Murray Cod Monitoring Program (Complete)
Project Overview
Murray cod have risen to star-status as one of Australia’s most iconic sportfish. The rapid increase in recreational angling targeting this species has led to many stocking programs introducing Murray cod to many waterways outside its natural range.
Since 2019, alongside SA Water’s plan to open South Australian reservoirs to recreational fishing, Murray cod have been stocked in all reservoirs open to recreational angling. This makes them the most accessible native freshwater sportfish in SA and represent a crucial species for tourism and recreation.
RecFish SA, with the support of SA Water, AusOcean and Pembroke school, have developed the “Murray Cod Monitoring Program” which aims to monitor the breeding behaviours of Murray cod through the deployment of camera-monitored nesting boxes in Happy Valley and Myponga reservoir.
Objectives
Science
To better understand the reproductive biology of reservoir-stocked Murray cod and record their spawning behaviour for the first time in an inland stocked reservoir.
Community
To increase public engagement and education of Australia’s most iconic freshwater fish, encourage stewardship among the public, and promote a strong respectful culture for natural resources.
Recreation
To grow South Australia’s reservoirs into a nation leader for Murray cod knowledge, recreational opportunities, and to boost tourism in the region.
The Monitoring System
The CodPod
- HDPE pickle barrel on a galvanised steel frame
- Built in consultation with NSW aquatic biologists
- Camera mount
The Rig
- Underwater camera system
- Temperature and humidity probes
- Live-stream router uploaded to YouTube
- Developed by AusOcean
Project Completion
Happy Valley
- CodPod Build 100%
- Rig Build 100%
- Site Approval 100%
- Mooring Lines Fixed 100%
- Deployment 100%
Myponga
- CodPod Build 100%
- Rig Build 100%
- Site Approval 100%
- Mooring Lines Fixed 100%
- Deployment 100%
Outcomes
Site Occupation
The speed in which cod found and occupied the codpod varied across each site. Happy Valley was the earliest, with the first cod finding and occupying the site within 48 hrs of deployment. The Myponga sites took longer for the cod to locate and occupy. It took the cod 23 days to occupy Myponga 1 and 26 days to occupy Myponga 2. The largest individual was observed in Myponga at an estimated length of 80-90cm. The site used by the most unique individuals was Happy Valley which recorded a minimum of four unique individuals using the codpod at different times.
Clockwise: Cod individuals at Happy Valley, Myponga 1, Myponga 2, and two individuals roaming around the Happy Valley codpod.
Clockwise: Cod flaring its gills at Happy Valley, cod chasing a challenger (likely both males), cod tidying the nest at Myponga 1, and the pearlescent cod eggs laid at Myponga 2.
Breeding Behaviours
Breeding behaviours were observed at all three sites to varying degree. Tidying and fanning the nesting site was observed at all sites, however, most breeding behaviour was observed at Happy Valley and Myponga 1. Happy Valley and Myponga 1 observed territorial behaviour including gaping, charging, chasing, and flaring of the gills. No co-habitation was observed in any site. Eggs were observed at Myponga site 2 with the earliest positive ID made on the 16th of October.
Species Diversity
A multitude of individual species were observed. Happy Valley had the lowest diversity observing Murray cod, zooplankton (daphnia and copepods), and a variety of annelids (worms) and molluscs (snails). Myponga had the highest diversity featuring Murray cod, golden perch, cormorants, freshwater shrimp, zooplankton (daphnia and copepods), eastern long-neck turtles, annelids (worms), molluscs (snails), and insect larvae (mudeyes/nymphs).
Clockwise: Two freshwater shrimp feeding on biofouling, an adult eastern long-neck turtle inspects the camera, a cormorant diving in search of food, and a large golden perch checking out the codpod.
Project Success!
This project has been a great success. The behaviour of Murray cod has been well researched but this to the best of our knowledge represents the largest database of observed Murray cod behaviour. This project discovered that not only are cod capable of breeding in South Australian reservoirs, but will readily do so if provided the right habitat.
This insight can help inform the way we manage native fish stocks in impoundments through stocking and habitat projects.
A massive thank you goes out to AusOcean, SA Water, Pembroke School, OzFish, and RFSA citizen scientists that made this possible.