Sand country ecology: The coastal dune lakes
New Zealand has no native fish of interest to sportsmen. Apart from eels, which are large and abundant, the native species are small and rarely occur in large numbers. Angling is for introduced species, mainly brown and rainbow traut or quinnat salmon and these fish are established in nearlv all waters suitable for salmanids. Interest in angling is increasing rapidly and it is necessary to develop additional waters. One group selected for study was the western coastal dune lakes of the North Island.
There are about 170 dune lakes in two series between Otaki and Hawera, and Waiuku and North Cape. The lakes are small and shallow, usually being under 400 acres in area and less than 15 m in depth. All lakes have a common feature of an impounding barrier of sand. The lakes are of two types-basin and dammed valley lakes. Basin lakes lie between the fore-shore dunes and the consolidated sandstones (e.g., Lake Kereta) or fill depressions in the consolidated dunes (e.g., Lake Waingata). Streams draining the consolidated dunes have been blocked by moving sand to form dammed valley lakes (e.g., Lake Herengawe). Water levels appear to be maintained by rainfall and seepage from the drainage basins. Levels fluctuate about two feet annually. Few have inflowing or outlet streams and outlet streams are often intermittent in flow. The mean annual rainfall varies from 30-50 inches, which is spread over the whole year, with a drier period over the summer. The mean monthly air temperatures range from 47¡ to 63¡ F. The majority of the lakes are exposed to the prevailing westerlies and water turnover occurs at all seasons. Less frequent eastern storms also assist water turnover.