bv minho

Slide1: 

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

Geographical location: 

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

Minho River Basin: Physical caracteristics: 

Minho River Basin: Physical caracteristics 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) 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 Estuary length: 30 Km Temperature: 9.6ºC (Jan.) – 20.4ºC(Aug.) Salinity: 0.1ups – 34.64 ups (Year reference: 2000) Basin limit Border

Slide4: 

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. Minho River Basin: Main tributaries

Images: 

Images Basin limit Border Minho River Basin

Dams: 

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

Dams: 

Dams Basin limit Border Dams affecting upstream migration ENVIRONMENTAL CONSTRAINTS

Point source pollution: 

Point source pollution Basin limit Border Non-point source pollution In: Antello et al., 1998 Norton, R., 1998 Lugo Urban Rio Barbaña Industrial Orense Urban Rio Louro Industrial Ponferrada Industrial and Urban VN Cerveira Industrial ENVIRONMENTAL CONSTRAINTS

Slide9: 

Exotic species Corbicula fluminea Gobio gobio Micropterus salmoides Cyprinus carpio Prochambarus clarkii Corbicula fluminea Basin limit Border ENVIRONMENTAL CONSTRAINTS

Slide10: 

Parasite Anguillicola crassus Basin limit Border ENVIRONMENTAL CONSTRAINTS

Number of fishermen: 

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 SPAIN Number of licences : 430 Fishery data declared : 60% of the fishermen Photograph by Eliseo Alonso EEL EXPLOITATION

Fishing gears : 

Fishing gears EEL EXPLOITATION

Fishing gear (glass eel) - “Tela”(stow net): 

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

Slide14: 

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

Slide15: 

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

Fishing gears (yellow eel) Fyke-nets: 

Fishing gears (yellow eel) Fyke-nets EEL EXPLOITATION

Fishing regulation: 

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

Historical evolution of catches: 

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

Slide19: 

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

Area of colonization: 

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

Accessible and “lost” areas: 

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

BIOLOGICAL STUDIES: 

BIOLOGICAL STUDIES

Slide23: 

Experimental glass eel fishery BIOLOGICAL STUDIES

Slide24: 

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 BIOLOGICAL STUDIES In average in the season fishing: 1 Kg of glass eels = 2800 glass eels

Slide25: 

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

Slide26: 

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

Slide27: 

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

Slide28: 

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

Slide29: 

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

• Management plan adapted to the new local reality: * Fishing licences number control  * Fishing period * Fishing area  : 

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