Wānaka author Shirley Deuchrass has learned “a lot” about the subject of her latest book: the native long-finned eel.

Shirley, who has written biographies, history and fiction, said as a grandmother of 12 her latest books have focused on children.

Mark and the Monster Eel is a picture book for three to seven year olds about a boy who is scared of eels because his sister tells him they will eat him.

“I believe that the story is worth publishing, for two reasons,” Shirley told the Wānaka App.

The book’s colourful illustrations are by MAC student Amber Leslie. IMAGE: Supplied

“Because kids are scared of something and it creates an opportunity for teachers and parents to say ‘what are you scared of?’; and the other thing is we’re losing our native long finned eel in leaps and bounds.”

Shirley said not enough is known about why the number of native eels is declining, but in her view there is one obvious culprit.

“It certainly doesn’t help that we have two dams [Clyde and Roxburgh] in this area,” she said.

She explained that the eels breed just once, at the end of their lives. The mature eels swim to the Tongan Islands to lay their eggs. When hatched, the larvae float back to New Zealand and the tiny eels (elvers) swim upriver.

While eels can slither past obstacles in their quest, dams are too challenging.

Mark and his Grannie. IMAGE: Supplied

Contact Energy runs a native fish management programme to assist fish migration pathways - including eels. 

The elvers are collected and transported past the Roxburgh and Clyde Dams, before being distributed into lakes and rivers.

Some mature eels are moved in the opposite direction, but most are lost to the dam turbines, Shirley said.

This is the “adult story” underpinning Mark and the Monster Eel, she said, and it’s one she hopes more people will become aware of.

The book is illustrated by Te Kura o Tititea Mount Aspiring College (MAC) student Amber Leslie, who worked with Shirley to bring her vision into colour.

“The really cool thing is I managed to get a student in her last year at college to do the art work,” Shirley said. “She’s a clever girl.”

Mark and the Monster Eel book will be launched at Wānaka Library on Wednesday November 26.