Tidal influence on a fringing mangrove intertidal fish community as observed by in situ video recording: implications for studies of tidally migrating nekton

Abstract

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...

Influence of tides on assemblages and behaviour of fishes associated with shallow seagrass edges and bare sand

“…More importantly, differences in abundances between seagrass edges and bare sand were contingent on tidal stage or tidal cycle (neap or spring). Our results are similar to previous studies within intertidal zones (Bretsch & Allen 2006, Ellis & Bell 2008, suggesting that tidal migrations resulting in highly dynamic fish assemblages in such habitats, also extend to the subtidal habitats Table 4. Mugilidae, Rhabdosargus holubi, Atherina breviceps, Gobiidae.…”

“…A key finding from the few published tidal studies using high frequency sampling is that different species do not enter a habitat together. Rather the responses are species-specific with many, particularly larger species and larger size classes within species, not moving into intertidal areas until late in the tidal cycle (Bretsch & Allen 2006, Ellis & Bell 2008. Habitat type had no influence on the tidal stage at which this threshold appeared to occur, with both taxa observed at seagrass edges and bare sand at approximately the same point in the tide.…”

“…Recently, new approaches have been employed in the study of estuarine fish that consist of uninterrupted observations using underwater cameras (Ellis & Bell 2008, Becker et al 2010, Smith et al 2011). These methods have proved useful in obtaining data from structured habitats and at small temporal scales.…”

“…However, the few studies to employ high frequency sampling within intertidal mangrove and marsh creeks (e.g. Bretsch & Allen 2006) have used equipment that is not transferable to other habitats, therefore alternative methods are required.Recently, new approaches have been employed in the study of estuarine fish that consist of uninterrupted observations using underwater cameras (Ellis & Bell 2008, Becker et al 2010, Smith et al 2011). These methods have proved useful in obtaining data from structured habitats and at small temporal scales.…”

Tidal influences on fish distributions on tropical eastern Pacific rocky shores (Colombia)

“…The small changes observed in the subtidal reef fish assemblage over the tidal cycle indicate that intertidal migrations were restricted to just a few species of the entire reef fish assemblage; and even more, to only one part of a population within these specific species. Similar results were obtained in mangrove systems of Florida by Ellis & Bell (2008), where only 1 group of species (Eucinostomus spp.) showed clear tide-related movements.…”