Ground truthing two degrees of separation in New Zealand with shark tagging

I received a message from a friend the other day.

“Hey Brit, Mike found one of your tags”.

I don’t know a Mike in New Zealand. But go Mike. Mike from Auckland found one of my tags washed up on a beach. Mike called up my friend, an avid recreational fisher who has helped with tagging programmes in the past, and my friend messaged me.

In March-April of 2024, I gave nine satellite tags to a fisheries observer to tag deepwater gulper sharks (Centrophorus squamosus). The purpose of these tags is to determine if gulper sharks can survive capture and release. In my previous blog I mentioned I did not expect to see any of those tags again. After all, those tags were heading far offshore, being attached to sharks that live in the deep ocean, and New Zealand is a rather small piece of land in a rather large Pacific Ocean.

Those tags sure are proving me wrong.

Of the nine tags, I have received three back in the past 10 months. Tag #1 popped up in July 2024 in Spirits Bay, the very northern tip of the country. Tag #2 made its way to Kapiti – just 20 minutes from home – days before Christmas. Tag #3 made an appearance just outside of Auckland in January 2025.

The approximate locations of where the tags were deployed and where the tags have been found. Image © Brit Finucci

From a science perspective, it is very helpful to retrieve a satellite tag. Finding a tag means you can download an extensive dataset that could not be transmitted via satellite. Two of the three returned tags were attached to sharks that survived capture and release. I now have some unique in-depth tagging data to provide insight into what those deepwater sharks were doing for the 60 days they were tagged.

While I am very pleased to have these tags back for the science, I’m finding it just as interesting that two of the three tags have been found by a friend of a friend.

There is an idea that in New Zealand most people can be connected to any other person in the country by no more than two degrees of separation because of its relatively small population (just over 5 million people). Yes, New Zealand is a small place, but I don’t think I know that many people. This, combined with the fact that New Zealand’s 15,000 km coastline is one of the longest coastlines in the world, makes it seem rather unlikely that 1) my tags would be found (assuming they wash up in New Zealand rather than Australia or Antarctica), and 2) my tags would be found by someone who knows someone who knows me. I’m not complaining, but if this trend keeps up, I may have to start a side project to calculate what my odds are here, and how many tags I can expect to arrive on my desk in the near future.

Tag #1 making its way back to my office desk. Photo © a good Samaritan