First assessment of estuarine space use and home range of juvenile white steenbras, Lithognathus lithognathus
- Authors: Bennett, Rhett H , Childs, Amber-Robyn , Cowley, Paul D , Næsje, T F , Thorstad, Eva B , Økland, F
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447517 , vital:74653 , https://doi.org/10.1080/15627020.2011.11407476
- Description: The spatial dynamics and home range sizes of early juvenile white steenbras (Lithognathus lithognathus Cuvier, 1829) in the permanently open Great Fish Estuary, South Africa, were assessed using acoustic telemetry. Seven individuals (154–184 mm fork length) tagged with acoustic transmitters spent the majority of their time in the mesohaline to oligohaline regions of the estuary, between five and seven kilometres from the mouth. Mean home range size was small (97 399 ± 22 557 m2, mean ± S.D.) relative to the size of the estuary (approx. 1 360 000m2). Mean length of the estuary used by an individual was 1707m(±S.D.=1663 m). The fish were highly resident within the estuary, and showed fidelity towards their site of capture.
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- Date Issued: 2011
Estuarine use by spotted grunter Pomadasys commersonnii in a South African estuary, as determined by acoustic telemetry
- Authors: Childs, Amber-Robyn , Cowley, Paul D , Næsje, T F , Booth, Anthony J , Potts, Warren M , Thorstad, Eva B , Økland, F
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124428 , vital:35612 , https://doi.org/10.2989/A JMS.2008.30.1.12.462
- Description: Estuaries are important in the life history and the maintenance of the diversity of coastal fish species because of their function as nursery areas for juveniles as well as feeding grounds for adults (Cyrus 1991). The dependence of many fish species on estuaries is well documented (e.g. Wallace et al. 1984, Lenanton and Potter 1987, Blaber et al. 1989, Whitfield 1990, Hoss and Thayer 1993). Spotted grunter Pomadasys commersonnii (Haemulidae) (Lacepède 1801) is an estuarine-dependent species which spawns in the KwaZulu-Natal inshore coastal waters, between August and December (Wallace 1975b, Wallace and van der Elst 1975, Harris and Cyrus 1997, 1999). The eggs and larvae are transported southwards by the Agulhas Current, and juveniles between 20 mm and 50 mm TL recruit into the KwaZulu-Natal and south-eastern Cape estuaries (Wallace and van der Elst 1975, Whitfield 1990). Juvenile spotted grunter make use of the abundant food resources in estuaries, where they grow rapidly and remain for a period of 1–3 years (Wallace and Schleyer 1979, Day et al. 1981). Upon attaining sexual maturity (at between 300 mm and 400 mm TL), they return to the marine environment (Wallace 1975b). Some adults, however, return to estuaries to feed and to regain condition after spawning (Wallace 1975b, Whitfield 1994). The return of post-spawning fish coincides with increased catches by fishers in estuaries between July and January. These events are known as ‘grunter runs’ (Wallace 1975a, Marais and Baird 1980, Marais 1988, Pradervand and Baird 2002). It is suggested that adults spend up to several months in estuaries, before moving back to sea where they undergo gonadal development and ultimately spawn (Wallace 1975b, Wallace and van der Elst 1975). It is believed that adult fish also enter estuaries in a prespawning state to gain condition en route to their spawning grounds in KwaZulu-Natal (Webb 2002).
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- Date Issued: 2010
Do environmental factors influence the movement of estuarine fish? A case study using acoustic telemetry
- Authors: Childs, Amber-Robyn , Cowley, Paul D , Næsje, T F , Booth, Anthony J , Thorstad, Eva B , Økland, F
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6772 , http://hdl.handle.net/10962/d1008070
- Description: Telemetry methods were used to investigate the influence of selected environmental variables on the position and movement of an estuarine-dependent haemulid, the spotted grunter Pomadasys commersonnii (Lacepède 1801), in the Great Fish Estuary, South Africa. Forty individuals (263–698 mm TL) were surgically implanted with acoustic coded transmitters and manually tracked during two periods (7 February to 24 March 2003; n = 20 and 29 September to 15 November 2003; n = 20). Real-time data revealed that spotted grunter are euryhaline (0–37) and are able to tolerate large variations in turbidity (4–356 FTU) and temperature (16–30 °C). However, the fish altered their position in response to large fluctuations in salinity, temperature and turbidity, which are characteristic of tidal estuarine environments. Furthermore, tidal phase had a strong influence on the position of spotted grunter in the estuary.
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- Date Issued: 2008