Connectivity (changed from natural)

Impoundments and habitat removal are the major cause of altered connectivity in estuaries. Impoundments can impact both lateral and longitudinal connectivity, firstly, by stopping flood water coming downstream and flooding floodplain areas, and secondly, by physically stopping fish movement up/downstream. Habitat removal can result in habitat fragmentation and form a barrier to the movement of species. Changes in the connectivity between freshwater reaches and the estuary/marine environment can have a major impact on diadromous fish life cycles.

View a conceptual model of potential causes of a change to connectivity and the condition responses observed as a result of this change.

Potential indicators

There are a number of causes and symptoms related to this stressor. The following indicators are recommended for the stressor ‘Connectivity’:

Pressure indicators

Indicators of altered connectivity sources:

  • Impoundment density
  • Percentage of freshwater reaches without access to the sea due to impoundments without an effective fish ladder
Indicators of direct pressure:
  • Percentage of estuarine ‘shoreline’ length modified
  • Percentage of estuarine ‘background habitat’ length modified

Vulnerability indicators

  • None

Condition indicators

Physical-chemical condition indicators:

  • None
Biological condition indicators:
  • Abundance of diadromous species
Possible causes Possible symptoms

The actions/events/situations that might induce this stress

  • Changes to hydrodynamics
  • Climate change
  • Development of area – fragmentation of habitat (e.g. roads and bridges, infrastructure, aquaculture, urbanisation, agriculture, rock walls, training walls)
  • Habitat removal – e.g. riparian clearing
  • impoundments (impedance to animal migration and water movement)
  • Modification of natural drainage pathways

The actions/events/situations that might arise from a change to the stressor:

Fact sheets on background science and economics

  • Nil

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