By Jackie Reuder, M.S. Graduate Student, Nova Southeastern U & Shark Angels Intern
Scientific Study: Temperature Measurements from Salmon Sharks, Lamna ditropis, in Alaskan Waters by Scot Anderson and Kenneth Goldman
When: This study took place from August 1996 to May 2000
Where: Gulf of Alaska
Background
Sharks that live in cold waters have a unique way of keeping themselves warm called countercurrent heat exchange. Muscles from the body, like the tail, create heat, just like when you work out, you get hot. This heat warms up the blood in part of the body. When cold water comes into the gills it makes the blood closest to the gills cold. The cool thing that happens is when that warm blood from the warm muscles comes close to the cold blood, the warm muscles share the warmth with the cold blood that can then travel throughout the rest of the body, keeping the shark warm.
Salmon sharks live in very cold waters in the North Pacific Ocean, mostly around Alaska, but can also be found in northern China, Russia, Japan, and down the western coast of the United States. They can be found in waters up to 6,000 feet in the open ocean. Their closest relatives are the Porbeagle shark and the Great White shark.
Methods
In this study, they sampled 31 salmon sharks. They took the temperature of the muscle, liver, stomach, heart, eye, and brain (and other smaller organs). They took a probe thermometer and inserted it into the shark after it was brought onboard a boat. The temperature of the surrounding water was taken and then compared to the internal temperatures of the different organs.
Findings & Conclusions
All temperatures taken, except for the heart, were significantly above the temperature of the surrounding waters. The highest temperatures taken were from the muscle and the liver. Previous studies found that internal muscle temperature was 11°C above the surrounding water temperature. In this study, they found that the internal temperature of the muscle was almost 16°C above the surrounding waters! Interestingly, the internal temperatures of the salmon shark were closest to their relative, the Great White shark. The only organ that was not higher in temperature than the surrounding waters was the heart. This is because the heart is receiving cold blood that has not been warmed. In conclusion, the higher internal temperature from multiple organs proves that countercurrent heat exchange is great at keeping salmon sharks warm in very cold waters.