leloch & hily-icsr05 pm/icsr05-le… · pelecypoda 28% polychaeta 2% crinoidea holothurioidea...
TRANSCRIPT
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”
Do not
disse
minate
withou
t auth
or au
thoriz
ation
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)
Do not
disse
minate
withou
t auth
or au
thoriz
ation
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
Do not
disse
minate
withou
t auth
or au
thoriz
ation
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
Do not
disse
minate
withou
t auth
or au
thoriz
ation
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
disse
minate
withou
t auth
or au
thoriz
ation
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?
Do not
disse
minate
withou
t auth
or au
thoriz
ation
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
ot dis
semina
te with
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
Do not
disse
minate
withou
t auth
or au
thoriz
ation
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
disse
minate
withou
t auth
or au
thoriz
ation
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
Do not
disse
minate
withou
t auth
or au
thoriz
ation
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?
Do not
disse
minate
withou
t auth
or au
thoriz
ation
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
disse
minate
withou
t auth
or au
thoriz
ation
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
Do not
disse
minate
withou
t auth
or au
thoriz
ation