By Dr. James Sulikowski, Professor and Associate Director, New College of Interdisciplinary Arts & Sciences, School of Mathematical & Natural Sciences, Arizona State University, Sulikowski Shark and Fish Conservation Lab
We often think of sharks as eating machines, cruising the waters looking for unsuspecting prey. However, many shark species carry their growing babies in side their uterus until birth, just like humans, until birth. The porbeagle is one such shark, but we think this mom is extra special.
So, what makes these sharks great moms? Not only do they nourish their growing babies like human mothers, but our research suggests they brave the cold harsh weather of New England in order to give birth in a pristine marine sanctuary called Stellwagon Bank.
How do we know this?
Good question! In October of 2020, our research team used both fin-mounted and pop off satellite tags (PSAT) to follow the movement of four moms captured off the coast of Cape Cod, Massachusetts. Fin-mounted tags are awesome because every time the shark’s fin breaks the surface of the water it transmits a location. When the shark is not at the surface, the PSAT records the shark’s depth, and also the temperature of the water. The combo of tags gives us a really good idea of when and where sharks are, and what habitats they prefer.
So how did we know they were pregnant?
This is the cool part! We used a portable ultrasound to look inside each female shark to see if they were pregnant.
So, what do we know so far?
We know that the moms stayed in almost the same spot we captured and tagged them in for about four months. Even though 70-degree water was not that far away, they stayed in water that was about 48 degrees! Not only that, but the females seem to follow a similar movement path offshore before disappearing from our sight in February. We spent almost two months wondering where these pregnant sharks were. But to our delight, they reappeared very close to where they originally disappeared, and look to be heading towards the Gulf of Maine.
So where did they go?
Deep, very deep…we are talking 3500 feet! This is the deepest recorded depth for this species! We are very excited to follow these sharks on their journey; will these moms go to Stellwagen Bank National Sanctuary to give birth? Is this area a nursery for baby sharks? We hope you are as excited as we are about this phantom shark and will follow their journey with us!
Dr. James Sulikowski is a Professor and Associate Director of the New College of Interdisciplinary Arts & Sciences and School of Mathematical & Natural Sciences at Arizona State University. Dr. Sulikowski and his laboratory of undergraduate and graduate students are dedicated to advancing our knowledge and conservation of sharks and other fish species. Dr. Sulikowski has masters’ degrees in marine biology and physiology as well as a PhD in Zoology. His interdisciplinary research integrates aspects of fisheries biology such as reproduction, maturity, age and growth, the physiological responses to stress and how these parameters influence by-catch mortality, as well as investigating the composition, movements, and spatial/temporal distribution of commercially valuable species in both the coastal and pelagic environments. Dr. Sulikowski’s 25 years of experience using and integrating a variety of techniques, including hormone analyses, electronic tracking, and ultrasound imaging, has resulted in over 100 peer reviewed publications and over 13 million dollars in external grant funding. His work has been featured on such media outlets as the BBC series “Rise of Animals”, “ocean mysteries series”, Discovery Channel’s Shark week, Nat Geo Wild, as well as many other local, regional and national affiliates.