Green Mussel
(Perna spp.)

Description: This mussel can be recognized by the distinctive greenish hue that colors the exterior of its shell, differentiating it from the blue-black colored Mytilus mussels found in this area. It is typically 80-100 mm in length, but can attain a length of 165 mm. Internally, the green mussel lacks a small patch of muscle fiber near the beak which is present in Mytilus mussels, and it has two separate shell closure muscles while the Mytilus mussels have one joint muscle. There are three similar species in this genus, Perna canaliculs, P. perna, and P. viridis, which all fit this description.

Habitat: Primarily in estuarine habitats with salinities ranging from 18-33 ppt and temperatures ranging from 11-32 °C temperature, but with tolerance for extremes beyond these ranges. The green mussel forms dense aggregations on natural and man-made substrata such as wharves, pilings, buoys and mariculture stands.

Origin: New Zealand (P. canaliculs), South Africa and South America (P. perna); Southeast Asia (P. viridis).

Invaded Areas: Widely introduced for aquaculture to localities including South Pacific islands and Caribbean sites.

Concerns: In invaded areas such as Australia, the green mussel has rapidly formed dense aggregations that can outcompete native sessile organisms, and that have had substantial economic impacts by clogging flow pipes, and by fouling ships and mariculture facilities. In our region, the green mussel might alter physical habitats in estuaries by increasing the amount of hard substrate, and it might compete with native species such as the California mussel. The green mussel spawns continually throughout the year, thereby increasing the chances that individuals arriving on boat hulls could found a new population in a local harbor or bay, and contributing to potential rapid growth rate of a newly established population.