Predation impact of juvenile<i>Gilchristella aestuaria</i>(Clupeidae) and<i>Atherina breviceps</i>(Atherinidae) on the zooplankton in the temperate Kariega estuary, South Africa

Froneman, P. William; Vorwerk, Paul D

doi:10.2989/16085914.2003.9626597

Cited by 13 publications

(7 citation statements)

References 16 publications

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“…In conclusion, this study has provided insights into dietary interactions between adult G. aestuaria and A. breviceps and the possible drivers that influence food availability and competition between the two species. Zooplanktivorous fish trophic ecology in the Kariega Estuary is consistent with previously recorded information on these species (Coetzee, ; Bennett, ; Froneman & Vorwerk, ), thus suggesting that there is indeed potential dietary competition between these taxa. This research, which covers all four seasons and different river‐flow conditions, has also provided improved knowledge of the possible links between river flow, physico‐chemical conditions, zooplankton abundance and the distribution and abundance of dominant zooplanktivorous fish species in a warm‐temperate estuary, thus providing a baseline for similar studies elsewhere in South Africa and the rest of the world.…”

Section: Discussionsupporting

confidence: 87%

“…The present study investigated the potential spatio‐temporal dietary overlap between G. aestuaria and A. breviceps and determined that the high degree of dietary overlap recorded for the middle reaches may be partially alleviated by the abundance of copepods, a preferred food source for both species in this region. Similar patterns of associative distribution between A. breviceps , G. aestuaria and their major zooplankton prey have been reported from both the Kariega and Sundays estuaries (Froneman & Vorwerk, ; Strydom et al, ). The loss however, of zooplankton prey from the middle zone (in particular) due to river flooding meant that competition could not be determined for this region due to the absence of both zooplanktivorous fish species.…”

Section: Discussionsupporting

confidence: 78%

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River flow, zooplankton and dominant zooplanktivorous fish dynamics in a warm‐temperate South African estuary

Mbandzi

Wasserman

Deyzel

et al. 2018

Journal of Fish Biology

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The possible links between river flow, zooplankton abundance and the responses of zooplanktivorous fishes to physico-chemical and food resource changes are assessed. To this end, the seasonal abundance, distribution and diet of the estuarine round-herring Gilchristella aestuaria and Cape silverside Atherina breviceps were studied in the Kariega Estuary. Spatio-temporal differences were determined for selected physico-chemical variables, zooplankton abundance and zooplanktivorous fish abundance and distribution. Results indicated that, following a river flood event in winter (>30 m s ), altered physico-chemical conditions occurred throughout the estuary and depressed zooplankton stocks. Abundance of G. aestuaria was highest in spring, with this species dominant in the upper and middle zones of the estuary, while A. breviceps was dominant in summer and preferred the middle and lower zones. The catch per unit of effort of both zooplanktivores also declined significantly following the flooding, thus suggesting that these fishes are reliant on zooplankton as a primary food source for healthy populations. Copepods dominated the stomach contents of both fish species, indicating a potential for strong interspecific competition for food, particularly in the middle reaches. Temporal differences were evident in dietary overlap between the two zooplanktivorous fish species and were correlated with river flow, zooplankton availability and fish distribution. The findings of this study emphasize the close trophic linkages between zooplankton and zooplanktivorous fishes under changing estuarine environmental conditions, particularly river flow and provide important baseline information for similar studies elsewhere in South Africa and the rest of the world.

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Section: Discussionsupporting

confidence: 87%

Section: Discussionsupporting

confidence: 78%

River flow, zooplankton and dominant zooplanktivorous fish dynamics in a warm‐temperate South African estuary

Mbandzi

Wasserman

Deyzel

et al. 2018

Journal of Fish Biology

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“…Many of these studies have focused specifically on the diet of individual species of larval fish (Puvanendran and Brown 1999;Parra and Yúfera 2000), prey selection (Rajasilta and Vuorinen 1983), larval fish feeding impacts on zooplankton density (Pepin and Penney 2000), and requirements for larval fish during first feeding and early growth (Dabrowski 1984;Osse et al 1997). In South Africa, a number of fish dietary studies have been undertaken (Masson and Marais 1975;Whitfield and Harrison 1996;Talbot and Baird 1985;Hecht and van der Lingen 1992;Schlacher and Wooldridge 1996;Froneman and Vorwerk 2003). However, very few studies have focused on larval fish diet or prey selection.…”

mentioning

confidence: 99%

Diet and prey selection in late-stage larvae of five species of fish in a temperate estuarine nursery

Strydom¹,

Sutherland²,

Wooldridge³

2014

African Journal of Marine Science

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The plankton assemblage of the permanently open Sundays Estuary in South Africa was sampled seasonally to provide further information on the feeding ecology of the larval stages of fishes in temperate estuaries. Collections were made between winter 2007 and autumn 2009 at eight sites by means of boat-based plankton tows. Physicochemical variability in the water column was typical for temperate systems. Mean density of larval fishes and zooplankton showed similar seasonal and spatial trends. Gut content analyses were conducted in five dominant larval fish species: Gilchristella aestuaria (Clupeidae), Pomadasys commersonnii (Haemulidae), Monodactylis falciformis (Monodactylidae), Myxus capensis (Mugilidae) and Rhabdosargus holubi (Sparidae). The first record of selective consumption of copepod eggs by G. aestuaria is reported. Insect larvae (chironimids) dominated the diet of some marine fish larvae (M. falciformis and M. capensis).The copepod Pseudodiaptomus hessei formed the largest volume of the diet of P. commersonnii whereas R. holubi selected for the amphipod Corophium triaenonyx, with P. hessei also being a frequently consumed prey item. Seasonal and spatial variability with salinity was evident in the diet. Larvae also showed changes in diet at different stages of development. Pelagic prey species constituted the largest volume of the diet of G. aestuaria whereas all other larvae consumed large volumes of bentho-pelagic prey. All larvae selected P. hessei as a prey item. Myxus capensis and R. holubi also selected this copepod and showed the largest diversity in diet.

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“…This may be a result of observed low stomach fullness (not quantified in our study), which was probably because the time of sampling (during the night) was not coincident with the time of peak feeding of G. aestuaria, which is in the afternoon (Blaber 1979;Froneman and Vorwerk 2003). Although Olivar et al (2009) maintained that the removal of the viscera from larvae might have an important effect on the individual RNA/DNA ratio because of the relatively high RNA concentration in the liver, Mustafa and Mittal (1982) showed that the quantity of RNA in the liver, unlike in other tissues such as the brain, exhibited high fluctuations following changes in food availability.…”

Section: Discussionmentioning

confidence: 78%

“…In the Sundays Estuary, the copepod Pseudodiaptomus hessei provides more than 50% of the food for larvae and juveniles of G. aestuaria (Blaber 1979;Whitfield and Harrison 1996;Sutherland et al 2013). In the Kariega system, however, individuals between 18 and 25 mm SL have been shown to have a more diverse diet (Froneman and Vorwerk 2003). In addition, G. aestuaria has been described as an opportunistic feeder, depending on prey availability (Blaber 1979;Coetzee 1982;Bennett 1989;Cyrus et al 1993).…”

Section: Discussionmentioning

confidence: 99%

Nutritional condition of fish larvae in South African estuaries: an appraisal of three biochemical methods

Costalago¹,

Strydom²,

Frost³

2014

African Journal of Marine Science

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Estuaries are exposed to a number of threats and many South African estuarine systems are functionally and structurally altered. The extent to which fish are affected by these alterations is not fully understood. The estuarine round herring Gilchristella aestuaria is an appropriate species to use when examining such effects. The most widely used approaches to evaluating the nutritional condition of fish larvae are based on biochemical methods. In order to identify the most suitable technique for assessing body condition of fish larvae in estuaries, the nutritional condition of post-flexion larvae of G. aestuaria from the Sundays and Kariega estuaries on the south-east coast of South Africa was evaluated using three different biochemical techniques: (i) total lipid content analysis and the triacylglycerol/cholesterol (TAG/CHOL) ratio; (ii) protein content analysis; and (iii) the RNA/DNA ratio. Results from techniques (ii) and (iii) revealed that G. aestuaria larvae from the Kariega Estuary were in better condition than larvae from the Sundays Estuary, probably due to a recent plankton bloom. It is concluded that the individual RNA/ DNA ratio can provide a reliable, sensitive and cost-effective method to assess the immediate effects of environmental changes on the nutritional condition of estuarine fish larvae.

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Predation impact of juvenileGilchristella aestuaria(Clupeidae) andAtherina breviceps(Atherinidae) on the zooplankton in the temperate Kariega estuary, South Africa

Cited by 13 publications

References 16 publications

River flow, zooplankton and dominant zooplanktivorous fish dynamics in a warm‐temperate South African estuary

River flow, zooplankton and dominant zooplanktivorous fish dynamics in a warm‐temperate South African estuary

Diet and prey selection in late-stage larvae of five species of fish in a temperate estuarine nursery

Nutritional condition of fish larvae in South African estuaries: an appraisal of three biochemical methods

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