Sharing the neighbourhood: assessing the impact of kelp harvest on foraging behaviour of the European shag

Abstract

Coastal kelp forest ecosystems create dynamic and productive habitats, supporting a wide range of epiphytic flora, invertebrates, fish and seabirds. Worldwide, kelp is harvested commercially, affecting kelp-associated animal communities. There is, however, limited knowledge of how fish and seabird respond to kelp harvest, highlighting the need to evaluate the ecological impact of harvest on all ecosystem levels. Using 6 years of GPS-tracking data, we examined the effects of kelp harvest on foraging behaviour of breeding European shags (Phalacrocorax aristotelis) from a colony in central Norway. We determined the spatial overlap between kelp harvest and foraging areas of shags and assessed the immediate, short- and long-term impacts of harvest on shag foraging behaviour. Our results demonstrated large spatial and temporal overlap in areas used by foraging shags and kelp harvest. We could not detect any clear alterations in the diving activity of shags due to kelp harvest. However, the broad temporal and spatial scale of our study constrained the detection of fine scale changes in shag behaviour in response to kelp harvest. Our study, nonetheless, identifies several issues that should be addressed before concluding on the effects of kelp harvest on seabird populations. This includes the need for experimental studies using directed and controlled harvest to investigate the effects of kelp harvest through the different trophic levels, including top predators. This is essential for ecosystem-based management of coastal resources, considering the many species composed in the coastal ecosystem.

Current Insights into the Molecular Mode of Action of Seaweed-Based Biostimulants and the Sustainability of Seaweeds as Raw Material Resources

“…While it was suggested that Phalacrocorax carbo foraging behaviour was altered due to harvesting, its population development was unchanged [ 128 ], suggesting no long-term effects. No alterations in the diving activity of Phalacrocorax aristotelis due to kelp harvesting were observed [ 129 ]. As birds such as P. carbo and P. aristotelis do not form obligate relationships with seaweed, the effects of harvesting on such species may be limited or absent.…”

Predicting Foraging Habitat of European Shags - A Multi-Year and Multi-Colony Tracking Approach to Identify Important Areas for Marine Conservation

“…Seabirds are among the most threatened taxonomic groups of birds, facing a multitude of mostly anthropogenic stressors (Dias et al, 2019). These range from oil exploration (Votier et al, 2005;Votier et al, 2008), establishment of wind farms (Garthe and Hüppop, 2004;Furness et al, 2013;Peschko et al, 2020), kelp harvesting (Lorentsen et al, 2010;Christensen-Dalsgaard et al, 2020), bycatch (Anderson et al, 2011;Z ̌ydelis et al, 2013), ship traffic (Dehnhard et al, 2020a) and fisheries (Cury et al, 2011;Saraux et al, 2020) to various impacts of climate change (e.g. Greḿillet and Boulinier, 2009;Keogan et al, 2018), but also include predation by introduced predators (Craik, 1997).…”

“…Shags are vulnerable to disturbance by boats (Velando and Munilla, 2011), and incidental mortality in gillnet fisheries (Z ̌ydelis et al, 2013;Christensen-Dalsgaard et al, 2019). Furthermore, kelp harvesting in areas used by shags for foraging has the potential to affect foraging success (Christensen-Dalsgaard et al, 2020). Finally, aquaculture installations can easily lead to a reduction in available coastal marine habitat, increased boat traffic and therefore higher disturbance effects, and shags are perceived as a pest by the aquaculture industry (Beveridge, 2001).…”