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Issues Water QualityConditionHarvesting and Marine FarmingGlobal Change |
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At a glance The issue The coastal waters of Tasmania are generally well-suited to marine farming activities, with cool, clean waters and an abundance of sheltered estuaries providing an ideal environment for marine farming. Marine farming is susceptible to a variety of environmental influences, including catchment condition, reduction of environmental flows, pollution of estuarine waters and algal blooms. Marine farming can be classified into two types: shellfish (bivalve and univalve) and finfish (salmonid) operations, as these two groups have different levels of impact on the marine environment. Marine farming has the potential to cause environmental harm if unregulated. These issues include potential deterioration of water quality associated with soluble waste emissions from farmed fish; and the deterioration of benthic habitats in the immediate vicinity of stocked fish pens associated with localised deposition of uneaten feed and faecal waste. There is also potential for the translocation of pest species and transfer of diseases. Pacific oysters and salmonids remain the dominant sectors of the industry in terms of value, total leased area and overall production, with the combined value of these sectors growing from $7.5 million in 1988/89 to $134 million in 2001/02 (DPIWE, unpublished data, 2003). Between 1996/97 and 2001/02, there was a significant increase in salmonid production relative to that of oysters, with levels rising by 87.7% from $64.9 million to $121.9 million. All marine farms require a licence and many leases are licensed to grow several species. There was a 31% increase in the number of licenced marine farming leases in Marine Farm Development Plan areas between 1997 and 2001. The Plan areas cover a total area of 466,111 ha, with 1.8% of this area being occupied by 185 marine farming leases (DPIWE unpublished data 2001). While there has been an overall increase in the number of leases, there has been a shift in the licensed species attached to the leases. An overall decline occurred in the range of species attached to licences, coupled with a consolidation and overall increase in the number of licences held for the two major species groups (Pacific oysters and Atlantic salmon) over this period. This 'At a glance' section provides an overview of marine farming in Tasmania. More detailed information and references are contained in the Marine Farming Issue Report. There are two indicators presented on marine farming effort and production in the 'Indicators' section of the Issue Report. A recommendation is provided on Marine Farming in this SoE Report. Favourable news- Prior to the passing of the Marine Farming Planning Act 1995 and the Living Marine Resources Management Act 1995 by the State Government, the growth of marine farming was largely subject to an ad hoc allocation process. Under the legislation, marine farm development planning was initiated and a number of marine farming regions around the State were identified as Marine Farm Development Plan areas. Since the last SoE Report (1997), a total of 14 Marine Farm Development Plan areas have been identified as being suitable for the controlled development of the industry. Each plan area has specific management controls that relate to the environmental and operational management of all designated marine farming zones. These controls set specific guidelines for the management of carrying capacity, environmental monitoring, disease, chemical usage and waste removal.
- Since the last SoE Report (1997), an environmental monitoring program has been implemented to monitor environmental conditions under and around finfish marine farms as specified in the Marine Farm Development plans and each individual licence. This is a requirement under the Living Marine Resources Management Act 1995 and the Marine Farming Planning Act 1995.
- The Tasmanian Shellfish Quality Assurance Program, set up in the mid-1980s, provides on-going water quality testing in all commercial shellfish farming areas in the State with routine bacteriological, chemical and biotoxin monitoring. In cases where monitoring indicates a possible health risk, farms in affected regions are closed until further testing indicates that consumption of shellfish will pose no risk to human health.
- A collaborative research project between researchers from the CSIRO and Tasmanian Aquaculture and Fisheries Institute (TAFI) is currently being undertaken to identify the most suitable parameters for monitoring the system-wide effects of soluble waste emissions from marine farming operations into the marine environment. Research by TAFI at two farm sites in south-east Tasmania indicates that several environmental parameters should be monitored as part of an ongoing monitoring program. This is because no one parameter is consistently representative of environmental change.
- TAFI is also undertaking research into post-stocking sediment recovery in order to assess the time that is required for sediments to return to near normal conditions, and the effects of environmental conditions and production levels at each farm on the rate of this recovery (TAFI 2000).
- In relation to the management of diseases that affect marine farming, TAFI is investigating the relationship between gill changes and environmental and husbandry factors. At present the amoebic gill disease is the only significant condition that has been identified.
- The Tasmanian Marine Farm Monitoring Project was set up as a trial program between 1998-99 to raise awareness of marine pest issues in the Marine Farming Sector in south-east Tasmania (Martin and Proctor 2000). The results of the program revealed that trapping of targeted introduced species such as Asterias amurensis and Carcinus maenus at farm sites with established populations was largely unsuccessful. Nonetheless, while trapping appeared to be ineffective, the program did raise industry awareness of introduced species.
Unfavourable news- Community opposition to increases in the area of fish farms in Tasmania is often expressed for reasons such as loss of visual amenity, impacts on navigable waterways, or the fear of translocations of pest species.
- Finfish culture poses a significantly greater risk to the marine environment than shellfish culture due to its need for an external source of feed. The build up of solid organic matter, including uneaten feed and fish faeces, can affect changes in the benthic environment directly under stocked pens, while soluble excretory wastes have the potential to influence broad scale changes to the environment if incorrectly managed.
- The presence of marine predators in the vicinity of farms and actual interactions with the farms are known to decrease salmon production (MMIC 2002). A 2001 survey estimated the total costs to farms due to seals to be $1,000 per tonne of salmon produced, amounting to $12.1 million in 2001 (see MMIC 2002). There have been seabirds, seals and cetaceans killed as a result of direct interaction with salmonid farms and some of these fatalities comprise threatened species (R. Gales pers. comm. and Kemper et al. 2003). However, there has been limited research into the methods of mitigation of these fatal interactions, other than for seals.
Uncertain news- Marine farming activities are only one of the potential sources of nutrients in coastal waters. There is uncertainty about the relative significance of different sources as they are variable in space and time. For example, an assessment of the nutrients in North West Bay (southern Tasmania) highlights that the contribution of nutrients to the estuary from marine farming relative to other sources, such as catchment landuse activities, sewage and septic inputs, and sub-Antarctic water, is unclear (Jordan et al. 2002).
- There is insufficient information available to comment on the sustainability of those fisheries supporting the feedstock for the aquaculture industry in Tasmania.
- It has not been possible to comment on the relationship between environmental flows and marine shellfish farming in Tasmania, although it is expressed as an issue of concern by the marine farming industry.
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