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

Indicang – Interreg III

Situation of European eel in the Oria river basin and progress of the project


The Oria river basin


Characteristics of the basin :

- Valleys fit in V

- 126.000 people through river axis

- Maximum height: 1.260 m

- Mean Temperature: 12,4 ºC

- Mean rainfall: 1.650 mm

- Mean basin discharge: 942 hm3/year

- Length: 75 km

Item Zero: environment


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


Leitzaran46,22,5047,6375,07812330,91LEITZARAN

Alegi25,93,21017,0278,625

Lasarte33,511,79144,83126,643

88277,29ORIA

Min.Max.Mean

Gauging station

Specific flow (l-1 km-2)

Mean anual flow (m3s-1)Surface (km2)

River length (km)

River


Fish-pass No Fish-pass

Obstacles Obstacles affectingaffecting migration: migration:

Hydroelectric use Other X Without use

Upstream Downstream



325124,55,61,2Oria (Irura)/1976

BMWP’DBO5 (mg/l)

DQODI (mg/l)NH4+Ox. Dis. (mg/l)

1 Cleaning up plant (station) for 40.000 people

9115.6001.80023.0002001

6116.0003.50025.0001997

21333.00029.00059.0001989

21662.00065.00097.0001982

01748.00061.00078.0001976

Factory Purifiers

Paper Factories amount

DQO

(kg/d)

Sól. Susp (kg/d)

Flow (m3/d)Year

Paper Factories Dumping Evolution in Oria River Basin


Historic evolution in the Oria Basin:- Water quality in 1975

- Cleaning up plan situation


DQODI (mg/l)DBO5 (mg/l)NH4+ (mg/l)Tendence DQODI

Water Quality evolution in Oria Basin: physical and chemical

DQO NH4+, DBO5

20

40

60

80

100

120

20

40

60

80

100

120

20

40

60

80

0

12

24

36

2

4

6

3

6

9

082 84 86 88 90 92 94 96 98 00 02

Year

High point

Low point

Medium point


Séminaire Indicang 18 et 19 mai 2005 Item Zero: environment

Water Quality evolution in Oria Basin: Biological

- Araxes river

0

20

40

60

80

100

120

1981 1989 1991 1993 1995 1997 1999 2001 2003

IBMWP

SPRING

SUMMER

Séminaire Indicang 18 et 19 mai 2005 Item Zero:resource

Eel abundance and distribution in Oria Basin:

Historic data:Abundant; >80/1000m2Abundant; >80/1000m2Moderate; 30-80/1000m2Moderate; 30-80/1000m2Poor; 8-20/1000m2Poor; 8-20/1000m2Very Poor; 1-3/1000m2Very Poor; 1-3/1000m2 AbsentAbsent

* These data are underestimated, mainly in low river basin, * These data are underestimated, mainly in low river basin, as we have seen in 2004 eel specific surveysas we have seen in 2004 eel specific surveys


102030405060708090

10 20 30 40 50 60 70

Distance to mouth (km))

Ee

ls/1

00

0 m

Eel abundance and distribution in Oria Basin:

Item Zero:resource


Eel fisheries in the basin

- Launch of fisheries monitoring plan. 2001

- New regulation issued. 2003. 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


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 reportItem Zero: explotation


Boat fishing Land fishing

Glass eel fishing types in the Oria river basin

Item Zero: explotation

•Sieve

•Wave

•Wall trawling

•Hoe

•Boat


Regular sampling net in the Oria Basin:

Automatic control stationsAutomatic control stations

Item Zero: available information

Biotic IndexesBiotic Indexes

Fish ComunityFish Comunity

FQFQ

Séminaire Indicang 18 et 19 mai 2005 Item Zero: available information

Most important studies carried out in theOria river basin

Diputación Foral de GipuzkoaWaterflow regime controlWaste Dumping controlWater quality controlFish populations management (Atlantic Salmon Reintroduction)River continuity, obstacles elimination

Gobierno VascoHydrological PlanningWaste Dumping controlWater quality control, Framewok DirectiveHabitat description, Framewok Directive


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


Description of fisheries 2003/2004

0

10

20

30

40

50

60

70

80

Oct. Nov. Dec. Jan. Feb. March

Date

Fis

he

rs

Trawling

Sieve

Boat

Wave

Total

- Fishermen/gear

- More fishermen in January

- More fishermen in boat and sieve

Results glass eel


Description of fisheries 2003/2004

- Catches/Fishing effort

- Significant differences in CPUES among fishing gears (p=0,0003),higher in boat and sieve

-

Trawling

Sieve

Boat

Wave

Total0,000

0,020

0,040

0,060

0,080

0,100

0,120

0,140

0,160

0,180

Oct. Nov. Dec. Jan. Feb. March

CP

UE

s (k

g/h

)

-Highest CPUEs in December but no significant differences among months in each modality

Results glass eel


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


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 siltingNot 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


1,5 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


2.0741.6103.7042.2742.9196.042Failure condition

81.39845.7802.16432.28624.6019.665valid.Var (N)

3.841g.l. 1; χ20,95

0.07102.53261.05422.15422.41965.1360χ2

0.5480.5950.4210.5300.4770.290P

152.0138.4339.5282.62160.142994.42Var (N)

114874527304260218514807Nsup./Ha

109534289214240616693790N/Ha

104204050123220914882774Ninf./Ha

44920324195195256CT

55266223568C3

125446634866C2

26913312110112122C1

20 - 3020 - 3030 - 12030 - 4030 - 12030 - 120Depth (cm)

441314 3430Width (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



243.732408.888838.927139.37756.996Failure

condition

0.5350.6690.5000.4270.5710.459P

1036.0396.6172.001702.63275.631239.41Var (N)

125344307299374616793185Nsup./Ha

111423928177285414412531N/Ha

9750354955196212031877Ninf./Ha

39417718173160188CT

125446634866C2

26913312110112122C1

20 - 3020 - 3030 - 12030 - 4030 - 12030 - 120Depth (cm)

441314 3430Width (m)

S.P. Desemb.

S.P. Andatza

Leitzaran Olazar

Leitzaran AndoainAndoainZubieta

2 passes- Seber & Le Cren (1967)

•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)



Density decrease, 3 dams between the two points

.

0

2

4

6

8

10

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

Length (cm)

% num.

Eel population structure. Andoain station. Oria river. Summer 2004

1.669 eels /Ha – Distance to mouth: 22 Km

Eel population structure. Zubieta station. Oria river. Summer 2004

.

0

1

2

3

4

5

6

7

8

9

10

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

Length (cm)

% num.

3.790 eels /Ha – Distance to mouth: 15 Km



.

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

Length (cm)

% num.

Eel population structure. Olazar station. Leitzaran river. Summer 2004

214 eels /Ha – Distance to mouth:25 Km

0

2

4

6

8

10

12

14

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

Length (cm)

% num.

Eel population structure. Leitzaran station. Leitzaran river. Summer 2004

2.406 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



Stream that flows in the estuary with high recruitment

.

0

1

2

3

4

5

6

7

8

9

10

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

Length (cm)

% num.

Eel population structure. Ab. Adantza station. San Pedro river. Summer 2004

4.289 eels /Ha – Distance to mouth4 Km

.

Eel population structure. San Pedro station. San Pedro river. Summer 2004

0

1

2

3

4

5

6

7

8

9

10

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

Length (cm)

% num.10.953 eels /Ha – Distance to mouth1,5 Km



- 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?


Documents

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