title: Long-term coexistence of non-indigenous species in aquaculture facilities.
abstract: Non-indigenous species (NIS) are a growing problem globally and, in the sea, aquaculture activities are critical vectors for their introduction. Aquaculture introduces NIS, intentionally or unintentionally, and can provide substratum for the establishment of other NIS. Little is known about the co-occurrence of NIS over long periods and we document the coexistence over decades of a farmed NIS (a mussel) with an accidently introduced species (an ascidian). Both are widespread and cause serious fouling problems worldwide. We found partial habitat segregation across depth and the position of rafts within the studied farm, which suggests competitive exclusion of the mussel in dark, sheltered areas and physiological exclusion of the ascidian elsewhere. Both species exhibit massive self-recruitment, with negative effects on the industry, but critically the introduction of NIS through aquaculture facilities also has strong detrimental effects on the natural environment.
authors.affiliation: Centre for Invasion Biology, Zoology Department, University of Cape Town, Rondebosch 7701, South Africa. mrius@ucdavis.edu
authors.forename: Marc
authors.initials: M
authors.lastname: Rius
authors.forename: Kevin G
authors.initials: KG
authors.lastname: Heasman
authors.forename: Christopher D
authors.initials: CD
authors.lastname: McQuaid
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017756:Aquaculture / Q000379:methods / Q000706:statistics & numerical data*; D002938:Ciona intestinalis / Q000502:physiology*; D017753:Ecosystem; D058865:Introduced Species; D049878:Mytilus / Q000502:physiology*; D011157:Population Dynamics; D012098:Reproduction / Q000502:physiology; D013019:South Africa