Use of remote underwater video to record littoral habitat use by fish within a temporarily closed South African estuary

Becker, Alistair; Cowley, Paul D.

doi:10.1016/j.jembe.2010.06.028

Cited by 44 publications

(43 citation statements)

References 35 publications

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“…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.…”

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“…Underwater videography has the added advantage in that it can collect continuous information on the behaviour of fish under natural conditions. This may help to identify processes responsible for the patterns observed in the distributions of fish in patchy habitat mosaics (Becker et al 2010).In this study, we test predictions regarding shallow water fish assemblages along the edge of seagrass patches and nearby bare sand and their responses to an incoming tide: (1) there will be differences in fish assemblages between seagrass edges and nearby bare sand and these will be affected by changes in water depth; (2) there will be differences in the abundances of common species between seagrass edges and nearby bare sand and the magnitude of these differences will be affected by water depth and tide cycles; (3) behaviour of common species will differ between seagrass edges and sand areas and will also be affected by the incoming tide. …”

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“…A marked pole provided depth measurements (cm) at the location of the camera and these were taken at 15 min intervals throughout each deployment. Turbidity can be highly variable, both spatially and temporally within estuaries, making it important in underwater video studies to ensure that visibility is consistent (Becker et al 2010). Accordingly, water samples were collected 3 times throughout each deployment and processed in the laboratory so that turbidity levels between sampling occasions could be compared.…”

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“…For each deployment a separate MaxN value was calculated for each taxon during each of the 16 slots. This normally resulted in separate frames being selected for each taxon.The behaviour of every fish was also noted and placed into one of 4 broad behavioural categories developed by Becker et al (2010) and included (1) 'Slow Meandering' (meandering through the field of view without stopping), (2) 'Start Stop' (swimming into view, stopping then moving on), (3) 'Rapid Swimming' (rapidly passing through the field of view), and (4) 'Feeding' (clearly feeding off the benthos or in the water column). If more than one behavioural category was displayed (e.g.…”

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“…Start Stop and Feeding) then the behaviour which the fish displayed for the majority of the time it was within the field of view was used. While these categories are broad, they have proved useful in examining how basic fish behaviour can differ among habitats and provide information relating to the way fish use various habitats (Becker et al 2010). …”

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

Becker¹,

Coppinger²,

Whitfield³

2012

Mar. Ecol. Prog. Ser.

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Seagrass beds and associated fish assemblages have been the focus of a large number of past studies. However, the influence of small water depth changes due to tides on fish species along shallow seagrass bed edges is unknown. In this study an underwater video camera was deployed to examine the fish community at 3 seagrass edge (Zostera capensis) and 3 sand sites over incoming spring and neap tides in the Bushmans Estuary, South Africa. Small changes in tidally driven water depth had significant effects on the abundance of common fish taxa, with gobies decreasing and others, including mullets, increasing in abundance. These general patterns were consistent in both seagrass and sand sites, as well as during spring and neap tidal cycles. There were inconsistent differences in the abundance of common fish taxa between seagrass edges and bare sand. Importantly, when differences did occur, these were contingent on tidal stage or linked to different tidal cycles (neap or spring), highlighting that small changes in depth may influence edge effects. The behaviour of fish did not appear to be influenced by water depth, but for some taxa there were distinct differences in swimming behaviour between those individuals associated with seagrass beds and those situated over bare sand. These small temporal scale changes in water depth are a previously overlooked aspect of littoral seagrass landscapes that may be important in structuring associated fish communities. KEY WORDS: Underwater video · Water depth · Estuary · Fish movements · Zostera capensis · South AfricaResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 456: 187-199, 2012 exception of a few studies from tidal marsh creeks (Bretsch & Allen 2006), collections are usually made at relatively low frequencies, normally 1 to 4 times over a tidal cycle (Thomas & Connolly 2001, Kimball & Able 2007.While the migration of fish into intertidal habitats has been the topic of previous research, the effect of tides and changing water depth along shallow patches of subtidal seagrass beds is still largely unknown. Some work has focused on the effects of depth on faunal assemblages associated with seagrass beds (Bell et al. 1992, Jackson et al. 2006. Results have been inconsistent, with most studies relying on spatially segregated 'deep' and 'shallow' sites, with depth ranges being relatively large (meters) and deeper sites often exposed to differing hydrological conditions or consisting of differing structure (Hovel et al. 2002).Similar to intertidal examples, studies that have examined seagrass sites at different tidal depths have been based on a relatively low frequency of repeat sampling (Sogard et al. 1989, Unsworth et al. 2007). Consequently these results may reflect coarse changes in the fish community and do not relate to the effects of smaller changes in depths which shallow littoral beds experience during tidal cycles.High temporal frequency sampling represents the best approach to studying sites that are subjected ...

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