A pregnant 8-foot porbeagle shark was found washed up on a beach in Marshfield, Massachusetts last week. Marine biologist John Chisholm received a call about the dead shark and went to the beach to investigate. He noted that it was a fresh find and the weather was bad, preventing immediate action. With help from the local fire department, the shark was moved above the high tide line.
Due to the bad weather and high surf, the marine biologist and first responders were unable to take immediate action when they discovered the dead shark. They enlisted to move the large shark above the high tide line and secure it until they could return on Saturday to conduct a further examination.
The next day, the team performed a necropsy on the shark and was pleased with the condition of the deceased animal. Chisholm, who works with the New England Aquarium, noted that they often do not get such high-quality specimens to study. He explained that sharks are usually dead or decaying by the time they are found, making it difficult to gather useful information. The team was excited to have a chance to study a "pristine" specimen.
Washed Little Embryonic Sharks
The mature female porbeagle shark that washed up on the beach in Massachusetts was also pregnant with four embryos, which Chisholm described as "unusual" to see. The team did not see any obvious signs of trauma and have taken tissue samples to be analyzed. Porbeagle sharks have an 8-9 month gestation period and a year-long reproduction cycle. In contrast, other shark species have varying lengths of pregnancy, with great white sharks having a 12-month gestation period and some species, such as basking sharks, estimated to have a gestation period of up to 3.5 years.
The team was able to gather valuable information on the reproductive history of porbeagle sharks from the necropsy. Chisholm explained that they were able to secure the embryos and examine their stage of development. This information is now being shared with a network of universities and facilities to be studied and used for research. The embryos collected from the shark are also available for examination.
According to Chisholm, the vertebrae from the shark will be used by researchers studying aging and growth, while tissue samples from the liver and other organs will be sent to institutions where scientists are studying the physiology of sharks. The porbeagle shark, also known as a mackerel shark, resembles a smaller great white and feeds primarily on mackerel. These sharks are found in the northern Atlantic Ocean, as well as in the southern Atlantic, Indian, and Pacific oceans, and even in the Antarctic Ocean.
Pictures of the porbeagle shark washed up on a beach in Marshfield, Massachusetts last week. After a necropsy it was discovered that the shark was pregnant.
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Shark Pregnancy Explained
The porbeagle shark is ovoviviparous, meaning that its eggs are fertilized internally and the young are born alive. During mating, the male porbeagle bites the female's pectoral fins, gill region, and flanks to hold on and court her. Out of over 500 species of shark, the majority give birth to live young. Porbeagle sharks typically give birth to 1-5 live pups, as per the University of Sydney.
Chisholm emphasized the importance of public reports of dead marine life, such as the porbeagle shark found on a beach in Massachusetts. He noted that many sharks are discovered by people walking on the beach and that public observations play a crucial role in finding and studying these animals. Without the report from a beachgoer, the team may not have been able to find the shark in such good condition.
Porbeagle sharks are known for their active and muscular bodies, which enable them to seasonally migrate for feeding and reproduction. Their endothermic (warm-blooded) system also allows them to maintain a body temperature higher than the surrounding water, contributing to their high activity level. These sharks are typically found in cold, temperate waters of the North Atlantic, southern Atlantic, Indian, and Pacific oceans, at depths of over 1300 meters. While they are not found in the North Pacific, their close relative, the salmon shark, is found in this region.
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