Imagine taking a nice, refreshing, dip in the ocean on a warm summer day. Floating in the vast sea without a care in the world, but then suddenly you realize you’re in the ocean… and sharks live in the ocean. Now you can’t stop thinking about the potential megalodon that could be circling directly beneath you, we’ve all been there. And while the megalodon became extinct over 2 million years ago, what isn’t extinct is our fear of sharks. While everyone should have a healthy fear of sharks, the reality is that sharks are entirely misunderstood, and there are many sharks that are completely harmless to humans.
Let me introduce you to the leopard shark (Triakis semifasciata), a small shark that navigates nearshore ecosystems like bays and estuaries. Characterized by prominent dark saddles and dots on their bodies, these beautiful creatures are found in the Eastern Pacific Ocean, ranging from Oregon to the Gulf of California, Mexico. They hug the coastline and are found in relatively shallow waters between 4-90 meters.
Not much is known about the abundance of leopard sharks, or their migratory range. We do know that they like to form relatively large same-sex schools that have been termed “nomadic.” When I first started researching leopard sharks’ behavior and life history, I asked myself: Why do leopard sharks wander? What are they searching for? I learned that we don’t fully understand the extent of leopard sharks’ migratory patterns, and this is an important component of their life history.
Female leopard sharks return to their place of birth and give birth to their own offspring, a strategy termed philopatry. One might ask, why can’t they give birth anywhere? What are the benefits of philopatry? Well, nearshore ecosystems are highly productive – meaning they offer favorable conditions that provide food and nutrients for many marine organisms. A mature female leopard shark that has found a mate to reproduce is the pinnacle of success for a fish or, for that matter, any marine or terrestrial organism in general. They have successfully completed the life cycle and are actively contributing to new generations of individuals. So, why wouldn’t a female leopard shark want to return to her place of birth? A place that provided her with the nutrients to grow and become a mature adult; she would be doing her young a disservice by giving birth at any other place.
Although leopard sharks are abundant, and appear to have a successful reproductive strategy, they are highly vulnerable to fishing pressure. Effective management has been introduced to protect leopard sharks from overfishing by recreational and commercial fishing operations. The hope for the future is to continually monitor leopard shark populations throughout their native range and implement management strategies, when necessary, e.g., if populations begin to decline from overfishing.
If you ever find yourself taking a leisurely dip in the ocean at La Jolla Cove, San Diego or Monterey Bay, CA and happen to see a leopard shark dwelling near the bottom, appreciate its beauty and respect its presence; and know that it means no harm.
Literature Cited
Ebert, David A., & Ebert, T. B. (2005). Reproduction, diet and habitat use of leopard sharks, Triakis semifasciata (Girard), in Humboldt Bay, California, USA. Marine & Freshwater Research, 56(8), 1089.
Knip, D. M., Heupel, M. R., & Simpfendorfer, C. A. (2010). Sharks in nearshore environments: models, importance, and consequences. Marine Ecology Progress Series, 402, 1-11.
Megalodon: the truth about the largest shark that ever lived. (n.d.). Nhm.Ac.Uk. Retrieved March 9, 2022, from https://www.nhm.ac.uk/discover/megalodon–the-truth-about-the-largest-shark-that-ever-lived.html
(N.d.-b). Marinebio.Org. Retrieved March 9, 2022, from https://www.marinebio.org/species/leopard-sharks/triakis-semifasciata/#:~:text=Leopard%20sharks%20are%20found%20in,%2C%20between%204%2D90%20m.
Conservation Ecology @ HSU 