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Minho River PORTUGAL

Minho River PORTUGAL. Carlos Antunes & Alfredo Oliveira Centre for Marine and Environmental Research (CIIMAR) –University of Porto. 2 nd Management Meeting of the INDICANG-35 project San Sebastian, 7-8 October 2004. Geographical location.

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Minho River PORTUGAL

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  1. Minho River PORTUGAL Carlos Antunes & Alfredo Oliveira Centre for Marine and Environmental Research (CIIMAR) –University of Porto 2nd Management Meeting of the INDICANG-35 project San Sebastian, 7-8 October 2004

  2. Geographical location International river: Spain and Portugal River spring: Spain, at “serra de Meira”, 750 m altitude. Course: 300 km, the first 230 km in Spain. The final 70 km are the border between Portugal and Spain. Basin limit Border

  3. Minho River Basin: Physical caracteristics Catchment area (total): 17 080 km2 International sub-basin area: 1 934 km2 Catchment area in Spain: 16 250 km2 Catchment area in Portugal: 800 km2 Total surface water area: 800 km2 Basin limit Border Min. yearly discharge (1975/1976): 127 m3s-1 Max. yearly discharge (1987/1988): 501 m3s-1 Mean annual discharge: 305 m3s-1 (in the estuary) Estuary length: 30 Km Temperature: 9.6ºC (Jan.) – 20.4ºC(Aug.) Salinity: 0.1ups – 34.64 ups (Year reference: 2000)

  4. 8 7 3 6 1 5 2 4 9 10 Minho River Basin: Main tributaries The Minho drainage basin is characterized by the existence of two main rivers, the Minho river and is main tributary, the Sil river. The source of the Sil river is located at 1500 m of altitude in “serra de Jistreda”, in the Cantabrian Mountains. The Sil flows through 226 km, and joins Minho river at 70 km before the beginning of the international stretch. The Sil sub-basin covers an area of 8 000 km², i.e., about 50% of the total of Minho‘s drainage basin.

  5. Minho River Basin Images Basin limit Border

  6. ENVIRONMENTAL CONSTRAINTS Dams Dam locations in Minho catchment area Basin limit Border

  7. ENVIRONMENTAL CONSTRAINTS Dams Dams affecting upstream migration Basin limit Border

  8. ENVIRONMENTAL CONSTRAINTS Point source pollution Non-point source pollution LugoUrban PonferradaIndustrial and Urban OrenseUrban Rio BarbañaIndustrial Rio LouroIndustrial Basin limit Border VN CerveiraIndustrial In: Antello et al., 1998 Norton, R., 1998

  9. FISHES INTRODUCTION Onchorhynchus mykiss old Micropterus salmoides old Gambusia affinis holbrooki old Carassius auratus old Cobitis calderoni recent Tinca tinca recent Cyprinus carpio recent Gobo gobio recent CRUSTACEA Prochambarus clarkii recent MOLLUSCA recent ENVIRONMENTAL CONSTRAINTS Exotic species Corbicula fluminea Basin limit Border Gobio gobio Micropterus salmoides Cyprinus carpio Prochambarus clarkii Corbicula fluminea

  10. ENVIRONMENTAL CONSTRAINTS Parasite Anguillicola crassus Basin limit Border

  11. EEL EXPLOITATION Number of fishermen • PORTUGAL • Number of licences in 1984: 1744 • Number of licences in 1989: 820 • Present: 800(plus specific glass eel licences for 2004) • Fishery data declared : 50% of the fishermen Photograph by Eliseo Alonso • SPAIN • Number of licences : 430 • Fishery data declared : 60% of the fishermen

  12. Glass eel fishery • Hand-held dip net -“rapeta” • Stow net - “tela” • Use of an illegal stow net called - “tela de saco” NOT ALLOWED IN OTHER NATIONAL RIVERS Yellow eel fishery • Fyke-nets -“nassa” • Baited hooks Fishing gears EEL EXPLOITATION

  13. EEL EXPLOITATION Fishing gear (glass eel) - “Tela”(stow net) Length of floatline = 10 m; Depth = 8 m; Leadline = 15 m; Meshsize = 1-2 mm

  14. EEL EXPLOITATION Fishing gear (glass eel) - “Tela”(stow net)

  15. EEL EXPLOITATION Illegal fishing gear (glass eel) - “Tela de saco”(stow net with bag) Length of floatline = 14 m; Length of the bag = 10 m; Meshsize = 1-2 mm

  16. EEL EXPLOITATION Fishing gears (yellow eel) Fyke-nets

  17. EEL EXPLOITATION GLASS EELS Stow net: O1 Nov. – 30 April Hand dip net: 01 Out. – 30 April Fishing regulation YELLOW EELS Fyke-net: 01 Sept.-30 Nov. Baited hooks: All year Length > 20 cm

  18. EEL EXPLOITATION Historical evolution of catches OFFICIAL DATA OF GLASS EEL CATCHES FROM PORTUGAL AND SPAIN IN THE MINHO RIVER (1974-2003) The data are underestimated.

  19. EEL EXPLOITATION Historical evolution of catches OFFICIAL DATA OF YELLOW EEL CATCHES FROM PORTUGAL IN THE MINHO RIVER (1983-2003) The data are underestimated.

  20. EEL STATUS Area of colonization Basin limit Border In: Hervella & Caballero, 1999

  21. EEL STATUS Accessible and “lost” areas Accessible area 1 934 km2 Basin limit Border 11 % of total hydrographic bassin area “Lost” area 16 250 km2

  22. BIOLOGICAL STUDIES

  23. BIOLOGICAL STUDIES Experimental glass eel fishery

  24. BIOLOGICAL STUDIES Biometric data and pigmentation stages Average length / weight range: 6.3 cm (Jun.) and 7.4cm (Sept.) / 0.17g (Aug.) and 0.380 g (Sept.) Year : 2000 In average in the season fishing: 1 Kg of glass eels = 2800 glass eels

  25. BIOLOGICAL STUDIES By-catch analyses Dias CS & Antunes C, 2004

  26. BIOLOGICAL STUDIES By-catch analyses Pisces – 20 species Crustacea – 20 taxonomic groups Mollusca – 7 species Annelida – 1 species Echinodermata – 1 species Dias CS & Antunes C, 2004

  27. BIOLOGICAL STUDIES Yellow eels (1988) Fyke-nets 0,9 eels/fyke-net/night 4,5 eels/fyke-net/night Basin limit Border 0,2 ind./m2 – 8.8 g/m2 2 ind./m2 – 78.6 g/m2 Electric fishery in small tributaries

  28. BIOLOGICAL STUDIES Parasites Prevalence of Anguillicola crassus (1995/996) 15% 87.5% Basin limit Border

  29. BIOLOGICAL STUDIES Glass eels and leptocephali - otolith microstructure analyses(1991 -1993) Time migration from Sargasso Sea to Minho River 22 – 26 months ? Age estimation dificulty: Difuse Zone LI LII LIII Antunes C & Tesch FW, 1997

  30. CONSTRAINTS ON THE EVOLUTION OF EEL STOCK • Management plan adapted to the new local reality: * Fishing licences number control * Fishing period * Fishing area • Lost of habitat• Absence of re-stocking programmes• Habitat quality (?)• Parasites (?)

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