Fish assemblage in the Pearl River Estuary: Spatial‐seasonal variation, environmental influence and trends over the past three decades

Abstract

The Pearl River Estuary is the largest estuary in South China and plays a considerable role in the local fisheries economy, yet little is known about the current state of fish assemblage in this ecosystem. To quantify spatial‐seasonal variations, environmental influences, and trends over the past three decades of the fish assemblage in the Pearl River Estuary, we sampled 11 sites seasonally from December 2013 to September 2016. Throughout the study, 285 species from 88 families and 195 genera were collected. There were obvious spatial and seasonal variations of the fish assemblage in terms of the dominant species, species richness, and composition of ecological types. Mouth distance, NH4+ N, chlorophyll‐a, flow, DO, salinity and water transparency were the main variables influencing the spatial‐temporal dynamic of fishes within the estuarine systems. Compared with the record of 330 species in the 1980s, the number of fish species in the Pearl River Estuary has declined by 45 fish species. The Jaccard's similarity of fish composition between the historical investigation (the 1980's) and the present investigation (2013–2016) was 0.62, with 95 species undiscovered and 50 species increased in the present study compared to the 1980s, indicating the assemblage structure has obviously changed. However, in term of ecological guilds, there was no significant difference in the composition of all the selected ecological traits between these two periods. Anthropogenic activities including overfishing, introducing alien fish, dam construction and pollution were considered the main disturbance on fish composition over the past three decades. We conclude that there existed pronounced spatiotemporal changes of fish assemblages, which arises from the compounding effects of environmental factors and anthropogenic activities. These findings are beneficial to understanding and developing suitable conservation strategies for the management and protection of fish resources in the Pearl River Estuary.

Assemblage Structure of the Ichthyoplankton and Its Relationship With Environmental Factors in Spring and Autumn off the Pearl River Estuary

“…This high richness and the fish yield from these waters from depths greater than 30 m render this area one of the most important fishing grounds in the SCS (Wang, 2012;Cai et al, 2018). However, fish resources in this region have decreased dramatically in recent decades, largely because of anthropogenic disturbance and climate change (Zeng et al, 2019;Zhou et al, 2019). Meanwhile, the Indo-Pacific humpback dolphin, Sousa Chinese Osbeck, 1765, Indo-Pacific finless porpoise Neophocaena phocaenoides (Cuvier, 1829), Eden's Whale, Balaenoptera edeni Anderson, 1879, Bryde's whale, B. edeni Olsen, 1913, and humpback whale Megaptera novaeangliae Borowski, 1781, which mainly prey on fishes, have all been reported from waters off the Pearl River Estuary (Jefferson et al, 2012;Peilie, 2012;Lin et al, 2019).…”

The Composition of Intestinal Microbiota From Collichthys lucidus and Its Interaction With Microbiota From Waters Along the Pearl River Estuary in China

“…Estuaries are transition zones between the land and the sea, and represent a dynamic system where freshwater meets seawater. These interactions make estuaries unique habitats in terms of habitat diversity and species productivity (Mitra, 2015;Kamrani et al, 2016;Zhou et al, 2019b). It was previously shown that protective estuary environments may facilitate the generation of over half of all marine fish (Mitra, 2015).…”

“…It was previously shown that protective estuary environments may facilitate the generation of over half of all marine fish (Mitra, 2015). Moreover, spatial differences in fish assemblages in estuaries were primarily attributed to unique salinity, water temperature, primary productivity, turbidity, and water nutrient conditions (Eick and Thiel, 2014;Zhou et al, 2019b). However, insights on how fish adapt to variable physico-chemical features in these environments requires further investigation (Molina et al, 2020).…”

A global assessment of fish estuary associations: A numerical approach to assessing estuary‐associated fish functional guilds

“…In a study of two large European estuaries, Thiel et al., (2003) found that the different life cycle (estuarine use) categories occurred mainly along a spatial gradient with marine and estuarine species arranged in the direction of increasing salinity and decreasing mouth distance, while freshwater species were grouped in the opposite direction. In a study of the fish assemblage of the Pearl River Estuary, China, Zhou et al., (2019) found that the composition of ecological types or estuarine use guilds varied both seasonally and spatially. A longitudinal change was observed which reflected the variable ability of various species to penetrate either fresh or marine waters.…”

“…Seasonal change in species richness and estuarine use functional guilds were also observed in relation to the reproduction, recruitment and migration patterns of the various groups of species. Numbers of amphidromous and freshwater species increased in spring with high numbers of marine species occurring in summer (Zhou et al., 2019).…”