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Cockle survey
Our Activities » Cockle survey
Cockle survey
Read current and previous NIWA reports: 1992 1995 1998 2001 2004 2007 2010
Read about cockles and cockle population trends in Cockles of the Inlet.
2010 COCKLE SURVEYNIWA's report on our seventh survey, carried out in November 2010, confirms our impression from the raw data that the total number of cockles has not declined since 2007. That is good news. Even better news is that there is now some evidence that the population has been steadily growing over the past decade. Cockles are not spread evenly over the Inlet shores. There are many patches where they are abundant and many where they are less common, even absent entirely. This 'patchiness' makes estimating the true size of the total Inlet population very difficult and results in the population size having to be expressed as a 'mean' number within a wide margin of error. In the chart below, the mean is represented by a black dot; the vertical line passing through the dot represents the upper and lower limits of the margin of error. For a mean value to be statistically significantly different from another mean, the two error bar limits must not overlap. The chart shows that there has been a steady increase in the mean value since 2001, with the 2011 mean being about 30% higher than that of 2001. Although the bar limits overlap, showing that the difference is not statistically significant, the trend is nevertheless encouraging. It may only be an informed guess that this trend may represent a real increase, but if the trend continues at the current pace, the 2013 survey may well reveal a true, scientifically acceptable increase.
The (possibly) bad news is that there has been a decline in the number of large cockles. This could be because the poor recruitment of larvae and the high mortality of juvenile cockles observed in 1998 and 2001 means that fewer cockles survived to grow to replace these larger sized cockles dying of old age. The 2010 data show that the much higher number of juveniles present in 2004 and 2007 are continuing to grow and in a few years may replenish this size class of senior citizen cockles.
Read the full 2010 report
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GOPI members and local residents have been surveying the cockles in the Inlet every three years since 1992. For families and individuals it's an enjoyable day out with a serious purpose. Students, families and individuals all took part in this year's survey.