Ecosystem overviews

Bay of Biscay ecoregion

Pressure: Selective extraction of species

​​​​​​Fishing is the main activity contributing to this pressure in the Bay of Biscay and the Iberian Coast ecoregion. Both demersal and pelagic commercial fisheries occur in most parts of the ecoregion. Recreational fishery is becoming a relatively important activity and is in some cases taken into consideration for the management of marine fisheries. Tourism is also linked to aquatic and marine activities that contribute to the increase of this pressure in coastal areas. This pressure has four main effects on the ecosystem and its components, described below.

Impacts on commercial stocks

Image A shows the historical evolution of fishing mortality and spawning-stock biomass relative to reference points by fish guild in the Bay of Biscay and the Iberian Coast ecoregion. A general decrease of fishing effort in the region (in many cases through reduction of the fleet) has contributed to an overall decline in the fishing mortality (F) of commercial fish stocks since 1988. The mean F is now closer to the level that produces maximum sustainable yield (MSY); as a consequence an increase in the mean spawning-stock biomass has been observed since 2002. Stocks of small pelagics like sardine and anchovy are highly influenced by natural recruitment variability and are therefore prone to periodic collapses linked to oceanographic variability. These stocks are closely monitored and regulated by strict management.

Impact on threatened and declining fish species

Stocks of several fish species have been adversely affected by fishing and are now on the OSPAR list of threatened and declining species (see full list below). These include the sturgeon Acipenser sturi, European eel Anguilla anguilla, gulper shark Centrophorus granulosus, skates and rays like Dipturus batis, Raja montagui, and Rostroraja alba, spurdog Squalus acanthias, and salmon Salmo salar. Although there are no TACs for these species and some are prohibited to be landed under EU law, several species are vulnerable to existing fisheries. Common skates, and less often spurdogs, are caught as bycatch in demersal trawl fisheries while deepwater sharks are caught in the mixed deep-water trawl fishery.
Impacts on foodwebs
Fishing can disturb the foodweb. Predator–prey relationships can change, depending on the species and on the amount of food (prey) that is available for a given predator. Poor management of fishing for one species could have an adverse effect on the whole foodweb. Multispecies assessment methods can account for some of these interactions and guide appropriate management measures.
Indicators like the large fish indicator (LFI) index (describing the proportion – by weight – of the demersal fish community on survey catch larger than regional length thresholds) can be used to monitor changes in the fish populations. In the Bay of Biscay, the LFI index has shown a positive temporal trend since the year 2000 (image B). There is no trend in the LFI in Portuguese waters. The index shows high interannual variability.

Impacts on seabirds and marine mammals

Observation of marine mammal bycatch has occurred in certain fisheries off France and in a few off Galicia. Harbour porpoises Phocoena phocoena are being caught as bycatch off Iberia in set nets to the extent that the local population of the species may become extinct. Set net fisheries and pelagic trawls, particularly those for seabass Dicentrarchus labrax, have caught common dolphins Delphis delphinus and striped dolphins Stenella coeruleoalba. Seabird bycatch seems likely to be part of the reason for the loss of the Iberian form of the common guillemot Uria aalge and some other seabird species.

​Other pressures in the Bay of Biscay and Iberian coast ecoregion

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​​ A. Time-series of average of relative fishing mortality (F to FMSY ratio) and biomass (SSB to BMSY trigger ratio) by fish guild. Mean F and mean SSB is by total number of stocks with reference points. Click image to enlarge.

B. Time-series of the large fish indicator (LFI) in the Bay of Biscay (ICES, 2013a). Click image to enlarge.
C. Time-series of the large fish indicator (LFI) in Portuguese waters (ICES, 2013a). Click image to enlarge.
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Bay of Biscay ecoregion

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