1. Study of the demersal fish community of the Flemish Cap (NAFO Div. 3M): Changes in community structure and common trends during the period 1988-2008. Alfonso Pérez-Rodríguez, Mariano Koen-Alonso*, Fran Saborido-Rey Institute of Marine Research, CSIC, Spain. *Northwest Atlantic Fisheries Centre, DFO, Canada. ICES/NAFO Symposium on the variability of the North Atlantic and its marine ecosystems during 2000-2009 Santander, Spain, May 10-12 2011 Fisheries Ecology

2. Introduction: Flemish Cap.

3. 1.- Study of the whole demersal fish community: common trends in time series of biomass of both commercial and non commercial species from 1988 to 2008. 2.- Evaluation of the importance of: - Oceanographic conditions - Fishing. - Post-larval predation. Aims of the study

4. Material & methods 1.- Material: Index of Biomass by swept area and temperature from the EU (IEO, IIM-CSIC, AZTI-Tecnalia and IPIMAR) July surveys in Flemish Cap for the period 1988- 2008. NAO index from the NOAA website: http://www.cpc.noaa.govhttp://www.cpc.noaa.gov Declared and estimated catches from the NAFO website and scientific assessments: http://www.nafo.int/about/frames/about.htmlhttp://www.nafo.int/about/frames/about.html 2.- Methods: Dynamic Factor Analysis (DFA) (Zuur et al, 2003). MDS and PERMANOVA.

5. Groups of demersal species Groups of species: Group 1: >0.05% total biomass Group 2: 15 years Group 3: <0.05% total biomass & < 15 years

6. DFA models. Groups I and II 1.- Models without explanatory variables, only common trends 2.- Models with explanatory variables: - NAO index: average value of 4,5,6 and 7 previous years - Index of Fishing pressure: AEF=Total catches/Total fish biomass - Predation: Piscivorous abundance

7. Results: Group of species I

8. AIC values Model fitResiduals

9. Results: Group of species II

10. AIC values Results: Group of species II

11. Values of coefficients in groups I and II: NAO index

12. Values of coefficients in groups I and II: AEF and Piscivorous Group IGroup II

13. Analysis of obtained common trends Group I Group II

14. Results: Group of species III

15. PERMANOVA: significant differences between “positive” and “negative” groups of years. MDS:

16. Recruitment or migration? For species of group III, Flemish Cap present suboptimum conditions. As the thermal conditions change, the “rare” species composition changes. No migration: previous works pointed to the isolation of the shallowest populations. The two years overlap of cold and warm periods points towards a recruitment process:  Larval “immigration”?  “Ghost” adults?

17. Conclusions 1.- The NAO index seems to be a good predictor for the dynamic of the fish demersal community in Flemish Cap due to its correlation with oceanographic conditions (mainly temperature). 2.- Fish predation is a key driver in the changes observed in the demersal community and its relative importance in relation to the other forcing factors is higher in the group of species II than in the group I. 3.- Fishing activity has shown a significant effect, although it was more important in the group of commercially important species (group I). Deviance from the expected negative effect could be ascribed to indirect effects (e.g. trophic cascades). 4.- In the group of rare species, changes could be related with variations in recruitment in relation with temperature preferences. Larval “immigration” is possible, although the existence of “ghost” adult individuals is a plausible hypothesis. 5.- The aim of this study are the global effects and global responses. Individual species studies, considering the spatial dimension are necessary in order to go deeper in the relationship of each particular species dynamics with the biotic and abiotic conditions surrounding it.

18. Special thanks to: Staff from the NAFC-DFO. AZMP programe Staff involved in the EU annual survey (IEO, IPIMAR, AZTI-Tecnalia and IIM) NEREUS program. Alfonso Pérez-Rodríguez, Mariano Koen-Alonso*, Fran Saborido-Rey Institute of Marine Research, CSIC, Spain. *Northwest Atlantic Fisheries Centre, DFO, Canada. ICES/NAFO Symposium on the variability of the North Atlantic and its marine ecosystems during 200-2009 Santander, Spain, May 10-12 2011 Fisheries Ecology