River and stream water quality and ecology - Greater Wellington ...

River and stream water quality and ecology in the Wellington region: State and trends
(c) Cautionary notes
Given that the state analysis period spans 20 years (1990 to 2010), it can be
expected that in some cases the REC landcover class may not accurately reflect
the dominant landcover at the time some of the earlier fish surveys were
undertaken (the same is true for landcover classes used in the trend analysis
carried out in Section in 7.2). In addition, there are several potential limitations
in using fish data from the NZFFD that should be borne in mind when
interpreting the results of the analyses undertaken:
7.1.2 Results
Not all catchments in the Wellington region have been surveyed equally
(in terms of the number of records and also the type, methodology and
effort of each individual survey).
NZFFD data have been collected using a range of survey methods and
while backpack electric fishing has been used to undertake the majority of
surveys in the Wellington region (>70% of all records), other methods
have also been used (eg, spotlighting and netting/trapping). Different
fishing methods have different biases in terms of both the habitat they can
be used effectively in and the range of species they are likely to catch (Joy
& David in prep) 27 . For example, the predominance of backpack electric
fishing – which is only suitable for use in wadeable rivers and streams –
indicates that larger/deeper rivers are likely to be under-represented in
NZFFD data. Furthermore, the ‘catchability’ of different species using this
method is also widely variable, suggesting that the presence of some
species (eg, large galaxiids and pelagic species) may be under-represented.
Many surveys undertaken target specific species, such as those that are
rare or considered threatened, and as such these species might be overrepresented
in the NZFFD records.
(a) RSoE data
A summary of species caught, along with relevant site information, from the
five RSoE sites fished between 2009 and 2011 is presented in Table 7.2. The
five sites surveyed ranged from being located relatively close to the coast
(Kaiwharawhara Stream at Ngaio Gorge and Whareroa Stream at Queen
Elizabeth Park) to 90 km inland (Beef Creek at Headwaters) and are located
across the four REC landcover types represented in the RSoE network
(indigenous forest, exotic forest, pasture and urban).
Across these five sites, a total of 11 indigenous as well as one introduced
(brown trout) species were caught. Indigenous species diversity at each site
ranged from two (Tauanui River at Whakatomotomo Road and Beef Creek at
Headwaters) to eight (Whareroa Stream at Queen Elizabeth Park) species and
the total number of fish caught at each site ranged from 23 (Beef Creek at
Headwaters) to 318 (Totara Stream at Stronvar). Longfin eels were the only
species caught at all five sites. IBI scores ranged from 28 (‘poor’, two sites) to
48 (‘very good’) (Table 7.2).
27 Different biases associated with different sampling methodologies should also be kept in mind when interpreting the RSoE site data
presented in this section.
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