Beam Trawling in the Noosa River and Lakes

Summary

• Reports specifically commissioned by vested interest parties has painted a very negative picture of beam trawling in the Noosa River.
• These reports were never specifically designed to research Beam Trawling yet their speculation has been that this practice destroys the benthic layer and in combination with over-fishing has destroyed prawn stocks.
• It is the report authors assessment that Prawn Beam Trawling should be stopped and the river and lakes potentially be restocked.
• State scientists and government departments hold a diametrically opposed view and state in their reports that the Beam Trawling Industry is very much sustainable and is an environmental low-risk activity.
• Beam Trawling has been practiced in the Noosa River and Lakes for some 60 years now and today only a handful of licence holders still trawl.
• The scale of beam trawling is so small (and has been for over a decade) that it is not possible to suggest that trawling continues to degrade the environment. In fact what it does do is shine a light on other factors such as sedimentation moreso.
• Noosa Councillors and staff must cease and desist from maligning the industry and in fact should be supporting our low-scale, sustainable practice proactively going forward. The facts a very clear.

Introduction

Since the recent release of the Skilleter Report: “Assessment of the status and options for recovery of prawns & estuarine biodiversity in the Noosa River. Final Report – October 2019” commissioned by, and presented to the Noosa Biosphere Reserve Foundation, Noosa Parks Association and The Thomas Foundation, there is now some in positions of significant influence already referring to this document as proof positive that certain strategic environmental outcomes are now justified. The end to Beam Trawling for Prawns being one.
But, like a wild west lynch mob should, we must ensure that we ‘hang the right man’ if justice is to be done. The evidence today is nowhere near compelling that would warrant any statutory change to what occurs here in Noosa with beam trawling today. It is clear that there is enough State and other data to demonstrate that use of the ‘Precautionary Principle’ – so loved by some in local government, is not even remotely justified on the subject of beam trawling and that far more work in this area is needed to isolate the extent and contribution this activity has if any.

What current evidence does strongly point to is that with continued urbanisation and farming activity up the entire eastern coast, all prawn fisheries are suffering declines as a result. Whether it be sedimentation or chemical runoff, human activity on land is directly impacting inland waterway fisheries with this being the No.1 State issue and in combination with our local issues – especially the hydrology of the river at the river mouth makes for easier identification of Noosa’s major issues as Skilleter found.

Of course, there are peripherally related issues that come into play, but the two macro-level ones for us are key to most if not all from what can be read in most scientific evidence.

One of the original driving forces for the Skilleter study was concerns over the impacts of prawn trawling within Lake Cootharaba, on the basis of anecdotal reports and populist and over-simplified interpretation of reported declines in the commercial catch.

Yet, profoundly critical is the fact that as Skilleter states that “….the current study was not done though to examine specifically any impacts from prawn trawling (Major findings 1 (iii)…’, but rather to investigate the current status of the benthic communities (of which prawns are one part) within the system and to examine the potential for using prawns as a sentinel species for detecting impacts.

On this point alone, those contemplating management and strategic change to Beam Trawling here must acknowledge that neither Thurstan’s nor Skilleter’s work is at all specific research nor conclusive. At best it confirms that little is known and that indepth, subject-specific, long-term research is required before action can be reasonably taken.

Skilleter makes the point that if there are environmental impacts associated with the decades of benthic prawn trawling in Lake Cootharaba, these effects are likely to be manifested over much larger spatial scales (i.e. the entire Lake) than they examined with their focus on shore- based activities, which could be masking any effects from the creeks and sediment inputs.

However, a reasonable question to ask is with only 6 active beam trawlers catching a small tonnage annually over the past decade, surely the river and lakes system has had plenty of time to recover from historical over-fishing and benthos degradation if that is a serious problem at all? 6 beam trawlers today with a 5 metre-wide net in a small area of the system alone cannot have the physical impact as some think?

Already, we have seen firsthand how statements made within the report, are taken as gospel. The underlying conclusion of this report (supported and promoted by many in the local environmentalist movement) is that given the long history of beam trawling for prawns and various forms of net fishing for finfish within the Noosa River system it is likely to have led to dramatic changes not only to the species being targeted, but to those species forming the by-catch.

The general public and many policy and decision makers has an exceedingly negative view of this activity based upon a very limited or scant understanding of what actually happens. Ask anyone what beam trawling is and how it is actually practiced and you will get quite divergent definitions. Ask anyone what the scale of prawning is in the river and again you will get a very broad range of answers. Essentially what most believe is that there are large trawlers cutting large swathes of river and lake bottom up today all year round which is irrevocably damaging the environment and fish stocks.

There is no doubt that all Councillors and senior staff are, at best, unsure about the impacts or, are directly in the camp of beam trawling must be causing the damage if the benthic layer and fish stocks are so bad as they are increasingly being told.

We would like to give you the opportunity to actually spend time on one of the remaining 6 prawn trawler operators in the river. This will be the only way you will get a firsthand understanding of our activity and have witnessed at close quarters some of the impacts. Failure to do so can only lead to personal opinion based upon emotion, subjectivity and vague, tailored data.

Are we biologists, environmentalists, zoologists, another expert? Of course not. But that said, we are able to provide an objective and honest demonstration of what actually happens and imparting this knowledge we would hope that public opinion and subsequent decision making reflect reality and fact as opposed to rhetoric, anecdote and emotional opinion which is what we all have done in the past on many important issues.

There are current State and Federal reports that have a significant bearing on decision making which have not been referred to nor acknowledged in either Thurstan’s nor Skilleter’s work. I will demonstrate later on this point.

The Noosa river System is part of the Trawl Fishing Area known as T5. This extends all of the way from Double Island Point in the north to the Logan River in the south.

It is critical that we all understand exactly, at least in broad terms what is Beam Trawling. Firstly, what equipment is used in prawn trawling?

Skilleter stated…”’The trawl gear commonly used is extremely damaging to benthic habitats and the associated faunal communities, and the discards attract scavengers and predators which can also affect benthic communities.’

With commercial trawl fishing there are 2 types of trawl gear – beam and otter – and they are both used to take prawns but in different locations. The main difference is in how they keep the net open.

• Beam trawl is used in inland waterways such as the Noosa River system.
• Otter Board trawling is used off-shore.
• In Queensland, only about 5% of the trawl harvest is taken by beam trawling each year.
• The Beam Trawl net is attached to 2 ‘sleds’ connected by a rigid pole, or beam, that holds the net open for fishing.

Beam Trawl Sled – Contrary to popular belief and what Skilleter states, that a trawl net sleds drag a wide path along the bottom, the fact is that there are only two small permanent contact points between the sled and the bottom are two pieces of metal that are curved at the front – much like a snow ski measuring some 4cm wide by 120cm long pieces -see photo below.

The second important part of the beam trawl is at the opening of the Beam Trawl Net. A chain known as a ‘Tickler chain’ is positioned just above the river/lake bottom either bounces across the bottom depending upon the surface structure or it causes a bow wave in front of it that scares prawns up and into the net.

By law, all nets must be fitted with a By-Catch excluder to allow all non-target species an escape out of the net.

The Otter trawl method is used off-shore.

The otter trawl net also has chains hung below the footrope to disturb the prawns as the net is towed along or just above the seabed, making them jump into the mouth of the oncoming net. Each end of the net is attached to an otter board. The sheer force of water on the angled board forces each board sideways until the net is spread and held open.

How is beam trawling in the Noosa River actually performed?

The actual beam trawl net is some 5 metres wide and is let out slowly behind the boat (an open aluminium boat or open deck half cabin boat) where it trails the vessel some 30-50 metres behind. The trawling speed is critical. Too fast and the net travels too high off the bottom and you do not catch any prawns. The other danger of a high speed is snags and logs – hit one at virtually any speed and the beam bar will bend easily and end fishing. Too slow and it bogs down and gets caught in the grasses, mud, sand, silt and the net fills with debris and not prawns. Typical speed is about 1.6 – 2.2 knots.

Observing this process, it is clearly evident that the beam net causes very minor disturbance to the river/lake bottom as virtually no sand disturbance evident (see photo below). What is clear is that propeller wash from an outboard motor in very shallow water (i.e. < 1metre depth) has an obvious impact stirring up sand and mud. Whether that be from a beam trawler vessel, tourists boats or recreational boats in shallow water, the effect is the same.

On the day of photographing our work, we were one of some 6 vessels (5 of which were recreational fishermen) in one area at the northern end of Lake Cooroibah where the Noosa River continues north. Similarly, at the southern end of the lake there were 7 recreational fishing vessels in shallow water. Logic would suggest that it is propeller wash from all vessels – trawlers, commercial, tour operators and recreational fishermen that is what exacerbates and compounds disturbance to the river/lake bottom as opposed to beam trawlers singularly. Increased recreational boat ownership in SE Queensland and increased tourist visitation in Noosa will only see this problem compound.

Sand/mud slurry from propeller as it passed over a sandbank – no disturbance behind the beam trawl net!

Today’s commercial prawn industry in the Noosa River supports a bait prawn fishery of up to 6 boats in a season from October to April, with most of the fishermen also involved in mixed-fish, crab and mullet net fishing.

These days, night-time and weekend closure in the river protects the prawn population from over exploitation. Metapenaeus bennettae and Penaeus plebejus form a significant portion of the commercial catch. P. plebejus leaves the river at a non-commercial size and is not present in large numbers on the common commercial fishing grounds or during the day. The timing of the life history of these three species is presented and is used to explain the seasonal nature of the fishery. With present legislative restrictions, the Noosa prawn fishery is unlikely to compete for prawn resource with the offshore king prawn fishery and is unlikely to over exploit the bait prawn populations.

Fisheries today is a highly regulated industry – one that is closely managed and monitored. Modern day legislated requirements result in greater capital investment and in combination with operating costs results in marginal viability form most license holders. Most focus on other fishing actives such as Spanner Crabs, Mullet, etc where operating profits tend to be better.

Looking at River and Inshore Beam Trawling for the Noosa River in isolation as has been the case so far easily leads to assumptions that are not necessarily unique to us here – especially macro environmental factors.

The concern with the NRBF, TNC and NPA commissioned research (Thurstan and Skilleter) is that pertinent State and Federal information has not been referenced. For example, the Department of Agriculture and Fisheries published a summary report for Queensland Fisheries showing Catch and Effort data for Queensland Commercial Fisheries 2018/9.
Slide 1 below shows the River and Inshore Beam Trawl Fishery (RIBTF) is 1 of 3 sub-fisheries within the Queensland East Coast Trawl Fishery (ECTF). Target species include greasyback (bay) prawns, banana prawns and school prawns. Minor quantities of other species are also landed.

Catch within the River and Inshore Beam Trawl Fishery have decreased over the past 2 years due to whitespot disease in prawns which has affected fishers’ movements and access within the fishery area. What the State data is also showing is that trends by species is not that dissimilar from what has happened here.

If we look at the CFISH database (June 14, 2011) for the Annual reported harvest (tonnes) of fished beam trawl species for the preceding period 2001 – 2010 the annual catch tonnage ranged from a low of 369 tonnes in 2001 and a high of 552 tonnes in 2004. The average over that 10-year period was 422 tonnes. Between 2010 and 2018 the average annual tonnage was 244 tonnes.

This means that in the Queensland RIBTF there has been a 42% decline in average annual prawn catch between the two most recent decades.

If we look at the amount of effort over the years for beam trawling, our own government log books show e.g. in 2001 there was a total of 33 trawl days in the year – 12 days Lake Cootharaba, 12 days Laguna Bay and 9 days the river in between the lakes. In 2019 no prawns were caught and in 2020 no prawns were found in the river system yet a ball was tracked into Laguna Bay where 2 tonnes over 9 days was caught. Bear in mind that the 2 leading trawl operators are aged 71 and 72 respectively. So seasonal effort has reduced by virtue of age also.

The T5 Fishery is by far the biggest in Queensland and represents some 70% of the total Queensland annual catch. This goes a long way in confirming that prawn catch decline in Noosa is very much part of an overall State (if not national) phenomena. State scientists find it difficult to interpret at a whole fishery scale but do believe that it may be caused by a combination of factors including a reduction of effort (reduced numbers of beam trawlers) resulting directly in reduced catch because simply put – less fishermen, less chance of finding prawn balls!

There is also a belief by State scientists that environmental variation e.g. extreme stream flows events (flooding) affecting banana prawns and Noosa’s main species school prawns has played a significant role in reduced catches.

Based upon research elsewhere, it is believed that some school prawns can have the capacity to spend their entire life cycle in an inland waterway. However, local commercial fishermen state that they have missed catching prawn balls in the river and lakes but have tracked them into Laguna Bay where they have caught them on odd occasions in the past.

It is commonly believed here in Noosa that prawns in our waterways return to open sea as part of their life cycle. The absolute timing of the aggregation of prawns into a ball and subsequent group journey to open water is not known. Experienced fishermen can only guess when all of the factors are aligned which will result in a successful catch. Again, with only a few boats trawling to find the prawn ball it is very much like finding the proverbial ‘needle in a haystack’ – the odds are stacked against them moreso today.

The number of active River and Inshore Beam Trawl licenses in Queensland has significantly reduced overall all not only as a result of industry consolidation, license buy-backs (Reduced from 222 in 1996 to 153 in 2004). In 2020 there are only 81 active licences.

Skilleter, Thurstan, et al have also hypothesised that the reduction in prawn catches in the Noosa River system is a direct result of over-fishing and damaged to the Benthic layer caused by the beam. Yet where Skilleter sampled versus where beam trawling is actually carried out shows the same results in Benthos composition as compared to areas where beam trawling is NOT carried out. In fact, where Skilleter sampled NO beam trawling ever occurs at all. The main trawling grounds for prawns are in Lake Cootharaba where Skilleter stated that the main impact on the Benthic layer was the creeks and sediment.

There are only a few areas where the river/lake bottom is suitable to practically conduct beam trawling and only a few areas where ‘balls of prawns’ aggregate – see photo below. It is not the case where beam trawlers just randomly tow a net anywhere until the net fills. It is a very target-area specific operation in reality. Tides, the moon, temperature, etc, etc all play a significant part in deciding whether there will be prawns in these areas or not.

Prawn trawling occurs in parts of Lake Cootharaba, parts of the river connecting Lake Cootharaba and Lake Cooroibah and parts of Lake Cooroibah.

Lake Cootharaba (>75% of total catch) is approximately 10 km long and 5 km wide, with an average depth of 1.5 m. Trawling does not occur along the western bank area nor the entrance to the northern reaches of the river because there is a sand bank running from the entrance to the lake along the bank to Boreen Point and further north rocky outcrops and a rocky bottom precudes any trawling. Trawling at best occurs further than 100 metres from the bank along this section.

There is a large sand bank in the north east of the lake that creates a channel between it and the mainland. Trawling is not carried out on the sand bank. Similarly in the south east near the entrance to the lake is a rocky shoreline that is avoided. The total area of the lake is some 50 square kilometres with approximately 18 square kilometres not trawled. Essentially 32 square kilometres is the trawl area.

1. Northern section Lake Cootharaba

2. Southern section Lake Cootharaba

Skilleter and his team sampled 3 areas – Lake Cootharaba, the lower reaches of the river and Lake Weyba. Only one of the sample areas sees beam trawlers – Lake Cootharaba.

Where the benthic layer and trawl samples were taken (see Fig. 1 below) it is important to recognise that commercial beam trawling does not occur in any of these locations and it becomes easy to understand how non-scientific folk could interpret the Lake Cootharaba-specific data taken in areas where trawling does not occur as a systemic issue – one that could lead to the direct conclusion that this activity is responsible for benthos degradation where samples were taken. Especially when statements such as beam trawl sleds crush creatures in the benthic layer are made in the report?

River between lakes – some 7 kms long and 85 metres wide the total area is approximately 6 square kilometres. Approximately 65% is trawled – 4 kms. In the section of river in between Lakes Cooroibah and Cootharaba being a narrow waterway, all waters cannot be trawled due to riverbed obstacles such as rocks, trees, and other obstructions. The river around John’s Landing and the eastern side of the river to the north east at the entrance to Lake Cootharaba are not trawled.

Finally, Lake Cooroibah. Virtually all of the western bank and the south eastern bank are not trawled because it is too shallow – weed, sand, rocks, etc. measuring some 6 square kilometres about 1 square kilometre is not trawled.

The total area of the 3 waterways is some 62 square kilometres. Of that 21 square kilometres or 35% is not trawled. If 35% is not trawled then why have we not seen a recovery of the benthic layer (assuming it was trawled in the past) or a much higher level of biodiversity there compared to areas that are trawled today?

This has a direct bearing upon the negative perception that the impact of 6 beam trawlers supposedly have and more importantly places a direct spotlight on the impact of other factors such as sedimentation, poor water quality, pollution, changed habitat conditions, changes to the components of the benthic communities, etc.

Skilleter sampling areas – Lake Cootharaba 2018.

Another key point – one that offers a real, practical alternate theory as to why prawn catch numbers here (and elsewhere) for school and greasy prawns has declined is that of technology. Unlike fin fishing, where electronic equipment such as fish finders, planes and today drones identify the location of schools of fish, there is no equipment used in inshore rivers and waterways apart from experience gained over many years of practice.

Signs such as water discolouration and birds congregating in a specific area can point to a ball of prawns. Local historical knowledge of the river and lake bottom formation also is key – there is nothing random about beam trawling. The enemy of beam trawler fishermen is nets filled with sea grasses and tree branches, etc. Veer too far off a known area and nets and gear are easily destroyed by rocks and other underwater obstacles.

As stated above, the ‘Timing’ of when to trawl is arguably the most critical. Many decades ago when many vessels trawled the river, it was a case of when one boat ‘found’ a prawn ball, most other trawlers would quickly go to that location to catch the ‘ball’. This would see many boats in the one general area and is probably the main reason why the anti-beam trawling sentiment has grown over several decades. Clouded shallow waters churned up by older technology nets and propeller wash had a result of creating a poor or negative image of this practice.

Fisheries Data:

What does compound the issue further is the State’s assessment of the practice versus what Skilleter/Thurstan imply at an environment impact level. Their suggestion is that historic widespread damage was caused and has resulted in the decline in prawn stocks because the riverbed has not been able to recover. But why?

Skilleter’s research shows that in 1998 the benthos was biodiversity rich at a time when there were some 220 licences. In 2018 the benthos was poor at a time when there were only 81 active licenses and only 6 trawler operators. Is it really possible that 6 active boats could be responsible to maintaining a level of degraded riverbed that has occurred over some 15 years or so?

To this point, there is also a conflict with the State’s scientific assessment. Most significantly, In 2018 DAF published a report – ‘An Ecological Risk Assessment of the Southern Queensland East Coast Otter Trawl Fishery and River & Inshore Beam Trawl Fishery”.

In summary, the East Coast Trawl Fishery (ECTF) provides significant benefits to the Queensland economy. Risks associated with the fishery are assessed and managed at both a whole-of-fishery and species-specific level with high emphasis placed on the long-term sustainability of both target and non-target species. The report describes outcomes of a comprehensive qualitative ecological risk assessment (ERA)……….as well as areas of the River and Inshore Beam Trawl Fishery (RIBTF). The assessment focused specifically on the prawn-trawl ……fishery, including both targeted and non-targeted species that interact with or have the potential to interact with the ECTF during normal fishing operations.

Results of the assessment indicate that trawling represents a relatively low risk for the majority of ecological subcomponents that were assessed. Of the 171 ecological subcomponents that were assessed, 87.8% were at low to intermediate risk from trawling. Only 9.9% of the ecological subcomponents were assessed as high risk over the same period. Based on the results, the following broader observations could be made with respect to the overall risks and the potential impacts of trawling within the study area over the next 20 years:

• the vast majority of harvest species and bycatch ecological subcomponents were assessed as being at low to intermediate risk due to trawl fishing activities;
• half of the marine habitat ecological subcomponents had an intermediate risk from trawling; however,
• risk ratings for the marine habitat ecological subcomponents should be considered preliminary as the broader applicability of these evaluations was limited by regional data deficiencies.

Importantly and in support of Skilleter, while varying between ecological components, regional data deficiencies were influential in a number of the overall risk ratings. Of the ecological components included in this analysis, bycatch species and the species of conservation concern were arguably most affected by data deficiencies.

This said, the target prawn species were deemed to be Low Risk:

So you can see why there is a ‘disconnect’ between what has been purported and being put as a case locally compared to other information in part. We have always advocated that all levels of governmental policy making reflects current, objective and meaningful data, knowledge and information and not any based upon anecdotal, speculative nor incomplete or misconstrued evidence. In the case of beam trawling this is clearly evident in our view.
It would appear today’s limited beam trawling activity in the Noosa River and Lakes is very much sustainable and is one that has a low risk of negative environmental impact. The State’s scientists who closely monitor fisheries really need to be brought in and consulted regularly to avoid conflicts and miscommunication.

On a final point, all beam trawler operators are reporting increased numbers of Pony Fish (Leiognathus equulus) caught in nets. It can extend its mouth into a downward pointing tube and feeds in the benthos. Prawns and crustaceans are favourites. It is suggested that specific monitoring of this species be included in any future research work as anecdotally, there are growing concerns that this also is having a growing detrimental impact on prawn stocks.

In summary, managerial and strategic focus should really be on the root cause or key identified problem for most issues i.e. sedimentation, as opposed to making assumptions based upon anecdote opinion, unrelated reports and emotion that has led some (and others increasingly) to condemn a few beam trawlers that, by most measures do carry out a sustainable and environmentally low risk activity as measured by State legislation. The State has been and is managing Fisheries extremely closely and sustainably – let’s leave it this way!