1. ICES/FAO Working Group on Fish Technology and Fish Behaviour
Questioning the effectiveness of implemented technical measures under the EU landings obligation: the Basque Otter Bottom Trawl fishery case study
Nekane Alzorriz, Luis Arrregi, Bent Herrmann, Manu Sistiaga, Jan Jaap Poos
(Lisbon, 4-7 May 2015)

2. The Fleet & the gear The fleet 7 vessels, (37-42 m)
Fishing mainly in ICES VIIIabd
Targeting demesal species (Monkfish, megrim, hake, squids, red mullet,…)
The trawl
Footrope length m
Floatline heith 1,8-2,4 m
Wingspread m
Towing speed 4 knots
Not very much evolution in last years. The evolutions have been focused on trawl doors (from wood to steel doors), bridles (covered with netting to increase wing length) and towing speed (from 3,5 to 4,0 Knots)

3. Technical measures Codend “Reg. (EC) 494/2002”
Material < 6 mm single twine or < 4 mm double twine
100 free meshes around (When 100 mm) or 120 free meshes around (When 70 mm)
100 mm Minimun mesh size or 70 mm mesh size and < 15% Hake
When 70 mm mesh Size:
Selective Device “Reg. (EC) 51/2006”
Square Mesh Panel (SMP) > 2 meter long & >1 meter width
Twine single < 4 mm
Mesh size > 100 mm
Set 12 meshes before the codend.

4. Sampling during 2010-2012 in OTB operating in Bay of Biscay
Year
Metier
Total trips
Sampled trips
Sampling coverage %
2010
OTB_DEF_>= 70
166 5
3,01%
OTB_MCF_>= 70 99 2
2,02%
2011
124 7
5,65%
129
5,43%
2012
102 3
2,94%
162 11
6,79%
Fishing and Sampling effort by metier (DCF Level 6)
during
Sampled hauls during Size
proportional to discarded catch (Kg)

5. Metier: Demersal
Discards: - Horse mackerel, dogfish, mackerel and blue whiting > 70% of total discarded weight species; 57 of them included in “other species”
Landings: - 67 species. Very mixed-species fishery. Main target species: Hake, Monkfish and Megrim.

6. Metier: Mixed Cephalopod & Demersal
Discards: - Horse mackerel and Mackerel >60% of total discarded weight.
- 89 species discarded (including invertebrates)
Landings: - European squid, common cuttlefish and striped red mullet ≈ 50% of landings
- 70 species (including invertebrates)

7. Fleet situation regarding discards
According to new EU policy and the fleet exploitation pattern referring to discards. Discard ban could be a threat for the fishing activity.
Solutions were needed
OPPAO Fishermen Organization required from AZTI to start a project dealing with discard reduction, focused on commercial species. All experiments were carried out on board commercial vessels.

8. Sea trials and data collection
A total of 73 hauls between Nov 2011 and July 2013
Species selected were bib (BIB), hake (HKE) and red mullet (MUR)
X Total selectivity estimation (SMP + C)
15 hauls under commercial fishing conditions
◊ Selection properties of the SMP alone
58 hauls under a research survey of fish abundance

9. Methodologies used Total selectivity estimation (SMP + C)
Dual selection model: Zuur et al. (2001) and O’Neill et al. (2006)
Based on a logit size selection model, following the procedure described in Sistiaga et al. (2010)
Parameters for the SMP: CSMP, L50SMP and SRSMP
Parameters for the C: L50codend and SRcodend
Parameters for the combined selectivity: L50dual and SRdual
Selection properties of the SMP alone
“SMP only size selection” with the same estimation procedure as the 3 compartment setup
Based on a logit model, similar to the one described in Herrmann et al. (2013)

10. Methodologies used Fall- through experiment:
To assess the potential size selection of the SMP and to solve potential problems with the estimation of the CSMP
Constraint: L50SMP ≥ 0.5 * L50fall
Herrmann et al. (2009)
Parameters of the SMP:
L05fall , L50fall and SRfall
L05fall can be interpreted as the size of fish with 95% escapement probability through the SMP

11. Methodologies used
Selectivity data were analyzed using SELNET Herrmann et al. (2012)
Selection parameters
Accounting for the uncertainty in estimation due to:
Within and between haul- variation
Subsampling in data
Fit statistics based on the p-value
Retention / Escapement probability of undersized individuals

12. Fall- through experiment
Results
Fall- through experiment
Potential selectivity
of the SMP
BIB
HKE
MUR
L50fall (cm)
26.10
( )
50.55
( )
31.49
( )
SRfall (cm)
1.72
( )
0.10
( )
( )
L05fall (cm)
23.79
( )
50.41
( )
31.36
( )
p- value
0.98
1.00 12

13. Total selectivity estimation (SMP + C)
Results
Total selectivity estimation (SMP + C)
3 compartment setup 13

14. Total selectivity estimation (SMP + C)
Results
Total selectivity estimation (SMP + C)
BIB
HKE
MUR
L50 (cm)
SMP
13.05
( )
37.58
( )
20.52
( )
Codend
18.08
( )
20.29
( )
13.36
(4.89 – 18.68)
Dual
18.15
( )
20.44
( )
13.47
( )
SR (cm)
5.51
( )
0.10
( )
( )
4.45
( )
8.40
( )
13.04
( )
4.41
( )
8.61
( )
13.19
( )
CSMP
0.15
( )
0.02
( )
0.01
( )
Dual retention <MLS (%) *
51.45
( )
45.20
( )
SMP escapement <MLS (%)
1.73
( )
0.87
( )
C escapement <MLS (%)
46.82
( )
53.93
( )
p- value
0.51
0.77

15. Selection properties of the SMP alone
Results
Selection properties of the SMP alone
2 compartment setup 15

16. Selection properties of the SMP alone
Results
Selection properties of the SMP alone
BIB
HKE
MUR
2012
2013
L50SMP (cm) *
49.51
( )
39.64
( )
29.56
( )
23.42
SRSMP (cm)
0.10
( )
7.80
( )
( )
( )
CSMP
0.00
0.04
( )
( )
0.01
( )
( )
SMP escapeme nt <MLS (%)
(0.00)
4.10
( )
4.84
( )
p- value
1.00
0.03
0.90
0.98 16

17. Conclusions
Multispecific fishery with more than 20 marketable species, with different morphological characteristics and MLS. Difficult to find a single selectivity device that satisfied all species.
Fall-through experiment have demonstrated that the SMP would allow the release of inmature and undersized fish.
The contact values for all three species suggest that the SMP contribution to the selectivity is very small. Less than 4% of the hake and red mullet were predicted to have a chance to escape through the SMP.
The selectivity for these three species is mainly attributed to the codend.
The limited effectiveness of the SMP for these species in this fishery highlights that gear-specific regulations should be tested before implementation.

18. Paper submitted to ICES Journal of Marine Science
Title: Questioning the effectiveness of implemented technical measures under the EU landings obligation: the Basque Otter Bottom Trawl fishery case study
Authors: Nekane Alzorriz1*, 2, Luis Arrregi2, Bent Herrmann3, Manu Sistiaga4, Jan Jaap Poos5
1 European Commission, Joint Research Centre; Institute for Protection and Security of the Citizen; Maritime Affairs Unit G.03; TP 051, Ispra (VA), Italy.
2 AZTI-Tecnalia; Marine Research Division; Txatxarramendi ugartea w/n; Sukarrieta; Spain.
3 SINTEF Fisheries and Aquaculture, Fishing Gear Technology, Willemoesvej 2, 9850 Hirtshals, Denmark.
4 SINTEF, Department of Marine Environmental Technology, Norway.
5 Wageningen IMARES, Institute for Marine Resources and Ecosystem Studies, PO Box 68, 1970 AB IJmuiden, The Netherlands.
* Corresponding author; tel: ; fax: ;