Ocean sunfish (Mola mola) necropsy

On August 19th 2013, an ocean sunfish (Mola mola) washed ashore Bar Road, St. Andrews, New Brunswick, Canada.
Tracey Dean, the education director at the Huntsman Marine Science Centre (HMSC), and myself drove down to see the fish in the afternoon. Lou Van Guelpen, the Curator of Fishes at the Atlantic Reference Centre, was on-site taking measurements. He estimated the fish to weigh 350 lbs.
A resident on the street, Henry Clark, offered to use his tractor to move the fish to HMSC. The evening, he placed the fish onto a wooden pallet, and covered it for the night.

Henry's tractor with the ocean sunfish on a wooden pallet. Photo taken by Dr. Catherine Hood 19/08/13
Henry’s tractor with the ocean sunfish on a wooden pallet. Photo taken by Dr. Catherine Hood 19/08/13

That night, the 21 students of the Biology of Marine Mammals course, and the instructors, Dr. Catherine Hood and myself (Amanda Babin) begun preparing for the necropsy, researching the species’ anatomy and separating into teams for efficiency. The teams were as follows:
Head (eye, brain, teeth) – Brittany Barbeau, Katheryn Kastner, Megan Mickle, Jaimie Wylie
Circulatory system (gills, heart) – Emily Guevara
Internal organs (liver, gall bladder, intestines, stomach) – Ashley Tang, Minh Thu Le, Julia Schertzer, Nour Zein
Documenters (photos, videos, sketches) – Melanie Badea, Tom Freeman, Rachel Gould, Alex MacKinnon, Yifu Wang, Sophie Wolvin

The HMSC team moving the ocean sunfish into the necropsy site, showing Tom Freeman as videographer. Photo taken by Alex MacKinnon 20/08/13
The HMSC team moving the ocean sunfish into the necropsy site, showing Tom Freeman as videographer. Photo taken by Alex MacKinnon 20/08/13

The next morning, August 20th 2013, at 8:30am, the fish was moved onto the back of an HMSC truck, and transported to the moose pasture behind the HMSC facilities. With much effort, the fish and pallet were pushed and pulled off the truck into the hole dug into the sand by the students.

Ocean sunfish being put into a sand hole behind HMSC facilities. Photo taken by Alex MacKinnon 20/08/13
Ocean sunfish being put into a sand hole behind HMSC facilities. Photo taken by Alex MacKinnon 20/08/13

Dissecting tools were gathered from the people around the facilities, and the necropsy began at 9:30am.

Necropsy:
I began by taking body measurements of the sunfish:
Dorsal fin to anal fin – 238 cm
Clavus to snout – 183 cm
Snout to front of cloaca – 100 cm
Snout to eye – 20 cm
Eye to gill – 19 cm
Total length – 175 cm
Total width – 220 cm
Dorsal fin length – 75 cm
Anal fin length – 74 cm
Pectoral fin length – 27 cm
Clavus length – 37 cm
Clavus width – 85 cm

Amanda Babin taking body measurements of an ocean sunfish. Photo taken by Alex MacKinnon 20/08/13
Amanda Babin taking body measurements of an ocean sunfish. Photo taken by Alex MacKinnon 20/08/13

We then made observations about the external appearance, namely the leathery skin which was beginning to decompose. We took samples of the sea lice living on the skin’s surface. Then we began the internal measurements, with each team doing it’s part.

Katheryn Kastner removing parasites from the skin of an ocean sunfish. Photo taken by Melanie Badea 20/08/13
Katheryn Kastner removing parasites from the skin of an ocean sunfish. Photo taken by Melanie Badea 20/08/13

Skin thickness – 5 cm (It took much longer than anticipated to get into the body cavity)

Skin thickness of ocean sunfish. Photo taken by Alex Mackinnon 20/08/13
Skin thickness of ocean sunfish. Photo taken by Alex Mackinnon 20/08/13
Opened body cavity of the ocean sunfish. Photo taken by Alex MacKinnon 20/08/2013
Opened body cavity of the ocean sunfish. Photo taken by Alex MacKinnon 20/08/2013

Eye diameter – 8 cm (preserved one whole eye)

Eye of ocean sunfish. Photo taken by Alex MacKinnon 20/08/13
Eye of ocean sunfish. Photo taken by Alex MacKinnon 20/08/13
Eye being extracted from ocean sunfish by Katheryn Kastner. Photo taken by Alex MacKinnon 20/08/13
Eye being extracted from ocean sunfish by Katheryn Kastner. Photo taken by Alex MacKinnon 20/08/13

Duct connecting intestine to stomach – 2.5 cm
Cyst(?) found attached to intestines (collected)

Cyst(?) attached to intestines. Photo taken by Alex MacKinnon 20/08/13
Cyst(?) attached to intestines. Photo taken by Alex MacKinnon 20/08/13

Sex determined to be male (testis collected)

Collection of ocean sunfish testis sample. Photo taken by Yifu Wang 20/08/13
Collection of ocean sunfish testis sample. Photo taken by Yifu Wang 20/08/13

Intestines and stomach felt to be full with gelatinous contents.

Gelatinous stomach contents collected by Julia Schertzer. Photo taken by Alex MacKinnon 20/08/13
Gelatinous stomach contents collected by Julia Schertzer. Photo taken by Alex MacKinnon 20/08/13

Samples were collected from the following organs: Skin, dorsal muscle, eye, gill, heart (whole, preserved), intestine, gall bladder, liver, testis, stomach, etc.

Gill of ocean sunfish collected by Emily Guevara, observed by Megan Mickle. Photo taken by Alex MacKinnon 20/08/13
Gill of ocean sunfish collected by Emily Guevara, observed by Megan Mickle. Photo taken by Alex MacKinnon 20/08/13
Heart of an ocean sunfish being collected by Emily Guevara (left) and Minh Thu Le. Photo taken by Yifu Wang 20/08/13
Heart of an ocean sunfish being collected by Emily Guevara (left) and Minh Thu Le. Photo taken by Yifu Wang 20/08/13
Nour Zein extracting the liver from an ocean sunfish. Photo taken by Yifu Wang 20/08/13
Nour Zein extracting the liver from an ocean sunfish. Photo taken by Yifu Wang 20/08/13

The fish was then buried with a fine mesh underneath, and will be dug-up in the future so HMSC may put any remaining pieces of the skeleton up on display.

Education director Tracey Dean, and student Megan Corrigan placing mesh in sand hole. Photo taken by Melanie Badea 20/08/13
Education director Tracey Dean, and student Megan Corrigan placing mesh in sand hole. Photo taken by Melanie Badea 20/08/13

CBC contacted HMSC, and I was interviewed by Neville Crabbe about the sunfish. The interview was broadcast on Information Morning on August 22nd 2013 , and an article was written about the topic.

I want to thank every one of my students who were willing to get their hands dirty with this project. I sincerely appreciate the help in making this necropsy happen!

Biology of Marine Mammals class of 2013. From left to right, top: Megan Corrigan, Megan Mickle, Danielle Lands, Tom Freeman; 2nd from top: Jaimie Wylie, Brittany Barbeau, Emily Guevara, Aoxue Tang, Alex Mackinnon, Sophie Wolvin, Veronique Despres; 3rd from top on right: Emily Boulanger, Nadia Dalili, Nour Zein, Rachel Gould, Yifu Wang; bottom: Yann Pouliot, Katheryn Kastner, Julia Schertzer, Minh Thu Le, Melanie Badea, Instructor: Amanda Babin
Biology of Marine Mammals class of 2013. From left to right, top: Megan Corrigan, Megan Mickle, Danielle Lands, Tom Freeman; 2nd from top: Jaimie Wylie, Brittany Barbeau, Emily Guevara, Aoxue Tang, Alex Mackinnon, Sophie Wolvin, Veronique Despres; 3rd from top on right: Emily Boulanger, Nadia Dalili, Nour Zein, Rachel Gould, Yifu Wang; bottom: Yann Pouliot, Katheryn Kastner, Julia Schertzer, Minh Thu Le, Melanie Badea, Instructor: Amanda Babin
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