The impact of river flooding and high flow on the demersal fish assemblages of the freshwater-dominated Great Fish Estuary, South Africa

Nodo, P.; James, Nicola C.; Childs, A-R; Nakin, M. D. V.

doi:10.2989/1814232x.2017.1404494

Cited by 11 publications

(4 citation statements)

References 45 publications

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“…Estuaries, which are important as nurseries for both larval and juvenile stage fish [22–24], are highly susceptible to climate change because they are relatively shallow and thus have low thermal inertia, and generally are in close proximity to anthropogenic stressors [25–28]. Evidence of increasing temperatures and large fluctuations in salinity due to climate change has been documented in estuarine systems in the northern and southern hemispheres [25, 29–32]. This includes along the east coast of the U.S. in large estuaries, like the Hudson River estuary and Narragansett and Delaware Bays, and small ones, such as the Mullica River-Great Bay estuary [23, 33, 34].…”

Section: Introductionmentioning

confidence: 99%

Change in larval fish assemblage in a USA east coast estuary estimated from twenty-six years of fixed weekly sampling

2019

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Climate change is leading to significant alterations to ecosystems all over the world and some of the resulting impacts on fish and fisheries are now becoming apparent. Estuaries, which are highly susceptible to climate change because they are relatively shallow and in close proximity to anthropogenic stressors, provide habitat to many fish species at a critical time in the life history, after transport and just prior to settlement in nurseries. Despite this, the long-term impacts of climate change on larval fish at this critical location/stage in the life history are not well documented. The larval fish assemblage of a coastal estuary was sampled once per week for twenty-six years at a fixed location in southern New Jersey, USA. We used ordination and regression analysis to evaluate the whole assemblage, individual species/family occurrence, and trends in total density and diversity over that time. The larval fish assemblage changed significantly in response to warming water temperatures. In addition, approximately one quarter of the species/families in the assemblage exhibited a statistically significant trend in individual occurrence over time. Of these, all five of the five northern-affiliated species decreased in occurrence while 18 of 21 southern-affiliated species increased in occurrence. Finally, total fish density and species diversity increased over the course of the study. The non-uniform response of the species/families in this larval assemblage is similar to what has been documented in other studies that evaluated the temporal trend of open ocean juvenile and adult fish assemblages.

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Section: Introductionmentioning

confidence: 99%

Change in larval fish assemblage in a USA east coast estuary estimated from twenty-six years of fixed weekly sampling

2019

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“…The high sediment load of the river results in very high turbidity (Nephelometric Turbidity Unit (NTU) >240) (Grange et al, 2000;James and Harrison, 2010;Froneman, 2010;Nodo et al, 2017). In contrast, the Kariega Estuary receives a negligible inflow of freshwater due to relatively low rainfall, a small catchment (686 km 2 ), as well as several impoundments along the river that severely reduce river flow.…”

Section: Seawater and Estuarine Water Collection Sitesmentioning

confidence: 99%

“…It has been suggested that high freshwater flow promotes the recruitment of larval and juvenile A. japonicus into estuaries (reviewed in Stewart et al, 2020). The prevalence of juveniles of the South African population in turbid versus non-turbid estuaries (Marais, 1981;Marais, 1985;Plumstead et al, 1985;Whitfield and Paterson, 2003;Nodo et al, 2017;James et al, 2020), suggests that turbid systems with fairly high freshwater input, such as the Great Fish Estuary on the south-east coast of South Africa, are the preferred nursery habitat for A. japonicus (Griffiths, 1996). Within turbid estuaries throughout their distribution, early juveniles are found predominantly in deeper waters in the upper reaches and are not associated with the shallow littoral vegetated fringes (Silberschneider and Gray, 2008).…”

Section: Introductionmentioning

confidence: 99%

Turbidity influences the recruitment of Argyrosomus japonicus to estuarine nurseries

et al. 2022

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Estuaries serve as important nursery habitats for several coastal fishery species. The successful recruitment of larvae and early juveniles into estuaries is paramount for population persistence and maintenance. Several factors have been proposed as stimuli that could elicit a recruitment response in estuary-associated fish species. Larvae and early juveniles may trace land-based cues back to an estuary by following the olfactory concentration gradient or use other visual or acoustic stimuli. Argyrosomus japonicus is an iconic estuarine-associated species. Due to overfishing, reduced freshwater input and habitat degradation in their estuarine nursery habitat, the South African population has suffered severe stock declines. Turbidity associated with high freshwater input is thought to promote recruitment into estuaries. We used choice-chamber laboratory experiments to test the hypothesis that settlement-stage A. japonicus are attracted to turbidity rather than olfactory gradients when recruiting into estuaries. Three choice experiments (with three replicate trials each) were performed over three consecutive days. Each experiment used paired combinations of six estuarine/seawater types with varying turbidity and olfactory characteristics. For each experiment, three trials were repeated in succession with six new fish for each trial. Settlement-stage A. japonicus showed a significant preference for turbid water (with and without olfactory cues) over seawater (no olfactory cues) and clear estuary water (with olfactory cues). No clear choice was made between clear estuary water (with olfactory cues) and clear artificial seawater (without olfactory cues), suggesting that turbidity gradients are most likely the primary factor governing the recruitment of settlement-stage A. japonicus into estuaries.

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“…Tidal dynamics often play a central role in controlling estuarine physio-chemical variability, but wind and fluvial forcings can also be relevant (Snedden G. , 2006). Diurnal, seasonal, inter-annual, and even decadal variability in flooding regimes and freshwater availability have been attributed to changes in estuarine community assemblages (Janousek & Folger, 2014;Baptista, Martinho, Nyitrai, Pardal, & Dolbeth, 2015;Nodo, James, Childs, & Nakin, 2017). Soil and soil pore-water characteristics are also known to have some influence on marsh communities (Carling, et al, 2013), although at least one study documents little to no importance on microbial assemblages (Koretsky, et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Partitioning biota along the Elbe River estuary: where are the community transitions?

Branoff,

Grüterich,

Wilson

et al. 2024

Preprint

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Estuarine zonation and community assemblages are frequently correlated with salinity, although the extent or nature of this correlation varies considerably among the published studies. While a smooth transition in biological communities is often conceptualized in association with estuarine fresh, brackish, and marine conditions, many studies have shown more distinct communities and the altogether absence of a brackish community. We explore these viewpoints in light of plant observations and soil and aquatic microbial analyses from permanent plots established on the Elbe River Estuary of northern Germany. Generally, two distinct communities were observed, a polyhaline assemblage towards the mouth of the system, and another that was associated with both the fresh and brackish mesohaline regimes further upriver. This was most pronounced among plant and soil bacteria communities, while aquatic 16S assemblages reflected little distinction at all. The proportion of marine classified taxa declined from the mouth to upriver and suggests that while the transition from marine to brackish or fresh vegetation falls within the sampled area, the same transition for microbial taxa could not be observed and may be further upriver. Thus, although we were able to identify two distinct communities, the limit of marine taxa was only evident for vegetation. While tidal and weather-related hydrology, as well as soil properties were also influential in distinguishing the communities, much of the variance remains unexplained. Further sampling, classification, and partitioning is necessary to determine the origin and/or autochthonous habitat, if any, for the Elbe River estuarine taxa.

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The impact of river flooding and high flow on the demersal fish assemblages of the freshwater-dominated Great Fish Estuary, South Africa

Cited by 11 publications

References 45 publications

Change in larval fish assemblage in a USA east coast estuary estimated from twenty-six years of fixed weekly sampling

Change in larval fish assemblage in a USA east coast estuary estimated from twenty-six years of fixed weekly sampling

Turbidity influences the recruitment of Argyrosomus japonicus to estuarine nurseries

Partitioning biota along the Elbe River estuary: where are the community transitions?

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