Adaptations in marine industries in response to climate variability

Planning for the potential effects on habitats which support fisheries and aquaculture

Our already variable weather patterns have seen our beaches, coastal wetlands, estuaries and reefs adapt naturally to past changes in climate and sea level over long time scales. In future, however, they are likely to face faster rates of change. In many cases the infrastructure we already have in place, such as coastal roads, and even houses, have been built in areas behind natural habitats such as wetlands, mangrove and other intertidal areas. If the shoreline were to move further toward the land because of sea level rises, in many areas these habitats may become smaller as the space to re-establish becomes limited.

Natural habitats are very important for fisheries production. Impacts to the coastal environment can impact the number of fish we catch out at sea. Seagrass beds and coastal wetlands provide important functions such as a shelter or habitat for very small prey, which are then eaten by juvenile prawns or fish for example. These fish and prawns later move out of the shallow areas where they may be caught by fishers for our dinner plates, or continue to function as important links in the food chain.

Wetland habitats also serve as an important water-cleansing function in that vegetation such as trees and grasses filter out pollutants and improve the general quality of water entering our waterways.

To maintain these important habitats so that what is called 'ecosystem function' can continue to occur to support our local fisheries and aquaculture industries, local governments and natural resource managers need to be planning now to adjust our existing activities so that potential impacts associated with climate change can be reduced where possible.

Coastal erosion.
Reproduced with permission.
© State of New South Wales through the Department of Planning

Local councils are already preparing local studies to identify areas of risk from coastal flooding and other coastal hazards. Public and private properties may be identified as being at risk of future flooding and coastal hazards. In the first instance engineering options such as building sturdy sea walls or beach retaining walls may be implemented to help reduce impacts to buildings caused by sand being eroded away from higher tide heights, and the impacts of heavy storms. For the future, however, new houses and buildings would likely be subjected to higher minimum floor heights relative to what the planning rules say now, so that if flooding occurs, the floor heights would be above flood height predictions under climate change scenarios.

For the coast and beaches, future planning options might include building up the sand dune systems or ensuring that the drainage systems can cope with additional amounts of water. Natural areas in close proximity to the coastal zone might also need to be reserved, so that new buildings are not built in areas where new wetland and mangrove habitat areas can establish should the shoreline move a long way inland.

Building wild fisheries health or resilience

Nepean River drain stencilling
Source: Penrith City Council

To further protect our wild fisheries so that we can enjoy fresh and sustainable Australian seafood, our existing ecosystems need to be protected from other stress factors such as pollution and overfishing. The many organisms making up the coastal ecosystems can then have the best chance of survival under changing environmental conditions. This is called 'building or maintaining ecosystem resilience'.

Pollution prevention actions such as public education (for example explaining how litter dropped in the streets can end up in our waterways), and ensuring there are measures such as riparian vegetation (that is, vegetation along watercourses such as creeks and rivers), can go a long way to protecting our coastal ecosystems.

Riparian vegetation

Excellent example of riparian vegetation along Crystal Creek in the Tweed River Catchment, just outside Murwillumbah on the North Coast.
Photo: Charlotte Jenkins

Riparian vegetation assists in capturing and filtering sediments and pollutants that are present in water run-off from the land before it reaches the estuarine environment. This provides a natural safeguard to the health of marine organisms.

If organisms live in a healthy environment, they have a better chance of recovering or slowly adapting to the predicted impacts of climate change. Predictions of extreme weather events include flooding, where a lot of fresh water is introduced, or hot spells, where daily temperatures reach the high thirties and water temperatures become elevated.

Management of fish populations

Management of fish populations becomes even more important in the face of predicted climate changes. If the distributions of different fish species change, more thought and further planning may be required for existing marine reserves and setting the maximum number of fish that recreational and commercial fishers may be permitted to catch.

Currently, fisheries management strategies are in place so that fish stocks can be maintained at sustainable levels. Should the environmental conditions vary too much from when strategies were established, a reassessment of sustainable levels of fishing may need to take place. Ongoing fish population research helps us understand how many fish we can take now, while ensuring those populations will continue to supply future generations with food and enjoyment for many years to come.

Aquaculture adaptations

In the aquaculture industry, investigations are underway to find appropriate temperature-tolerant strains of fish and invertebrates.

Oyster farming

Oyster lease area containing racks cooled by sprinkler system.
Source: John Stubbs, Broken Bay Oysters, Berowra Waters, NSW.

The oyster industry has already seen some innovative measures that help farmers continue to produce oysters despite the kind of climate variability we already experience. One such adaptation which may have further application in the future is the use of sprinkler systems over oyster production areas.

At low tide on a very hot day, the oysters can be exposed to high temperatures for several hours. In an area that has little wind exposure, for example in a valley, these oysters can almost cook inside their shells. The sprinkler system helps to keep the oysters' temperature just that little bit lower until the tide returns. This small adaptation can mean the difference between saving three years work on more than 100 000 oysters, which equates to a lot of money!

Oyster farmers also make important decisions about on which days stock can be transported and the types of farming equipment used in the estuaries. During times of extreme weather, the oyster farm yards are brimming with activity at night, because the farmers choose to sort stock when it's cooler, so that the oysters aren't unnecessarily stressed in the heat of a summer day.

Oyster farming equipment has changed in some areas and farmers now have better access to their leases at any time of the day. Where racks were previously stationary at a fixed depth in the estuary, the move towards floating baskets, which hold the oysters, means that the oyster stock can be worked at any time of the day, and the oyster farmer doesn't need to wait until low tide to collect the stock.

Floating oyster baskets at Merimbula, South Coast of NSW

It is predicted that extreme weather events are likely to become more frequent in the future. Intense rainfall and sometimes flooding, introducing large amounts of fresh water to estuaries, affects oyster production. While severe weather can have major impacts on infrastructure, such as trays and racks being structurally damaged, introducing a great volume of fresh water into a usually salty estuary lowers the salinity, or salt content, in the estuary waters, and can wash pollutants such as faecal matter from the land into the estuary.

NSW Food Safety Authority prevents farmers from selling oysters when rainfall reaches a set level, to prevent customers from eating potentially contaminated oysters after high rainfall has caused pollutant runoff. To combat this, some farmers have different finishing areas so that if they look at the weather report and see major storms and prolonged rainfall, they can get very busy shifting all their oysters, sometimes many hundreds of thousands of oysters, by barge, to another area that will not be affected by rainfall runoff. These areas are usually located closer to the sea where there is more flushing and clean salty water. If the NSW Food Authority has approved their finishing area, the farmers may still sell their stock provided it was shifted prior to exposure to sizeable rainfall runoff.

Source: www.smh.com.au

Read about the damage done to oyster farms after flooding near Coffs Harbour in 2009:
http://www.smh.com.au/national/oyster-industry-in-ruins-after-virus-flood-20090221-8e68.html

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