What is going on with our eel population? Photo:
Uncovering he mystery behind eel breed has proven to be a difficult task, but passionate scientists are far from calling it quits.
Senior lecturer at AUT, Dr Amandine Sabadel is a chemist, ecologist, environmental scientist and an eel expert.
She told The run home to Christmas that tracking technology has helped scientists find the first clues as to how and where eels spawn but there is still more to go in understand the process and location.
What's going on with our eel populations?
"In New Zealand, we have two-slash-three visitors... we have the shortfin, and we have the longfin eels. But we also have, from time to time, the Australian longfin that comes visit our shores.
"The suspected thing is that there is a big spawning event, so they gather in a place that they know where to go."
However, she said they are still unsure how eels know where to go.
After the spawning event many eggs are hatched quickly, and the baby eels are only a few millimetres in length.
They then start growing and growing as they make their way back to New Zealand.
Dr Sabadel's interest lies specifically in the mystery of where the eels go throughout this process.
She said while they can currently track eels using satellite tags, the technology cannot track live and must be pre-programmed.
"This is an issue, because the eels are actually diving very deep when they're doing their migration... it can be to thousands of metres.
Although the trackers can stand the pressure, they can't transmit meaning they have to be pre-programmed, which can cause issues.
"They can detach from time to time, or the eel can be predated," Dr Sabadel
Spawning, unlike migration, happens around 100 to 140 metres in the sea, however there are still difficulties.
"You're not going to see like a big cloud of egg material at the surface. So, you can't satellite track it."
"Tracking has given us the first clues, because over the years now, we have kind of a direction.
She said many research cruises from Japan have already been catching very small eels but are yet to catch the New Zealand longfin, which she says is the "holy grail' of eel research.
The research Dr Sanabel is doing in her lab looks at indirect clues left behind by eels like DNA that the shed in the water
"We've narrowed it down to kind of three different places. So, we think that there is two spawning sites for the shortfin, and we believe that there's one that goes to Australia, and one that goes to New Zealand."
She said in general conditions for eels in New Zealand could be better, with pollution having a major impact on their environment.
"We have a problem with pollution of the rivers, obviously, that doesn't make a suitable habitat for them.
"Even if they are very resilient animals, the health of our river is very important, and we should really think about this and looking at the type of pollutants, we put in them."
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