Successful eradication of a non‐indigenous marine bivalve from a subtidal soft‐sediment environment

Abstract

Summary 1.Biofouling, the accumulation of biological growth on submerged surfaces such vessel hulls and artificial structures, is an important transport pathway that can facilitate the establishment of marine non-indigenous species in new locations. Despite efforts to develop effective tools to eradicate newly established populations before they become widespread and beyond control, eradication successes are scarce in the marine environment. This paper describes a dredge-based eradication of the brown mussel Perna perna from a deep (c. 44 m) soft-sediment habitat in central New Zealand, following the discovery of this species amongst biofouling organisms physically removed (i.e. defouled) from a drilling rig. 2. We evaluated the efficacy of dredging in removing P. perna and other target species, and determined whether a density-based eradication success criterion had been achieved. The catchability coefficient (q) of the defouled material was estimated using catch data, and the dredge efficiency (E) was determined. Initial and remaining mussel densities were then calculated using estimates of E. The reliability of these estimates was tested by simulations. 3. A total of 227 dredge tows covering c. 94% of a 12AE6 ha target area were undertaken, and an estimated 35 tonnes of material defouled from the rig was dredged from the seabed and disposed of in a landfill. 4. Estimates of q and E were 0AE0054 and 0AE30 (respectively) and mussel densities at the completion of the eradication programme were estimated to be c. 0AE5 m )2 , well below the success criterion of 10 m )2 . From our simulations, it was estimated that 71 dredge tows would be required to remove 50% of the initial population, whilst 232 dredge tows would be needed to achieve a 90% reduction in population size. 5. Synthesis and applications. The eradication of non-indigenous bivalves from a relatively deep (>40 m) soft-sediment environment is unprecedented and highlights that, with appropriate tools and other resources, eradication is feasible even in challenging circumstances. Where complete elimination of a pest is not feasible, alternative density-based success criteria can be developed that, if achieved, can effectively mitigate risks. This study highlights the need for further development of both vector treatment options and pest eradication tools, and improved policy surrounding in-water defouling in the coastal environment.

Exploiting Allee effects for managing biological invasions

“…2004). The use of culling and habitat fragmentation through dredging techniques was used against the brown mussel, Perna perna (L.), and effectively reduced populations below a minimum density required for survival and reproduction (Hopkins et al. 2011).…”

“…Management of the non-native plant Spartina alterniflora Loisel is thought to be optimized by the culling of plant subpopulations, effectively exploiting an Allee effect due to pollination failure . The use of culling and habitat fragmentation through dredging techniques was used against the brown mussel, Perna perna (L.), and effectively reduced populations below a minimum density required for survival and reproduction (Hopkins et al 2011). A modelling approach has suggested that culling sufficient numbers of P. carbo sinensis could led to extinction by effectively exploiting cooperative breeding behaviour (Frederiksen et al 2001).…”

“…The loss of habitat and fragmentation, which are a detriment to rare and endangered species, are complementary in attempts to eliminate unwanted species from an area. Consequently, selective and spatially limited habitat modifications could be used to exploit an existing Allee effect if done on a limited time scale but one of sufficient duration to achieve eradication, such as in the case of terrestrial (Suckling & Brockerhoff 2010) or aquatic animals (Hopkins et al 2011). A population or metapopulation of non-native species could be spatially managed through site-specific control tactics so that large populations are fragmented, or that certain smaller patches across a metapopulation connected through dispersal are targeted.…”

Invasive blue mussels threaten regional scale genetic diversity in mainland and remote offshore locations: the need for baseline data and enhanced protection in the Southern Ocean

“…This history suggests that the Northern Hemisphere M. galloprovincialis on the rig originated in South Africa (into which country they were introduced in the 1960s or 1970s - Grant & Cherry, 1985), were several years old and therefore reproductively mature and were moved between NZ and Australia providing opportunity for spread into both countries. In NZ, the rig was defouled in-water by divers (Hopkins & Forrest, 2010) at which time the biosecurity threat posed by another species, the Asian green mussel (Perna viridis), was recognized and a successful programme of eradication was put in place (Hopkins et al, 2011b). However, the biosecurity threat posed by the blue mussels was not appreciated because they were not recognized at the time as Northern Hemisphere M. galloprovincialis.…”

Some Bryozoa species recently introduced into the Azores: reproductive strategies as a proxy for further spread

“…As a consequence, the risk that populations of potential invaders establish themselves in recipient environments is rapidly increasing [35]. Marine invasive species may create and modify habitats, prey upon or outcompete native species, and act as either disease agents or vectors, or both.…”