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The vegetated intertidal zone has long been acknowledged as an important habitat for fish, but our understanding of the dynamics of intertidal migrations by these fish is limited. Using in situ video recordings, we examined fish movements into and out of the waterward margin of a fringing mangrove forest during spring tides at 27 haphazardly chosen sites throughout the Rookery Bay National Estuarine Research Reserve, Florida. Our results indicate that fish respond to tide stage in a species-specific manner. Based on the changes in relative abundance throughout the tide cycle, we identified 4 general intertidal migration patterns: (1) tide-level proportionate, with greatest abundance during high tide; (2) flood-and ebb-tide concentrated, with lowest abundance during high tide; (3) peak abundance at ebb and low tide; and (4) depth-limited but tidally independent. Given that the distribution of the fish within the intertidal zone was heterogeneous, we suggest that the placement of sampling gear within the intertidal zone and the timing of samples within the tide cycle can greatly influence the species composition of fish inventories.KEY WORDS: Fish · Tidal migration · Intertidal · Mangrove · Video · Sampling 370: 207-219, 2008 Our knowledge of the habitat use and dynamics of intertidal migrations has been limited by the logistic difficulties inherent to sampling mobile fauna in structurally complex aquatic habitats (see review by Rozas & Minello 1997). Such sampling is often laborintensive, may require habitat alteration (e.g. removal of vegetation) for the placement of sampling gear, and commonly relies on the ebbing tide to concentrate targeted species for collection. These challenges limit both spatial and temporal sampling replication, and largely prohibit in situ sequential sampling designs that are ideally suited for the study of the within-tide movements of intertidal migrants (Gibson 2003). Resale or republication not permitted without written consent of the publisherMar Ecol Prog SerIn studies of nekton associated with mangrove habitats, the sampling period, when reported, has often been restricted to a single stage of the tide cycle (usually high tide), or if sampling was conducted over multiple tide stages, results have been reported as a cumulative total of individuals captured without mention of within-tide dynamics (Table 1). Quantitative sampling in the mangrove intertidal zone (sensu Rozas & Minello 1997) using enclosure gear has been, to our knowledge, restricted to high tide (Table 1). Passive sampling gear (e.g. fyke nets and block nets, Table 1) that collects fish from generally undefined areas of the intertidal zone as they are drained is positioned at high tide or late flood tide. In each of these instances, the usually implicit, and untested, assumption upon which the sampling designs were based was that most fish swim into the mangrove habitat with the flood tide and depart the intertidal zone as it is drained during the ebb. This assumption is revealed when these studies are in...

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