Title: Investigation of Ocean Sunfish, Mola mola, that strand on the shores of Cape Cod, MA. 

Presenter: Carol “Krill” Carson

Affiliation: New England Coastal Wildlife Alliance

Investigation of Ocean Sunfish, Mola mola, that strand on the shores of Cape Cod, MA. 

The ocean sunfish, Mola mola, feeds in the waters off New England each summer and fall then migrates south, to more tropical waters as winter approaches. Some individuals become trapped by the physical presence of Cape Cod and eventually become cold-stunned as water temperatures drop below 50°F. Unable to regulate their body temperature, many of these individuals die and wash ashore on local beaches,with the majority washing up on northern beaches of Cape Cod. The New England Coastal Wildlife Alliance (NECWA) created a community-sighting network in 2005 for this species, never realizing that they would be asked to respond to strandings of live ocean sunfish as well as perform necropsies on carcasses. Each fall and early winter, NECWA staff and interns rescue 2 to 3 individual fish and necropsy between 10 - 50 carcasses. Necropsies involve both internal and external examinations including, the collection of body and weight measurements, gender determination, and tissue sampling. One aspect of this research has focused on the development of a meaningful aging technique for this species. Although ocean sunfish are classified as the heaviest bony fish in the world, their otoliths are reduced in size and underdeveloped, making standard aging techniques not possible. An alternative aging method for this species is needed, but preliminary analysis of reproductive tissues by Dr. Rich McBride (NMFS) and staff indicates that all carcasses examined to date are immature fish that have not spawned. This information combined with the examination of the banding pattern in the centrum of the vertebra may lead to a successful method for aging ocean sunfish found in the waters of New England.