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In conservation biology, knowing the life history strategy of a species is crucial for deciding which stage needs the greatest protection: reproduction, juveniles, or adults. Here, we compiled biological data for 83 Yangtze River fish species, constructed their life tables and conducted elasticity analyses, which calculates the proportional contribution of each vital rate (age-specific survival and fecundity) to the annual population multiplication rate. Life tables showed that, for our analyzed species, the survival rate of age 0 fish was extremely low, ranging from 1.25 × 10 to 1.74 × 10 year. All species showed a type III survivorship curve. Elasticity analysis revealed slow-fast continuum life histories ranging from species with a high contribution of fertility elasticity to the population growth rate, but lower juvenile and adult survival elasticity, as well as early maturation and short generation time to species that mature late, possess a long generation time, exhibit low fertility elasticity, and a high adult or juvenile survival elasticity. In addition, the analysis of all the species showed that fertility elasticity was significantly smaller than the sum of juvenile and adult survival elasticity, indicating the need to increase the juvenile and adult survival rates of Yangtze fish rather than focusing only on protecting reproduction and age 0 survival via a breeding season fishing ban which is the current conservation practice. Since overfishing has been proposed as the major factor responsible for the decline of Yangtze fish populations, we further suggest that controlling fishing pressure on juvenile and adult fish is another key conservation requirement. [ABSTRACT FROM AUTHOR]

The aim of this study is to evaluate the application of magnetic resonance imaging (MRI) to assess ovarian maturation in live female Rhinogobio ventralis (Sauvage & Dabry de Thiersant, 1874). The fish were randomly collected from the Jiangjin area of the Yangtze River between January and April 2014. Magnetic resonance imaging was performed using a 3.0 T clinical MRI scanner with a brain coil and two pulse sequences (IDEAL and 3D CUBE) were employed. Magnetic resonance and histologic images at different stages of ovarian maturation (I–IV) were acquired. An empirical equation (y = −0.1 + 1.56 × x) was derived by traditional method to describe the relationship between the gonadosomatic index (y) and the percentage volume of the ovary (x). A significant correlation (R 2 = 0.977, P < 0.01, N = 53) was found between measurements of the percentage volume of the ovary by MRI and traditional methods. The research findings suggested that MRI was a reliable, rapid, and noninvasive method to assess stages of ovarian maturity in female R. ventralis . [ABSTRACT FROM AUTHOR]

Rock carp is an endemic fish in the upper Yangtze River basin. Its populations have dramatically declined in the recent years due to human activities, such as overfishing and damming. In the present study, with the aim to give suggestions for better conservation, we investigated age, growth, and reproductive biology of the rock carp using samples collected between 2007 and 2013 from the Chishui River. The results indicate that there are no significant differences between the length-weight relationships of females and males ( W = 0.015SL). The von Bertalanffy growth curves computed by the observed length-at-age data could be expressed as L = 64.9(1 − e). The estimated length at 50 % sexual maturity for males is 24.2 cm (approximately aged 4) and 37.0 cm for females. Female gonad analysis suggests that rock carp is a batch spawner, which can spawn at least twice during the reproductive season, from April to August. Standard length and age of 86.5 % individuals were below 25 cm and 4 years, respectively, indicating that the exploitation is too intensive and that populations are undergoing miniaturization. These data corroborate that a combination of natural and anthropogenic factors has caused a sharp decline in wild populations during recent years, calling for immediate design and implementation of conservation measures for this species. [ABSTRACT FROM AUTHOR]

The Tongling ore district of the Middle-Lower Yangtze metallogenic belt is a famous Cu-Au-Fe-S polymetal region, and its tectonic deformation, magmatic evolution, and metallogenic processes have been studied for decades. In this article, we propose a comprehensive tectonic-magmatic-metallogenic model of the ore-forming mechanism constrained by magmatism and regional deformation. In the Tongling district, the tectonic regime underwent two transitions. (1) In the Middle Triassic, the tectonic regime transitioned from quiescence to intense compression. During contraction, the lithosphere thickened and a series of NE-trending folds developed in the cover sequence; because of the multi-layered structure of this caprock, bedding faults, typically cut by steeply dipping faults, developed widely. (2) From 134 to 150 Ma, the tectonic regime changed from compression to extension. During this transition, mantle-crust interaction was prominent; ore-bearing magma was generated by the mixing of crust-derived and mantle-derived melts triggered by delamination of the thickened lithosphere. Meanwhile, detachment faults developed along the interfaces, for example between the lower and upper crust, serving as emplacement sites for several magma chambers. Ore-bearing magma dikes containing large amounts of volatiles derived from a shallow chamber at about -10 km depth migrated into the cover sequence along the pre-existing steeply dipping faults. Melt injection reworked the structural framework, facilitating further development of steeply dipping faults, as well as the vertical transport of ore-bearing fluids. Hydrothermal fluids derived from the emplaced magmas not only formed a range of deposits, including skarns, porphyries, and cryptobreccias around the intrusions but also widely replaced carbonates along bedding-parallel faults and formed so-called stratabound skarn ore bodies, as well as superimposing synsedimentary orebodies developed in the quiescence stage to form several large polymetallic hydrothermal ore deposits. Various types of ore deposits at different depths are clustered in a single orefield, composing a multi-layered mineralization network. In the network, skarn deposits dominate and are characterized by fluid immiscibility processes and diverse element enrichments. The intense mineralization in the Tongling region was caused by the abundance of metals derived from the mantle, favourable ore-controlling structures, and widespread fluid boiling of magmatic hydrothermal fluids, which facilitated metal deposition during the Mesozoic, as well as the superposition of Mesozoic hydrothermal reworking of earlier Palaeozoic sedimentary ore bodies. [ABSTRACT FROM AUTHOR]