Time-series studies have reported trophic cascades in land, freshwater and marine environments in many geographic areas. However, the spatial extent of habitats, a key metric of ecosystem structure, has not been mapped in these studies. Marine reserves can provide experimental, before-after and inside-outside (control-impacted), situations for assessing the impact of fishing on ecosystems. We mapped seabed habitats and their associated communities (biotopes) in New Zealand's oldest marine reserve for comparison with pre-reserve maps created about 30 years previously.Areas grazed bare by sea urchins were entirely replaced in the centre of the reserve by kelp, or alga turf, an intermediate biotope between heavily grazed encrusting algae and lightly grazed kelp. Urchins declined following increased abundance and body size of spiny (rock) lobsters and fish (especially snapper) in the reserve but maintained bare rock outside. While this gradient in habitat change matched the gradient of predator abundance, it also matched the extent of reef habitat area. Thus the trophic cascade may be influenced by the effect of habitat on the abundance and behavioural interactions of urchins and their predators. Further ecosystem changes may arise should the abundance of mega-predators, such as seals, cetaceans and large sharks, increase in the region; if parasites become pathogenic; and/or when invasive species reach the reserve.No-take marine reserves provide real-world experiments that show the importance of species in food webs, and the consequences of fishing for ecosystems. Because these changes in ecosystem structure may continue, and will vary with environment, climate and species distributions, reserves need to be permanent and replicated geographically. Habitat maps should be produced for all reserves to enable ecological changes in the ecosystem to be spatially quantified.
Fishes were observed and collected at the Kermadec Islands in 1984 and 1985. Five families and 16 species were newly recorded from the New Zealand region and a further 18 species were newly recorded from the Kermadec Islands. The number of coastal fishes known from the Kermadec Islands is now 112. Seventy-seven coastal fish species were classified into five abundance classes at five Kermadec Islands localities; 27 showed north-south abundance trends. Of the 112 Kermadec Islands species, 55% are found in temperate New Zealand, but only 20% are common there. The fish fauna at the Kermadec Islands has greater affinity with that at Lord Howe Island (64%) and also has significant links with Rapa and Easter Islands (both 22%) which are at similar latitudes in the eastern Pacific Ocean. Two (possibly three) coastal fish species are endemic to the Kermadec Islands.
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