Checking in on the health our scalefish fisheries

Based on the fisheries stock assessments by the Institute for Marine and Antarctic Studies (IMAS), we know that some of our favourite scalefish species are really struggling. Addressing some of the challenges facing these species was the focus of the 2023 Scalefish Rules Review.

Here's a check-in (and a bit of the science) on what's going on with these species.

The information below is based on the 2020-21 Tasmanian Scalefish Fishery Assessment by IMAS.

Sand flathead - Depleted

Fish illustration by Peter Gouldthorpe  

For the first time, sand flathead stocks have been classified as depleted. Ninety-eight percent of sand flathead are caught by recreational fishers, and there is too much fishing in many areas around Tasmania for sand flathead stocks to be able to replenish themselves - up to 4x too much in some areas.

Biomass of mature females and the number of eggs females produce before dying are also below the critical levels for sustainability in most regions due to overfishing.

Sand flathead stocks have been depleting since they were first formally assessed in 2015. Increasing the legal size from 30cm to 32cm in the 2015 scalefish review saw some temporary recovery. However, continued overfishing has prevented any long term stock recovery.

You can read more about what’s happening with sand flathead stocks, and how we are working to help them on the Flathead for the Future page.

Calamari - Depleting

Fish illustration by Peter Gouldthorpe 

Calamari is one of the most popular fish species for commercial and recreational fishers. It’s usually fished around spawning time, where large groups make it easier to catch. But because calamari only live for one year or less, overfishing before or during spawning can significantly affect what can be caught the following year. Fishing spawning groups also leaves calamari at risk of something called ‘hyperstability’- where catch might remain stable, even if the fishery isn't doing well.

Despite seasonal closures during parts of the calamari spawning season, calamari are not doing well. There is too much fishing, particularly on the north coast, where catch has started to show significant variability, including sharp drops even with more fishing effort. If the amount of fishing does not change, there are concerns that the north coast calamari fishery will follow the path of the south coast stocks – some of which have been depleted and might not return to earlier levels.


Usually the number of fish you catch for the amount of effort you put in is a good indicator about how a fish stock is doing. More fish means better fish stocks, while less fish might suggest populations are struggling.

But for schooling fish, or those that gather together for spawning, this isn't always the case. Often for these species, so long as you can find a group, catching many fish is easy - even if the overall population is actually declining. This is called hyperstability and it can make declining fish stocks difficult to spot until stocks are in such poor condition that catch starts being affected. Calamari, southern garfish and blue warehou are all prone to hyperstability.

Striped trumpeter - Depleted

Fish illustration by Peter Gouldthorpe

Striped trumpeter stocks have been depleted since 2000/01. The biggest challenge facing this fish is how variable recruitment success can be. The current minimum size limit for striped trumpeter is below the size where they start breeding. This means that fish are being caught before they have had the chance to spawn and contribute to the next generation. For a long time, there was no sign of any significant number of new fish in the population, despite a seaonal closure for spawning introduced in 2009.  

This changed in the 2017/18 stock assessment, when new, younger fish were seen for the first time, leading to hopes the stock should be recovering. But there’s been no sign since then that the population is doing better. New methods introduced in the 2019/20 and 2020/21 stock assessments indicate that fishing pressure in the south-east coast region is too high to allow for recovery. Some stocks in other regions (including the west coast region) are likely to be a bit better, but there isn’t currently enough data for a robust assessment of stock status in all regions.  

Recreational fishers are playing an increasingly important role in the striped trumpeter fishery, accounting for 67% of total catch in 2017/18.  

Variable recruitment

Stocks like striped trumpeter, with ongoing limited or failed recruitment, are very vulnerable to overfishing because fish that are caught and kept are not being replaced by younger fish - and the more adults that are caught, the less recruitment occurs in the future.

Bastard trumpeter – Depleted

bastard trumpeter  

Trends in commercial and recreational catches of bastard trumpeter suggest its population is at historically low levels. Bastard trumpeter catch is split relatively evenly between recreational and commercial fishers. Commercial fishers most often catch them as by-catch of the banded morwong fishery, while recreational fishers largely catch bastard trumpeter by netting.  

Changes to bag, possession and size limits (recreational) and trip limits (commercial) were introduced in 2009. However, bastard trumpeter stocks today are still depleted and are not showing any sign of recovery. Like striped trumpeter, bastard trumpeter has a lot of variability in recruitment success, and the size limit for the species is currently below when they start reproducing, further affecting the ability of this stock to recover.  The phasing out of recreational netting by 2030 in addition to other management action will benefit this species.

Southern garfish - Depleted

FIsh illustration by Peter Gouldthorpe 

The southern garfish fishery is largely commercial with a very small recreational catch. The fishery was first assessed as depleting in 2006/07 and has been classified as depleted since 2017/18 following declines in catch despite significant fishing effort. Southern garfish are a schooling fish, meaning that like calamari, they are vulnerable to hyperstability. Southern garfish are also short-lived, so their population at any given time is highly dependent on recent breeding success.   

Seasonal spawning closures for the commercial sector in 2009 saw some population recovery, but it was short-lived. The spawning closure was extended to recreational fishers in 2023 as an added action to help the stock.

Blue warehou – Depleted

Blue Warehou 

Blue warehou is a Commonwealth assessed species, and stocks have been in poor condition since the early 2000s. This is mostly due to significant overfishing in the 1990’s by the Commonwealth trawl fishery. The species is primarily caught and managed by the Commonwealth, but there is also a small State fishery, which has seen a significant catch decline in recent years. Despite Commonwealth and Tasmanian management measures, there has been no evidence of stock recovery.   

This species is particularly at risk from gillnetting because blue warehou often don't survive after being released from gillnets. This makes effectively managing blue warehou catch challenging. Size limits and bag limits cannot be effectively applied to catch from gillnets for this fish, since blue warehou are unlikely to survive in good enough condition to be released. However, as part of the commitments of the Recreational Fishing Strategy, the use of gillnets is being phased out, which may benefit this species. Like southern garfish, blue warehou are particularly vulnerable to overfishing because they are a schooling fish. 

Jackass morwong – Depleted (Commonwealth assessment)

Jackass morwong 

Jackass Morwong has recently been assessed as depleted by the Commonwealth, which manages and assesses this species. The state catch of jackass morwong is relatively small with about two thirds coming from recreational fishers and one third from the commercial fishery .

In the most recent Commonwealth stock assessment by CSIRO, the stock was assessed as depleted – and this will be reflected in the upcoming IMAS stock assessment.

The Australian Fisheries Management Authority has introduced management actions for the Commonwealth trawl fishery, including significantly reduced total allowable catches and planned closures. Although the Tasmanian catch of jackass morwong is low compared to the Commonwealth catch, management is needed across both sectors to ensure fishery sustainability.

Published on: 5/10/2023


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