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Adour basin
INDICANG – 7-8 oct 2004 - San Sebastian
Adour Basin
Information : Adera-Cereca, Ifremer, Institution Adour, Migradour
Presentation : Institution Adour, Migradour
Mapmaking : Agence de l’Eau Adour Garonne, Cereca, Ifremer, Observatoire de l’Eau des Pays de l’Adour, Migradour
Situation
Geographical information
16,000 km²
2 “régions”
4 “départements”
1,238 “communes”
960,000 inhabitants
57 inhab./km²
64
32
65
40
AQUITAINEAQUITAINEAQUITAINEAQUITAINEMIDIMIDI
PYRENEESPYRENEESMIDIMIDI
PYRENEESPYRENEES
Physical aspects
Adour axis- plain river pattern- rich alluvial water table- inundating floods- severe low levels
Midouze- many underground
water tables- moderate floods
and low levels
Gaves and Nives
- sustained flow- late low levels- rich alluvial water table- torrential floods
Hillsides - contrasted pattern- sudden and short flood- severe and early low levels
ESTUARY
NOTICEABLE RIVERS
BARTHES(wetlands)
SALIGUES (wetlands) ALLUVIAL
CORRIDORS
BAS-ARMAGNACPONDS
« GREEN ZONES »
Noticeable milieus
Rivers with migratory fish
Axis priority # 1
Axis priority # 2
Pressure – land use“artificial” territories
ploughed lands
grasslands, heterogeneous lands
forests, semi-natural milieus
wetlands
permanent cultivation
Pressure on the environment
Pressure on the environment –hydromorphology
Pressure on the environment – agriculture
crayfish…
Cattle evolution in the Adour basinfrom 1970 to 2000
0
5 000
10 000
15 000
20 000
25 000
30 000
35 000
40 000
1970 1979 1988 2000
Num
bers
Bovine
Poultry (nb/10)
Equine
Sows
Ewes
Swine (fattening)
Pressure on the environment – domestic activities
Pressure on the environment – industry
Pressure on the environment – overall ecological risk
Pressure on the environment – diseases
parasitism by Anguillicola crassus
one study Adour-Nivelle-Bidassoa (1998)determination of prevalence and intensity
ratesMIGRADOUR, CSP, IFREMER, GDSAA19 rivers, 26 stationsglass eel: no traceyellow eel: whole basin contaminated
(prevalence ~50%; variable intensity)
Anguillicola crassus
prevalence intensity
Eel exploitation
glass eel: economic stake
yellow eel: commercial fishery decreasing
silver eel: not in the basin
Glass eel exploitation
a fishery dating back to the beginning of the 20th century
Evolution of CPUEthrough the 20th century
Glass eel exploitation
a fishery dating back to the beginning of the 20th century
a commercial fishery + a leisure fishery
around 200 commercial fishermen (among them, 70% fish only glass eel)
Evolution of commercial fishermen in the maritime part of the estuary
30
40
50
60
70
80
90
1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004
Lice
nse
num
ber 70 licenses maximum, since 1993
Glass eel exploitation3 commercial fishing methods 1 hand net 2 trawl nets (since 1995) 2 nets, anchored ship (experimental since 2003)
1 leisure fishing method 1 hand net
fishing gear of “modest” dimensions commercial net: 1.20m in diameter leisure net: 0.50m in diameter
Glass eel exploitation
Glass eel exploitation
CPUE evolution by gear type (hand net, trawl net)
Glass eel exploitation
a fishery dating back to the beginning of the 20th century
a commercial fishery + a leisure fishery
a heavy economic importance in the commercial fisheries
Glass eel fishery turnover (maritime estuarine fishermen)
57% 61%
Yellow eel exploitation
a commercial fishery with decreasing number of fishermen
0
2
4
6
8
10
12
1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Année de capture
Pro
duct
ion
(ton
s)
prod
uctio
n pe
r fi
sher
man
(t/1
0)
0
5
10
15
20
25
Num
ber of fishermen
production prod / fisherman fishermen
Yellow eel exploitation
Yellow eel exploitation
a commercial fishery with decreasing number of fishermen
an unknown leisure fishery
Silver eel exploitation
not in the Adour basin, strictly speaking
2 commercial fisheries in coastal short rivers, stopping for good at the end of 2004
Eel status
Eel distribution gradient
Biological studies
migration
biology and physiology
stock and exploitation
Biological studies
migrationglass eel estuarine behaviour modelling
Cereca, Ifremer, Université de Grenoble, Université de Pau
Description of behavioural model
conditions of current (river flow / tide)one-dimension model (IFREMER-UPPA)
light conditionsestimated turbiditymoon phasecloud cover
Conceptual behavioural model
Moon phase
FQ and LQ NM
FM
column surface
NO
MES>40 NTU ?
surface
NOYES
Daytime?
on the bottom
YES
NO
River flow < -0.3 m/s ? buried
YES
Cloudy?
surface
much
column
little
Question:
does it migrateor
not?
Biological studies
migrationglass eel estuarine behaviour modelling
study of downstream migration on a hydroelectric production unit
EDF, INRA location : Halsou, on the river Nive
Biological studies
migration
biology and physiologyglass eel “flows” characterisation
Cereca, Université de Perpignan for example : otolithometry
Type 1
Type 3Type 2
Transition marks and pigmentation stages
Biological studies
migration
biology and physiology glass eel “flows” characterisation
parasitism (seen earlier)
Biological studies
migration
biology and physiology
stock and exploitationsurveys
eel network - Migradour
Eel network
Migradour + CSP, FDAAPPMA, AAPPMA
fish surveys 29 stations 18 rivers
complementary studies age/length keys
(otolithometry) characterisation of silvering
(ocular index) parasitism survey
(Anguilicola crassus)
Eel network
resultsdifficulty to detect density trends on a short
period
prospects redefining the choice of stations and
sampling method
Biological studies
migration
biology and physiology
stock and exploitation surveys
glass eel “flow” estimation (from daily to seasonal) and estimation of exploitation rate by commercial fishing in the marine part of the estuary
Cereca, Ifremer, Université de Grenoble, Université de Pau
Estimation of glass eel “flow”
30 samplings3 years
Estuary samplingData base
BiometryDensityCatch
HydrodynamicsEnvironment
ClimateSeasonalbiomass
Dailybiomass
Statistical modelling ofglass eel “flow”
biomass estimation for one tide, through scientific sampling
comparison with catch intensity by commercial fishermen in the same area
estimation of daily exploitation rate
median between 6 and 26%, for fishing seasons 1998/99 to 2000/2001
M od è le co m p os ite
ca m p ag ne s e xpé rim en ta lesse lon sta tio n d e ré fé ren ce
p lan d 'échan tillon na ge d éd ié
in d ice d 'a bo nd an cesu r fa ce e t fo nd
e s tim atio n b iom asse
T au x d 'exp lo i ta tionm od u la tion
p a r c lasse hydro clim a tiq ue
M od è le h yd ro dyna m iqueu n id im ens ion ne l
co rre ction b a th ym étr iq ue
M od è le h yd roc lim a tiq uetu rb id i té , tem p éra tu re
d é b it, m arée
cap tu rab i li tép a r c lasse
se lonm od è le co m p o rte m e nta l
b iom asse e n tran tee stu a ire in fé r ieu r
e n kg p ar jo u r
zo ne de d isp ers ion d u f luxca p tu re s p ro fe ss ion n e lles
kg p ar jou rta m is p ou ssé
From point estimation to global estimation
fished days
“hydroclimate”
scientific sampling
daily estimation
extrapolation to neighbourhood
catchability evaluation
Season biomass = 77.54 TonsCI(95%) = [55.87; 99.21]
Nov Dec Jan Feb1999 2000
10
00
20
00
30
00
40
00
50
00
60
00
*
* ****
*
*
*
Biomasse estimée sur certains joursBiomasse extrapolée sur la saisonBiomasse observée
Extrapolated season biomass = 89.37 TonsCI(95%) = [74.29; 111.04]
Biological studiesmigration glass eel estuarine behaviour modelling study of downstream migration on a hydroelectric production
unit
biology and physiology glass eel “flows” characterisation parasitism
stock and exploitation surveys glass eel “flow” estimation (from daily to seasonal) estimation of exploitation rate by commercial fishing in the
marine part of the estuary
Pressure on the continental life phases of eel
heavy impact of human activites on eel habitat availability (reduction of wetlands) accessibility (migration interference) functionality (damage to quality)
moderate impact of fishing exploitation glass eel (moderate exploitation rate,according to first
estimates) yellow eel (decreasing fishery) silver eel (no fishery at all)
Thank youfor your attention
