When was your first encounter with a shark?

I was too young to remember it - I was an infant in my mother's arms. I was brought up around boats. My father was a fisherman. So was my grandfather and most of my extended family, for many generations. I was also a fisherman, following in the family tradition. I still fish, and I'm very active in educating people to participate in sustainable fishing.

The first encounters with sharks that I remember were when I was about 7 years old. I was on board my father's commercial tuna boat all through that summer. Whenever a fish was caught the dog would bark and I'd get very excited and be told to stay out the way. When they caught a shark, the dog and I would get even more excited.

One formative experience was when I was 11 or 12. It was at a place where I had fished for leopard sharks since I was a kid, usually at night. I went swimming there with some friends in the daytime and we were jumping off the pier. Looking down we could see dozens of leopard sharks congregating there, silhouetted along the sandy bottom.

I thought, I don't need a fishing rod to experience these animals. After that during the summers I would free-dive with them, and I went so far as to pack my pockets with squid to try to lure them closer. They were rather shy but I got within metres of them. I don't think there has been a summer since when I haven't been in the water with sharks.

And when did you first experience a great white shark?

I was coming out of Anchorage, Alaska, on a commercial fishing boat belonging to a friend of the family, the summer when the movie Jaws came out. That was when I was 12. We came right by a great white shark eating an elephant seal. I stared at that for several minutes. It was life-changing.

The shark looked huge to me. The elephant seal was also very large, and there was an impressive amount of blood in the water. I remember bounding up to the wheelhouse and pounding on the door, and the skipper telling me to go easy on the window. I was trying to get him to turn the boat around so we could stop and spectate some more.

How scientifically accurate is Jaws?

It's a great piece of art, but it is a bit inaccurate at times and sometimes quite surreal. Sharks don't hunt humans. They never have. They do bite, and they have taken people. But if you compare them with other predators they are quite well behaved. If they did hunt humans, they would be getting people every day, all over the world.

Some reports say shark attacks have increased recently. You have to realise, though, that there are more people in the water now than ever before - and increasingly there are people in the water in remote areas that used to be little-visited. People are seeing sharks more often, but the sharks have always been there.

Sharks have a strict menu, and most of them stick to it. There are more than 400 species of shark, and perhaps only a dozen are even capable of coming after and biting a human, let alone consuming one. The word "shark" carries a lot of baggage.

What is it like being close to a great white?

It's really thrilling. These animals have changed relatively little in tens of millions of years. It's like witnessing a prehistoric creature. My imagination has always run wild with that idea since I was a kid, so it's like a visionary thing for me every time. You never get used to it. It always gets your heart rate going.

What do they look like?

They are huge, heavily shouldered, muscular beasts. They're beautiful. You immediately know it's something formidable - what you see is what you get. They'll move so slowly - then all of a sudden with a flick of the tail they're gone leaving a huge boil - from 0 to 60 in a nanosecond. They are immensely powerful. They are obviously capable of huge destruction. Yet with all our interactions we have never had an aggressive shark come after us.

Do you get frightened?

What causes the most anxiety when you are with sharks is the weather. A lot of our work takes place during the winter when most boats stay in port. The waves can be 6 metres high. So we are working in small boats, near the shore, during the winter, in big swells with big sharks - what could possibly go wrong?

Actually the sharks are rather reticent or indifferent in most cases. Our contact with them is very brief. They don't come up and confront the boat. We have to sneak around to get to them and tag them.

How do you tag a great white shark?

For decades the conventional method has been to anchor a boat in an area where sharks are known to be, and then bait them in - enticing them with anything from tuna to horse legs when they get close. That has limited scientific appeal to me. It's a little too invasive. Feeding them risks changing their behaviour.

My method uses a series of lures that look like the seals or sea lions that the sharks eat. We have different lures for different conditions. Along with that we use a small piece of real elephant seal or whale blubber, suspended in a burlap bag in the water close to the boat. With their keen sense of smell, the sharks will detect that.

So we set up the boat to drift on a particular course, we throw the lure out with the bait, and then as we drift along the sharks pick up the smell. They look up, and they see the familiar silhouette. Often they'll come up to investigate it. We never feed the shark. If it starts to take a close interest in that bait we'll remove it from the water.

When we notice the shark we use a GPS device to plot the location. Then we wind the lure in towards the boat. Often enough the shark will follow it. At that point we can video it, under and above the water, and take still photographs, to identify it. As we draw it in still closer, we can reach over with the lance and carefully attach an ID tag and an acoustic or satellite transmitter, or take a tissue sample. Using this method we have tagged nearly 100 great white sharks, which is a record for the western hemisphere.

How do you fix the tag and the satellite device?

We attach it to the end of a lance which has a pin at the end of it, and use that to place it in the shark's hide right at the base of the dorsal fin. It is very important not to place it too far forward or back - if you do, the motion of the head or tail will eventually make the tag chafe on the shark's hide or fall off. You need to place it amidships where it's stable.

What gave you the idea for the lure?

It was modelled from research that used surfboards to attract sharks. The surfboard works because it vaguely resembles a prey animal. Given that, we asked, why not make it as much like the prey animal as possible?

Have you ever been attacked by a shark while doing this?

No, but we've been tail-swatted on a few occasions. That can be alarming. A couple of buckets of water get dumped on you. You take a deep breath and get back to work.

The very first time we actually approached a shark to tag it, back in 1995, was during a feeding event. We motored up to this shark that was eating a seal and turned the motors off. But we got a little too close and encroached on its meal without sussing it out properly.

The shark went off for about 10 minutes - and then came back, surfaced under the stern of the boat and lightly grabbed the propeller, which was off at the time. It wagged the back end of the boat back and forth. Everybody turned a bit pale. We learned from it.

What kind of work does the Pelagic Shark Research Foundation do?

We are an independent and non-profit, research, education and advocacy group. We specialise in field research to bolster the existing database on shark behaviour, which still has vast holes in it. We make our data available and sometimes use it to argue for shark conservation.

In 1990 there were a couple of non-fatal shark attacks near here in Santa Cruz. We had people arming themselves, wanting to go out and thin out the shark population. We went out with slide shows and told people sharks were mostly not dangerous at all. California is considered a hotbed for dangerous sharks, but there have been fewer than a dozen fatalities from shark attacks here since 1946. On the other hand, humans are wiping out sharks at a far more alarming rate.

What has your work turned up?

We have found out a lot about shark behaviour and migration that people didn't know. For instance, people thought great whites lived off the coast - that they weren't "pelagic", that they didn't live in the open sea. In 1996 I made the wild speculation that great whites only visited the coast periodically. We were observing a number of sharks that carried debris from commercial fishing such as swordfish harpoon lanyards and gill-netting. As a fisherman I recognised that as equipment that was only used offshore.

And ever since I was a kid the old-timers would tell me they would see white sharks offshore, during periods of heavy tuna fishing and around dead whales. It was common knowledge among the fishermen but a lot of the scientists didn't know it.

Then in 2000 we put satellite transmitters on four great whites - and they showed up in the open Pacific, often at great depths. These sharks apparently spend at least as much time offshore as they do near the coast.

You don't have a college degree or any formal academic training. Has this mattered?

I couldn't afford the conventional training. Anyway I am a field operative, so no one teaches what I do. I have ended up consulting for a number of top-rated scientists and shown a number of them their first white shark.

To go back to school would mean missing a lot in the field. I would not trade my route for the other. That is not to begrudge or belittle academics at all. I enjoy a good relationship with quite a few. And I have acquired some rivals who have admonished me for not having a conventional academic background.

You're not going to learn most of the applied experiential aspects of marine science in a lab or a classroom or from a book. There are some brilliant scientists who suffer from seasickness or cannot stand up to wind chill. A PhD is not the be all or end all. Some of the most experienced people in this field do not have a degree.