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Shuai F.M.,Pearl River Fisheries Research Institute | Shuai F.M.,Key Laboratory of the Conservation and Ecological Restoration of Fishery Resource in the Pearl River | Li X.H.,Pearl River Fisheries Research Institute | Li X.H.,Key Laboratory of the Conservation and Ecological Restoration of Fishery Resource in the Pearl River | And 6 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2016

Bighead carp, Aristichthys nobilis (Cyprinidae, Hypophthalmichthys), is one of the four big traditional domestic carp species (along with black carp, grass carp, and silver carp). It is a large fish of high commercial importance because of its palatability and popularity with Chinese consumers. The size of the bighead carp population in China has decreased significantly in recent years, because of various environmental stressors and habitat losses due to dam construction, pollution, and overfishing. In this study, we investigated the ecology of bighead carp breeding in the Pearl River, which is a large subtropical river and the longest river in southern China. This study was based on a dataset generated by sampling at a fixed station (23° 2’ 4G” N, 112° 27’ 5” E) every 2 d, from 2GG6 to 2013. The earliest bighead carp larvae were captured on April 13, 2008, and the latest were found on October 7, 2006. The breeding season primarily lasted from May to August and accounted for 99% of all annual spawning. The total number of larvae found decreased gradually from 2006 to 2011, and then increased significantly in 2011. The date of the earliest recorded spawning did not change over the years, but the date of the latest spawning day occurred earlier each year, indicating that the length of the spawning period (interval between the first and last spawning days of the year) has decreased over time. Our results also show that peak spawning occurs earlier each year. We used cross-wavelet analysis with phase angle and coherency parameters to analyze the relationship between the abundance of bighead carp larvae and the local hydrological conditions. Simulation studies have shown that the spectral signature produced by the cross-wavelet method is a useful approach to developing an objective and quantitative understanding of how river discharge affects the population size of bighead carp larvae. Discharge was positively correlated with the abundance of bighead carp larvae, though larval occurrence always lagged behind discharge. That is, water discharge acted as a trigger for the spawning of bighead carp. Simulation studies have shown that an increase in water discharge >5 × 103 m3/s and lasting at least 2 d is a prerequisite for the bloom spawning of bighead carp in the Pearl River. This study was undertaken as part of a long-term investigation of the Pearl River’s wild fisheries resources, and our results will help guide their protection and management. The wavelet approach is a particularly promising method of analyzing ecological data such as the relationship between hydrological conditions and fish larva occurrence. Our results will help pave the way for the quantitative analysis of the impact of the environment on an organism. We propose that frequency and scale domain methods, in the form of wavelet transforms, can serve as useful probes during preliminary investigations of fisheries data, in order to elucidate the mechanisms underlying changes in fish diversity and abundance. We conclude with a discussion about the role wavelet analysis could play in appropriately guiding flexible probabilistic models linking fisheries with environmental covariates. © 2016, Ecological Society of China. All rights reserved.

Shuai F.,Pearl River Fisheries Research Institute | Shuai F.,Key Laboratory of the Conservation and Ecological Restoration of Fishery Resource in the Pearl River | Shuai F.,University Paul Sabatier | Li X.,Pearl River Fisheries Research Institute | And 8 more authors.
PLoS ONE | Year: 2016

Knowledge of temporal patterns of larval fish occurrence is limited in south China, despite its ecological importance. This research examines the annual and seasonal patterns of fish larval presence in the large subtropical Pearl River. Data is based on samples collected every two days, from 2006 to 2013. In total, 45 taxa representing 13 families and eight orders were sampled. The dominant larval family was Cyprinidae, accounting for 27 taxa. Squaliobarbus curriculus was the most abundant species, followed by Megalobrama terminalis, Xenocypris davidi, Cirrhinus molitorella, Hemiculter leuscisculus and Squalidus argentatus. Fish larvae abundances varied significantly throughout the seasons (multivariate analyses: Cluster, SIMPROF and ANOSIM). The greatest numbers occurred between May and September, peaking from June through August, which corresponds to the reproductive season. In this study, redundancy analysis was used to describe the relationship between fish larval abundance and associated environmental factors. Mean water temperature, river discharge, atmospheric pressure, maximum temperature and precipitation play important roles in larval occurrence patterns. According to seasonal variations, fish larvae occurrence is mainly affected by water temperature. It was also noted that the occurrence of Salanx reevesii and Cyprinus carpio larvae is associated with higher dissolved oxygen (DO) concentrations, higher atmospheric pressure and lower water temperatures which occur in the spring. On the other hand, M. terminalis, X. davidi, and C. molitorella are associated with high precipitation, high river discharge, low atmospheric pressure and low DO concentrations which featured during the summer months. S. curriculus also peaks in the summer and is associated with peak water temperatures and minimum NH3-N concentrations. Rhinogobius giurinus occur when higher atmospheric pressure, lower precipitation and lower river discharges occur in the autumn. Dominant fish species stagger their spawning period to avoid intraspecific competition for food resources during early life stages; a coexistence strategy to some extent. This research outlines the environmental requirements for successful spawning for different fish species. Understanding processes such as those outlined in this research paper is the basis of conservation of fish community diversity which is a critical resource to a successful sustainable fishery in the Pearl River. © 2016 Shuai et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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