Calling all Ichthyologists!
Epilogue (a few days later)
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We have found our species, well at least the genus. We went to the National Park office armed with our photos and found someone there who studies fish and was very interested. She told us that it was indeed a deep sea fish, called an Oarfish or Peces Remo, which means paddle (Regalecus sp), so named because it is so flat. It is almost never seen alive, only washed up dead or nearly dead. The longest ever recorded fish is of this species, and one washed up in Western Australia a couple days ago and made the news (amazing what you can find on Google). She also kindly gave us these photos which show the fish with more colour. Mystery solved.
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