Mytella strigata (Bivalvia: Mytilidae): an alien mussel recently introduced to Singapore and spreading rapidly

ABSTRACT

The American brackish-water mussel Mytella strigata is reported from Singapore for the first time. In 2016 a survey of intertidal hard structures in the Johor Straits revealed its almost ubiquitous presence in high mean densities, up to 124 ± 32 individuals 25 cm⁻² along the shoreline. Subtidal nets employed by floating fish farms were also fouled with this species. Densities exceeding 10,000 individuals 100 cm⁻² were observed, to the exclusion of its relative Perna viridis, the Asian green mussel. Size-frequency analyses of shells indicated the presence of both juveniles and adults. Juveniles have an extremely variable shell surface pigmentation. The adults, reaching 5 cm in shell length, generally have a thick dark greenish brown to almost black periostracum, but bright green and olive green individuals, some with distinctive brown streaks, have also been observed. However, sequences of the mitochondrial COI gene were consistent with mussels from Brazil, Colombia and Ecuador, where they are natively distributed, while shells were reconcilable with type material. The species may have been transported in ballast water and/or with fouling directly from its native provinces, or spread from the Philippines where there are already established populations of M. strigata, possibly since the nineteenth century.

KEYWORDS:

• Alien invasion
• bivalve
• Johor Strait
• non-indigenous species
• Southeast Asia

Acknowledgements

Staff of National Parks Board, Singapore Armed Forces Yacht Club and Singapore Police Coast Guard provided access, and granted permission, to collect material from shorelines under their care. We also wish to thank the Hydrographic Department of the Maritime and Port Authority Singapore for allowing us to collect mussel samples from Gedong buoy at the Brani Buoy Depot. Gary Chang kindly provided space on his floating fish farm off Changi for our nets to be suspended underwater to collect mussel spat. Grateful thanks are due to Andreia Salvador and Wai-Yee Cooper at the Mollusca Section, The Natural History Museum in London, UK for tracking down elusive specimens and references. We also appreciate the constructive comments from two anonymous referees which have improved the manuscript. This study was carried out at the St. John’s Island National Marine Laboratory, a national research infrastructure under the National Research Foundation, Singapore.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

K. S. Tan http://orcid.org/0000-0002-4599-9482

Additional information

Funding

The authors are grateful for the financial support provided by the Singapore Maritime Institute to carry out this project [grant number SMI-2015-MA-13].