Research projects

• the discard rate of Snapper in the Marine Scalefish Fishery (MSF)
• the survival rates of released fish.

A targeted study using electronic tags will quantify the survival rates of Snapper captured at different depths and released using different methods.

The findings of the study will inform the development of a Code of Practice through consultation with industry to promote responsible capture, handling, and release practices for Snapper to optimise survival.

The project is expected to be finalised in late 2024. Learn about barotrauma and handling practices for Snapper.

Quantifying post-release survival and movement of Snapper (Chrysophrys auratus): Informing strategies to engage the fishing community in practices to enhance the sustainability of an important multi-sector fishery

FRDC project number: 2019-046

Snapper populations in South Australia are characterised by highly variable recruitment (the number of juvenile fish that enter the population each year).

Snapper spawn annually during the summer months, but this doesn’t always result in juvenile recruitment. Occasional strong recruitment events every 5 to 7 years sustain the population through periods of poor recruitment.

Monitoring the abundance of juvenile Snapper each year provides a relative indication of recruitment. This can be used to forecast trends in the population, such as the influx of legal sized fish in 3 to 4 years’ time.

This project aims to compare sampling methods for juvenile Snapper and develop a protocol to monitor juvenile abundance into the future.

The project is expected to be finalised in early 2025.

Cost-effective, non-destructive solutions to developing a pre-recruit index for Snapper

FRDC project number: 2019-085

A national workshop for Snapper was held in Adelaide in November 2019. This involved researchers, managers, and industry representatives from each state in Australia that supports a Snapper fishery.

The main objectives of the workshop were to:

• identify key issues and challenges for Snapper
• explore a national approach to collaborate and manage cross-jurisdictional Snapper stocks
• determine a set of national research and development priorities
• develop a tool kit that supports fishery managers to recover Snapper stocks.

National Snapper workshop: Rebuilding our iconic Snapper stocks

FRDC project number: 2014-019

The daily egg production method (DEPM) is a fishery-independent technique used to estimate spawning biomass. It is based on:

• the relative density of fish eggs in the water column
• the number of eggs produced by an adult fish.

The method determines how many Snapper were required to spawn the measured density of eggs. This information indicates the size of a fish stock, assisting fisheries in sustainably managing Snapper stocks.

An essential part of the DEPM is identifying fish eggs in mixed plankton samples. However, this was challenging for Snapper due to similarities in appearance with other fish species.

The study developed a molecular technique (in situ hybridisation) which uses a DNA marker to turn all Snapper eggs a blue colour, making it easier to see the eggs and larvae in samples.

The novel method re-invigorated the application of the DEPM to estimate Snapper spawning biomass.

Developing a fishery independent estimate of biomass for Snapper

FRDC project number: 2012-020

There was a change in the spatial structure of the Snapper fishery in South Australia from 2007 to 2012. The fishable biomass declined significantly in the northern Spencer Gulf, which had previously supported the highest biomass and the most productive regional Snapper fishery in Australia.

At the same time, fishable biomass in Gulf St Vincent and the Southeast Region increased to unprecedently high levels. There was a need to understand the underlying processes responsible for these changes in the fishery.

This project aimed to improve the understanding of Snapper population dynamics and stock structure throughout southeastern Australia. There were 2 main components of the study:

1. A broad scale electronic tagging study in northern Gulf St Vincent to provide insight into the movement of Snapper over 3 years. The tagging demonstrated that Snapper were mobile throughout the region and generally operated over small spatial scales (10’s to 100 km).
2. Investigation into population dynamics and stock structure from the analysis of fish otoliths (‘ear bones’). This work identified 3 different stocks of Snapper in SA waters – the Spencer Gulf, West Coast stock, the Gulf St Vincent stock, and the Western Victoria Stock. Each stock is dependent on spawning and recruitment into a primary nursery area.

The influence of fish movement on regional fishery production and stock structure for South Australia's Snapper (Chrysophrys auratus) fishery

FRDC project number: 2002-001

In the early 2000s, there was considerable concern about the differences in fishery production between Spencer Gulf and Gulf St Vincent. This included the continued low catches from Gulf St Vincent since the 1980s.

These differences called into question the hypothesis that Snapper in South Australia were a single, large stock. This study investigated the stock structure of SA's Snapper through:

• the regional comparison of fishery statistics
• length and age structures
• otolith chemistry.

The study identified significant differences in the length, age, and growth rates of Snapper between regions. The otolith chemistry indicated that fish from each region had experienced different environmental conditions for most of their lives.

Based on these findings, the understanding of stock structure was updated to support a division between the gulfs and the Southeast Region. There was also evidence that most fish originated from up to 2 places and then dispersed at 3 to 4 years of age.

Adult migration, population replenishment and geographic structure for snapper in South Australia