EEA mobility grant – Habitat and fish interactions

The beneficiary, Stefan Aki Ragnarsson, received an EEA mobility grant between October 2014 and April 2015, during which time he carried out his research at CSIC, Vigo. The main objectives of this research included habitat mapping and examination of habitat and fish interactions.


Fish and habitat interactions in cold-water coral grounds off SE-Iceland. 

This work was based on findings from the EU-funded CoralFISH project (2008-2013), (, in which the Marine Research Institute of Iceland participated.  The main aim of the CoralFISH project was to investigate the role of cold-water coral habitats for fish. Within Icelandic waters, studies were carried out in Lónsdjúp, off SE-Iceland, which comprises several ridges intersecting a trough. Cold-water coral habitats, mainly comprising the reef-building species Lophelia pertusa and various gorgonian coral species, were mainly found on the ridges. The beneficiary worked on two manuscripts derived from this work. In the former, composition and densities of fish caught inside and outside coral habitats were compared. The data for analysis originated from two long-line cruises carried out in 2009 and 2010. Among the 15 species recorded, tusk (Brosme brosme) contributed ~80% to the total abundance in both surveys (Fig. 1).

Fig. 1. Tusk (Brosme brosme) in a typical cold-water coral habitat in the Lónsdjúp study area.

Catch rates of tusk were twofold higher on the ridges (where the coral habitats were found) compared to off the ridges (Fig. 2), while the remaining species tended to be more common off the ridges. Further statistical analyses showed that the fish community was highly influenced by the overall seascape rugosity (mainly the ridges). However, this study found no evidence that fish were strongly associated with cold-water coral habitats (after analyses had accounted for all remaining variation), but this may be due to the fact that these associations may take place at finer spatial scales than this study examined. The latter manuscript describes findings from a study where the interactions between the dominant species and three-dimensional habitats were examined.

Fig. 2. Location of the Lónsdjúp case study area within Icelandic waters (upper panel). The relative catch per unit effort of tusk (Brosme brosme) caught on long-lines (red dots) within Lónsdjúp (lower panel). Blue stars show the locations of cold-water corals based on video surveys, and green stars show the locations of coral caught as bycatch on long-lines.

Redfish (Sebastes spp.) contributed 77% to the total fish abundance, with most of the remaining individuals belonging to tusk and flatfish species (Fig. 3). The data for analysis was derived from analysis of video footage that was obtained with an underwater camera platform (Campod) during two cruises (2009 and 2010).

Fig. 3. Relative cover of the cold-water coral Lophelia pertusa (upper) and relative densities of redfish (lower). The lines show the video tracks obtained by the underwater camera platform (Campod). Two redfish species were recorded but it was not possible to identify most individuals to species level. Note elevated densities of redfish in the ridge areas, where the coral cover is highest.

This data allowed examination of how the dominant fish species interacted with habitat features, e.g. in terms of behaviour. Two different approaches were applied to describe fish-habitat interactions across a range of spatial resolutions. First, we evaluated the small-scale (mostly <10 m) habitat use of fish, with emphasis on the redfish (Sebastes spp.), the most abundant fish taxon within the study area. At these spatial scales, redfish (Sebastes spp.) were found to be highly associated with various types of three-dimensional habitats, e.g. cold-water corals and boulders.  Second, fish and habitat interactions were examined at larger spatial scales (100 – 3000 m).  For this purpose, the spatial distribution patterns of the dominant fish species were modelled as a function of a combination of eight substrate-type variables, five terrain variables and several spatial predictors. This allowed identification of the most important environmental drivers influencing the fish community and the relevant spatial scales at which these took place. Redfish were found to be significantly influenced by the coverage of coral framework, of isolated colonies and of coral rubble and by various terrain parameters that characterise the ridges and other abrupt seascape features. The level of significance of each of these variables was highly influenced by the spatial scale (Fig. 4).  Flatfish avoided complex seabed. Tusk were mainly associated with complex seabed but not necessarily with cold-water corals.

Fig. 4. Multivariate redundancy analysis portraying the correlations between abundances of the dominant fish taxa, bottom descriptors (bottom type and topography) and spatial predictors. The fish taxa shown are Sebastes spp. (SEB), Hippoglossoides platessoides (HIP) and Pleuronectiformes (PLE).


Habitat mapping in the Atlantic Islands of Galicia National Park.

A workshop with participants from CSIC and the University of Vigo was held on the 8th of April to discuss the steps needed to obtain baseline data on seabed habitats, benthic invertebrates and fish within the Atlantic Islands of Galicia National Park. Operationalising such a project would require funding for the purchase of an underwater camera platform, for vessel time, and for salaries.  If this baseline data were obtained, this would allow further studies to be carried out that specifically examine fish and habitat interactions.

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