Shark Nets: The Australian Beach Meshing Program

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The Australian Beach Meshing Program.

The mistake we make either in seeking to destroy sharks or in not caring if we inadvertently destroy them is one of cosmic stupidity.   If I have one hope it is that we will come to appreciate and protect these wonderful animals before we manage, through ignorance, stupidity and greed, to wipe them out altogether.

– Peter Benchley.  Author of JAWS.

For anyone traveling to a country that is known for its large marine predators, sharks must surely be on the mind when entering the water.  Shark ‘attacks’ make for a dramatic news story and it is often these stories, perhaps accompanied by the JAWS theme tune, that play through swimmers heads when they find themselves alone in deeper water.

This same fear of what is lurking in our waters, is one of the contributing factors that initiated a positive vote for beach meshing, also known as shark nets, along beaches in some countries visited by pelagic shark species, and what keeps the nets in place today. But in an ironic twist many of these same countries also now sustain thriving shark diving businesses.  As governments lay traps to reduce the number of large sharks around their shores, dive operators are encouraging positive interactions with these sharks and providing education by enabling an up close encounter.

Most people have a strong opinion either way on the beach meshing debate, but do we really know enough about it to make up our own minds – you might be surprised!

Sharks and why they are important

The earth is approximately 4.5 billion years old. Covered by 72% water, the adage that we know more about the moon than we do about what is in our oceans is old but true. There is little doubt that sharks are one of the greatest marine predators on the earth.  Inhabiting the planet for over 400 million years (Ma), the original species looked a little different to the ones that we share the globe with today. They still possessed similar features to their modern counterparts (e.g. paired fins, replaceable teeth) but were in many respects very different.  ‘Modern day’ sharks first evolved from their ancestors around 150Ma whilst species that we might be more familiar with in our oceans today, those like the great white and hammerhead evolved even more recently 16Ma – 50Ma.  It is even possible the most famous extant shark, the great white, evolved from the most famous of extinct sharks, Megaladon, a 15 meter leviathan with teeth about three times the size of a present day great whites’ tooth.

With over 400 species of sharks inhabiting all the waters of the earth, from the polar seas to tropical and temperate oceans, even venturing into freshwater, sharks are a diverse and adaptable class.  Members of the Chondrichthyan family of fishes that contain sharks and rays, sharks are perfectly suited to their role as apex predators of our oceans.  As an apex predator, they resemble a CEO of the ocean, responsible for multiple tasks in order to keep ocean business running smoothly.  They are responsible for the clean up of rotting carcasses; responsible for maintaining fish stock health through the removal of sick or injured fish and perhaps most importantly, responsible for keeping populations of each species in its place and not allowing any one to become greater than can be supported by the surrounding ecosystem. A lobster fishery in Australia for example is now threatened due to the demise of shark populations in the area.  With a decrease in shark numbers, there is nothing to keep octopus numbers in check and of course, the favorite food of the octopus is lobster. You can figure out the rest.

What is a shark net and what does it do?

Shark nets were introduced to beaches to try and decrease the incidences of shark bites on beach goers. Beach meshing programs can be found in several countries around the world, including Australia, New Zealand, Hong Kong and South Africa. The target sharks for these areas are mostly larger adult pelagic sharks, those that might be considered ‘man-eaters’ such as the great white, bull shark, tiger shark and the oceanic white-tip.  As each beach meshing program varies slightly in how they operate, this article will focus primarily on the Australian beach meshing program.

Introduced to Australian beaches in 1937 by the Department of Primary Industries (DPI), the first beach meshing installations were only on the coastline of New South Wales (NSW).  Queensland (QLD) followed suit 30 years later implementing the program along its beaches.  Being the most populated areas, these are currently the only two states in Australia to have a beach meshing program running. Despite this fact, although occasionally occurring in these two states, the larger shark species, such as the great white are more prevalent in the waters off the states to the south and west.

The nets (figure 1), which hang from buoys on the surface of the water set adjacent to the shoreline, are 186 meters long in QLD, 150 metres long in NSW, and six meters deep.  As the nets are set in water of about 12m depth, the six meter height of the net sits approximately mid water allowing substantial room above and below.

net image

Drumlines are another more modern method of shark control.  These are becoming more popular due to the possibility of reduced bycatch.  Drumlines are in place along the beaches of QLD and can either be used instead of nets or in association with them.

Figure 2 shows an example of a drumline set.  These are quite simply baited hooks hanging from surface buoys weighed down by a weighted anchor. The QLD DPI states that the drumlines are set to target actively feeding sharks.

Drumline diagram

The issues with beach meshing.

Whilst there is no doubt that many beach goers feel a little more secure in the knowledge that shark nets are in place, the feeling of security comes at a price. All data regarding the beach meshing program is released by the DPI to the public, including numbers of by-catch, species catch and release plus the number of human injuries and fatalities on meshed and unmeshed beaches pre and post installation of these programs.

With a little research, we are able to identify the issues associated with the implementation of beach meshing.  Despite this information being available to the public, most of these facts do not filter down through the media, or they become skewed in their translation and interpretation. To be able to make an informed decision regarding the necessity and the future of the beach meshing program, a little self-education is necessary as beach goer attitudes are the reason the nets are still in place.

Human Protection.

Lets look at the theory that the nets create an impenetrable barrier to protect swimmers from sharks.  The DPI states on their website that the nets are in place to…

 “..reduce the numbers of sharks and thereby reduce the risk of shark attacks.  The shark mesh nets do not act as a complete barrier to sharks reaching beaches as they are not permanently set in the water, do not cover the whole length of the beach, and do not extend from the water surface to the seabed. In fact, approximately 40% of shark entanglements occur on the beach side of the nets, because sharks are able to swim over and around the nets.”

We hear little in the media of sharks becoming entangled on the beach side of the nets and yet the figure of 40% is only the proportion of sharks we see caught in the nets. It is possible that more than 40% of sharks are gaining access to these beaches and back out to sea again.  Presenting these figures isn’t meant to alarm, but to show that if swimming in the ocean, even at a meshed beach, the chances of unknowingly swimming with sharks is fairly high.

It is also stated in media that there have been no deaths since the nets have been introduced, compared to a large figure pre beach meshing.  Once again, we can consult the NSW DPI website for the data. Figure 3 below shows as an example the number of fatalities and injuries pre and post beach meshing for NSW.

Dates

Number of Years

Number of Fatalities

Number of Injuries

Number of Uninjured

Total Number of Incidents

1791-1936

Pre beach meshing

145

48

33

2

83

1937-2009

Post beach meshing

72

22

81

36

139

Figure 3.  Simplified table using data taken from DPI.  www.dpi.nsw.gov.au

The information in this table shows an interesting set of data and raises a couple of questions.

1) As we can see, the rate of incidents per year has more than tripled from pre beach meshing.  Some scientists have hypothesized that an increased presence of sharks closer to our beaches could be due to overfishing.  Declining fish stocks in our oceans mean sharks migrate closer in to shore to find food. Increased population size and popularity of water activities are also important factors in these figures.

2) Human fatalities have indeed decreased post beach meshing. We can expect that advances in medical technology and medical response time should increase the survival rate of victims.  Twentieth century medical technology is light years ahead of that experienced in the eighteenth century, so victims in the post beach meshing era should have an elevated chance of survival.

Even when taking into consideration the increases in population as well as the increases in medical technology when looking at these figures, it seems that the nets have a very limited effectiveness.

Sharks.

Sharks targeted for the beach meshing program are over two metres in size according to the QLD DPI.  This aims to eliminate the possibility of smaller sharks becoming unnecessarily entangled in the sets.  It is believed that some species of shark such as the great white are actually born at two metres.  With a late reproductive maturity, a high probability of pre reproductive mortality makes their populations vulnerable to rapid decline. Data from the QLD DPI shows that out of 7,619 sharks caught between 1999 and 2006, 51% were less than two metres in length – the non-target group.

On meshed QLD beaches there are usually one to three nets and up to six drumlines.  The main issue concerning drumlines is that they contain baited hooks.  We know that sharks possess an incredible sense of smell and are able to detect one drop of blood in 100 litres of water.  It begs the question, by putting baited hooks near beaches are we not attracting sharks into the area that may not have been there initially? We may be contributing to the problem and not the solution.

By-Catch.

Along with target and non-target shark species caught, there is a huge problem with by-catch caught in the nets and on drumlines. Everything from whales, dolphins, turtles, birds and dugongs to fish and other shark species can fall victim to the program.

The QLD DPI is credibly trying to improve the effectiveness of the nets and drumlines to reduce by-catch.  Pingers have been installed on nets to try to deter whales and dolphins, however numbers of these animals still become entangled.  Plastic hook guards have been introduced to drumlines to prevent turtles and dolphins becoming victims. Despite there being a reduction in by-catch, these animals are still being caught.

Encouragingly the NSW DPI also took steps to minimize the impact of the program on larger marine mammals. NSW now removes their nets between May 1st and August 31st during the humpback whale migration. QLD nets remain in place seeing five humpback whales (some of them calves) tangled in the nets during one month in 2009.

Investigations by the Fisheries Scientific Committee determined that the beach meshing program adversely affects two or more threatened species and could cause other species that are not yet threatened to become so.  They have therefore listed the beach meshing program as a key threatening process to our marine life.

Conclusions

What are the conclusions from these facts?  We have to look at the viability of the nets.  Are they providing the service that was required of them initially, are they outdated and when is it decided that enough by-catch is enough?

The nets constitute a large financial loss to QLD and NSW governments as each year QLD pays $1.8 million and NSW $750,000 towards the upkeep of the nets.  It is not only the financial loss that is a problem; there is the loss of marine fauna and the flow-on effect these losses have on marine ecosystem functions.  Data contained in the DPI information is far too extensive to show in one article, however with a little analysis we are able to calculate the effectiveness of the beach meshing program.  In NSW for the years 1950-2008, the total catch of target sharks as well as by-catch was 16,323 specimens. The percentage of target sharks caught during this time and therefore the effectiveness of the nets is 23% with the remaining 77% composing by-catch.  It seems a simple conclusion.

In 2004 a tag and release program for harmless shark species was established to help understand their behavior upon release.  There is interesting on-going work by the NSW DPI on Sydney beaches through the catch and release of target species, however it would also be beneficial to perform tag and release for target sharks caught in nets rather than solely tagging netted non target species.  This would provide a clearer understanding of their behavior and perhaps enable a more sustainable solution to be implemented.

This article is not meant to paint a rosy picture of sharks. We have to be realistic and sharks remain the apex predator in the ocean, still posing a risk to anyone who is a water user.  A negative interaction with a shark is never something that one would wish for.  However this risk can be minimized with a little education.  The number of shark bites each year around the world are so few that we are still more at risk from car crashes, smoking, going to the toilet using vending machines and plenty more simple every day tasks.

The change in attitude after some shark education can be no better portrayed than that of Peter Benchley, the author of the movie ‘Jaws’.  After penning his detrimental story on sharks that has been one of the greatest contributors to their demise, Mr. Benchley became an advocate for sharks in the latter years of his career.  Before his death in 2006 and after spending many years studying these creatures, he summed up his feelings about sharks:

I couldn’t write ‘JAWS’ today.  The extensive new knowledge of sharks would make it impossible for me to create, in good conscience, a villain of the magnitude and malignity of the original.

On a final and more positive note, there is one other country that used to have a beach meshing program – Hawaii.  Running from 1959 to 1995, the program ended when the public put pressure on the government to remove the nets citing there were no measurable effects on shark incidents.  The government listened to the people.

                         

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