Adour basin INDICANG – 7-8 oct 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 AQUITAINEAQUITAINE MIDIPYRENEESMIDIPYRENEES

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-ARMAGNAC PONDS « 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 basin from 1970 to 2000 Numbers 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 rates MIGRADOUR, CSP, IFREMER, GDSAA 19 rivers, 26 stations glass eel: no trace yellow eel: whole basin contaminated (prevalence ~50%; variable intensity)

Anguillicola crassus prevalenceintensity

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 20 th century

Evolution of CPUE through the 20 th century

Glass eel exploitation a fishery dating back to the beginning of the 20 th 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 License number 70 licenses maximum, since 1993

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

CPUE evolution by gear type (hand net, trawl net)

Glass eel exploitation a fishery dating back to the beginning of the 20 th 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

Année de capture Production (tons) production per fisherman (t/10) Number of fishermen productionprod / fishermanfishermen 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 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 migrate or not?

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

Type 1 Type 3 Type 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 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” 30 samplings 3 years Estuary sampling Data base Biometry Density Catch Hydrodynamics Environment Climate Seasonal biomass Daily 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

fished days “hydroclimate” scientific sampling daily estimation extrapolation to neighbourhood catchability evaluation

Season biomass = Tons CI(95%) = [55.87; 99.21] Extrapolated season biomass = Tons CI(95%) = [74.29; ]

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)

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