

100

1 10 100

log rank

Cu

mu

lati

ve p

erc

en

tag

e

(%)

Epifauna

Area A

Area DDo not

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Epifauna taxonomic composition

Biological indicators

Eumala

costracea

25%

Polyplacophora

1%Scaphopoda

1%

Hexacorallia

4%

Ascidiacea

2%

Gastropoda

21%

Pelecypoda

28%

Polychaeta

2%

Crinoidea

1%Holothurioidea

2%Echinoidea

2%Ophiuroides

5%Astroidea

6%

05

10152025303540

A-C B-D

Epifauna species richness

050

100150200250300350400450

A-C B-D

Epifauna abundance (n.1000 m-2)

Molluscs = 50%Crustaceans = 25%Echinoderms = 17%

How has trawling activity affected habitat and associated benthic communities of Norway lobster fisheries?

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How has trawling activity affected habitat and associated benthic communities of Norway lobster fisheries?

0,00

0,02

0,04

0,06

0,08

0,10

0,12

A-C B-D

Ratio sessile/mobile epifauna (abundance)

Ophiura texturata

E.Svensen

Pennatula phosphorea

Ratio carnivorous/primary consumers (biomass)

0

5

10

15

20

25

30

A-C B-DPagurus pridauxii

Leptometra celtica

Biological indicators

0

10

20

30

40

50

60

70

80

90

100

A-C B-D

Very fragile

Fragile

Sensitive

Opportunistic

Indifferent

Bottom trawling sensitivity index of epifauna (abundance) Trawling impactsTrawling impacts

on the organismson the organisms

Very fragileVery fragile

FragileFragile

SensitiveSensitive

IndifferentIndifferent

OpportunisticOpportunistic

Damaged, no survivalDamaged, no survival

Damaged, possible survivalDamaged, possible survival

facilitated predation facilitated predation

Few damagedFew damaged

facilitated predationfacilitated predation

Escape or resistantEscape or resistant

no damagedno damaged

Few or no damagedFew or no damaged

indirect beneficial effectsindirect beneficial effectsDo n

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out a

uthor

autho

rizati

on

How has trawling activity affected habitat and associated benthic communities of Norway lobster fisheries?

What about the evolution during the last 40 years ?What about the evolution during the last 40 years ?

We sampled the same stations as Glémarec in 1966 (54 stations)

using the same methodology (Rallier du Baty drag + fall sampling)

Few change on the external marginSediment became less muddy on the Grande Vasière

=> Homogenization (Muddy sand)

Sediment type has changed for 78% stations

•••• Sampling station

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How has trawling activity affected habitat and associated benthic communities of Norway lobster fisheries?

0

10

20

30

40

50

60

70

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41

Number of stations

Specie

s n

um

ber

1966

2001/2002

“Rare” species (40%)

Species occurrences

223 species for the 2 periods

82

(36%)shared

77

(35%) found only in 2001

64 (29%)found only in 1966

� Total 223 species

only 82 species shared

���� Homogenization

���� Species richness :144 identified species in 1966163 identified species in 2002

N. britannica T. stroemi

L. impatiens

G. rouxii

T. stroemi

G. rouxiiDo not

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20021966Benthic communities map established with 1966 data

Benthic communities map established with 2002 data

How has trawling activity affected habitat and associated benthic communities of Norway lobster fisheries?

Benthic communities evolution

Changes in species compositions and occurrences, associated with sediment type modifications have lead to modifications within the bio-sedimentary communities

The major species remain

⇒ Communities

But the leading species

have changed

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Current benthic communities spatial variability

- No clear disturbance trends of the endofauna communities (less sensitive)

- Disturbance of the epifauna communities :

• less sessile and fragile species

• more carnivorous and scavengers species

Long term evolution

- Communities changes on the Nephrops fishery (Grande Vasière)

=> Trawling disturbance (direct impacts : physical destruction,

indirect impacts : modification of the trophic interactions)

- Sedimentary changes (less fine fraction) : fine erosion

=> Climatic forcing (storms, sedimentary movements)

=> Fishing impact (re-suspension by bottom trawling)

- Community stability : Hyalinoecia/Ditrupa sand on the external margin

=> Natural population dynamics

=> Trawling impacts (physical damaged and discards : facilitated predation)

Conclusion

How has trawling activity affected habitat and associated benthic communities of Norway lobster fisheries?

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The Bay of Biscay Nephrops fishery have undergone changes during the past decades (habitat and community)

partly due to fishing impacts

ProspectsProspects

It is essential to understand these evolutionsto maintain diversity and productivity of these benthic communities

as well as sustainability of the benthic and demersal fisheries

Specifically, the vulnerability of the benthic habitats to fishing impacts must be incorporated in fisheries management to understand their

feedback on the benthic fisheries of the Bay of BiscayDo not

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Thank you

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Bay of Biscay speciesBay of Biscay speciesFishing impacts on the faunaFishing impacts on the fauna

Very fragileVery fragile

FragileFragile

SensitiveSensitive

IndifferentIndifferent

OpportunisticOpportunistic

damageddamaged

no survivalno survival

Damaged, possible survivalDamaged, possible survival

facilitated predation facilitated predation

Few damagedFew damaged

facilitated predationfacilitated predation

Escape or resistantEscape or resistant

no damagedno damaged

Few or no damagedFew or no damaged

indirect beneficial effectsindirect beneficial effects

LeptometraLeptometra, , AtrinaAtrina, , PennatulaPennatula

HyalinoeciaHyalinoecia, , AmphiuraAmphiura, , PandoraPandora

CalliostomaCalliostoma, , TurritellaTurritella, , ScaphanderScaphander, , PoraniaPorania

EusirusEusirus

Liocarcinus, Liocarcinus, MunidaMunida, , PagurusPagurus

Bottom trawling sensitivity index of epifauna

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