Shocking Ability of Sharks to Sense Electricity

Sharks possess an amazing sense called electroreception.  The ability to sense tiny electrical currents is outside of our range of abilities and may not seem all that useful.  But I think you'll be surprised at how remarkably handy this sense can be if you are a shark searching for food in the vast ocean realms. 

The electro-sensory system of a shark is so sensitive that it can detect the tiny electrical currents generated by the muscles of a fish swimming nearby, a great advantage for those trying to find prey in the pitch-black.  This ability would be like a magic sixth sense to us, considering that a shark can detect the electrical signals given off by the beating of a fish’s heart (or human’s heart for that matter). 

Consider the implications!  As soon as you jump into the ocean, every shark in the vicinity knows you are there.  There’s no hiding behind a boat or chunk of coral.  If your heart is beating or your muscles are twitching, sharks will sense the electrical current. 

Sharks have by far the highest level of electrical sensitivity of any animal on the planet.  

Electroreception is based on a system of sensory organs called the ampullae of Lorenzini (see my article to learn more).

Electroreceptor pores on the snout of a Leopard Shark. Photo by Albert Kok on Wikimedia CC-by-03

The electrical sensitivity of a shark is equivalent to being able to detect the electric field of a flashlight battery connected to electrodes placed 10,000 miles (16,000 kilometres) apart in the ocean.  Seems like a stretch, doesn’t it! Believe me, this is based on extensive research.

How many senses do sharks have?  How does electroreception work?  What are the lateral lines used for?

If you want to learn how electroreception works and about all seven of the amazing senses that sharks possess, check out my recent article on biogeoplanet.com.

The Fascinating Role of Sharks

Many of the shark species are apex predators, and we're only beginning to understand how important their role is in the functioning of healthy marine ecosystems.  Here's an excellent short video produced by the Cape Eleuthera Institute in the Bahamas.

This film, through humor, simplicity, and scientific theory, describes our predicament with a drastically declining shark population worldwide, and offers a new perspective on how to view the most feared fish on our planet. Through stop motion, we tell the story of our ocean's greatest predators by focusing on the vital role they play in our economies, ecosystems, and cultures. It is the story of our decision between an ocean with, or without, them. It is the story of how we only have one logical choice left. It is the story of sharks.

Here's what the researchers at the Cape Eleuthera institute have to say:
Sharks are threatened worldwide due to unsustainable levels of fishing and other human disturbances. Exploitation of sharks has increased dramatically due to declining catch rates in traditional fisheries and an increasing demand for shark fins in Asian markets. The recent economic boom in Asia has led to a rapid increase in demand for shark fin soup, a dish that is considered a status symbol and a sign of wealth amongst many eastern cultures. The disproportionate value of the fins compared to the rest of the shark has led to the wasteful practice of fining whereby the fins of the shark are removed and the majority of the carcass is discarded, often while still alive. This brutal and wasteful practice is illegal in many territorial waters however it is commonplace in the unregulated waters of the high seas. The high demand in Asia has led to a rapid escalation in direct and indirect shark fisheries all over the globe. 
Recent research estimates that 1.7 million tones are harvested each year however the figure could be as high as 2.29 million tones, roughly equaling 73 million individual sharks. Further studies estimate that the total number of sharks in the north Atlantic has declined by two thirds in the last fifty years and the global biomass of sharks has declined 80% since the industrialization of fishing.

These are frightening numbers -- roughly 73 million sharks being killed every year cannot be sustainable!  We can only contemplate the long-term ecological impact of reducing shark biomass by 80% throughout the world's oceans.

To learn more about sharks visit the Shark Trust, committed to "Advancing the worldwide conservation of sharks through science, education, influence and action."

I'm looking forward to cruising through incredibly rich shark waters on our way down the east coast of Africa in April on board the ms Amsterdam.  This is one area where living sharks provide a huge boost to the economy through tourism -- it seems lots of (crazy!) people love to dive with Great White Sharks (usually separated by bars of steel!).  Not me!!