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Issue: Pressures on biodiversity - Pressures on marine biodiversity: pressures of fishing

This is an issue under the Biodiversity theme of the Data Reporting System.

Why we need to know about this issue

Humans place pressures on the ocean’s biodiversity through their demand for organic materials harvested from marine biodiversity, mainly for food. In addition to biodiversity removed from the oceans to satisfy human demands, these activities result in further losses of biodiversity via bycatch (including animals and plants both accidentally retrieved and those killed, eg drowned, by the process but not retrieved), benthic disturbance, and indirect impacts of depletion of one species on other species. Fishing activities may also introduce new species from one part of the ocean to another part where they may place pressure on resident organisms. The effects of harvesting marine species include the effects of both legal and illegal commercial harvesting and of recreational and Indigenous fishing. They also include impacts of both wild fisheries and aquaculture.

Indicators

• CO-16 Status of Australian fisheries 
  Fishing places pressure on marine biodiversity. Status of fisheries is indicative of the status of species and ecological communities more generally, and therefore provides insight into this pressure.
• CO-17 Change in species and trophic structure of fish species caught 
  Change in trophic structure in commercially exploited species could be indicative of significant ecological change, resulting from the pressures of fishing on marine biodiversity. Although any such change may not be entirely attributable to the impacts of fishing, fishing (including illegal, recreational and Indigenous) is the most probable cause of this kind of change because larger (and generally more predatory fish) are the most sought after in terms of food value and are also more vulnerable to modern netting techniques.
• CO-19 Estimated tonnage taken by illegal fishing; estimated number of illegal boats, estimated number of individuals of threatened species taken 
  All forms of fishing, including illegal fishing, place pressure on marine biodiversity. The suggested indicators, read collectively, would provide some baseline for estimating the contribution of illegal fishing to pressures on the condition of marine biodiversity.
• CO-20 Non-target effects: Area of seabeds trawled 
  Removal of seabed by trawling can place pressure on marine biodiversity. Area of the seabed trawled would provide a surrogate for the extent of benthic ecosystems potentially disturbed by commercial fishing activities. It is a crude indicator because it does not estimate either the sensitivity or the ecological importance of different areas of seabed disturbed, nor the extent or particular effects of the actual disturbance. However, in the absence of any more sophisticated assessment tools, it would give us a rough idea.
• CO-21 Non-target effects: Number and/or weight taken as bycatch, and change since introduction of exclusion devices 
  Non target effects of commercial fishing, such as bycatch, potentially impact on marine biodiversity. Changes in the total numbers of other animals affected may be at least initially ambiguous: increases may reflect improved reporting, decreases a decline in wildlife species themselves, so that they are no longer available to accidentally catch or interact with. However, changes would be a reasonable indicator of reduced or increased pressure.
• CO-22 Aquaculture: extent of habitat disturbed or removed 
  Displacement of coastal habitats to make way for aquaculture can place pressure on marine biodiversity. The extent of habitat disturbed is a surrogate indicator for the extent of ecosystem damage caused by this removal and/or modification.
• CO-23 Aquaculture: volume of discharged sediments and nutrients 
  Discharges of pollutants from aquaculture activities place potential pressure on marine biodiversity. Volumes of nutrients released will some measure of the extent of this pressure.
• CO-24 Aquaculture: origin species and tonnage of stockfeed used 
  Introductions of foreign species from stockfeed for aquaculture activities can place potential pressure on biodiversity. Origin species and tonnage of stock feeds are crude indicators of this pressure. They give no indication of escape rates, or what the impacts (if any) would be if they did escape. However, they do give some indication of the potential risk.
• CO-25 Aquaculture: instances of disease and exotic species introduction from movement of live material 
  Introductions of foreign species aquaculture activities can place potential pressure on biodiversity. Reported instances of disease and exotic species escapes from the movement of live aquacultural material is a crude indicator of this pressure. It does not measure the actual or potential impacts of the escape and there may also be escapes that go unreported. However, it does give some indication of the potential risk.
• CO-62 Estimated number of marine animals harvested by recreational fishers 
  All fishing activities place pressure on biodiversity. Changes in number of animals harvested by recreational fishers is broadly indicative of changes in the pressure exerted on marine ecosystems by recreational fishing. Comparison of the number of animals harvested by Indigenous, recreational and commercial fishers also gives a basis for comparison of the significance of these pressures.
• CO-63 Estimated number of marine animals harvested by indigenous fishers 
  All fishing activities place pressure on biodiversity. Changes in number of animals harvested by Indigenous fishers is broadly indicative of changes in the pressure exerted on marine ecosystems by Indigenous fishing. Comparison of the number of animals harvested by Indigenous, recreational and commercial fishers also gives a basis for comparison of the significance of these pressures.
• CO-65 Correlation between various human activities and introduction of coastal and marine species 
  Introduction of foreign species via fishing related activities is a pressure on marine biodiversity. The correlation between intensity of fishing activity (or other marine uses) and intensity of species introduction may shed light on the relative importance of the various ways in which species are introduced to new waters.
• AAT-20 Fishing by-catch numbers and/or weight taken as bycatch 
  Each year thousands of seabirds and fish, in Antarctic, as well as other fisheries, are accidentally killed on longline hooks and trawling lines (i.e. they are not the target species for the fishing operation), including in . The level of by-catch that occurs in these fisheries is not sustainable for many populations of fish and especially for seabirds. Changes in the total numbers of other animals affected may be at least initially ambiguous: increases may reflect improved reporting, decreases a decline in wildlife species themselves, so that they are no longer available to accidentally catch or interact with. However, changes would be a reasonable indicator of reduced or increased pressure.
• AAT-19 Annual catch in tonnes of marine species harvested in Australian Antarctic and sub-Antarctic waters - legal and illegal 
  By examining both legal and illegal unregulated and unreported fishing, including fishing in Antarctic waters, and comparing those catches to agreed catch limits, this indicator provides an insight into the extent of the pressure of fishing on marine biodiversity.

Related issues

• Coasts and Oceans - Condition of the ocean and coastal waters - Condition of fisheries 
• Coasts and Oceans - Contributions of the coasts and oceans to human life - Food