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Results - data and trends

At each site we collect information on the type and number of sediment-dwelling animals present. Our monitoring results from 2001 to 2011 have been reported on in a previous indicator, and further detail can be found on the REMP website, and in technical publications

In this indicator we report on monitoring results from 2012 onwards using an estuarine health index called the Traits Based Index (TBI). The TBI summarises animal community characteristics based on the animals’ biological traits. Biological traits are the physical and behavioural characteristics that define a particular species (e.g. body size, mobility, feeding behaviour). The TBI tells us about the health of our estuaries. It ranges between zero and one, with one being most healthy and zero being least healthy. We can use the TBI to track the health of our estuary sites over time, and to compare the health of different estuaries.

The graphs below show the TBI score for each monitoring site in the three currently monitored estuaries for 2012 and 2017.

Comparison of the three estuaries shows:

  • Most of the sites are moderately healthy (having a TBI score between 0.3 and 0.4). 
  • All the sites in the Firth of Thames had similar TBI scores indicating that these sites are broadly similar to one another in terms of estuarine health.
  • There was much greater difference between sites in Whaingaroa (Raglan) Harbour, when compared to the differences between sites in other estuaries. Haroto Bay was the least healthy, and Okete Bay and Whatitirinui Island was the most healthy.
  • There were differences between sites in Tairua Harbour, with Pauanui and Manaia Road having slightly higher TBI scores (indicating a healthier environment) than those at Pepe Inlet, Gumdigger Gully and Oturu Stream.
  • There were only slight changes in the TBI (and therefore in estuarine health) between 2012 and 2017 at the monitored sites. We expect the TBI score to vary slightly from year-to-year due to natural variability. There were no consistent increasing or decreasing trends in TBI scores at any of the monitored sites.

Coastal Biology Indicator: TBI Scores 2012 to 2017

The Excel spreadsheet below contains the source data to this indicator's graph and any additional data.

Download the data file  [XLSX, 10 KB]