Friday, December 30, 2011

December 27th necropsy on Sandy Neck

Ocean Sunfish Necropsy on Sandy Neck, Barnstable MA.
Written by Michael O'Neill and Krill Carson

On Friday, December 23rd, a fresh ocean sunfish carcass washed up on Sandy Neck Beach in Barnstable MA. NECWA was notified of this carcass a few days later and a team of volunteers headed down to the Cape Cod on Tuesday, December 27th. Our goal was to try and relocate and necropsy this animal. If we were successful, this would be the latest date for any fresh carcass to wash ashore. The NECWA team included Tammy, Patty, Nick, Michael and Krill.

When we arrived at the gatehouse at Sandy Neck Beach Park (click here for website) we met Ranger Matthew and Ranger Nina. Both were super helpful in learning more about this carcass and its location on the beach. Ranger Matthew offered to drive us and all our gear to the site of the carcass and assist if needed during the examinations. We really appreciated that offer since we were not familiar with this barrier beach area that includes over 4,700 acres of dunes, maritime forest and marshes.

As we drove down the beach, we marveled at the excellent and unseasonably warm weather were were blessed with. Did this have anything to do with this late date stranding of a relatively fresh carcass? We found the carcass where Ranger Matthew had last seen it the day before. Luckily it was above the high tide line so it had not moved even with the strong winds from the night before.

It was amazing to see an animal in as good a condition as this one was, even after 4 days on the beach. Typically scavengers can do quite a bit of damage to a fresh carcass and the eyes of the animal are one of the first things to go, but this sunfish had everything intact, with only a few minor external patches of scavenger damage.

Our first order of business was to erect NECWA's new portable weighing tripod and get an accurate weight for this animal. It was the first time that most of the team had seen and used the tripod. It took us a few tries rigging the carcass in the straps so the body lifted evenly above the sandy beach. When all parts of the carcass were above the sand, the scale recorded 364 pounds!

This isn't the heaviest carcass that we have weighed this season, but it is only the third fresh carcass that has been weighed to date. Thanks again to David Clapp and Sam McGee for helping put this is amazing tripod together. And thanks to our NECWA supporters for your donations allowed us to make this dream a reality.

Our next task was to conduct a Level A examination that includes photographing/videotaping the external features of the animal and collecting a series of body measurements. The team worked very hard to collect accurate measurements that will be added to our database. Nick took the lead on videotaping the necropsy as well as helping to cut when needed. We hope to use this video footage in the future to create a "how to" guide to necropsying ocean sunfish.

Since we began this project in 2005, NECWA has worked hard to collect
one of the largest databases on ocean sunfish of any research group in the area. Recently, researchers from England, Japan and Sweden have contact us asking if we would be willing to collaborate on a variety of research studies. We said "Yes," of course!

Once we completed the Level A examination, Tammy took the lead on the necropsy. Her first job was to locate the gonad in order to determine the sex of this animal. To do this, Tammy through the skin and into the thick layer of reticulated collagen that complete encases the insides of this animal.

We are still not sure what function the reticulated collagen plays, but one thing that we noticed is that its thickness does vary in different areas of the body. The image above shows us measuring the thickness of the reticulated collagen just above the pectoral fin.

The sex of this ocean sunfish was determined male and we collected sections of the teste for future analysis back at the lab. So far, our data indicates an even number of males and females stranding each fall on our New England beaches.

Since this was Michael's and Ranger Matthew's first ocean sunfish necropsy, we spent more time than usual examining the internal organs and structures of this fascinating creature. We even measured the entire GI tract and recorded a length of 430 cm from the beginning of the stomach to the end of the intestine.

We also examined the gill structure where we found several large parasitic copepods (see photo above). After looking at the gills we also checked out the eye of the sunfish and the rows of pharyngeal teeth in the fish's throat (photo directly above).

Our experienced necropsy technicians, Nick and Krill, then worked on the difficult task of removing the entire spinal column from the carcass. This is made more complicated by the thick layer of collagen present under the skin of the fish, as well as the desire to keep the entire spine intact. Because NECWA can use bioartifacts like the sunfish's vertebrae for public education and research, it was extremely important not to accidentally cut through the vertebrae while trying to remove it from the carcass.

While all of these events were going on, our diligent photographer and data logger Patty was documenting every aspect of the necropsy with photos and notes. This is a vital aspect of the necropsy process because detailed notes and photos allow us to examine the information more accurately and prevent the loss of any valuable information that we may have missed out in the field.

Once the necessary samples had been taken, and our examination of the carcass was complete we buried all the parts of the animal that we had removed. Now that the remaining carcass was considerably lighter, Nick, Mike, and Tammy dragged the carcass down the beach to the ocean where the incoming tide quickly swept it away. Ranger Matthew was then kind enough to drive us and our gear back to the entrance of the beach park so we could load up our gear and head for home!

A very successful day on Sandy Neck Beach. Let's hope this is the last ocean sunfish stranding for the season. Happy holidays to everyone and we wish you the best in the coming new year!