Nesting box may help save endangered cod fish, researchers say

ABC NEWS (Australia)

Here's something you've probably never heard of... cod hotels. They're breeding boxes which replace lost habitat for the endangered eastern freshwater cod, and researchers were thrilled when the fish used them.

Transcript

00:00 What lies beneath this stretch of the Nimboida River could give nature a helping hand in

00:15 saving an endangered native species.

00:18 We just have a little look in there.

00:20 We're hoping that nesting boxes to help them along to provide them with small bedrooms

00:25 and we've luckily had one really good success.

00:29 It was this vision of baby eastern freshwater cod in one of the boxes that's excited researchers.

00:36 And it means that we're starting to cue in to the biological needs of this fish.

00:40 So being able to supplement a key part of their habitat and know that that design is

00:45 appropriate for its needs is a huge boost to our confidence and moving forward to develop

00:50 and refine nest boxes into the future.

00:53 [Music]

01:00 On the surface the Nimboida and waterways of the Clarence catchment may look beautiful,

01:05 but under the water sediment from historic mining and natural disasters has smothered

01:10 caves and destroyed the cod's breeding habitat.

01:14 One of the most important things with this fish is the fact that it actually has quite

01:18 limited breeding opportunities in the wild.

01:20 That's why we're starting to see the decline of this fish over previous decades.

01:26 Eastern freshwater cod was one of more than 100 species identified as in urgent need of

01:30 help after the 2019 bushfires in the Clarence Valley, attracting a $300,000 federal government

01:37 investment into cod conservation projects.

01:42 In a bid to reduce the cod's decline, local land services has teamed up with the NSW Department

01:48 of Primary Industries to create an alternative breeding space for the species.

01:55 The team tested different breeding box designs at the Grafton Fisheries Centre.

02:00 It's been a really interesting challenge because we've got design constraints around building

02:04 these things and securing them so that they don't get washed away and not fill up with

02:08 too much sediment themselves and then we've got to make them so that it works for the

02:12 fish.

02:14 Training breeding age wild cod, which are usually about five years old, to use the box

02:18 was an additional challenge.

02:21 The male needs to do all the cleaning up of the kitchen, get everything ready to attract

02:24 his lady, then she comes into the room and if she's happy with what he's done then she'll

02:30 lay her eggs, he'll fertilise them, she'll move off and swan off with her life and he's

02:35 left to do the heavy lifting for the next three weeks, which means tending to the little

02:40 ones which are eggs that are glued to the bottom of the nesting box which we got to

02:44 see, which is really neat.

02:50 The final design was put to the test during breeding season last spring when 30 boxes

02:55 were installed along the Nimboida River.

03:00 While breeding was seen in only one out of 30 boxes, Sean Morris says it's a significant

03:05 feat for a population of less than 250 mature fish.

03:10 With just one breeding event in one box we could have produced thousands of fish and

03:15 so it's a huge boost to the population.

03:17 (bubbling)

03:19 [BLANK_AUDIO]

Category

Transcript

Recommended