Establishment of Blue Mussel Beds to Enhance Fish Habitats

Abstract

Abstract. Human activity has impacted many coastal fjords causing degeneration of the structure and function of the fish habitats. In Nørrefjord, Denmark, local fishermen complained of declining fish catches which could be attributed to eutrophication and extraction of sediments over several decades. This study aimed to establish blue mussel beds (Mytilus edulis) to increase structural complexity and increase the abundance of fish and epifauna in Nørrefjord. It was expected that the mussels would improve water transparency and increase the depth range and coverage of eelgrass (Zostera marina). New methods for mussel production and -bed construction were investigated in collaboration with local volunteer fishermen. The effect of the artificial mussel beds was most evident on a small scale. Video observations directly at the beds (Impact area) demonstrated increased biodiversity and a three times higher abundance of mesopredator fish compared to the Control area. Water clarity and eelgrass coverage were unchanged. Two methods for establishing mussel beds were tested. A total of 44 tons of blue mussels were produced and established in beds over an area of 121,000 m 2 . Production of blue mussels directly on hemp sacs hanging on long-lines was the most effective method. This new method is potentially a useful management tool to improve fish habitats.

Harvesting geo-spatial data on coastal fish assemblages through coordinated citizen science

“…From the interviews, the scientists gained awareness of local problems, which initiated several projects. An example of this was the Nørre Fjord project, which aimed to restore a fjord area affected by historic sand mining activities, confounded by more recent eutrophication (Kristensen et al, 2015;Poulsen et al, 2012).…”

The ecological function of intertidal shellfish reefs for benthic algae

“…This shows that bivalves are autogenic and allogenic ecosystem engineers at the same time (Jones et al 1994). Our study demonstrates that mussel beds not only facilitate animal biodiversity on many different trophic levels as shown in previous studies (Albrecht and Reise 1994; van der Zee et al 2012; Kristensen et al 2015), but they also provide excellent growing conditions for benthic primary producers across the intertidal. Together, this demonstrates that mussel beds are hot spots that fuel primary production in intertidal areas and support a productive and diverse food web far beyond its physical borders.…”

“…In soft bottom intertidal areas, bivalve reefs are often the only hard surfaces that can be used by other sessile organisms for attachment, favoring habitat forming algae and rich communities of epifauna (Albrecht and Reise 1994). Bivalve reefs are also important nursery grounds for many economically important organisms such as fish (Kristensen et al 2015). In addition to locally modifying the habitat with their physical presence, they also have long distance effects by creating sediment conditions around them that are beneficial for many benthic organisms including infauna species (van der Zee et al 2012; .…”

The benefits of bivalve reef restoration: A global synthesis of underrepresented species

“…Where changes in abundance of associated species were recorded, the bivalve habitats were widely found to support increased numbers of individuals relative to unstructured habitats (e.g. Cook et al, 2013;de Montaudouin, Audemard, & Labourg, 1999;Kristensen et al, 2015;Norling, Lindegarth, Lindegarth, & Strand, 2015; Supporting Information Table S2).…”