Chelidonichthys cuculus - GUR Eutrigla gurnardus - GUG. Trigla lyra - GUN. Chelidonichthys lastoviza - CTZ. Chelidonichthys obscura - GUM. Separating by ...
Finding ways to solve species misclassification in landings: application to gurnards in ICES Division 9.a Rocha A.1, Feijó, D. 1, Moreno, A. 2, Silva, C. 2, Azevedo, M. 2 1Modeling 2Modeling
and Management of Fishery Resources, IPMA Matosinhos, Av. General Norton de Matos, 4; 4450-208 Matosinhos, Portugal; arocha@ipma.pt and Management of Fishery Resources, IPMA Algés, Rua Alfredo Magalhães Ramalho, 6; 1495-165 Algés, Portugal
Across the NE Atlantic, the category “gurnards” may include as many as 8 different species. However, ICES landing statistics are not discriminated to species level. In Portugal, “tub gurnard” is the only species reported since 2000. The market sampling of the Data Collection Framework is the only reliable source of data for the definition of allocation keys for species composition in landings. Portuguese DCF market sampling data for the period 2009-2016 in Division 9.a was used to estimate the total annual gurnard landings by the polyvalent fleet.
Material and Methods: sampling a fishing trip all species sampled concurrently
Chelidonichthys lucerna - GUU
mix of gurnards in a box
Trigla lyra - GUN
Separating by species, measuring lenght and weight per species Chelidonichthys cuculus - GUR Eutrigla gurnardus - GUG
Chelidonichthys obscura - GUM Chelidonichthys lastoviza - CTZ
Allocation keys: Mixture proportions aggregated by • Port • Month • Year • Fishing Gear
Results:
Figure 1 – Proportion of gurnard landings by port and by area.
Figure 2 – Ports and areas considered for this study
Gurnard landings in NW (77.3%) > SW (21.3%) > S (1.3%) Most important ports: Matosinhos, Aveiro, Peniche Mixture proportions are consistent within the areas throughout years Mixture proportions differ across the areas NW: C. lucerna (GUU) is the most abundant species, instead of L. cavillone (LVD) SW: C. cuculus (GUR) and C. lucerna (GUU) are the most abundant species. L. cavillone (LDV) was not observed S: DCF/NP sampling was inconclusive as far as species composition of gurnard landings is concerned L. cavillone, the most abundant species on landing reports, was never observed. It has no commercial value and is discarded at sea
Conclusions:
Figure 3 – Left to right: proportion of species in total gurnard landings, of landings covered by DCF/NP and estimates based on DCF/NP sampling.
Table 1 – Gurnard landings and DCF/NP based-estimates, by gurnard species, in the period of 2009-2016. Projections of Projections of sampled total landings landings (ton) (ton)
Species
Total Landings (ton)
Landing coverage (%)
Sampled Landings (ton)
CTZ
0.000
0,00%
0.00
GUG
2.116
94.34%
1.99
1.74
2.69
GUM
0.000
0,00%
0.00
51.14
78.95
GUN
9.908
93.86%
9.30
44.59
68.84
GUR
374.164
50.84%
190.23
165.51
255.52
GUU
282.676
56.05%
158.45
706.24
1 090.32
GUX
15.941
34.55%
5.51
46.80
72,26
LDV
907.861
73.37%
666.14
0.000
0.00
15.21
23.49
GUR LDV
GUU GUN GUM CTZ
Estimates based on DCF/ NP sampling suggest that official reports on gurnard landings are innacurate and unsuited for use in stock status assessment of commercially relevant gurnards (C. cuculus – overreported, E. gurnardus – underreported and C. lucerna – severely underreported). Improvement of current estimates of gurnard landings via modeling would require a more species focused sampling effort that falls outside the current scope of DCF/NP.
Acknowledgements:
Bibliography:
This work has been done under the European Commission’s Data Collection Framework PNAB/EU-DCF Programa Nacional de Amostragem Biológica (Reg. EC 2008/199). PNAB’s Technicians in fish auctions and specially Bernardo Alcoforado, Catarina Maia and Andreia Silva for their help in this work. Prof. Paulo Santos for all the support and incentive to study gurnards.
Feijó D., Rocha A., Santos P., Saborido-Rey F. 2008. Statistical Species characterization of Gurnard Landings in North of Portugal. Conference handbook (ICES CM 2008/K:15) ICES Annual Science Conference, Canada. pp. 10. Rocha A, Feijó D, Santos P. 2008. An insight on gurnard Fisheries in North of Portugal Foro Ac. Rec. Mar. Rías Gal. 10: 609-615.
IX Simpósio da Margem Ibérica Atlântica 2018 - Coimbra, Portugal – 4-7 September 2018
