Minho RiverMinho RiverPORTUGALPORTUGAL
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
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 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
SpainSil (1) 8000 km2
Left bankArnoya (2) 725 km2
Neyra (3) 832 km2
Tea (4) 411 km2
Right bank
Avia (5) 670 km2
Ferreira (6) 266 km2
Ladra (7) 886 km2
Támoga (8) 233 km2
Portugal Mouro (9) 141 km2
Left bankCoura (10) 268 km2
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.
1
2
3
4
5
6
7
8
910
NameArea 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
LugoUrban
Rio BarbañaIndustrial
OrenseUrban
Rio LouroIndustrial
PonferradaIndustrial and Urban
VN CerveiraIndustrial
ENVIRONMENTAL CONSTRAINTS
Exotic species
Corbicula fluminea
CRUSTACEA
recentProchambarus clarkii
MOLLUSCA
recent
recentGobo gobio
recentCyprinus carpio
recentTinca tinca
recentCobitis calderoni
oldCarassius auratus
oldGambusia affinis holbrooki
oldMicropterus salmoides
oldOnchorhynchus mykiss
INTRODUCTION FISHES
Gobio gobio
Micropterus salmoides Cyprinus carpio Prochambarus clarkii Corbicula 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 (1974-2003)
The data are underestimated.
EEL EXPLOITATION
0
10
20
30
40
50
60
1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002
Ton
P SP total
The data are underestimated.
0
1
2
3
4
5
6
1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003
Ton
OFFICIAL DATA OF YELLOW EEL CATCHES FROM PORTUGAL IN THE MINHO RIVER (1983-2003)
EEL EXPLOITATIONHistorical 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
1 934 km2
16 250 km2
“Lost” area
11 % of total hydrographic bassin area
BIOLOGICAL STUDIES
Studies Periods Organisation Locals
Experimental glass eel fishery
1981-1983; 1987-1989; 1991-1993; 2000-2001
CIIMAR; ICBASEstuary: 18 km upstream; and
river entrance
Biometric data and pigmentation stages
1981-1983; 1987-1989; 1991-1993; 2000-2001
CIIMAR; ICBASEstuary: 18 km upstream; and
river entrance
By-catch analyses1981-1983; 1991-1992; 2000-
2001CIIMAR; ICBAS
Estuary: 18 km upstream; and river entrance
Culture experiment of monthly captured glass
eels1988-1991 ICBAS Estuary
Abundance and distribution of yellow eels, biometric and food regime data
1987-1989 ICBAS International Minho River
Parasites 1995-1996 ICBAS International Minho River
Glass eel and leptocephali otolith
analises1991-1993 ICBAS Estuary
Experimental glass eel fishery
0
1000
2000
3000
4000
5000
Nov81
J82
M M Jl S N J83
M Mar00
M Jl A O D F A J A O D F
month
glass eels (g/h)
BIOLOGICAL STUDIES
Biometric data and pigmentation stages
0%
20%
40%
60%
80%
100%
Fev00
Mar Abr Mai Jun Jul Jul'' Ag Set Out Nov Dez Jan01
Fev Mar Abr Mai Jun Jul Ag Set Out
VA VB VIAo VIA1 VIA2 VIA3 VIA4
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
By-catch analyses BIOLOGICAL STUDIES
Dias CS & Antunes C, 2004
Presences (nº of months) Order (Class for Mollusca)
Family Species Total nº of presences (months)
Tela (max.12)
Saco (max.15)
Presences (nº of months) Order (Class for Mollusca)
Family Species Total nº of presences (months)
Tela (max.12)
Saco (max.15)
ANNELIDA 3 0 3 MOLLUSCA Gastropoda Patellidae Patina pellucida 1 1 1 Nassariidae Hinia reticulata 1 1 0 Bithyniidae Bithynia tentaculata Bivalvia Mytilidae Mytilus
galloprovincialis 3 1 3
Cardiidae Cerastoderma edule Cephalopoda Sepiolidae Sepiola atlantica 4 0 4 Lologinidae Loligo vulgaris 2 0 2 CRUSTACEA Thoracica Balanidae Balanus improvisus 1 0 1 Cumacea Bodotriidae Euphausiacea 5 0 5 Mysidacea # 1 species 11 7 9 # 2 species 9 5 9 Isopoda Gnathiidae Paragnathia formica 5 1 5 Cirolanidae Eurydice pulchra Sphaeromatidae Sphaeroma serratum 9 3 8 Idoteidae 7 1 7 Chaetiliidae Saduriella losadai 12 7 11 Amphipoda >1 species 15 8 10 Jassa falcata 2 0 2 Decapoda Palaemonidae Palaemon
longirostris 12 12 11
Palaemon serratus 4 0 4 Hippolytidae # 1 species 2 0 2 # 2 species 1 0 1 # 3 species 1 1 1 Crangonidae Crangon crangon 14 10 12 Scyllaridae 2 0 2 Portunidae Polybius henslowi 1 0 1
ECHINODERMATA Forcipulata Asteriidae Asterias rubens 1 0 1 PISCES Petromyzoniformes Petromyzonidae Petromyzon marinus 1 1 1 Syngnathiformes Syngnathidae Syngnathus acus 15 7 14 Nerophis
lumbriciformes 3 1 2
Clupeiformes Clupeidae Sardina pilchardus 4 0 4 Alosa alosa 1 0 1 Atheriniformes Atherinidae Atherina presbyter 16 8 15 Perciformes Gobiidae Pomatoschistus
microps 14 10 12
Aphia minuta 13 4 11 Ammodytidae Ammodytes tobianus 15 6 13 Mugilidae 15 9 14 Trachinidae Echiichthys vipera 15 8 14 Callionymidae Callionymus lyra 6 0 6 Sparidae Diplodus sargus 4 1 4 Anguilliformes Anguillidae Anguilla anguilla 5 0 5 Congridae Conger conger 5 2 4 Gadiformes Gadidae Ciliata mustela 4 0 4 Beloniformes Belonidae Belone belone 1 1 0 Scorpaeniformes Triglidae Lepidotrigla cavillone 1 0 1 Pleuronectiformes Pleuronectidae Platichthys flesus 4 0 4 Soleidae Solea vulgaris 3 0 3
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./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
0
5
10
15
20
25
30%
14-17 18-21 22-25 26-29 30-33 34-37 38-41 42-45 46-49 50-53 54-57 58-61 62-65 66-69 70-73 74-77 78-81 82-85
length (cm)
N=680
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(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
CONSTRAINTS ON THE EVOLUTION OF EEL STOCK
• Lost of habitat
• Absence of re-stocking programmes
• Habitat quality (?)
• Parasites (?)
