Crisis or not? A review & analysis of Noosa River fish stocks

By Nick Hluszko
President, Noosa North Shore Association Inc

Introduction

I want to be very clear from the start. I (like most NNSA members) support most initiatives that do anything to protect the river, coastline and our environment for now and importantly the future.

There has been much said and written about fish stocks, prawns, sustainability etc and the critical need to address these perceived problem areas. One outcome is that this is very likely to lead us to a declaration of a marine park that fills in the gap between the existing parks to the north and south of us. This obviously makes a lot of sense to do, providing local needs and nuances are acknowledged and included in the management of the park.

But here is my problem and ongoing major concern about fish stocks/oysters/prawns in the river system.

There is so much anecdotal information and growing opinion based upon this information that many people who I have spoken to on the subject now believe it to be fact as opposed to just hearsay in the main. As such, as time goes by, strategic initiatives get based upon this information and outcomes driven to address the now significant aquatic life problems we purportedly have in the river.

What got me more than interested in digging deeper was that, when I started reading various reports and data, not much supported the anecdotally based strategic direction.

In all fairness to those who have driven the strategy so far, it is in some ways understandable that there has been such a heavy reliance upon anecdotal evidence simply because no accurate records existed at all in the first half of the 20th century. So with way too much time on my hands I decided to have a really close look at the situation.

Firstly, I would never insult anyone’s intelligence by suggesting that I am a man of science such as being a botanist, biologist, environmentalist etc. I am simply a person who has a natural curiosity and the ability to quickly find facts and to assess a situation (at least at a macro level initially).

So nobody feels that what I report on are the rantings of some radical trouble-maker on the North Shore, here’s a little about me to demonstrate that I have enough academic skills and practical experience to understand data, research and ultimately strategy.

My Background

I have, from Monash University in Melbourne, Bachelor of Business and a Master of Business Administration degrees. I have completed specialist programs at Harvard University (USA), INSEAD (France) and the Australian Graduate School (Sydney). As part of my post-graduate studies, I took and completed courses in advanced qualitative and quantitative research.

In over 35 years of corporate life I have been directly and indirectly involved in many research projects – so many so I have forgotten most. The reason for bringing this up is that before recent retirement I ran big businesses (up to $US300 million in revenues and with 3,500 staff.

We would never make investment decisions or create and drive strategy without robust empirical data that, through research, I was always involved in. It was also critical that, after implementation of strategic outcomes, we regularly tested if the desired results were being met. It is with this background that I have approached the subject at hand.

The Dilemma of the Noosa River

Upon my return to Australia and to my home here on the North Shore, there was much in the media and other circles about ‘Bringing Back the Fish’ …. a crisis with sustainability of fish stocks …. the Noosa River Plan …. etc etc.

From what I read, things looked pretty bad and the perception was that unless we acted now it would all be a disaster and nothing would be sustainable at all – a very critical situation indeed. So, armed with a lot of free time, a fast modem and a good internet plan, I got to work.

I first started with fish stocks because the NPA/Thomas Foundation and Noosa Biosphere Reserve Foundation had just funded and commenced an oyster bed trial in the Noosa River. First I read with interest Dr Ruth Thurston’s report which formed the basis of Noosa Council’s position then and now.

Her study objective was: ‘This study aims to develop an understanding of historical fisheries productivity in the Noosa Estuary. It does not intend to prescribe targets for management; rather, it aims to inform the wider community about ecological changes that occurred prior to their lifetimes….’

What was compelling for me was this excerpt:

“Dr Ruth H Thurstan states in her study, ‘Historical ecology of the Noosa Estuary Fisheries’, that our ability to judge the extent to which marine ecosystems have been degraded is impeded due to a lack of long-term data, making it difficult to know what appropriate management or restoration targets should be.

“She also states that ‘Commercial fishing records are limited and for the most part do not provide us with Noosa-specific catch. It is clear from the available records that landings of the main species have always been variable, and no significant declines in catch are recorded’.”

The pertinent points in Dr Thurston’s comment above are:

• aquatic life of most species have always varied from year-to-year;
• that it is not possible to measure degradation of fish or other stocks going back to the first half of the 1900’s because there was no data available for a Noosa River-specific catch

So if Dr Thurston is cited as the definitive source for Council’s strategy, why is hearsay and anecdotal comment accepted as being fact and now forms a basis in the psyche of our Council leadership?

From the Council, here are a couple of prime examples of the issues at heart on recreational – not commercial – fishing.

From a report in 1901:

“…whiting are now in the [Noosa] river in immense quantities, as well as many of the larger denizens of the deep. Mr Acting-Judge Byrne, and Mr Benson, several times bringing home 60 and 70, and once or twice well over the century.”

From a report in 1913:

“In 21 days at Tewantin three persons caught about 3,000 fish, principally whiting, flathead, tailor, tarwhine, grunter, and bream. Mrs RW Thurlow and her son also had good sport, creeling over 1,500 fish in about three weeks.”

A report from 1923 noted a gentleman and his three children caught 440 flathead in two days.

But then, in 1928, DISASTER. The Brisbane Courier noted that a party caught 85 fish one day and 97 the next. But in 1928 they were already complaining that “the fishing is not as good as it was 20 years ago.”

So is the argument that in 20 years from 1910 to 1928 thereabouts there was a big drop off in fish catches which has purported to have continued to this day?

In my view it certainly feels like this is the heart of Council’s position and that we all must return fish stocks, oysters etc to historical levels. But this is where it gets really tricky. Dr Thurston correctly states there is no data and if all you really have is anecdotal data then how do you objectively measure degradation?

My initial question to myself was – could tourists at the turn of the century using nets decimate fish stocks to a serious degree?

Back in 1911 the population in Noosa was only 87 people plus local aboriginals so local consumption would arguably be unlikely to be a cause. Was there a commercial impact? (Local mullet was sold, for example, in the Gympie gold fields?). Or, could a reported decline be contributed to by other factors?

I looked at Bureau of Meteorology rainfall data for the four years 1901, 1913, 1923 and 1928 to see if it was possible to make any assumptions about the comment about a drop in fish caught in 1928.

I thought that, if there was more rainfall, then levels of fish and other stocks would be less. Looking at each year specifically, there is nothing apparent in the data. But, if you look at the yearly averages for the period between 1900 and 1919, you will see that average rainfall was 1,614 mm.

If you look at the next 10 years from 1920 to 1930, it is 2034mm – a 26% increase! I believe that this is a significant fact and may well have directly contributed to the decimation of, for example, oysters through disease and a reduction of fish stocks around that time.

Why? What most people do not understand is that fish (including prawns) are migratory. They do not habitat a river system full-time because they have to go to open ocean as part of the reproductive cycle.

Their frequency and abundance in the river is determined by many factors with food abundance, salinity and water temperature being just three important factors. This is a very important point and is one that makes absolute measurement and management from year-to-year challenging.

Measuring, say, just fish catch is not an absolute determinant of sustainability – it is far more complicated than that.

Data Overview

There is a lot of data out there if you dig deep enough. Some of the Queensland State level data states:

• Dr Elizabeth Woods Director-General of Department of Agriculture and Fisheries (DAF), in the DAF 2017-18 Annual Report (p4 ‘Protecting the Environment’), states that, with regard to fish stocks, 82% of key Queensland fish stocks assessed have no sustainability concerns. In fact not one of the popular fish species caught in our waterways is identified as ‘unsustainable’.
• DAF 2018: Commercially and recreationally important fish species found in the Noosa River do not only live in the Noosa River. Because of processes such as migration, larval dispersal and reproductive biology, they also form part of broader stocks in the state and elsewhere.

• • A stock can be described as semi-discrete population of fish that is distinct from other populations of the same species
  • Measurable characteristics such as genetics, distribution, catchment and fishery boundaries are used by fishery managers and assessment scientists to help define the spatial extent of a stock
  • An assessment of the sustainability status of an estuarine fish stock in Queensland considers all available commercial and recreational catch and monitoring data
  • DAF has data on all commercially and recreationally harvested ‘fish stocks’ present in the Noosa River but these data may have come from areas outside the Noosa River but from the same ‘stock’. For example, dusky flathead in Queensland is considered one stock and also extends into NSW
  • Based on the data DAF have for fish stocks, no Queensland estuarine fish stocks that occur in the Noosa River have been classified as depleting or overfished
  • For some local areas where there is high fishing activity (commercial and/or recreational), there may be examples of localised depletion, but this may not impact the sustainability of the overall stock due to replenishment etc. There is no evidence of this in the Noosa River.

Oysters

Many people believe that humans wiped out oysters in the river through simple exploitation. Dr Thurston wrote: “By the turn of the 20th century, millions of oysters had been removed from the Noosa system, destined for consumption in Brisbane and other Australian cities. Despite high levels of exploitation, the beds continued to operate until the 1920s, after which oyster leasing was largely discontinued.”

Oysters – once plentiful – are now commercially and functionally extinct. But there are explanations for this beyond historical eco-terrorism.

Many authors and scientists have studied the decline of oysters in South East Queensland and all agree it was due to a combination of events potentially including overfishing, disease and declining water quality.

However, there is some disagreement about the extent of the respective roles of these events. Outbreaks of ‘mudworm disease’ due to infection by spionid polychaete mudworms was the main reason why oystering for S glomerata in subtidal dredge sections was abandoned (Smith 1981).

Indeed, in hindsight, it is much more likely that acute post-flood mass mortalities were due to either prolonged hyposalinity, smothering of oyster beds with silt, and/or infection by then unknown diseases such as QX disease.

According to the Shellfish Reef Habitats TropWATER Report No 15/60 2015: “An important component of management and restoration efforts for shellfish reefs in southern Queensland is therefore improvement of inshore water quality by reducing influx of sediment, nutrients and other pollutants from both point and non-point sources.”

In my view the oyster bed trial has to be commended for trying, but just installing a few oyster test beds in isolation without addressing river catchment issues is ever likely to ever prevent the probable historic causes of oyster decline.

Going forward, it is critically important that salinity and water temperatures are reported upon as part of the ‘oyster bed trials’ as these play such a significant role in aquatic life here.

Prawns

This is a fascinating area in that historical trawl catch numbers have been used as the definitive case for why all commercial trawling needs to be banned in the river system.

The problem with prawn catch data has been that published statistics are hard to get and when quoted usually include tonnage of Eastern King Prawns caught offshore – this is the bulk of the stock whereas the ‘greasyback, banana or bait/bay prawns’ caught in the river account for a very minor share.

According to Ian A Halliday, Southern Fisheries Department of Primary Industry, in 1995:

• Most commercial prawn species caught in subtropical waters are dependent on shallow inshore or estuarine environments during some stage of their life cycle
• About 85% of the total prawn catch is Penaeus plebejus
• According to Mulley and Latter 2006, large populations of the school prawn, Metapenaeus macleayi, are found in the Noosa River. The Noosa River prawn population did not genetically differ significantly from that of the Tweed River population but they do differ from NSA prawns of the same species.
• They enter estuaries in flood tide currents and quickly settle onto the substratum to prevent the ebb tide from taking them back out to sea (Hughes 1969, 1972: Young and Carpenter 1977)
• This places post-larval prawns within the estuarine environment but not necessarily on their preferred nursery areas
• Juvenile prawns may spend up to a year in the estuary, depending on water temperature, salinity and food abundance (Racek 1959). A prawn typically lives for 12-18 months
• Nursery areas must provide suitable food and water temperature for growth as well shelter from predation
• Prawn nurseries typically extend from high water mark to 1-2 metres below low water (Penn 1981) with juvenile prawns feeding in the intertidal and subtotal zones during the tidal cycle
• Estuaries with high nutrient inputs and large expanses of shallow water such as our lakes provide productive nursery areas
• Different prawn species prefer different salinity levels (Young 1975)

Robert Coles from James Cook University’s Centre for Tropical Water & Aquatic Ecosystem Research has had a long history translating scientific research into effective management advice and policy. He has worked as an entomologist, a fisheries scientist, a fisheries manager in the Torres Strait, as environment and regional manager for the Queensland Government and as a seagrass scientist and research administrator. He was the founding secretary of the World Seagrass Association and has promoted seagrass and coastal management research in the Indo Pacific region. He is one of a rare few that has specifically done scientific wok in our river system. He found:

“Three penaeid prawn species, Penaeus plebejus (Hesse), Metapenaeus bennettae (Racek & Dall) and M macleayi (Haswell) were sampled using a beam trawl at four sites for 16 months in the Noosa River, Queensland, and data collected are used to provide generalized life histories for the three species and to discuss the composition and timing of the commercial bait prawn fishery.

“P plebejus individuals were recruited to the river throughout the year, M bennettae between March and June, and M macleayi between April and July. P plebejus juveniles remained only briefly in the river and were most numerous at sites near the river mouth. There was no distinct period of migration of this species from the river. M bennettae and M macleayi individuals remained in the river until December and March, respectively, when, in the absence of obvious abiotic stimuli such as rainfall runoff and reduced salinities, there was a marked egress from the river.

“While in the river, both of these species could be caught through the zone of salt-water penetration up to 35 km from the sea, and both were most numerous in the southern half of Lake Cootharaba in a zone of approximately 19 × 10-3 mean salinity. Similarity between these and other distribution patterns recorded in topographically different rivers suggests salinity is an important determining factor in the distribution of these prawns.”

According to the Food and Agricultural Organisation of the United Nations (source document CSIRO: ‘Bait prawns in the Noosa river: a study of the commercial fishery’, Queensland [1986 Coles, RG (Queensland Dept. of Primary Industries, Brisbane (Australia). Fisheries Research Branch) Greenwood, JG (Queensland University, St Lucia (Australia)]:

“Abstract – The Noosa supports a bait prawn fishery of up to 20 boats in a season from October to April, with most of the fishermen also involved in mixed-fish and mullet net fishing. 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 Noosa River prawn fishery. With present legislative restrictions, the Noosa bait 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.”

The Australian government’s Department of the Environment and Heritage ‘Assessment of the Queensland River and Inshore (Beam) Trawl Fishery’ (February 2006) also does not identify any sustainability concerns with prawns in the trawl zone.

2017 –  DAF Noosa Fishing Factsheet ‘Sustainable Fisheries Strategy’ 2017-2027 states:

“Beam trawlers are used in shallow inshore waters or lower estuaries to target school prawns as part of the River and Inshore Beam Trawl Fishery. Beam trawling occurs to low effort levels in the Noosa River and lakes.

“There are a number of rules in place that confine where beam trawling can occur, the equipment that can be used as well as the size of the boat. For the 2017 fishing season a total catch of approximately 2.1 tonnes was recorded for school prawns for the fishery in this area.”

If you look at say the last 10 years data, you will see that in 2007 there was only one active beam trawl license that fished for 25 days and caught 0.01 tonnes. In 2012 there were six active fishing licenses that fished for 78 days and caught 12 tonnes. In 2017 there were three active licenses that fished for 11 days and caught 2 tonnes of prawns.

The data from the last few decades suggests that overfishing of prawns is a real issue. Irrespective of this, the practice of beam fishing in many ways has become redundant and economically unviable because of the variability of stock levels and a very shallow river system which has been adversely affected by sediment from the catchment area.

Two tonnes of prawns were caught in 2017 which may not seem like much at all, and with only a few licenses left one could argue that no change is needed. But that said, real change occurs in small increments and in the longer-term it is best to stop beam trawling entirely.

For those of you who are interested in seeing the detail of the data I can send you links to or copies of the reports cited throughout.

Where To From Here?

Well the reality of more than a century ago was that in 1911 the population in Noosa was 87 people at which point no-one had changed the hydrology of the river. Today we are already fast approaching our cap of 60,000 and then add up to two million visitors a year and who knows how many motor boats churning up the river.

We are not about to change the hydrology of the river and return the river mouth back to its original position. Therefore siltation, salinity and water temperatures will always have a major impact upon aquatic stocks in the river. We are not going to return population levels back to pre-war levels nor stop tourists coming. It is also unlikely we will stop boats from coming.

What we can do of course is manage better as Noosa Council is attempting but the difference is that we have to accept that the best empirical data comes from the past 30 years and that this should form the basis more setting objectives for sustainability and then measure them in an ongoing basis. We need to also acknowledge that we are not in some crisis situation. We can do things better but there is no critical situation.

So my issue is that when we talk about sustainability of fish stocks and the introduction of licenses etc, we need to be very clear as to what this level was and then clearly show degradation of level of fish stocks through data to justify the need for e.g. a paid fishing licence. I have not seen any data that does this as yet.

Any work should also include measurement future stock levels by species. If this is not done then getting the estimated 10,000 recreational fishermen/women (2017 DAF estimates) to pay for a license that will support a department that will manage sustainability in the river will be seen as simply a revenue raiser by Council.

Most of the Noosa River is Declared Fish Habitat (FHA-051). Another option to licenses that could be worthwhile considering is to declare specific areas of the river as ‘Closed (Regulated Waters)’ to prevent people from fishing in certain areas, and these may be:

• where a population of endangered or threatened species lives
• where fish congregate during or before spawning
• where fish may mass or get trapped near artificial barriers and be susceptible to overfishing
• to separate incompatible uses, e.g., spearfishing in bathing area.

It is an idea I will raise with Council.

In summary, I am lobbying and recommending to the State and Noosa Council to:

• Move away from basing a case upon historical anecdotal information to more recent robust empirical data/opinion consistent with State and Federal sources;
• Set a ‘Base Case’ of data which marks a ‘start point’ – one upon which all future objectives will be based and measured from
• Abolish the idea of introducing fishing licenses and to establish defined ‘Closed’ areas
• Acknowledge that fish (all aquatic) stocks are not in crisis but can be further improved over time to achieve more guaranteed sustainability
• Accelerate all initiatives that address catchment problems i.e. sediment and other runoff
• Include more science in reporting, e.g., salinity, water temperature, rainfall, etc.