Séminaire Indicang 18 et 19 mai 2005 Indicang – Interreg III Situation of European eel in the Oria river basin and progress of the project

Séminaire Indicang 18 et 19 mai 2005 The Oria river basin

Séminaire Indicang 18 et 19 mai 2005 Characteristics of the basin : - Valleys fit in V people through river axis - Maximum height: m - Mean Temperature: 12,4 ºC - Mean rainfall: mm - Mean basin discharge: 942 hm 3 /year - Length: 75 km Item Zero: environment

Séminaire Indicang 18 et 19 mai 2005 Situation of the habitat -10 Native or non defined origin fish species, 3 introduced fish species - 24 % of total riverbank affected by hard bank reinforcement - More than 100 obstacles, 1-3 m high - Poor habitat quality - Poor water quality in general, pollution Item Zero: environment Leitzaran46,22,5047,6375, ,91LEITZARAN Alegi25,93,21017,0278,625 Lasarte33,511,79144,83126, ,29ORIA Min.Max.Mean Gauging station Specific flow (l -1 km -2 ) Mean anual flow (m 3 s -1 )Surface (km 2 ) River length (km) River

Séminaire Indicang 18 et 19 mai 2005 Fish-pass No Fish-pass Obstacles affecting migration: Hydroelectric use Other X Without use Upstream Downstream Item Zero: environment

Séminaire Indicang 18 et 19 mai ,55,61,2Oria (Irura)/1976 BMWP’DBO5 (mg/l) DQODI (mg/l)NH4 + Ox. Dis. (mg/l) 1 Cleaning up plant (station) for people Factory Purifiers Paper Factories amount DQO (kg/d) Sól. Susp (kg/d) Flow (m 3/d ) Year Paper Factories Dumping Evolution in Oria River Basin Item Zero: environment Historic evolution in the Oria Basin: - Water quality in Cleaning up plan situation

Séminaire Indicang 18 et 19 mai 2005 DQODI (mg/l) DBO5 (mg/l) NH4+ (mg/l) Tendence DQODI Water Quality evolution in Oria Basin: physical and chemical DQONH4+, DBO Year High point Low point Medium point Item Zero: environment

Séminaire Indicang 18 et 19 mai 2005 Item Zero: environment Water Quality evolution in Oria Basin: Biological - Araxes river IBMWP SPRING SUMMER

Séminaire Indicang 18 et 19 mai 2005 Item Zero:resource Eel abundance and distribution in Oria Basin: Historic data: Abundant; >80/1000m2 Moderate; 30-80/1000m2 Poor; 8-20/1000m2 Very Poor; 1-3/1000m2 Absent * These data are underestimated, mainly in low river basin, as we have seen in 2004 eel specific surveys

Séminaire Indicang 18 et 19 mai Distance to mouth (km)) Eels/1000 m Eel abundance and distribution in Oria Basin: Item Zero:resource

Séminaire Indicang 18 et 19 mai 2005 Eel fisheries in the basin - Launch of fisheries monitoring plan New regulation issued Agreed with the fishermen. License and daily catches report - Decline in the stock: intuitively, no any historical data series. - More than a century of fishery activity and sale in glass eel although no regulation existed. Item Zero: explotation - No fishery of yellow and silver eel

Séminaire Indicang 18 et 19 mai 2005 A license per person & fishing basin. Catches report: fishing type, fishing gear,fishing time, catches,… Fishing season: October – March. Fishing gears: only sieve and hoe. Not allowed the catches sale. Not a proffesional fishery. License and daily catches report Item Zero: explotation

Séminaire Indicang 18 et 19 mai 2005 Boat fishing Land fishing Glass eel fishing types in the Oria river basin Item Zero: explotation Sieve Wave Wall trawling Hoe Boat

Séminaire Indicang 18 et 19 mai 2005 Regular sampling net in the Oria Basin: Automatic control stations Item Zero: available information Biotic Indexes Fish Comunity FQ

Séminaire Indicang 18 et 19 mai 2005 Item Zero: available information Most important studies carried out in the Oria river basin Diputación Foral de Gipuzkoa Waterflow regime control Waste Dumping control Water quality control Fish populations management (Atlantic Salmon Reintroduction) River continuity, obstacles elimination Gobierno Vasco Hydrological Planning Waste Dumping control Water quality control, Framewok Directive Habitat description, Framewok Directive

Séminaire Indicang 18 et 19 mai 2005 Catches report 2003/2004 Validation with samplings and data of distribution companies Lack of precision of data Underestimation of catches It is obligatory to deliver the catches report to obtain the new license. Apply it. Low response Data from 40,3% of fishermen SolutionsProblems First time we have data! Results glass eel

Séminaire Indicang 18 et 19 mai 2005 Description of fisheries 2003/ Oct.Nov.Dec.Jan.Feb.March Date Fishers Trawling Sieve Boat Wave Total - Fishermen/gear - More fishermen in January - More fishermen in boat and sieve Results glass eel

Séminaire Indicang 18 et 19 mai 2005 Description of fisheries 2003/ Catches/Fishing effort - Significant differences in CPUES among fishing gears (p=0,0003), higher in boat and sieve - Trawling Sieve Boat Wave Total 0,000 0,020 0,040 0,060 0,080 0,100 0,120 0,140 0,160 0,180 Oct.Nov.Dec.Jan.Feb.March CPUEs (kg/h) -Highest CPUEs in December but no significant differences among months in each modality Results glass eel

Séminaire Indicang 18 et 19 mai 2005 Experimental samplings - With a motor boat, two fishermen and two sieves of 1.60 diameter (surface and depth) - Just three samplings because: - Temperature, salinity, turbidity, water current speed - In the mouth - Upstream - Samples given by the fishermen - Only when high entrance: change of strategy - started in December No validation Results glass eel

Séminaire Indicang 18 et 19 mai 2005 Experimental samplings - Trap: Installation of a gadget to keep clear the entrance Leafs obstruct the entrance  ????  To increase the ramp High flow variability:  Flooding and silting  Not enough water to reach the base of the sample. SolutionCause It has just worked properly in 25 % of the days (just one sample obtained): No validation this year Results glass eel

Séminaire Indicang 18 et 19 mai ,5 KmSan PedroDesemb. San Pedro6 4 KmSan PedroA. ab. Andatza5 25 KmLeitzaranOlazar4 23 KmLeitzaranLeitzaran Andoain3 22 KmOriaAndoain2 15 KmOriaZubieta1 Distance to mouthRiverStationNº Specific sampling stations 2004 Results yellow and silver eel

Séminaire Indicang 18 et 19 mai Failure condition valid.Var (N) 3.841g.l. 1; χ 2 0, χ2χ P Var (N) Nsup./Ha N/Ha Ninf./Ha CTCT C3C C2C C1C Depth (cm) Width (m) S.P. Desemb. S.P. Andatza Leitzaran Olazar Leitzaran AndoainAndoainZubieta 3 passes- Carle & Strub (1978) (MEMAPO) Zubieta: no constant catchability Leitza Olazar : no valid sampling Results yellow and silver eel

Séminaire Indicang 18 et 19 mai 2005 Leitzaran Olazar : no valid sampling In stations with high catchability the estimations are better when passing three times Zubieta: valid sampling but underestimated (see 3 passes) Results yellow and silver eel

Séminaire Indicang 18 et 19 mai 2005 Density decrease, 3 dams between the two points Length (cm) % num. Eel population structure. Andoain station. Oria river. Summer eels /Ha – Distance to mouth: 22 Km Eel population structure. Zubieta station. Oria river. Summer Length (cm) % num eels /Ha – Distance to mouth: 15 Km Results yellow and silver eel

Séminaire Indicang 18 et 19 mai Length (cm) % num. Eel population structure. Olazar station. Leitzaran river. Summer eels /Ha – Distance to mouth:25 Km Length (cm) % num. Eel population structure. Leitzaran station. Leitzaran river. Summer eels /Ha – Distance to mouth:23 Km Strong decrease between 1,5 and 2kms: A nearly insuperable dam. Upstream few eels and the population structure does not fit to this point Results yellow and silver eel

Séminaire Indicang 18 et 19 mai 2005 Stream that flows in the estuary with high recruitment Length (cm) % num. Eel population structure. Ab. Adantza station. San Pedro river. Summer eels /Ha – Distance to mouth4 Km. Eel population structure. San Pedro station. San Pedro river. Summer Length (cm) % num eels /Ha – Distance to mouth1,5 Km Results yellow and silver eel

Séminaire Indicang 18 et 19 mai The stations with higher area and depth (Zubieta, Andoain, Olazar): -The stations with lower area and depth (S.P. Andatza, S.P.Desem- bocadura, Leitzaran Andoain): - Litter stations: 3 passes -Low catchability, when passing two times population underestimated (sometimes even with three) - High catchability, passing three times better estimations than with two, tighter confidence limits Bigger stations: what method would fit better in these cases? Results yellow and silver eel