Active management is required to turn the tide for depleted Ostrea edulis stocks from the effects of overfishing, disease and invasive species

• Published in: PeerJ
• Main Authors: Helmer, Luke, Farrell, Paul, Hendy, Ian, Harding, Simon, Robertson, Morven, Preston, Joanne
• Format: Article in Journal/Newspaper
• Language: English
• Published: PeerJ 2019
• Subjects: theme:invasion management; active management; Bonamia ostreae; ecological niche; invasive species; Ostrea edulis; invasive species management; invasion management; overfishing; Pacific; Pacific oyster
• Online Access: http://www.wikidata.org/entity/Q64091544; https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6397756; https://doi.org/10.7717/PEERJ.6431

<jats:p>The decline of the European oyster<jats:italic>Ostrea edulis</jats:italic>across its biogeographic range has been driven largely by over-fishing and anthropogenic habitat destruction, often to the point of functional extinction. However, other negatively interacting factors attributing to this catastrophic decline include disease, invasive species and pollution. In addition, a relatively complex life history characterized by sporadic spawning renders<jats:italic>O. edulis</jats:italic>biologically vulnerable to overexploitation. As a viviparous species, successful reproduction in<jats:italic>O. edulis</jats:italic>populations is density dependent to a greater degree than broadcast spawning oviparous species such as the Pacific oyster<jats:italic>Crassostrea</jats:italic>(<jats:italic>Magallana</jats:italic>)<jats:italic>gigas</jats:italic>. Here, we report on the benthic assemblage of<jats:italic>O. edulis</jats:italic>and the invasive gastropod<jats:italic>Crepidula fornicata</jats:italic>across three actively managed South coast harbors in one of the few remaining<jats:italic>O. edulis</jats:italic>fisheries in the UK. Long-term data reveals that numbers of<jats:italic>O. edulis</jats:italic>sampled within Chichester Harbour have decreased by 96%, in contrast numbers of<jats:italic>C. fornicata</jats:italic>sampled have increased by 441% over a 19-year period. The recent survey data also recorded extremely low densities of<jats:italic>O. edulis,</jats:italic>and extremely high densities of<jats:italic>C. fornicata</jats:italic>, within Portsmouth and Langstone Harbours. The native oyster’s failure to recover, despite fishery closures, suggests competitive exclusion by<jats:italic>C. fornicata</jats:italic>is preventing recovery of<jats:italic>O. edulis</jats:italic>, which is thought to be due to a lack of habitat ...