By Bridget Altman
For the past two years, record numbers of hammerhead shark sightings were reported in San Diego County waters. Is this another El Niño anomaly (like all of those Tuna Crabs washing inshore) or are these sharks trying to tell us something about our changing waters? As the hammerhead sharks are starting to appear in the waters near San Diego again, this is exactly what shark researcher Victoria Vásquez of the Pacific Shark Research Center at Moss Landing Marine Labs is investigating.
Both smooth hammerhead sharks (Sphyrna zygaena) and scalloped hammerhead sharks (Sphyrna lewini) were reported in 2014 and 2015 between the months of July and November. This year, several sources have already begun reporting smooth hammerheads.
There are 10 species of hammerhead sharks, just a small drop in the bucket of the more than 500 species of sharks worldwide. Many sharks, such as these hammerhead sharks, keep our oceans in check by grazing on fish down the food chain. The oceans rely on sharks to maintain a delicate balance in the ecosystem, and we rely on the ocean for everything from the food we eat to the air we breathe. Thus we need sharks to keep on living the lives we have grown accustomed to.
Even though Southern California is within the historical range for both the smooth and scalloped hammerheads, the International Union for the Conservation of Nature (IUCN) considers sightings “occasional” and “rare” in these waters, respectively. Seeing these sharks more frequently, and in latitudes as north as Monterey Bay (according to one unconfirmed report from last year), could mean that their food sources (rays, smaller sharks, various species of bony fish and invertebrates) have either been removed or displaced, leading the sharks to seek their prey in new areas.
This brings up some important questions: Is their food moving? If so, why? How far will their food continue to move? It could also mean that the ever so slight warming of the waters is allowing these sharks to thrive in new territories. If so, what does this mean for the overall health of our oceans? More research is needed to get a true conclusion.
One way to gather the data necessary to answer these questions is through citizen science. Citizen science is when the general public can contribute observations and data that will be used by professional scientists. Any person who encounters a hammerhead shark in the water off the coast of California should go to the following website to report the data: Hammerheads in Southern California Public Survey or email email@example.com.
Any information is appreciated, but the following can really help Vásquez and her team answer some more specific questions: images of the shark’s cephalofoil (the iconic hammerhead, to confirm species) and the underside near the tail (to confirm sex), date, time, GPS coordinates/location, number of sharks, water temperature, how long it was visible, and sex & species ID (or best guess at the species identification). Not sure what species you’re looking at? Don’t worry, the scientists on this project already thought of that: check out the species and sex ID guide on the flyer and in the survey link.
So far, contributors from local fishing vessels, research institutions and whale watching boats have submitted information that was compiled, analyzed and presented at the 2016 Joint Meeting for Ichthyologists and Herpetologists (JMIH) in New Orleans in July.
Vásquez says, “Sharing this work with other researchers was immensely beneficial to the project. Like the citizen scientists who have helped thus far, collaboration from others is the foundation of this project. Spreading the word all throughout California to any type of water users also helps diversify the types of reports that are gathered. For example, it helps to get reports from divers because they do not use the same locations as fisherman. Similarly, it helps to get reports from multiple cities in Southern California so we understand just how far north the hammerheads go.”
Our hope is that you, kind reader, will share the word about this project and encourage your ocean dwelling friends to look out for these sharks and report the sightings. This project is not possible without YOUR observations. So let us band together and work to save our oceans, one 5-minute survey at a time!
Copyright © 2016 by Marine Science Today, a publication of Marine Science Today LLC.