Potential ecological impacts of harvesting kina (Evechinus chloroticus) in Fiordland

High densities of Evechinus chloroticus are common in the rocky subtidal of outer Dusky Sound, Fiordland. Within this area, organisms are zonated into three habitats. These habitats are a shallow fucoid fringe; a mid-depth barren zone dominated by crustose forms (algae and sessile invertebrates) and devoid of most large algae; a deeper algal meadow where smaller herbaceous and turfing algae predominate. In many sites, a fourth (deeper) zone dominated by a dense Ecklonia radiata forest is found. Evechinus is most abundant in the two shallowest zones and its abundance decreases noticeably thereafter. In a large two-year experimental study, sea urchins were removed, causing the community structure to change dramatically by allowing large algal habitat forming species to form a more homogeneous, taller, algal canopy. However , two years of continual sea urchin removal was not enough time for the community to reach a stable structure. During the experimental period, there was no evidence that diversity of taxa smaller than large brown algae varied when sea urchins were removed. However , the loss of the so-called`barren habitat' (middle zone) due to the large community structure changes can be considered as a reduction in habitat diversity. The implications of the loss of the barren habitat for the whole community (sessile and mobile species) are not known. Longer-term predictions (longer than two years), for at least two important taxa, Carpophyllum spp. and Ecklonia , were possible using additional information from a comprehensive observational study. In the upper zone (range 0-3.5 m), it appears that the changes detected for Carpophyllum density in the short term (2 years) do not last longer. Ecklonia could increase its density up to 0.6 plant/m 2 if urchins were removed below a threshold of 2 indi-viduals/m2. In the middle zone (range 3.5-6.5 m), as for the upper zone, it appears that the short-term Carpophyllum density increases do not last longer. Ecklonia increases its density up to 1 plant/m 2 when sea urchins are removed below the sea urchin threshold of 2 individuals/m 2. In the lower zone (range 6.5-11.5 m), as for the shallower depth zones, the available evidence shows that we cannot expect significant differences in Carpophyllum densities between areas with and without sea urchins in the longer term. Ecklonia could increase its mean density to 1.55 plants/m 2 when sea urchins are removed below threshold levels.