Biofouling leads to reduced shell growth and flesh weight in the cultured mussel Mytilus galloprovincialis

Abstract

Competitive interactions between cultured mussels and fouling organisms may result in growth and weight reductions in mussels, and compromised aquaculture productivity. Mussel ropes were inoculated with Ciona intestinalis, Ectopleura crocea or Styela clava, and growth parameters of fouled and unfouled Mytilus galloprovincialis were compared after two months. Small mussels (≈50 mm) fouled by C. intestinalis and E. crocea were 4.0 and 3.2% shorter in shell length and had 21 and 13% reduced flesh weight, respectively, compared to the controls. Large mussels (≈68 mm) fouled by S. clava, C. intestinalis and E. crocea were 4.4, 3.9 and 2.1% shorter than control mussels, respectively, but flesh weights were not significantly reduced. A series of competitive feeding experiments indicated that S. clava and C. intestinalis did not reduce mussels’ food consumption, but that E. crocea, through interference competition, did. Fouling by these species at the densities used here reduced mussel growth and flesh weight, likely resulting in economic losses for the industry, and requires consideration when developing biofouling mitigation strategies.

Keywords:

• Ciona intestinalis
• Ectopleura crocea
• Styela clava
• aquaculture
• competition
• feeding rate

Acknowledgments

The authors thank Lance Wiffen and staff at SeaBounty Mussels Pty Ltd for transport to the mussel farms and the supply of mussels and materials. They also thank staff at the Victorian Marine Science Consortium and the Collaborative Shellfish Research Facility and Hatchery (Department of Primary Industries, Queenscliff) for the use of their facilities. The project was funded by the Fisheries Research and Development Corporation (FRDC) (project no: 2012/202).