Minho River PORTUGAL 2 nd 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 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 Min. yearly discharge (1975/1976): 127 m 3 s -1 Max. yearly discharge (1987/1988): 501 m 3 s -1 Mean annual discharge: 305 m 3 s -1 (in the estuary) Catchment area (total): km 2 International sub-basin area: km 2 Catchment area in Spain: km 2 Catchment area in Portugal: 800 km 2 Total surface water area: 800 km 2 Estuary length: 30 Km Temperature: 9.6ºC (Jan.) – 20.4ºC(Aug.) Salinity: 0.1ups – ups (Year reference: 2000) Basin limit Border
Spain Sil (1)8000 km 2 Left bank Arnoya (2)725 km 2 Neyra (3)832 km 2 Tea (4)411 km 2 Right bank Avia (5)670 km 2 Ferreira (6)266 km 2 Ladra (7)886 km 2 Támoga (8)233 km 2 Portugal Mouro (9)141 km 2 Left bank Coura (10)268 km 2 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 km², i.e., about 50% of the total of Minho‘s drainage basin Name Area of the sub-basin Minho River Basin: Main tributaries
Images Basin limit Border Minho River Basin
Dams Basin limit Border Dam locations in Minho catchment area ENVIRONMENTAL CONSTRAINTS Bassin Limit Border Hydroelectric Other Out of use
Dams Basin limit Border Dams affecting upstream migration ENVIRONMENTAL CONSTRAINTS Bassin Limit Border With fish-pass With fish-pass for eels No fish-pass No information
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
Exotic species Corbicula fluminea CRUSTACEA recentProchambarus clarkii MOLLUSCA recent Gobo gobio recentCyprinus carpio recentTinca tinca recentCobitis calderoni oldCarassius auratus oldGambusia affinis holbrooki oldMicropterus salmoides oldOnchorhynchus mykiss INTRODUCTIONFISHES Gobio gobio Micropterus salmoidesCyprinus carpioProchambarus clarkiiCorbicula fluminea Basin limit Border ENVIRONMENTAL CONSTRAINTS
Parasite Anguillicola crassus Basin limit Border ENVIRONMENTAL CONSTRAINTS
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 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 EEL EXPLOITATION
Fishing gear (glass eel) - “Tela”(stow net) Length of floatline = 10 m; Depth = 8 m; Leadline = 15 m; Meshsize = 1-2 mm EEL EXPLOITATION
Fishing gear (glass eel) - “Tela”(stow net) EEL EXPLOITATION
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 EEL EXPLOITATION
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 OFFICIAL DATA OF GLASS EEL CATCHES FROM PORTUGAL AND SPAIN IN THE MINHO RIVER ( ) The data are underestimated. EEL EXPLOITATION
The data are underestimated. OFFICIAL DATA OF YELLOW EEL CATCHES FROM PORTUGAL IN THE MINHO RIVER ( ) EEL EXPLOITATION Historical evolution of catches
Area of colonization Basin limit Border In: Hervella & Caballero, 1999 EEL STATUS
Accessible and “lost” areas Basin limit Border EEL STATUS Accessible area km km2 “Lost” area 11 % of total hydrographic bassin area
BIOLOGICAL STUDIES StudiesPeriodsOrganisationLocals Experimental glass eel fishery ; ; ; CIIMAR; ICBAS Estuary: 18 km upstream; and river entrance Biometric data and pigmentation stages ; ; ; CIIMAR; ICBAS Estuary: 18 km upstream; and river entrance By-catch analyses ; ; CIIMAR; ICBAS Estuary: 18 km upstream; and river entrance Culture experiment of monthly captured glass eels ICBASEstuary Abundance and distribution of yellow eels, biometric and food regime data ICBASInternational Minho River Parasites ICBASInternational Minho River Glass eel and leptocephali otolith analises ICBASEstuary
Experimental glass eel fishery BIOLOGICAL STUDIES
Biometric data and pigmentation stages Average length / weight range: 6.3 cm (Jun.) and 7.4cm (Sept.) / 0.17g (Aug.) and g (Sept.) Year : 2000 BIOLOGICAL STUDIES In average in the season fishing: 1 Kg of glass eels = 2800 glass eels
By-catch analyses BIOLOGICAL STUDIES Dias CS & Antunes C, 2004
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
Yellow eels (1988) Electric fishery in small tributaries 2 ind./m 2 – 78.6 g/m 2 0,2 ind./m 2 – 8.8 g/m 2 Fyke-nets 4,5 eels/fyke-net/night 0,9 eels/fyke-net/night Basin limit Border BIOLOGICAL STUDIES
Parasites Prevalence of Anguillicola crassus (1995/996) 87.5% 15% BIOLOGICAL STUDIES Basin limit Border
Glass eels and leptocephali - otolith microstructure analyses( ) 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 CONSTRAINTS ON THE EVOLUTION OF EEL STOCK Lost of habitat Absence of re-stocking programmes Habitat quality (?) Parasites (?)