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We examined the effects of recreational trampling on wetland sediments, saltmarshes, and macroinfauna in November 2006 and April and July 2007. We used penetration resistance to measure sediment compaction at the Kaomei wetland, a protected intertidal coastal wetland harboring the largest tuberous bulrush marsh grass bed in Taiwan. We also examined the relationship of sediment compaction to visitor intensity and distribution of macroinfauna. Four compaction levels (low, medium-low, medium-high, and high) were identified using hierarchical cluster analysis. The spatial contour of sediment compaction was consistent with the level of visitor intensity, suggesting that human trampling is the main cause of sediment compaction in this wetland. Macroinfaunal abundance in low and medium-low compacted sediments was 4968 and 3376 ind. m -2 , while no macroinfauna was recorded in highly consolidated sediments. Compared to those at medium-low compaction, taxon richness and community density at medium-high compaction were significantly reduced by 80.5 and 52.6%, respectively. Polychaetes were more sensitive to sediment compaction than amphipods and bivalves, and could thus serve as a bioindicator of human trampling impact. A decrease in polychaete abundance may be attributed to their life history, which is controlled by substratum compaction. Our results showed that 25.7% of the study area was significantly compressed and that muddy vegetated areas were more vulnerable than sandy areas. We conclude that losses of macroinfauna and microhabitats are serious, and we propose management strategies to prevent further deterioration of this wetland.

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The critically endangered Formosan landlocked salmon Oncorhynchus masou formosanus is one of the southernmost natural salmon populations in the world, which only occurs in Chichiawan Stream and its tributaries in the Wuling basin of subtropical Taiwan. We examined habitat uses by different size classes of the Formosan salmon and the sympatric shovelmouth minnow Varicorhinus barbatulus, and identified the relative importance of environmental variables, biotic components and seasonal effects in explaining the variance in the relative occurrences of fish at the catchment scale. After removing seasonal effects, 74.9% of the variation in the relative occurrence of fish was explained by the measured environmental variables and biotic components. Habitat uses by the Formosan salmon and shovelmouth minnow were distinct. The shovelmouth minnow occurred more frequently at sites with a high concentration of NH 3 -N and high proportions of gravel and riffles, while the Formosan salmon utilized sites at high elevations. Habitat uses by Formosan salmon of different size classes varied slightly. Juvenile and subadult salmon inhabited sites with lower temperatures and current velocities, but adult salmon occurred more frequently with large-grain-sized substratum. Our study showed that variations in the relative occurrence of fish in the Wuling basin were best explained by physicochemical parameters (38.8%), followed by substratum composition (11.4%). The variations exclusively explained by mesohabitat composition, seasonal effects, and biotic components were not significant. This conclusion has important consequences for local managers and conservationists. KEY WORDS: Physicochemical parameter · Substratum · Habitat composition · Biotic component · Chichiawan Stream · TaiwanResale or republication not permitted without written consent of the publisher Aquat Biol 10: 227-239, 2010 depended on fish species and size. Habitats being occupied by different size classes may reflect ontogenetic habitat shifts (Nowak et al. 2004), showing microhabitat segregation of fishes of different sizes (Greenberg et al. 1996, Mäki-Petäys et al. 1997. Many stream fishes also shift habitat use by season (Baltz et al. 1991, Harvey & Stewart 1991, Heggenes et al. 1991, Bonneau & Scarnecchia 1998, Nagayama & Nakamura 2007. Other factors, such as predation and competition, are of great importance in habitat use by stream fishes , Schlosser 1987, Greenberg 1994.Integration of catchment-scale considerations into management and conservation planning has recently gained momentum (Smith et al. 2003). Most of the above-mentioned studies on habitat use by stream fishes focused on attributes at the scale of the microhabitat (i.e. the position of the fish) or mesohabitat (i.e. riffles and pools). For stream management, knowledge of habitat requirements at the micro-or mesohabitat scale is valuable in mitigating the effects of habitat alterations caused by stream regulation and restoring stream habitats for fish conservation. However, habitat prefere...