6 New Zealand Aquaculture Industry Initiative: Collingwood Case Study
67
The river catchment is 709 km
2 and the river winds its way to the sea through
pristine native bush in Kahurangi National Park (including the popular Heaphy
Track) and a rich alluvial valley used extensively for dairy, beef, sheep and deer
farming.
The nearest settlement to the growing area is Collingwood, with a population of
just 300 – but this may double in the peak summer holiday times. Collingwood has
a sewage treatment facility that is controlled by the local Council. There are some
local residential homes and a few holiday homes in the area, providing an additional
population of approximately 30 people serviced by septic tanks. An adjacent black
swan colony rounded out a wide range of potential of sources of contamination.
Collingwood marine farms occupy approximately 80 Ha, growing Greenshell
mussels and producing around 4,000 tonnes pa. Significant expansion is planned in
the area increasing the importance of solving this puzzle. The majority of production
is exported and therefore subject to the regulatory requirements of domestic and
export markets.
In 1994 this Growing Area was classified as conditionally approved (that is open
subject to specified criteria) and has operated under differing harvest criteria since
that time.
Shellfish harvesting is carried out year-round subject to sanitation and biotoxin
closures. The initial harvest criteria was based on the level of the Aorere River.
However, the currents and prevailing wind often took the river plume away from
the farms. Frequently the shellfish farms would be closed under this criterion, but
frustratingly farmers could clearly see the river plume well away from their farms
and product. That led to investigation of the usefulness of salinity monitoring for the
area based upon real time telemetered salinity data from buoys situated in the farms.
Salinity monitoring based upon the rate of dilution of the sea water by the fresh
water from the river was implemented in 1997, significantly increasing the number
of days open for harvest.
Our quality programme requires ongoing monitoring to ensure that the harvest
criteria continue to meet the regulatory standards. In 2002/2003 industry’s routine
monitoring began to detect with increasing frequency bacteria levels that exceeded
the regulatory standards for human consumption.
To ensure ongoing compliance and market access, the harvest criteria was
tightened several times between 2003 and 2004. This reduced the time open for
harvesting from 72 % of the time to only 50 %. This threatened the viability of
shellfish production in the area.
Warning Signs, Results and Options
The sanitary survey for the area had identified all potential and actual pollution
sources. In the absence of any definitive evidence as to the pollution source or
sources we had to consider:
67
The river catchment is 709 km
2 and the river winds its way to the sea through
pristine native bush in Kahurangi National Park (including the popular Heaphy
Track) and a rich alluvial valley used extensively for dairy, beef, sheep and deer
farming.
The nearest settlement to the growing area is Collingwood, with a population of
just 300 – but this may double in the peak summer holiday times. Collingwood has
a sewage treatment facility that is controlled by the local Council. There are some
local residential homes and a few holiday homes in the area, providing an additional
population of approximately 30 people serviced by septic tanks. An adjacent black
swan colony rounded out a wide range of potential of sources of contamination.
Collingwood marine farms occupy approximately 80 Ha, growing Greenshell
mussels and producing around 4,000 tonnes pa. Significant expansion is planned in
the area increasing the importance of solving this puzzle. The majority of production
is exported and therefore subject to the regulatory requirements of domestic and
export markets.
In 1994 this Growing Area was classified as conditionally approved (that is open
subject to specified criteria) and has operated under differing harvest criteria since
that time.
Shellfish harvesting is carried out year-round subject to sanitation and biotoxin
closures. The initial harvest criteria was based on the level of the Aorere River.
However, the currents and prevailing wind often took the river plume away from
the farms. Frequently the shellfish farms would be closed under this criterion, but
frustratingly farmers could clearly see the river plume well away from their farms
and product. That led to investigation of the usefulness of salinity monitoring for the
area based upon real time telemetered salinity data from buoys situated in the farms.
Salinity monitoring based upon the rate of dilution of the sea water by the fresh
water from the river was implemented in 1997, significantly increasing the number
of days open for harvest.
Our quality programme requires ongoing monitoring to ensure that the harvest
criteria continue to meet the regulatory standards. In 2002/2003 industry’s routine
monitoring began to detect with increasing frequency bacteria levels that exceeded
the regulatory standards for human consumption.
To ensure ongoing compliance and market access, the harvest criteria was
tightened several times between 2003 and 2004. This reduced the time open for
harvesting from 72 % of the time to only 50 %. This threatened the viability of
shellfish production in the area.
Warning Signs, Results and Options
The sanitary survey for the area had identified all potential and actual pollution
sources. In the absence of any definitive evidence as to the pollution source or
sources we had to consider: