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Fig. 13 in The non-native freshwater fishes of Hong Kong: diversity, distributions, and origins

Fig. 13. Hypophthalmichthys nobilis, aquarium trade, photographed by Heok Hui Tan.

Fig. 15. Colossoma macropomum, 295 in The non-native freshwater fishes of Hong Kong: diversity, distributions, and origins

Fig. 15. Colossoma macropomum, 295 mm SL, aquarium trade, photographed by Heok Hui Tan.

Fig. 18. Synodontis eupterus, 112.6 in The non-native freshwater fishes of Hong Kong: diversity, distributions, and origins

Fig. 18. Synodontis eupterus, 112.6 mm SL, Tai Po Kau Nature Reserve.

Fig. 24. Channa striata, 220 in The non-native freshwater fishes of Hong Kong: diversity, distributions, and origins

Fig. 24. Channa striata, 220 mm SL, Pui O Stream.

Fig. 12. Hypophthalmichthys molitrix, 52 in The non-native freshwater fishes of Hong Kong: diversity, distributions, and origins

Fig. 12. Hypophthalmichthys molitrix, 52 mm SL, Pak Ngau Shek Stream.

Fig. 20 in The non-native freshwater fishes of Hong Kong: diversity, distributions, and origins

Fig. 20. Ophichthys cuchia, Lau Shui Heung Reservoir, photographed by Tommy C.H. Hui.

Fig. 21. Anabas testudineus, 70.7 in The non-native freshwater fishes of Hong Kong: diversity, distributions, and origins

Fig. 21. Anabas testudineus, 70.7 mm SL, Shui Hau Stream.

Fig. 14 in The non-native freshwater fishes of Hong Kong: diversity, distributions, and origins

Fig. 14. Opsariichthys sp., 93.5 mm SL, Tai Lam Chung Reservoir.

opencc-by-4.0May 2023View details →

Assessing the conservation status of Chinese freshwater fish using deep learning

The lack of information on the extinction risk of most species is a fundamental challenge in prioritizing conservation strategies and bending the curve of current biodiversity decline. Machine learning methods have shown promising potential to fill this gap, but their applicability remains to be validated at different taxa (especially aquatic species) and spatial scales. We assessed the extinction risk of 1,162 freshwater fish species in China that have not yet been included in the latest IUCN Red List using multiple neural network algorithms based on datasets of species occurrences, biological traits, phylogeny, and relevant environmental layers. The best deep learning models dramatically improved the assessment coverage from 29.9% (496 species) to 93.2–93.9% (1,545–1,557 species) of the whole fauna with an accuracy of 95.4–99.0%. By combining our prediction results with the IUCN Red List, we found that 23.8–26.5% (394–440 species) of Chinese freshwater fishes were identified as possibly threatened species, which is roughly four times the IUCN assessment. Newly assessed species and threatened species were mainly from the orders Cypriniformes (prediction added: 837–846 species; final threatened: 325–350 species), Siluriformes (113–122; 28–37) and Perciformes (74–76; 18–25). The increase in threatened species richness based on predictions was led by the upper reaches of the Pearl and Yangtze. Overall, our findings suggest that deep learning algorithms can provide robust and time-saving assessments of extinction risk for entire freshwater fish fauna on a large national scale, thereby facilitating relevant conservation prioritization.

opencc-zeroJul 2023View details →

Is my model fit for purpose? Validating a population model for predicting freshwater fish responses to flow management

Models based on ecological processes ("process-explicit models") are often used to predict ecosystem responses to environmental changes or management scenarios. However, models are imperfect and need to be validated, ideally by testing their assumptions and outputs against independent empirical data sets. Examples of validation of process-explicit models are rare. Recently, stochastic population models have been developed to predict the likely responses (over 10-120 years) of a riverine fish (golden perch, Macquaria ambigua) to flow management in the Murray-Darling Basin (MDB) in eastern Australia, one of the world's most regulated river basins. Declines of golden perch (and other species) are a direct consequence of altered hydrology, and managers require information to predict how fish will respond to possible future hydrological conditions to guide the substantial investments in flow management. Here, we use two independent field data sets to validate our population model. We compared model predictions to observed trends to ask: (1) how do predicted population sizes and growth rates compare to observed data? (2) does the correlation between predicted and observed population sizes and growth rates vary among populations? (3) does the correlation between predicted and observed population sizes and growth rates vary across observed hydrological conditions? and (4) how do modelled and observed fish movement rates compare? We found reasonable correlations between fish population sizes and growth rates as predicted by the model and observed in independent data sets for several populations (Aim 1) but the strength of these correlations varied among populations (Aim 2) and hydrological conditions (Aim 3). Predicted and observed fish movement rates were strongly correlated (Aim 4). Population models are frequently used in conservation decision-making but are rarely validated. We demonstrate that: (1) validation can identify model strengths and weaknesses; (2) observed data sets often have inherent limitations that can preclude robust validations; (3) validation is likely be more common if appropriate observed data sets are available; and (4) validation should consider the purpose of modelling. Wider consideration of these messages would contribute to more critical examinations of models so they can be most appropriately used in conservation decision-making.

opencc-zeroAug 2023View details →

Data from: Freshwater fishes maintain multi-trait phenotypic stability across an environmental gradient in aqueous calcium

Reductions in a limiting nutrient might be expected to necessitate compromises in the functional traits that depend on that nutrient; yet populations existing in locations with low levels of such nutrients often do not show the expected degradation of functional traits. Indeed, we previously found that fish of three species, Logperch (Percina caprodes),Pumpkinseed Sunfish (Lepomis gibbosus), and Yellow Perch (Perca flavescens) residing in low-calcium water in the Upper St. Lawrence River nevertheless maintained levels of scale calcium comparable to those of conspecific populations in high-calcium water. However, it remains possible that the maintenance of one functional trait under nutrient-limited conditions could come at the expense of maintaining other functional traits that depend on that same nutrient. Hence, we here extend prior work by examining other calcium-dependent traits: skeletal element sizes and bone densities in the same fish species in the same area. Using radiographs of 101 fish from the three species across four locations (two in high-calcium water and two in low-calcium water), we document multi-trait "homeostasis" along the gradient of water calcium. That is, we did not detect any effect of calcium regime (low-calcium versus high-calcium) on any of the measured variables. Further, effect sizes for the skeletal traits were very low – lower even than effect sizes previously documented for scale calcium. Our results thus show that native fishes maintain phenotype stability across a suite of functional traits linked to calcium regulation, perhaps pointing to an "organismal-level homeostasis" scenario rather than a "trait-level homeostasis" scenario.

opencc-zeroAug 2023View details →

Erosional exhumation of carbonate rock facilitates dispersal-mediated allopatric speciation in freshwater fishes

A fundamental goal of evolutionary biology is to understand the mechanisms that generate and maintain biodiversity. Discovery and delimitation of species represent essential prerequisites for such investigations. We investigate a freshwater fish species complex comprising Etheostoma bellator and the endangered E. chermocki which is endemic to the Black Warrior River system in Alabama, USA, a global hotspot of temperate freshwater biodiversity. Phylogenomic analyses delimit five geographically disjunct species masquerading as E. bellator. Three of these new species exhibit microendemic distributions comparable to that of E. chermocki raising the possibility that they also require protection. The species of the complex are found in streams flowing over carbonate rock and they are separated by waterways flowing over siliciclastic rock, a geographic pattern dictated by the underlying stratigraphy and structural geology. Over time, rivers have eroded downward through layers of siliciclastic rocks in the basin, gradually exposing underlying carbonate rock, the substrate of suitable habitat today. Our results suggest that episodic dispersal to patches of suitable habitat set the stage for allopatric speciation in the species complex. Our study suggests that the presence of heterogeneous rock can facilitate dispersal-mediated allopatric speciation in freshwater organisms in the absence of external tectonic or climatic perturbations.

opencc-zeroOct 2023View details →

A key evolutionary step determining osmoregulatory ability for freshwater colonisation in early life stages of fish

<div class="page"> <div class="layoutArea"> <div class="column"> Colonisation of freshwater habitats by marine animals is a remarkable evolutionary event that has enriched biodiversity in freshwater ecosystems. The acquisition of tolerance to hypotonic stress during early life stages is presumed to be essential for their successful freshwater colonisation, but very little empirical evidence has been obtained to support this idea. This study aimed to comprehend the evolutionary changes in osmoregulatory mechanisms that enhance larval freshwater tolerance in amphidromous fishes, which typically spend their larval period in marine (ancestral) habitats and the rest of their life history stages in freshwater (derived) habitats. We compared the life history patterns and changes in larval survivorship and gene expression depending on salinity among three congeneric marine-originated amphidromous goby species (Gymnogobius), which had been suggested to differ in their larval dependence on freshwater habitats. An otolith microchemical analysis and laboratory-rearing experiment confirmed the presence of freshwater residents only in G. urotaenia and higher larval survivorship of this species in the freshwater condition than in the obligate amphidromous G. petschiliensis and G. opperiens. Larval whole-body transcriptome analysis revealed that G. urotaenia from both amphidromous and freshwater-resident populations exhibited the greatest differences in expression levels of several osmoregulatory genes, including aqp3, which is critical for water discharge from their body during early fish development. The present results consistently support the importance of enhanced freshwater tolerance and osmoregulatory plasticity in larval fish to establish freshwater forms, and further identify key candidate genes for larval freshwater adaptation and colonisation in the goby group. </div> </div> </div>

opencc-by-4.0Jun 2017View details →

Figure 1 in A review of amphidromous freshwater fishes of the Chocó biogeographical region (Colombia and Ecuador): diversity, ecology, fisheries and conservation

Figure 1. – Map of the Chocó Biogeographical Region in the Pacific of Colombia and Ecuador.