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Blue Shark Tagging

Riley Elliott is gearing up for another season of Blue shark tagging in NZ waters.

This summer, he is more prepare than ever thanks to the amazing tracks of last years sharks. Clear age/gender segregation has been observed, with mature males migrating north, nearly to the equator!
As summer nears, and the East Australian/Auckland current begins to flow south, the male blues are following. All 7 males (2-2.7m long) have resided in warmer, deep oceanic waters for the NZ winter.

Contrary to this, Hannah, the NZUA tagged blue shark, and only female, continues to show preference for NZ coastal waters. Riley’s hypothesis is that mature females move north with males at the end of summer, to the Kermadecs, intercepting departing males for mating, leaving them on their journey north, and returning to NZ coastal waters to maintain sexual segregation (a behavior used by many sharks to reduce breeding pressures – which in sharks can kill females) as they grow their young ready for birth in the following summer.

Riley hopes to track down Hannah this summer, in person, to see how she is fairing and whether she is heavily pregnant and about to give birth! Watch this space and visit www.rileyelliott.com for updates over the summer.

Permanent link to this article: http://nzu.org.nz/diving-in-nz/environmental/blue-shark-tagging/