For Antonella Preti, every week is Shark Week! Antonella researches shark biology and ecology at the NOAA (National Oceanic and Atmospheric Administration) Southwest Fisheries Science Center in La Jolla, California. Basically, she finds out what sharks eat, and as you can imagine, those fish can add up quickly!
I was always interested in the beach, even as a little kid – I loved collecting and cataloging shells. I wanted to know the name of everything at the shore. As a grown-up, I’ve researched many animals – marine worms, crabs, dolphins, whales – but I chose to focus on sharks because they get less attention than other endangered animals. People are less sympathetic to sharks, even though they are a beautiful and necessary part of the ocean ecology.
We have to look inside sharks’ bellies to see what they’ve eaten, but we certainly don’t hurt or “hunt” any sharks to do that. When fishing boats accidentally catch sharks, they donate shark stomachs for us to study. We examine sharks just like medical doctors examine people in order to help protect other sharks and their environment. It’s not always easy to know what sharks eat. We can spend hours looking at a fish bone of prey that a shark ate under the microscope to identify which fish species it came from.
Well, it doesn’t just matter for the sharks; it matters for the whole ocean ecology, or “food chain,” which includes people fishing. When we know what sharks are eating, then a change in their diet can alert us to all sorts of other things – changing water temperatures, the amount of oxygen in the water, if fisheries caught too much of a certain kind of fish in the previous year, or just new behavior from marine animals.
For example, jumbo squid were very rare in our Californian waters before 2003, but most blue and mako sharks we studied after 2003 had eaten jumbo squid. That allowed us to understand and study the new behavior of jumbo squid, which were now swimming as far north as the cold Alaskan waters. Something similar happened with El Nino in 1997 – thresher sharks were eating red crabs, because the red crabs were everywhere thanks to the warm water.
It’s just like categorizing shells on the beach, except with many sharks and much more data. After sorting sharks by their species, size, and gender, we can analyze their diets based upon the species and amount of fish they are eating. Understanding shark diets can help us establish more accurate fishing quotas – the amount or limit of different kinds of fish that boats can catch. Those quotas help everyone – they make sure that there will be fish to catch year after year, and they also guarantee that there will be fish for sharks and other marine animals to eat. We can learn so much about the ocean from studying sharks because some species of sharks will basically eat whatever they can find – so if we find that sharks have suddenly stopped eating sardines, that could alert us to a larger problem.
There are obviously a lot of size and weight measurements when we’re examining sharks and their diet. The more precise you are in gathering that data, the better your overall outcome will be. After you have all those numbers, then you need to be able to spot trends, calculate averages, read graphs, compare values, convert units…it’s mostly statistics, but there’s a little bit of every branch of math in my work! I’d say the more kids explore the possibilities of numbers, the more they’ll be able to learn about any topic that excites them.
Image licensed by Ingram Publishing