Recently I met up with Helen Cadwallader, a PhD student with Waikato University Coastal Research. She is studying the three species of Stingray commonly found in Tauranga Harbour, with particular interest in the Short Tail Blacks – Dasyatis brevicaudata. It is these Rays that the Yellowtail Kingfish cruise alongside and use to ambush prey. After a couple of years of emails and phone calls it was good to finally meet Helen and see how she goes about her research.
Having just welcomed a newborn into the world not much more than 24 hours prior it was a good excuse to get our 2.5 year old and his mate outside for an activity. As with anything involving animals there can be a fair bit of patience required, the group being buzzed by a few Rays before one finally committed and curiosity got the better of her.
The trap was simple yet effective, a large piece of shade cloth with two aluminum poles each side sat in a foot of water. A fish frame placed in the middle acted as bait and the surrounding water was scented with scraps thrown about. The boat ramp utilized is home to some commercial fishing vessels and consequently the area is a hive of fish life. Once a Ray plucks up the courage to have a go at the bait it is slid up the ramp into very shallow water and the team get to work.
A heavy wet blanket is used to wrap the tail and then held securely by one person as the rest take photos, record data and insert tags. The tag used is a modified dart tag similar to our Kingfish tags in use – the one exception being two individual coloured ID bands at the top. Also used is a coloured plastic disc tag, essentially three different ID colours used for later visual identification.
The professional team have the whole ordeal completed within a small time frame ensuring minimal stress to the fish and zero harm – aside from some small pieces of jewelry to swim away with and some visible mating scars from earlier. Once all data has been recorded all that is left to do is name the Ray. This one aptly named Margot, in honour of our newborn girl.
Helen and I continued talking about the rays, discussing feeding habits, behaviors, seasonal movement and concluded that in reality not much is really known about these critters. Whilst in the early stages of its progress Helen already has 18 (possibly a few more now) individually tagged Rays going about their business and showing up here and there. Our first sighting that afternoon was a previously tagged Short Tail happily cruising past, proof they have no impact on the population whilst conducting their research.
I take my hat off to Helen, the unsung hero of Stingrays. She plans to also include the impact of environmental factors in various areas of the harbour and offshore regions, plus a few other topics. Her studies so far have also resulted in helping put an end to some outdated practices that involved killing them for points accrual in some hunting competitions. Shooting fish in a barrel essentially, then dumping the body after proof of kill.
Please go check out the website for this cool project, you can also report any sightings of any tagged Stingrays there.