After over a year of planning, writing, rewriting, applying and waiting I've finally started this thing!
Based at the Waikato University Coastal Marine Field station in Tauranga New Zealand, I'll be studying the ecology of the Batoid elasmobranchs (rays) in Tauranga harbour.
New Zealand has few species of these iconic critters, the short-tail stingray (Dasyatis brevicaudata) and the eagle ray (Myliobatis tenuicaudatus) being the most well recognised. I'll post some species profiles at some point when I get a bit of time.
So what am I going to be studying?
This is still very much in the infancy stages, theres an idea, some animals and a huge area, so whatever I write about today will undoubtably alter slightly (or more likely alot) over the course of the next few months while the final proposal gets written and refined. In the most basic outline...
I've got a study site:
The Tauranga harbour is a 218km2 natural harbour separated from the Bay of Plenty by Matakana Island. The harbour is frequented by large numbers of Stingray and Eagle ray as well as other species of elasmobranch, such as (but definately not restricted to) the blue shark (Prionace glauca) and the bronze whaler shark (Carcharhinus brachyurus)
We've begged and borrowed some acoustic receivers from various sources including the Department of Conservation and are in the process of possibly blagging some more. I plan to catch some rays, kit them out with 'pingers', acoustic transmitter tags, which send out ultrasonic coded signals to these receivers which will be anchor around the harbour. The coded messages are stored in the receivers with time, date, and which animal it is, allowing us to work out where each ray is spending its time.
I want to find out if the short-tailed stingrays are only using the harbour during the summer, as it is locally thought, whether they come in at certain times or whether they're constantly in the harbour while they're here, which areas the rays use and whether individuals are resident in one area within the harbour. Eventually I'd like to tag some eagle rays as well, to see if there's any difference between the species.
I'm also planning to take biopsy samples from the animals, and test them to see if there's any heavy metal contamination there. Rays are particularly vulnerable to accumulation of heavy metals, and this is a growing risk in coastal ecosystems adjacent to industrial areas. The southern end of Tauranga harbour is heavily urbanised with alot of industry and a large international port and as it is populated by a large number of rays, this makes it an ideal location to study the possible contamination from these sources. I'm planning to compare the levels of heavy metals in the Tauranga rays to rays caught in the upper harbour, which is much more rural and untouched and those in a more pristine estuary system, such as the Ohiwa estuary further down the coast.
I'm currently researching tagging methods as the short-tailed stingray is huge, up to two metres across so previous methods of surgically implanting these 'pingers' in their underneath after turning them over may be somewhat impossible...