Appropriate Assessment Conclusion Statement for aquaculture activities in Castlemaine
Harbour SAC and SPA (Natura site)
This Conclusion Statement outlines how aquaculture activities are being licensed in compliance
with the Birds and Habitats Directives.
The Appropriate Assessment (AA) of Castlemaine Harbour SAC and SPA assessed the potential
ecological impacts of (wild fishing) and aquaculture activities on the conservation features of this
Natura site.
Description of the aquaculture projects including size, scale and objectives
The projects involve the renewal of existing aquaculture activity and the licensing of new
aquaculture activity within Castlemaine Harbour SAC/SPA.
There are approximately 50 aquaculture operations in Castlemaine where licences have either been
issued or at the application stage. The aquaculture involves the cultivation of oysters, mussels and
clams. The majority of these sites are found in the inner part of the Castlemaine Harbour SAC/SPA.
There are 14 renewal applications, covering in excess of 60 hectares and 28 new applications
covering in the region of 180 hectares, one review application consolidating two clam sites into one
area, and 7 licensed sites covering in the region of 67 hectares.
Description of Ecological and Environmental issues including Conservation Objectives
Ecological effects:
The potential generic ecological effects on the qualifying interests of the site relate to the physical
and biological effects of dredging and culture of shellfish species which overlap with invertebrate
communities found in inter-tidal and sub-tidal habitats (Table 4 – p.19 and Figure 4 – p.25 of the
“Appropriate Assessment of the impact of mussel fishing and mussel, oyster and clam aquaculture
on Castlemaine Harbour SAC and SPA” refers - Castlemaine Harbour AA).
Bird populations may also be affected by these habitat changes and by disturbance caused by
fishing vessels, by human disturbance on the shore associated with shellfish production and also by
changes in the availability of prey species as a result of changes in habitat brought about by mussel
production.
Details of potential ecological effects of each activity described above, on the SAC and SPA
Conservation Objectives, their sources and the mechanism by which the impact may occur are
outlined on Table 5 – p.24 in Section 4 of the Natura Impact Statement , Castlemaine Harbour AA.
Conservation Objectives for the SAC:
NPWS provided a description of the Conservation Objectives for all qualifying interests of the
SAC. The proposed wild fishery and aquaculture activity overlaps habitat (estuaries) and mud and
sand flats not covered by seawater at high tide in particular.
Estuaries and mud and sand flats not covered by seawater at high tide:
1. In the case of these habitats the important attributes that must be conserved are Habitat area
and Habitat structure and function.
1. Castlemaine Harbour Special Area of Conservation (site code IE 000343)
2. Castlemaine Harbour Special Protection Area (site code IE 4029)
Habitat area:
2. The likely area occupied by the constituent communities of Habitats should be stable or
increasing with overall target areas of 5696 ha and 4287 ha respectively.
Habitat structure and function
3. The communities of habitats should be stable in distribution and composition.
Conservation Objectives for the Special Protection Area:
NPWS provided a description of the Conservation Objectives and targets for species of waterbirds
and the wetlands which support them.
1. Population trends and distribution, as measured by the % change in population size and the
numbers of birds and range of areas used, should be stable or increasing.
2. The area of subtidal, intertidal and supratidal habitats should be stable or increasing and not less
than the areas of 7471, 3983 & 312 hectares for subtidal, intertidal and supratidal habitats,
respectively other than that occurring from natural patterns of variation.
Appropriate Assessment of Castlemaine Harbour SAC and SPA:
The Appropriate Assessment (AA) assessed the potential ecological impacts of wild fishing and
aquaculture activities in and adjacent to Castlemaine Harbour SAC and SPA on the Conservation
Objectives and special conservation interests of the Natura site. From an aquaculture perspective,
this assessment was based on a list of licensed aquaculture activities and applications provided by
Department of Agriculture Food and Fishery (DAFM) to the Marine Institute (MI). The nature of
these activities includes the on-growing of mussels inter-tidally and sub-tidally as well as the
aquaculture of oysters and clams intertidally.
Potential Adverse Impacts of the aquaculture projects on Castlemaine Harbour SAC and
SPA
SAC Features
The interaction between the existing and proposed level of aquaculture (and wild fishery) activities
are summarised in Table 10 in Section 8 of the AA for Castlemaine (p.130-131) with the general
conclusion that the activities (both benign and potentially disturbing) proposed will not have a
significant impact on the Conservation Objectives for the Castlemaine Harbour SAC.
In addition, the AA concluded that the activities highlighted in the table referenced above are not
likely to have any impact on species of conservation interest i.e., Salmon, Otter, Lamprey, by virtue
of the fact that no spatial overlap or no direct or indirect interaction is envisaged.
SPA Features
The AA concluded that the existing level of aquaculture activity within Castlemaine Harbour will
not significantly affect the baseline ecological conditions or Conservation Objectives for the
qualifying interests of the Castlemaine Harbour SPA. The reliability of each of the individual
assessments is considered to be moderate or high, apart from the impact of the existing clam
cultivation on the Ringed Plover and Sanderling.
1. Castlemaine Harbour Special Area of Conservation (site code IE 000343)
2. Castlemaine Harbour Special Protection Area (site code IE 4029)
A substantial expansion of intertidal oyster and mussel cultivation in the Douglas Strand - Cromane
area could have a significant impact on the Bar-tailed Godwit. Expansion of clam cultivation could
have a significant impact on the Ringed Plover and Sanderling. However, there is a high level of
uncertainty about these potential impacts.
A summary is provided in Table 11 in Section 8, p. 132-133 of the AA for Castlemaine highlighting
the likely interactions between the existing and proposed level of aquaculture and fishery activities
on the Conservation Objectives for the Castlemaine Harbour SPA.
Mitigation Measures
As indicated above the findings of the Appropriate Assessment in relation to the possible effects of
existing/proposed aquaculture on the SAC were considered generally benign or were below the
15% overlap threshold in the case of potentially disturbing activities; however, concerns were raised
on the potential impact on the SPA.
The main finding in relation to the SPA was that existing activity could be accommodated apart from
the existing clam culture which impacts on Ringed Plover and the Sanderling, however a substantial
expansion of intertidal oyster and mussel cultivation in the Douglas Strand Cromane area could have a
significant impact on Bar-tailed Godwit.
Mussels
The proposed mussel conditions/mitigations measures attached to licensing of aquaculture in
Castlemaine take account of adaptive management of the sites informed by appropriate monitoring.
The findings of AA would allow for 12% mussel coverage with a comfortable “no scientific doubt as to
absence of an adverse effect” on the integrity of the site Additional information would need to be
available prior to any decision being made on permitting an increase in this level of coverage
The findings of AA have been operationalised by providing that new aquaculture activity on the south
side of the harbour (intertidal) could be accommodated on a phased basis only, i.e. initial mussel cover
should average 12% of site with possible 10% increases after three years cycle subject to favorable
monitoring outputs. Where the Castlemaine site specific monitoring framework provides
information/data that indicates a risk of significant effect on, or adverse impact on, the integrity of the
SPA, decreases in the average percentage cover of mussels shall be mandated by the Minister,
incrementally or directly, to the initial 12% average percentage cover.
Oysters
Licensing of Oyster culture in the Harbour will be based on the Oyster trestle density. The trestle
density should not exceed 10% average occupancy of the licensed area. The AA assessed Oyster trestle
culture on the basis of 100% site occupancy and hence 10% initial coverage proposed in the licence is
pre-cautionary. Increases in trestle density may be allowable, (10% increments) subject to favourable
monitoring outputs. Where the Castlemaine site specific monitoring framework provides information
/ data that indicates a risk of significant effect on, or adverse impact on, the integrity of the SPA
decreases in the average occupancy shall be mandated by the Minister, incrementally or directly, to
the initial 10% average occupancy.
1. Castlemaine Harbour Special Area of Conservation (site code IE 000343)
2. Castlemaine Harbour Special Protection Area (site code IE 4029)
Clams
The AA concluded that the locations of the two existing clam licences represent a significant impact but
this could be mitigated by re-location to a nearby area, which has less effect on the habitat of Ringed
Plover and Sanderling. To comply with this recommendation the two existing clam licences are being re
configured to an alternative area which is less suited to the protected species.
Timescale and mechanisms through which the mitigation measures will be secured,
implemented and monitored
1. A 3-year monitoring program will be put in place.
2. Any incremental increases will be on a 3-year basis and not on an annual basis to allay any risk
that the monitoring will not be sufficiently sensitive to determine changes on such a short
temporal scale.
3. The monitoring data will be generated at the site and thus will have a higher level of confidence
associated with conclusions derived from it.
1. Castlemaine Harbour Special Area of Conservation (site code IE 000343)
2. Castlemaine Harbour Special Protection Area (site code IE 4029)