Spawning and recruitment

Murray cod

Introduction

Murray cod fisheries continue to improve in many areas. Much of this recovery is due to better conditions and stocking programs. However, more research is needed on spawning and recruitment.

What is the difference between spawning & recruitment?

Murray cod spawning site during dry conditions.

Recruitment occurs when larvae or small fish survive and have the opportunity to grow to adults.

Spawning is the process of fertilisation of eggs.

Successful spawning doesn’t always mean successful recruitment.
Fertilised eggs may not hatch and larvae  may not survive

How is DPI monitoring cod spawning and recruiting?

Wild juvenile Murray cod from central and western NSW

Electrofishing is used to monitor recruitment, juvenile habitat preferences and survival of stocked fish.

Radiotracking, larval sampling and underwater video are used to monitor spawning, habitat use and larval survival.

Why have a closed season?

This video shows a Murray cod guarding its nest.

Murray cod display care of eggs and monitor their nest for debris and predators. Keeping adults near the nest during the breeding season gives the greatest chance of natural recruitment. 

How do we know what is happening during the spawning season?

Tracking Murray cod allows us to identify spawning sites and determine spawning success. This is also used to ensure we have the right closed season.

Male Murray cod are surgically implanted with tags, which allows them to be tracked to the nest.

The nest can then be monitored with underwater cameras and larval fish trapping.

How else are DPI monitoring Murray cod fisheries?

3) Angler fishing catch and effort with citizen science & angler surveys. 

2) Effectiveness of stocking through tag recaptures. 

1) Population size structure in the Murrumbidgee, Gwydir & Dumaresq  

The recreational fishery for Murray cod is further monitored by examining:

What's next for Murray cod monitoring?

Keep an eye out for some new work on movement of big Murray cod in impoundments and our new project on stocking bigger cod the speedy recovery.

Follow the DPI website and Facebook pages for regular monitoring updates.

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