Aquaculture Europe 2023

September 18 - 21, 2023


Add To Calendar 20/09/2023 16:45:0020/09/2023 17:00:00Europe/ViennaAquaculture Europe 2023USE OF STEREO BAITED REMOTE UNDERWATER VIDEO SYSTEMS (STEREO-BRUVS) TO ASSESS THE OCCURRENCE AND ABUNDANCE OF WILD BENTHIC FISH SPECIES AT AQUACULTURE SITESStolz 2The European Aquaculture Societywebmaster@aquaeas.orgfalseDD/MM/YYYYaaVZHLXMfzTRLzDrHmAi181982


L. Bromann*1 , C. Stolz1 , A. Stene1 and S. Bakke1

1 Department of Biological Sciences Ålesund, Norwegian University of Science and Technology, Larsgårdsvegen 4, 6009 Ålesund, Norway.

Email : lara.b



Sea -based aquaculture sites attract a  wide  range of wild marine species  (Barrett et al. 2019). These species  can either be attracted to the shelter provided by the marine infrastructure, or to wastes discharging from the fish farm,  such as  feed or excrements.  Artificial habitats in natural environments can  disrupt  the natural behavior of the attracted species . For instance, the organisms  may prefer the artificial habitat over the natural one, even if this means that it leads to impaired reproduction, altered body conditions and reduced survival (Dempster et al. 2011, Tanner & Williams 2015). The existence of such ecological traps has been well documented in terrestrial systems, however, the studies on ecological traps in the marine environment is limited. 

 Previous studies on the interaction between intensive aquaculture and wild fish have been very much focused on pelagic species occurring in immediate proximity to the net pens (Dempster et al. 2009). However, benthic impact  assessment has suffered from the lack of a holistic approach, with very few studies focusing  on the effects of aquaculture on larger (epibenthic) biota in greater depths (below 50 m).

The aim  of this ongoing study i s to examine  the effect of aquaculture  on  demersal fish living in  temperate  deeper waters.  Specifically,  the goal is to  provide a  systematic  overview of the  fish species visiting the seafloor beneath fish farms and explore  differences between aquaculture locations , seasons and production status along Norwegian fjords.

Material and methods

Stereo baited remote underwater videos systems (BRUVs) consisting of a metal frame with two cameras, lights and a bait container  (Fig. 1)  were deployed  from November 2021 to March 2023 at  10 aquaculture locations in Storfjorden and Romsdalsfjorden in Møre and Romsdal county (Norway) .  Of 51 BRUV deployments 19 were taken at farms with ongoing production , 9 were taken at farms  during a fallow period of minimum 2 months and  23 were taken at c ontrol  areas (ca. 1 km away from farming site),  uninfluenced by  the fish farm activities and discharge. BRUVs were lowered onto the seabed (75 – 200 m ) and stereo videos were recorded  for 60 minutes.

 The video recordings were  systematically  analyzed  to extract  species identification and counts (maximum number of finfish present in the field of view of the cameras , MaxN ) (Watson et. al 2010). As a measure of fish density in the vicinity, the parameter “time to the first appearance of finfish” was used.  Measurements were conducted using the EventMeasure  software  by SeaGIS (20 21). Th e effect of fish farms  and certain environmental factors  on the  demersal  fish community will be tested with hierarchical multivariate statistics. Specifically, it will be tested if fish farms  itself (farm vs. control) or their production status (production vs fallow period)  have an effect on finfish abundance,  presence and community composition across seasons.


 Data of the experiment is still  being analyzed.  Preliminary results indicate that the seafloor in around 100m under aquaculture sites is visited by a rather high diversity of finfish species, albeit infrequently.  Across all different farming sites, a total of 15 different finfish species were observed, of which respectively 10 species were observed at farms with ongoing production, 10 at control areas and 14 at fallow farms. An average of 2.7 (SD 1.8) finfish were observed within a 60min deployment.

 As a first  statistical  trend, no significant  influence of fish farms on the abundance or presence of demersal finfish close to the bottom under deep fjord aquaculture sites. Both the site (fish farm vs. control) and status (production vs. no production) do not seem to have any significant impact on species composition, presence , and abundance.


Although aquaculture sites  presumably have a huge environmental effect on their surroundings, t he study  indicates that  occurrence and abundance of benthic demersal fish at a depth of 75 -200m  is not affected  by aquaculture  farming activities. Furthermore,  it  showcases  that  BRUVs offer a low-cost alternative to diver operated observations and  have great potential not only in shallow, tropical but also  in  deeper temperate waters . However, the influence of light and associated bait  on attracting finfish and leading to biased estimates needs to be further investigated.


Barrett LT, Swearer SE, Dempster T (2019) Impacts of marine and freshwater aquaculture on wildlife: a global meta‐analysis. Rev Aquac 11:1022–1044.

Bernard ATF, Götz A, Parker D, Heyns ER, Halse SJ, Riddin NA, Smith MKS, Paterson AW, Winker H, Fullwood L, Langlois TJ, Harvey ES (2014) New possibilities for research on reef fish across the continental shelf of South Africa. S Afr J Sci 110:1–5.

Dempster T, Sanchez-Jerez P, Fernandez-Jover D, Bayle-Sempere J, Nilsen R, Bjørn P-A, Uglem I (2011) Proxy measures of fitness suggest coastal fish farms can act as population sources and not ecological traps for wild gadoid fish. PLoS One 6:e 15646.

Dempster T, Uglem I, Sanchez-Jerez P, Fernandez-Jover D, Bayle-Sempere J, Nilsen R, Bjørn PA (2009) Coastal salmon farms attract large and persistent aggregations of wild fish: an ecosystem effect. Mar Ecol Prog Ser 385:1–14.

 Tanner JE, Williams K (2015) The influence of finfish aquaculture on benthic fish and crustacean assemblages in Fitzgerald Bay, South Australia. PeerJ 2015:1–19.

 Watson DL, Harvey ES, Fitzpatrick BM, Langlois TJ, Shedrawi G (2010) Assessing reef fish assemblage structure: How do different stereo-video techniques compare? Mar Biol 157:1237–1250.