Riding the tide: estuarine movements of a sciaenid fish, Argyrosomus japonicus

Abstract

The movement behaviour of juvenile dusky kob Argyrosomus japonicus (n = 25) was studied in the 12 km long Great Fish Estuary, South Africa, by collecting telemetry data in relation to tidal conditions over 6.5 mo. Two behavioural patterns were observed. Tagged fish either moved in circatidal rhythms over long stretches up and down the estuary, corresponding to the speed and direction of the rise and fall of the tide, or remained stationary, often in deeper or structured habitats. All individuals alternated between moving (mean 61% of the time) and stationary behaviour. Moving periods occurred during both light and dark periods. However, up-estuary movements were initiated most frequently at night, while down-estuary movements were initiated most frequently at dawn and dusk. The mean distance of the unidirectional movements was approximately 3.2 km. Ground speed for up-estuary movements (0.29 m s ). These findings suggest that juvenile A. japonicus adopt 2 distinct feeding strategies within their turbid estuarine nursery habitats. 'Riding the tide', with minimal energy expenditure, may be a successful strategy when feeding on prey that follow the tidal current. Alternatively, in periods when they adopt a stationary behaviour, they may fulfil their foraging requirements by feeding on stationary and/or passing prey, while at the same time reducing predation risk in sheltered, structured habitats. KEY WORDS: Circatidal rhythms · Movement behaviour · Environmental factors · Telemetry · Argyrosomus japonicusResale or republication not permitted without written consent of the publisher OPEN PEN

Fish Movement Through an Estuary Mouth Is Related to Tidal Flow

“…Emerging work has shown larvae and small juveniles can swim against an ebb tide into estuaries (Pattrick & Strydom 2014). Our work shows that these patterns also extend to larger sized fish and appears to signify that while many fish may Bride the tide^ (Gibson 2003;Naesje et al 2012), substantial numbers of fish will also make movements against the tide. Significantly more fish swam out of the estuary into coastal habitats with the ebb tide compared to during flood tides, although the total numbers did not differ greatly.…”

“…Typically, these larvae have limited energy stores and it is believed this passive transport reduces energy requirements (Forward 2001). Tracking of limited numbers of adult fish has also shown tidal currents may be used for both short (<1 km) and long (70 km) distance movements (Arnold, Greer Walker, Emerson, & Holford 1994;Lacoste, Munro, Castonguay, Saucier, & Gagné 2001;Naesje et al 2012), which has also been attributed to minimising energy use. While more fish travelled with the tide, we did observe fish swimming against the flow into the estuary on ebb tides.…”

Nine decades of fish movement research in southern Africa: a synthesis of research and findings from 1928 to 2014

“…Movement within estuaries is constrained and particularly suited to fine-scale acoustic tracking, which has focused predominantly on spotted grunter Pomadasys commersonnii (Kerwath et al 2005;Naesje et al 2007;O'Connell 2008;Childs et al 2008a, b, c) and to a lesser degree on white steenbras Lithognathus lithognathus (Bennett et al 2011 and dusky kob Argyrosomus japonicus (Cowley et al 2008;Naesje et al 2012). Although logistically more difficult, fine-scale habitat usage has also been investigated to a lesser degree in the marine environment with both acoustic telemetry (Hissmann et al 2006;Kerwath et al 2007b;Jewell et al 2012;Kock et al 2013) and conventional mark-recapture (Attwood 2002;Kerwath et al 2007a;Maggs 2011;Maggs et al 2013b).…”

“…The remaining 5 % of studies were conducted completely ex situ within laboratories. From the early 2000s, movement research in estuaries escalated with the increasing accessibility of electronic tagging techniques (Kerwath et al 2005;O'Connell 2008;Naesje et al 2012), which due to small-scale area utilisation by estuary-associated fishes yielded appropriate, high resolution data compared to conventional tagging methods. Thirteen percent of field-based studies included aquariumbased research, often as pilot studies or for tagging method evaluation, including tag-effect assessments.…”

Tidal amplitude and fish abundance in the mouth region of a small estuary

“…Tidal‐related lateral movements of fishes from subtidal habitats to intertidal marshes and mangroves have been well established for a broad range of species (Kneib & Wagner, ), but longitudinal movements related to tides, towards or away from the mouth is less understood. Acoustic telemetry studies are starting to reveal some of these longitudinal movement patterns (Cowley et al , ), including the effects of tides (Childs et al , 2008 a ; Næsje et al , ). Acoustic cameras offer an alternative approach to study the movement patterns of fishes.…”