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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. Adour Basin.

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Adour basin

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  1. INDICANG – 7-8 oct 2004 - San Sebastian Adour basin

  2. 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 Adour Basin

  3. Situation

  4. Geographical information • 16,000 km² • 2 “régions” • 4 “départements” • 1,238 “communes” • 960,000 inhabitants • 57 inhab./km² 40 32 AQUITAINE MIDI PYRENEES 64 65

  5. Physical aspects Midouze - many underground water tables - moderate floods and low levels • Adour axis • - plain river pattern • rich alluvial water table • inundating floods • severe low levels Hillsides - contrasted pattern - sudden and short flood - severe and early low levels Gaves and Nives - sustained flow - late low levels - rich alluvial water table - torrential floods

  6. Noticeable milieus « GREEN ZONES » BARTHES (wetlands) BAS-ARMAGNAC PONDS ESTUARY SALIGUES (wetlands) ALLUVIAL CORRIDORS NOTICEABLE RIVERS

  7. Rivers with migratory fish Axis priority # 1 Axis priority # 2

  8. Pressure – land use “artificial” territories ploughed lands permanent cultivation grasslands, heterogeneous lands forests, semi-natural milieus wetlands

  9. Pressure on the environment

  10. Pressure on the environment –hydromorphology

  11. Pressure on the environment – agriculture

  12. crayfish…

  13. 40 000 35 000 30 000 25 000 20 000 15 000 10 000 5 000 0 1970 1979 1988 2000 Cattle evolution in the Adour basinfrom 1970 to 2000 Poultry (nb/10) Numbers Bovine Ewes Swine (fattening) Equine Sows

  14. Pressure on the environment – domestic activities

  15. Pressure on the environment – industry

  16. Pressure on the environment – overall ecological risk

  17. 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)

  18. Anguillicola crassus prevalence intensity

  19. Eel exploitation • glass eel: economic stake • yellow eel: commercial fishery decreasing • silver eel: not in the basin

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

  21. Evolution of CPUEthrough the 20th century

  22. 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)

  23. Evolution of commercial fishermen in the maritime part of the estuary 90 80 70 licenses maximum, since 1993 70 License number 60 50 40 30 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004

  24. 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

  25. Glass eel exploitation

  26. Glass eel exploitation • CPUE evolution by gear type (hand net, trawl net)

  27. 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

  28. Glass eel fishery turnover (maritime estuarine fishermen) 61% 57%

  29. Yellow eel exploitation • a commercial fishery with decreasing number of fishermen

  30. production prod / fisherman fishermen Yellow eel exploitation 12 25 10 20 8 production per fisherman (t/10) 15 Production (tons) Number of fishermen 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

  31. Yellow eel exploitation • a commercial fishery with decreasing number of fishermen • an unknown leisure fishery

  32. 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

  33. Eel status

  34. Eel distribution gradient

  35. Biological studies • migration • biology and physiology • stock and exploitation

  36. Biological studies • migration • glass eel estuarine behaviour modelling • Cereca, Ifremer, Université de Grenoble, Université de Pau

  37. Description of behavioural model • conditions of current (river flow / tide) • one-dimension model (IFREMER-UPPA) • light conditions • estimated turbidity • moon phase • cloud cover

  38. Daytime? YES on the bottom NO River flow < -0.3 m/s ?  YES buried NO MES>40 NTU ? YES NO surface FQ and LQ Moon phase NM FM Cloudy? column surface little much surface column Conceptual behavioural model Question: does it migrate or not?

  39. 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

  40. Biological studies • migration • biology and physiology • glass eel “flows” characterisation • Cereca, Université de Perpignan • for example : otolithometry

  41. Transition marks and pigmentation stages Type 1 Type 2 Type 3

  42. Biological studies • migration • biology and physiology • glass eel “flows” characterisation • parasitism (seen earlier)

  43. Biological studies • migration • biology and physiology • stock and exploitation • surveys • eel network - Migradour

  44. 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

  45. Eel network • results • difficulty to detect density trends on a short period • prospects • redefining the choice of stations and sampling method

  46. 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

  47. Estuary sampling Data base Biometry Density Catch Hydrodynamics Environment Climate Daily biomass 30 samplings 3 years Seasonal biomass Estimation of glass eel “flow”

  48. 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

  49. From point estimation to global estimation

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