Sunday, October 25, 2009

Ocean Sunfish Necropsy on October 25, 2009 - Sandwich Beach, MA

NECWA staff, interns and friends returned to Sandwich Beach to find the ocean sunfish that had stranded on the beach just the other day. When any marine animal strands and then washes onto a beach, it is a very sad event and one that we try to prevent whenever possible. In fact, NECWA had responded to this same ocean sunfish the other day when it was still alive but was in danger of stranding on this beach. Although we were not successful in saving this fish, the carcass can still provide valuable information to us so in an sense, their death is not a waste. 

So starting around 10 am, Krill, Nick Schromburg and Cory Heston began a 5 hour long process of conducting an external and internal examine of this animal. They were assisted by other NECWA staff members and friends including Belinda Rubinstein and Rick. Many people walking the beach were very curious as to what was going on, and this also provided an opportunity for NECWA to educate and involve many members of the general public, both young and old.

As this team collected measurements on the ocean sunfish, it was apparent that this was a very large individual close to 6 feet in length. Due to this animal's great size, it is impossible to weigh this fish on the beach, let alone try to move it. But the fish was probably close to 400 pounds in weight. 

As soon as the external exam was finished, Cory started the internal examination by cutting into the ventral (bottom) part of the ocean fish. These fish are not easy to necropsy since they have a very thick layer of hard reticulated collagen just under the thin, gray skin. But results from this necropsy provided a number of valuable bits of information.  

This fish turned out to be a female that looked in excellent condition. This fish had a very low parasite load and had very thick reticulated collagen. The function of this collagen layer is not clear, but it may help this tropical fish stay warm in our cold waters or it could be important in allowing this fish to dive deep in search of its favorite food, jellyfish and other gelatinous critters.

All in all, this necropsy was a huge success for it helped NECWA staff better understand the basic body plan, internal and external, of this very strange and unusual species. And many tissue samples were collected and these samples will be shared with other scientists also studying this species.