The structuring role of artificial structure on fish assemblages in a dammed river of the Pearl River in China

Abstract

To address the fish use patterns of artificial structures mimicking floating macrophytes deployed in a impounded tributary of the Pearl River, China, field experiments were performed from December 2014 to June 2016 using multi-mesh gillnet. The fish assemblages using artificial structures differ in terms of species richness, abundance, body size, diversity indices, and ecological traits from fish assemblages on natural barren habitats of this river. Overall, fish abundance, species richness, Shannon diversity index, and functional richness were higher at the artificial structures than at the control sites, while fish length and functional evenness was greater at the control sites in comparison to artificial structures. The introduction of artificial structures did not result in statistically significant effects on fish biomass as artificial structures attracted more individuals with smaller size. Seasonal changes of chlorophyll-a and transparency may affect the efficiency of artificial structure in harboring fishes. This study revealed that artificial structures, as synthesized habitats, are effective in acting as a “fish attractor” and an alternative tool to provide new habitats for smaller individuals in a dammed river like the Youjiang River which is a structure-less ecosystem.

Use of artificial structures to enhance fish diversity in the Youjiang River, a dammed river of the Pearl River in China

“…The Youjiang River (a major tributary of the Pearl River) extends for 727 km and drains an area of 4.02 × 10 4 km 2 . The Youjiang River is a major tributary of the Xijiang River, which begins in eastern Yunnan and joins the Zuojiang River near Nanning to form the Youjiang River (Zhou et al., 2018). The Youjiang River is regulated by six cascading medium/large sized dams in Wacun, Baise, Dongsun, Naji, Yuliang, and Jinjitan.…”

“…The Youjiang River is regulated by six cascading medium/large sized dams in Wacun, Baise, Dongsun, Naji, Yuliang, and Jinjitan. In a research study done on the fish diversity of the Youjiang River, 80 fish species being recorded in a research of and the dominant species were Hemiculter leucisculus , Toxabramis houdemeri , Oreochromis niloticus , and Squalidus argentatus with relative abundances of 19.55%, 13.56%, 7.71%, and 6.55%, respectively (Zhou et al., 2018). The study area (Donghong Village) was located at 23°46.390′N 106°40.102′E, between the Baise and Naji reservoirs (Figure 1), where the width of the river was 100–150 m. The average water depth in the study area was 6 m, with a water level fluctuation of about 0.5–1 m daily due to the operation of the reservoir.…”

“…Fish sampling was conducted every 3 months from February 2016 (3 months after deployment of structures) to November 2017. All fish were sampled using multimesh gillnets that were 18 m long, 1.5 m height with mesh sizes between 6.25 and 60 mm of the following order: 45, 20, 6.25, 10, 55, 40, 12.5, 25, 15, 60, 35, and 30 mm (Zhou et al., 2018). Three groups of artificial habitats and three control sites were selected for sampling, and three multimesh gillnets were placed in each site.…”

“…The schematic diagram of artificial habitat 7:30 p.m. and were hauled out between 6:30 p.m. and 7:30 a.m. the following day (Zhou et al, 2018). All fish caught in each multimesh gillnet were identified at species level, measured (total length, cm), and weighed (g), separately.…”

“…The Pearl River is the third‐longest river in China, with an abundance fishery resources and rich fish biodiversity. The river supports 385 species of fish, with Cypriniforms being the most dominant (Zhou et al., 2018). However, aquatic habitats have been degraded dramatically, fishery resources have decreased, and fish biodiversity has been continuously threatened over the past few decades due to either direct or indirect human activities.…”