Bassin de l`Adour

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Bassin de l`Adour
INDICANG – 7-8 oct 2004 - San Sebastian
Adour basin
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
40
AQUITAINE
32
MIDI
PYRENEES
64
65
Physical aspects
Midouze
Adour axis
- plain river pattern
- rich alluvial water table
- inundating floods
- severe low levels
- many underground
water tables
- moderate floods
and low levels
Hillsides
Gaves and Nives
- sustained flow
- late low levels
- rich alluvial water table
- torrential floods
- contrasted pattern
- sudden and short
flood
- severe and early
low levels
Noticeable milieus
« GREEN ZONES »
BARTHES
(wetlands)
BAS-ARMAGNAC
PONDS
ESTUARY
SALIGUES
(wetlands)
ALLUVIAL
CORRIDORS
NOTICEABLE
RIVERS
Rivers with migratory fish
Axis priority # 1
Axis priority # 2
Pressure – land use
“artificial” territories
ploughed lands
permanent cultivation
grasslands, heterogeneous
lands
forests, semi-natural milieus
wetlands
Pressure on the environment
Pressure on the environment –
hydromorphology
Pressure on the environment –
agriculture
crayfish…
Cattle evolution in the Adour basin
from 1970 to 2000
40 000
Poultry (nb/10)
35 000
30 000
Numbers
25 000
20 000
Bovine
15 000
10 000
Ewes
Swine (fattening)
5 000
Equine
Sows
0
1970
1979
1988
2000
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
rates
 MIGRADOUR, CSP, IFREMER, GDSAA
 19 rivers, 26 stations
 glass eel: no trace
 yellow 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 CPUE
through 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
90
License number
80
70 licenses maximum, since 1993
70
60
50
40
30
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
Glass eel exploitation
3 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
12
25
10
20
8
15
6
10
4
5
2
0
0
1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Année de capture
production
prod / fisherman
fishermen
Number of fishermen
Production (tons)
production per fisherman (t/10)
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
migration

glass 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 conditions
estimated turbidity
 moon phase
 cloud cover

Conceptual behavioural model
YES
Daytime
?
Question:
on the bottom
NO
does it migrate
or
not?
YES
River flow < -0.3
m/s ?
buried
NO
YES
NO
MES>40
NTU ?
FQ and LQ
surface
NM
Moon
phase
FM
Cloudy?
column
little
much
column
surface
surface
Biological studies
migration

glass 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 physiology

glass eel “flows” characterisation
Cereca, Université de Perpignan
 for example : otolithometry

Transition marks and
pigmentation stages
Type 1
Type 2
Type 3
Biological studies
migration
biology and physiology

glass eel “flows” characterisation

parasitism (seen earlier)
Biological studies
migration
biology and physiology
stock and exploitation

surveys

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
results

difficulty 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”
Estuary sampling
30 samplings
3 years
Data base
Biometry
Density
Catch
Hydrodynamics
Environment
Climate
Daily
biomass
Seasonal
biomass
Statistical modelling of
glass 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
From point estimation to global estimation
Modèle composite
zone de dispersion du flux
captures professionnelles
kg par jour
tamis poussé
Taux d'exploitation
modulation
par classe hydroclimatique
capturabilité
par classe
selon
modèle comportemental
indice d'abondance
surface et fond
estimation biomasse
Modèle hydroclimatique
turbidité, température
débit, marée
campagnes expérimentales
selon station de référence
plan d'échantillonnage dédié
Modèle hydrodynamique
unidimensionnel
correction bathymétrique
biomasse entrante
estuaire inférieur
en kg par jour
fished days
“hydroclimate”
scientific
sampling
catchability
evaluation
daily
estimation
extrapolation
to
neighbourhood
Season biomass = 77.54 Tons
5000
6000
CI(95%) = [55.87; 99.21]
2000
3000
4000
Biomasse estimée sur certains jours
Biomasse extrapolée sur la saison
Biomasse observée
*
1000
*
***
*
*
Dec
Nov
1999
*
*
Feb
Jan
2000
Extrapolated season biomass = 89.37 Tons
CI(95%) = [74.29; 111.04]
Biological studies
migration


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 you
for your attention

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