Response of demersal fish assemblages to an extreme flood event in a freshwater-deprived estuary in South Africa

2018 ◽  
Vol 69 (2) ◽  
pp. 253 ◽  
Author(s):  
P. Nodo ◽  
N. C. James ◽  
A.-R. Childs ◽  
M. D. V. Nakin
Keyword(s):  
South Africa ◽  
Fish Assemblage ◽  
Large Scale ◽  
Fish Assemblages ◽  
Salinity Gradient ◽  
Demersal Fish ◽  
Flood Event ◽  
Estuarine Fish ◽  
Water Abstraction ◽  
Extreme Flood

The Kariega Estuary in South Africa, is an example of a freshwater-deprived estuary. Large-scale water abstraction and droughts have resulted in this estuary either being uniformly marine or hypersaline. A major episodic flood event in October 2012, the largest ever recorded in this system, provided us with an opportunity to investigate the prolonged effect of an episodic flood on the demersal fish assemblage of a freshwater-deprived estuary. A beam trawl net was used for sampling the fish assemblages from December 2013 to November 2014. The flood event before the sampling period ‘reset’ the system, such that there was a longitudinal salinity gradient from the head to the mouth, which resulted in ‘normal’ estuarine conditions, typical of most estuaries. There was an increase in the abundance of benthopelagic marine migrant species, particularly early juveniles of important fishery species, in the middle and upper reaches during the present study relative to previous studies conducted in this freshwater-deprived system. This suggests increased recruitment of these species into their estuarine nursery habitat. The present study highlights the importance of understanding the effect of freshwater inflow on the demersal estuarine fish assemblage and the nursery role of this and other estuarine systems and their management.

scholarly journals Fish Assemblage Structure Comparison between Freshwater and Estuarine Habitats in the Lower Nakdong River, South Korea

2020 ◽  
Vol 8 (7) ◽  
pp. 496
Author(s):  
Joo Myun Park ◽  
Ralf Riedel ◽  
Hyun Hee Ju ◽  
Hee Chan Choi
Keyword(s):  
Fish Assemblage ◽  
Fish Assemblages ◽  
Estuarine Fish ◽  
Freshwater Species ◽  
Fish Assemblage Structure ◽  
Nakdong River ◽  
Structure Comparison ◽  
Significant Difference ◽  
Freshwater Habitats ◽  
The Nakdong River

Variabilities of biological communities in lower reaches of urban river systems are highly influenced by artificial constructions, alterations of flow regimes and episodic weather events. Impacts of estuary weirs on fish assemblages are particularly distinct because the weirs are disturbed in linking between freshwater and estuarine fish communities, and migration successes for regional fish fauna. This study conducted fish sampling at the lower reaches of the Nakdong River to assess spatio-temporal variations in fish assemblages, and effects of estuary weir on structuring fish assemblage between freshwater and estuary habitats. In total, 20,386 specimens comprising 78 species and 41 families were collected. The numerical dominant fish species were Tachysurus nitidus (48.8% in total abundance), Hemibarbus labeo (10.7%) and Chanodichthys erythropterus (3.6%) in the freshwater region, and Engraulis japonicus (10.0%), Nuchequula nuchalis (7.7%) and Clupea pallasii (5.2%) in the estuarine site. The fish sampled were primarily small species or the juveniles of larger species at the estuary region, while all life stages of fishes were observed at the freshwater habitats. The diversity patterns of fish assemblages varied greatly according to study site and season, with higher trends at estuarine sites during the warm-rainy season. No significant difference in diversity between freshwater and estuarine sites during the cold-dry season were found. Multivariate analyses of fish assemblage showed spatial and seasonal differences of assemblage structures. Higher effects of between-site variability but not within seasonal variability at each site were observed. Variations in assemblage structures were due to different contributions of dominant species in each habitat. Common freshwater species characterized the fish assemblage in the freshwater region, while marine juveniles were significantly associated with the estuarine habitat. The results from the ecological guild analyses showed distinct ecological roles for freshwater and marine species, and overlapping roles for fish sampled at the fishways. The lower reaches of the Nakdong River are an important ecosystem for both freshwater and marine juveniles. Nakdong River estuarine residents and migrant fishes, however, have been negatively affected by the construction of the weir (gravity dam), due to the obstruction to migration from and to freshwater habitats. Conservation and management policies aimed at minimizing anthropogenic influences on estuary ecosystems should focus on evaluating ecological functions of estuary weirs.

scholarly journals Impact of seasonal hydrological variation on tropical fish assemblages: abrupt shift following an extreme flood event

Ecosphere ◽  
2020 ◽  
Vol 11 (12) ◽  
Author(s):  
Ratha Chea ◽  
Thomas K. Pool ◽  
Mathieu Chevalier ◽  
Pengbun Ngor ◽  
Nam So ◽  
...  
Keyword(s):  
Fish Assemblages ◽  
Tropical Fish ◽  
Flood Event ◽  
Abrupt Shift ◽  
Extreme Flood ◽  
Hydrological Variation

Channel hydraulics and geomorphic effects of an extreme flood event on the Sabie River, South Africa

CATENA ◽  
2004 ◽  
Vol 58 (2) ◽  
pp. 151-181 ◽  
Author(s):  
G.L. Heritage ◽  
A.R.G. Large ◽  
B.P. Moon ◽  
G. Jewitt
Keyword(s):  
South Africa ◽  
Flood Event ◽  
Extreme Flood ◽  
Channel Hydraulics

Changes in demersal fish assemblages on the west coast of South Africa, 1986–2009

2011 ◽  
Vol 33 (1) ◽  
pp. 157-170 ◽  
Author(s):  
LJ Atkinson ◽  
RW Leslie ◽  
JG Field ◽  
A Jarre
Keyword(s):  
South Africa ◽  
West Coast ◽  
Fish Assemblages ◽  
Demersal Fish ◽  
The West

Temporal variability in fish assemblage structure and recruitment in a freshwater-deprived estuary: The Coorong, Australia

2010 ◽  
Vol 61 (11) ◽  
pp. 1298 ◽  
Author(s):  
Brenton P. Zampatti ◽  
Christopher M. Bice ◽  
Paul R. Jennings
Keyword(s):  
Fish Assemblage ◽  
Fish Assemblages ◽  
Marine Species ◽  
River Regulation ◽  
Assemblage Structure ◽  
Estuarine Fish ◽  
Fish Assemblage Structure ◽  
Murray River ◽  
Eastern Australia ◽  
Freshwater Inflows

River regulation can diminish freshwater flows to estuaries and compromise estuarine functionality. Understanding biotic responses to altered flow regimes is imperative to effectively manage aquatic ecosystems. The present study investigated temporal variation in fish assemblage structure and the recruitment of catadromous fish in the Coorong estuary at the terminus of the Murray River, in south-eastern Australia. Over the three-year study period, freshwater inflows to the estuary diminished and ultimately ceased, disconnecting freshwater and estuarine environments. It was hypothesised that these conditions would lead to (1) increases in estuarine salinities and concomitant changes in fish assemblage structure and abundance, and (2) decreased recruitment of catadromous fish. As freshwater inflow decreased, salinities immediately downstream of a series of tidal barrages increased from brackish to marine–hypersaline, species richness and diversity decreased, freshwater and diadromous species became less abundant and assemblages were increasingly characterised by marine species. Furthermore, the abundance of young-of-year catadromous fish decreased dramatically. Excessive regulation of freshwater inflows is resulting in the Coorong estuary resembling a marine embayment, leading to a loss in species diversity. We suggest, however, that even small volumes of freshwater may promote diversity in estuarine fish assemblages and some recruitment of catadromous species.

scholarly journals Spatial and temporal patterns of fish assemblages in mountain streams of the Ren River, southwest China

2021 ◽  
Author(s):  
Fei Liu ◽  
Pengcheng Lin ◽  
Huanzhang Liu ◽  
Jun Wang
Keyword(s):  
Fish Assemblage ◽  
Large Scale ◽  
Southwest China ◽  
Fish Assemblages ◽  
Cold Water ◽  
Temporal Patterns ◽  
Mountain Streams ◽  
Small Scale ◽  
Spatial And Temporal Patterns ◽  
Landscape Factors

The spatial-temporal patterns of fish assemblages in lotic systems can provide useful information in developing effective conservation measures. This study aimed to explore the spatiotemporal changes in fish assemblage and their association with environmental factors in mountain streams of Ren River, southwest China. Filed investigations were conducted at 18 sites during rainy and dry season in 2017. A total of 21 species, belonged to 3 orders, 8 families and 19 genera, were collected. Analysis of similarities (ANOSIM) showed fish assemblages structure varied significantly at the spatial scale, but not at the temporal scale. In low order sites, fish assemblages were mainly dominated by cold water and rheophilic species (e.g. Rhynchocypris oxycephalus, Scaphesthes macrolepis, Metahomaloptera omeiensis and Gnathopogon herzensteini), while those in high order sites were predominated by warm water and eurytopicity or stagnophilic species (e.g. Squalidus argentatus, Hemiculter leucisculus and Zacco platypus). Canonical correspondence analysis (CCA) showed fish assemblages were structured by a combination of large-scale landscape factors (e.g. altitude and C-link) and small-scale habitat features (e.g. channel width, water temperature and depth). Among these factors, landscape factors had the greatest influence on fish assemblage, while local habitat measures played less important roles or just acted in certain season.

scholarly journals Effects of a large-scale and offshore marine protected area on the demersal fish assemblage in the Southwest Atlantic

2012 ◽  
Vol 70 (1) ◽  
pp. 123-134 ◽  
Author(s):  
Daniela Alemany ◽  
Oscar O. Iribarne ◽  
Eduardo M. Acha
Keyword(s):  
Fish Assemblage ◽  
Protected Area ◽  
Large Scale ◽  
Marine Protected Area ◽  
Demersal Fish ◽  
Fishing Effort ◽  
Fish Assemblage Structure ◽  
Target Species ◽  
Southwest Atlantic ◽  
Before And After

Abstract Alemany, D., Iribarne, O. O., and Acha, E. M. 2013. Effects of a large-scale and offshore marine protected area on the demersal fish assemblage in the Southwest Atlantic. – ICES Journal of Marine Science, 70:123–134. There are few extensive and offshore located marine protected areas (MPAs) in the world oceans and their performance is still being debated. We evaluated the effects of a large-scale offshore MPA located on the Southwest Atlantic Patagonian Shelf (43°S 63°W) on the demersal fish assemblage. Compliance of the Patagonian MPA was assessed by analysing eight years of satellite vessel monitoring system (VMS; 2000–2008) data, which showed compliance and fishing effort concentrated near the protection boundaries. MPA effects were studied by employing a five year database collected by a scientific research vessel in protected and fishing locations, before and after the MPA establishment. We assessed 152 scientific trawling stations using multivariate analysis of fish assemblage structure, fish abundance (discriminating target and non-target species), and mean size and proportion of juveniles of the target species (Argentine hake, Merluccius hubbsi). The identified MPA effects were a trend towards increasing abundance of the demersal fish assemblage, the target and non-target fish species, and hake juvenile size, and a higher proportion of juveniles aged 2+ inside the MPA. These positive trends support the case for offshore, large-scale MPAs.

scholarly journals Responses of stream invertebrate and fish assemblages to an extreme flood event in the Shigenobu River, southwestern Japan

2019 ◽  
Vol 22 (1) ◽  
pp. 35-49
Author(s):  
Kosuke SUMIDA ◽  
Yo MIYAKE ◽  
Yuya WATANABE ◽  
Mikio INOUE
Keyword(s):  
Fish Assemblages ◽  
Flood Event ◽  
Extreme Flood
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