Tasmania’s Estuary Perch are disappearing

Less than 2 000 remain. Endemic and Endangered - can they be saved?

by Mike Stevens and Bryan van Wyk

Isat on the Inland Fisheries Advisory Council (IFAC) around 2014. One of my concerns at that time - and continuing, is the status of estuary perch (EP) in Tasmania. I am embarrased to say I achieved nothing to help rehabilitate estuary perch and it seems there is little desire by anyone else to re-establish a viable and diverse population of this species. They are a fantastic sport fish and in Tasmania are only found in the Arthur River on the West Coast. As far as I can find there has been a report by IFS staffer, Tim Farrell and a thesis by Bryan van Wyk. Both papers and others mentioned here can be viewed at www. tasfish.com.

Whilst estuary perch are revered in mainland states the Inland Fisheries Service has never sought funding to protect and/or rebuild EP here in Tasmania.

At the IFAC meeting October 31st 2015 there was an Action item 5. It said:

Action 5 - Estuary Perch – Mr. Farrell had prepared a discussion paper considering the options for the development of a fishery in the future. The matter was discussed and the next steps in the assessment process were to consider two options for importation of fish one from hatcheries in New South Wales or the transfer of fish from the

Arthur River population. Both these options would require consideration of biosecurity issues in the first instance. IFAC commended Mr. Farrell for the paper.

It appears nothing was done.

Action that has been undertaken since then has been the listing of the species as ‘rare’. Under section 131 of the Inland Fisheries Act 1995 a fish may be declared as a Protected Fish by Ministerial Order preventing the take of any protected fish, fine not exceeding 50 penalty units.

The listing of the species under threated species legislation would make it difficult to remove such protection should the status of the species change due to establishment of further populations. A declaration of the species as a Protected Fish allows for this flexibility.

The Inland Fisheries Protected Fish Order affords the species legislative protection that prohibits ‘take’ of the species. This is how estuary perch are now managed - as a ‘no take’ fish. In fact it is illegal to even fish for or target them.

Where to from here?

We asked Bryan van Wyk for his input. Bryan did a UTAS Thesis on EPs and is now a fisheries manager in Northern Australia. He still has a keen interest in this fish.

Does estuary perch have a future in Tasmania, or will it become another Tasmanian extinction?

Growing up in Tasmania with a passion for recreational fishing and a craving for understanding made sure I was always on the hunt for knowledge during my explorations. I was based in the NorthWest and spent a lot of time searching for large trout in untouched regions of the West Coast, so it didn’t take long before I found myself venturing into the Arthur River. It’s a place blessed with lush tarkine rainforest, a complicated network of timber snags and endless opportunities for trophy sea run trout. Little did I know at the time, it was also the last remaining stronghold for Tasmania’s largest native freshwater fish, estuary perch.

The rise of estuary perch

For most tassie fishers, estuary perch was a fish you only saw on TV, with many elite anglers targeting them in rivers on the mainland. To a lot of anglers, their existence in Tasmania was merely a rumour and for a lucky few who knew about them, they were considered the “holy grail” of light tackle sportfish for their elusiveness. When the word finally got out on fishing forums, many anglers were traveling as far as Hobart to the Arthur River for the opportunity to tick this species off their bucket list. As the years went by, techniques and technologies changed. With side scan imaging, GPS electric motors and an arsenal of soft plastics available, a handful of anglers were able to successfully crack the EP code and produce consistent catch and release results. In a way, these were essentially the only people in the state monitoring the stock.

But where did these fish come from, why were they only found in the Arthur River and how many were left? Those were the questions asked by recreational anglers for many years with no answers.

The first significant biological estuary perch study in Tasmania

Six years later, those questions were still unanswered and after completing my degree in fisheries management, I put together a project proposal for a 1-year population study on the Arthur River with Dr James Haddy. James is a highly passionate and respected fisheries biologist in Tasmania. He has worked on many key estuary species and we both agreed that critical research was needed on this species. Estuary perch falls under the jurisdiction of the Inland Fisheries Service (IFS), so we presented our proposal as the first significant biological study ever undertaken for the species in Tasmania. The aim was to develop a better understanding of the Arthur River population and provide crucial information to the IFS to guide future management decisions.

What happened to estuary perch?

Prior to the commencement of field work, extensive background research was undertaken to understand where estuary perch were once found and what happened to the species in Tasmania. The only other documented evidence of estuary perch outside the Arthur River was in the Ansons River in the early 80s. However, given ocean currents, their spawning strategy and tendency to migrate to other rivers during flood events, it is likely that they were once found in more rivers in the state. Unfortunately, this information is not well documented but there were numerous anecdotal reports of estuary perch in the Pipers River, Scamander River and Georges River. It’s widely believed that in the 1950s-1960s they were often caught in large quantities as bycatch with gillnets, referred to as razor fish (for their sharp gill plates), and discarded. Estuary perch are also known to have trouble spawning if conditions aren’t right and given that they are also migratory spawners (moving into the saltwater regions to breed), it’s believed that culverts and weirs had a big role to play in their disappearance. Overfishing, combined with barriers to migration and poor recruitment are all factors that likely caused their decline in Tasmania.

Study Results - Understanding the Arthur River population

In 2015 we secured permits and approvals to sample the river. As the status of this population was uncertain, we used extreme caution with our sampling and collected as few individuals as possible for biological processing. We also tagged and released any individuals not subject to biological dissections for some early indications of population size. To make sure we were not wasting this unique opportunity, we also collected various DNA samples (later used by Department of Environment, Land, Water and Planning VIC) and scales and fin spines for nondestructive ageing experiments. Unfortunately, scales and fin spines could not be accurately used for ageing.

Our findings were concerning

The population displayed extreme cases of episodic recruitment. Almost 70% of the fish sampled came from 3 good years between 2001 and 2003. Given that most of these fish are now over 20 years old, a population crash could occur if environmental conditions remained unfavourable for spawning.

Unlike their cousins on the mainland which spawn around winter-spring, these fish spawn in summer. In the Arthur River, there are known periods of low dissolved oxygen around that time of year which can reduce the success of recruitment.

These fish are long-lived and slow growing (oldest fish was 34 years at 38cm FL).

Population estimates were low at around 1,500 fish. 81 fish were tagged and released in 2015. A total of 27 recaptures have been recorded with the last recapture reported in 2019. With no tagged estuary perch reported in the past 3 years, this could be a concerning sign of a population reduction or, be a result from the legislation change that excluded recreational anglers from targeting estuary perch.

Further Research Undertaken

Our genetic samples taken in 2015 were analysed by the Department of Environment, Land, Water and Planning VIC as part of a larger genetic study on estuary perch in Australia. Their findings outlined that the Arthur River population displays low levels of genetic variation and that restocking with mainland populations is recommended to increase diversity and strengthen the Arthur River gene pool.

Restocking/Breeding Potential

Breeding and restocking estuary perch in Tasmania is an idea that has been proposed for many years, long before our study in 2015. In Victoria, recreational license fees funded an estuary perch breeding program where over 200,000 fingerlings were released into several waterways. This was part of a larger initiative to increase recreational fishing activity. The results were promising with estuary perch observed to be thriving in lakes and dams, growing to half a kilo within 3 years. It has been noted that estuary perch are excellent candidates for captive breeding with high recruitment success from wild broodstock. Due to the natural vulnerability of estuary perch and their importance as a key recreational species in Australia, restocking strategies are used throughout NSW and VIC to boost population numbers in the wild. There are a wealth of resources, knowledge, and people available that can be accessed to aid the implementation of a successful restocking program in Tasmania.

What we know about estuary perch:

Estuary perch is a native fish that has been neglected and historically declined in Tasmania.

The estuary perch population in the Arthur River have recruitment difficulties. If this population was lost, this fish would be yet another iconic species to become extinct in Tasmania.

As, estuary perch are listed as a protected species under the Inland Fisheries Act, the Inland Fisheries Service are currently responsible for their conservation. However, given that this is an estuarine species, there could be jurisdictional gaps with DPIPWE which could potentially hinder conservation ownership.

Estuary perch are easily bred in captivity and frequently stocked in several waterways in VIC and NSW to boost wild populations.

Weirs and culverts disrupt the breeding migrations of estuary perch. There are proven modifications that can be made to these man-made structures which can maintain access for migratory fish.

Estuary perch can also be stocked into freshwater impoundments with impressive growth rates as a recreational fishing alternative.

So what has occurred since our study:

When we completed our estuary perch study in 2015, James Haddy and I envisioned that this research would catalyse further studies and conservation efforts in Tasmania. We believed that this species had potential for a strong recovery and a future in Tasmania as a recreational species.

As I write this article almost 6 years later, I am deeply saddened on the lack of effort, funding and attention given to such an iconic native fish despite a clear track record of declines in the state, evidence of natural recruitment difficulties and poor gene pools.

To my knowledge, there has been little to no engagement with recreational anglers. The only action taken to safeguard the species since our study was a legislation change which stopped anglers from targeted catch and release and enforced accidental catches to be returned to the water immediately. This means you are in breach and could be fined if you stop to take a photo or even record tag details of an estuary perch.

While I do support precautionary decisions in fisheries management, locking out the very people pushing for estuary perch conservation, and the only people who were monitoring the stock, especially after such an evident catch and release survival rate from our gillnet surveys (+33% tag recaptures) is counterproductive. As a consequence of this decision, future tag data or catch information may not be reported, awareness of this species will drop, and the recreational community will lose trust in the Inland Fisheries Service.

There is a significant opportunity lost where tag/ release equipment, training and permits could have been given to recreational anglers as “citizen scientists” to collect vital information that could be used to monitor this stock in a cost-effective manner.

What could happen in the future:

Conservation grants and funding need to be applied for estuary perch.

A follow up survey and long-term monitoring plan needs to be developed for estuary perch in the Arthur River. This is where recreational anglers can add value.

A feasibility study and proposal should be developed for a wild restocking plan in the Arthur River. Stocking can be contracted to established facilities on the mainland or replicated in Tasmania. Any released fingerlings should be marked and incorporated into the monitoring plan.

An ecological survey should be undertaken on the Anson’s River to identify relevant spawning habitat and water parameters, potential interactions with other native species and modifications to barriers of migration. The re-introduction of estuary perch into the Anson’s River with on-going re-stocking and monitoring should be considered as there is clear evidence that this species was established there in the past.

A feasibility study and project should be developed to increase recreational fishing activity in Tasmania by stocking estuary perch into appropriate impoundments. A pilot study could be conducted with UTAS/IMAS to assess the growth rates of Tasmanian estuary perch in freshwater lab tanks.

Regular updates on all estuary perch related management decisions, projects and news should be transparently given to the recreational fishing community.

Bryan van Wyk

Estuary perch can be rehabilitated, but it will need the IFS to take up the challenge. The IFS undertake a lot of work on galaxiids and native fish. We have also seen an enormous effort by IFS to eradicate carp, so skills and determination are there. We encourage the IFS to rebuild the EP population. It could be a future sport fishery again. Ed.

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