Mitochondrial DNA diversity of <Emphasis Type="Italic">Glyptothorax zanaensis</Emphasis> (Wu et al., 1981) populations in Nu River,China

The hillstream fish, Glyptothorax zanaensis (Wu et al., Oceanol Limnol Sin 12:74–79, 1981) is a freshwater teleost species belonging to the order Siluriformes, endemic to Nu River and Lancang River basin. Because wild stocks of G. zanaensis have declined substantially in recent years, owing to overexploitation, pollution, illegal fishing practices and the development of hydroelectricity in the Nu River, the populations of G. zanaensis have markedly declined in recent years. We studied the mitochondrial DNA cyt b gene to assess the genetic diversity of G. zanaensis in seven tributaries of the Nu River. Seventy variable sites defined 15 haplotypes in 153 individuals. Haplotype diversity and nucleotide diversity were 0.542 ± 0.014 and 0.011 ± 0.007, respectively. The Sunzu River site had the highest haplotype diversity (Hd, 0.893 ± 0.014) and nucleotide diversity ( Pi, 0.010 ± 0.012). Genetic diversity was low in the Dong River, Fengwei River and Mengtong River. Pairwise F _ST values ranged from 0.00 to 1.00. Significant F _ST values were found for Sunzu River sampled sites paired with all other populations and Mengtong river sampled site paired with the others. Furthermore, the Nanpeng River sampled site was significantly differentiated from the Luoming River, Dong River and Fengwei River sampled sites. Such knowledge is essential for developing appropriate policies for the rational management of G. zanaensis.     

中国银鱼的多样性及其保护对策

中国是世界银鱼（银鱼科Salangidae的简称）的起源地和主要分布区,在中国东部近海和各大水系的河口共分布有世界17种银鱼中的15种,其中特有种6种。银鱼营养价值和经济价值均很高,是重要的经济鱼类。银鱼生活周期短、世代离散、生殖力和定居能力强。作为典型的r对策者,银鱼对环境变化敏感且反应迅速,种群消长快,在漫长的进化过程中形成了其种间食性、生长和繁殖等生物学和生态学特征的丰富的多样性。然而我国的银鱼天然资源却因围湖造田、过度捕捞、环境污染和生境破碎化等多种因素的影响而持续衰退,各种银鱼的天然资源都不同程度地下降,物种分布范围显著缩小,个别物种渐危。本文在综述我国银鱼生物学、生态学和生物多样性研究的基础上,分析了我国银鱼研究及其物种多样性和种质资源保护工作中所面临的问题;呼吁审视银鱼移植增殖的生态效应,加强银鱼的基本生态学研究和生物多样性保护,并提出我国银鱼资源保护和可持续利用的对策。     

Status of research on Yangtze fish biology and fisheries

The Yangtze is the largest river in China and the third largest river in the world. Being pregnant with plentiful fish resources, it is not only the representative of the areas with biological diversity, but also a cradle of freshwater fisheries in China. In the Yangtze, at present, the fishery resources are seriously depleted; the fishery yield by fishing is significantly reduced; significant changes have occurred on the structure of fish community, with decrease in migratory fish species, reduction in the quantity of the populations of rare, peculiar and economically important fish species and increase in the number of exotic fish species, and severe trend in fish stunting. Habitat fragmentation and shrinkage, resources overexploitation, water pollution and invasion of exotic species are the main causes for threatening fish stocks in the Yangtze River. Since 1950’s, a lot of scientific researches have been conducted on biology of fishes from the Yangtze River and its fisheries to provide scientific basis for their protection. In recent years, measures such as closed spring, fish reserves, artificial enhancement & release, ecological rehabilitation, fishery management and international cooperation have played important roles. Nevertheless, researches on fishes from the Yangtze cannot adequately meet the demand for their protection. Especially, those in the aspects of population ecology of Yangtze fishes, species endangerment mechanism, ecological effects of large hydraulic projects and protection strategy are not deep enough. It is recommended that scientific researches should be conducted in comprehensive survey of Yangtze fish resources, fish endangerment mechanism, techniques in artificial enhancement and release of key species, risk assessment of exotic species, ecological rehabilitation of major fisheries functional zones, etc.     

Antarctic icefishes (Channichthyidae): a unique family of fishes. A review, Part II

Icefish or white- blooded fish are a family of species unique among vertebrates in that they possess no haemoglobin. With the exception of one species which occurs on the southern Patagonian shelf, icefish live only in the cold-stable and oxygen-rich environment of the Southern Ocean. It is still questionable how old icefish are in evolutionary terms: they may not be older than 6 Ma, i.e. they evolved well after the Southern Ocean started to cool down or they are 15–20 Ma old and started to evolve some time after the formation of the Antarctic Circumpolar Current. Individuals of most icefish species with the exception of species of the genus Champsocephalus have been found down to 700–800 m depth, a few even down to more than 1,500 m. Icefish have been shown to present organ-level adaptations on different levels to compensate for the ‘disadvantages’ of lacking respiratory pigments. These include a low metabolic rate, well perfused gills, increased blood volume, increased cardiac output, cutaneous uptake of oxygen, increased blood flow with low viscosity, enlarged capillaries, large heart, and increased skin vascularity. Biological features, such as reproduction and growth, are not unique and are comparable to other notothenioids living in the same environment. Icefish produce large yolky eggs which have a diameter of more than 4 mm in most species. Consequently, the number of eggs produced is comparatively small and exceeds 10,000–20,000 eggs in only a few cases. With the exception of species of the genus Champsocephalus which mature at an age of 3 to 4 years, icefish do not attain maturity before they are 5–8 years old. Spawning period of most icefish species is autumn–winter. The incubation period spans from 2 to 3 months in the north of the Southern Ocean to more than 6 months close to the continent. Growth in icefish to the extent it is known is fairly rapid. They grow 6–10 cm in length per annum before they reach spawning maturity. Icefish feed primarily on krill and fish. Some icefish species were abundant enough to be exploited by commercial fisheries, primarily in the 1970s and 1980s with Champsocephalus gunnari as the main target species. Most stocks of this species had been overexploited by the beginning of the 1990s, some had further declined due to natural causes. Other species taken as by-catch species in fisheries were Chaenocephalus aceratus, Pseudochaenichthys georgianus, and Chionodraco rastrospinosus. Chaenodraco wilsoni was the only species exploited on a commercial scale in the high-Antarctic. Part I was published in the preceding issue of Polar Biology. DOI 10.1007/s00300-005-0019-z.     

SITUATIONS AND CONSERVATION STRATEGIES OF FISH RESOURCES IN THE YANGTZE RIVER BASIN北大核心CSCD

The Yangtze River basin harbors a high degree of fish diversity, with 378 fish species distributing in the mainstream and its attached waters, and 149 of these species are endemic to this river. Meanwhile, the Yangtze River is an important fishery ground in China, contributing more than 60% of the total catch of freshwater fishery. Therefore, the Yangtze River plays important roles in both biodiversity conservation and capture fisheries. However, due to the increasing human activities in the past decades, fish resources in the Yangtze River have declined sharply. Firstly, more and more species have been assessed as threatened and the endangerment categories of many species have been upgraded. Secondly, the population size of many iconic species, such as Acipenser sinensis, the four famous Chinese carps and Coreius guichenoti, have declined continuously. Thirdly, the miniaturization tendencies of major fishing targets have become more and more obvious. Last but not the least, the total fishery catch reduced significantly. Overfishing, water projects construction, enclosing-lake cultivation, water pollution and alien invasion were the main reasons contributing to these changes. In most situations, these factors interacted together, which imposed more damage to the fish resources and increased the difficulty of conservation. In order to protect the fish resources in the Yangtze River effectively, following conservation strategies are suggested: establishing specialized nature reserve, banning commercial fishing completely, implementing river ecological restoration, strengthening scientific research and establishing comprehensive regulation mechanism. © 2019, Institute of Hydrobiology, Chinese Academy of Sciences. All rights reserved.     

Fish and fisheries in the Upper Mekong: current assessment of the fish community, threats and conservation

The Mekong flows north to south, through six countries in south–east Asia. Many studies have concentrated on fish and fisheries in the Lower Mekong, which has been identified as one of the largest inland fisheries in the world with an incredibly rich diversity of species. In contrast, fish and fisheries in the Upper Mekong (Lancang River) have remained relatively undocumented. In this paper, we synthesized information on freshwater fish biodiversity and fisheries in the Upper Mekong and documented 173 species and subspecies (including 87 endemic species) among 7 orders, 23 families and 100 genera. We divided the Upper Mekong into 17 sub-basins based on Digital Elevation Model (DEM) and then used fish species data to cluster the sub-basins. Four parts (the headwater, the upper reach, the middle reach and the lower reach) and one lake have distinct fish species communities associated with them. There was a linear relationship between fish species (x) and endemic species (y) as y = 0.5464x − 3.2926. Relationship between species number or endemic species number (y) and mean altitude (x) can be described as y = −54.352 ln(x) + 460.79 or y = −30.381 ln(x) + 253.85, respectively. Fisheries kept as about 6,000 t from 1989 to 1998, and then steadily increased to 10,000 t in 2004. We reviewed the overall threats to the Upper Mekong fish and fisheries, and found that hydrological alteration is the largest threat in the basin, followed by over fishing and the introduction of exotic species. In terms of specific river sections, water pollution was the most serious threat to fishes in the upper reach of the Upper Mekong, whilst migratory fishes in the lower reach of the Upper Mekong are seriously threatened by the construction of cascade dams. The Buyuan River and the Nanla River were identified as important feeding and spawning habitats for upstream migrant species and should be considered as a priority for conservation.     

Antarctic icefishes (Channichthyidae): a unique family of fishes. A review, Part I

Icefish or white-blooded fish are a family of species, unique among vertebrates in that they possess no haemoglobin. With the exception of one species which occurs on the southern Patagonian shelf, icefish live only in the cold-stable and oxygen-rich environment of the Southern Ocean. It is still questionable how old icefish are in evolutionary terms: they may not be older than 6 Ma, i.e. they evolved well after the Southern Ocean started to cool down or they are 15–20 Ma old and started to evolve some time after the formation of the Antarctic Circumpolar Current. Individuals of most icefish species with the exception of species of the genus Champsocephalus have been found down to 700–800 m depth, a few even down to more than 1,500 m. Icefish have been shown to present organ-level adaptations on different levels to compensate for the ‘disadvantages’ of lacking respiratory pigments. These include a low metabolic rate, well perfused gills, increased blood volume, increased cardiac output, cutaneous uptake of oxygen, increased blood flow with low viscosity, enlarged capillaries, large heart, and increased skin vascularity. Biological features, such as reproduction and growth, are not unique and are comparable to other notothenioids living in the same environment. Icefish produce large yolky eggs which have a diameter of more than 4 mm in most species. Consequently, the number of eggs produced is comparatively small and exceeds 10,000–20,000 eggs in only a few cases. With the exception of species of the genus Champsocephalus which mature at an age of 3 to 4 years, icefish do not attain maturity before they are 5–8 years old. Spawning period of most icefish species is autumn-winter. The incubation period spans from 2 to 3 months in the north of the Southern Ocean to more than 6 months close to the continent. Growth in icefish to the extent it is known is fairly rapid. They grow 6–10 cm in length per annum before they reach spawning maturity. Icefish feed primarily on krill and fish. Some icefish species were abundant enough to be exploited by commercial fisheries, primarily in the 1970s and 1980s with Champsocephalus gunnari as the main target species. Most stocks of this species had been overexploited by the beginning of the 1990s, some had further declined due to natural causes. Other species taken as by-catch species in fisheries were Chaenocephalus aceratus, Pseudochaenichthys georgianus, and Chionodraco rastrospinosus. Chaenodraco wilsoni was the only species exploited on a commercial scale in the high-Antarctic. Part II will be published in the following issue. DOI 10.1007/s00300-005-0020-6.     

Length–weight relationship of clown knifefish Chitala chitala (Hamilton 1822) from the River Ganga basin, India

This study describes the length–weight relationship (LWR) of the clown knifefish, Chitala chitala, in the River Ganga basin, India. A total of 221 specimens ranging from 31 to 120 cm total length (TL) and 550 to 12 000 g total weight (TW) were collected. Chitala chitala constitutes an important component of riverine fisheries of India and is considered one of the most commercially important and highly priced foods in addition to being an aquarium fish. The species has recently undergone heavy fishing pressure, leading to an alarming decline in natural populations and deserving of high conservation importance. Length–weight relationships of C. chitala from wild populations had not yet been studied. Hence, the study objective was to evaluate length–weight relations of C. chitala from eleven populations in order to help in conservation and management of the riverine population.     

An individual-based model applied to the study of different fishing strategies of Pintado Pseudoplatystoma corruscans (Agassiz, 1829)

The decline in stocks of commercial fish species has been documented in several regions of the world. This decline is due partially to the effect of evolutionary pressure caused by the management of fishing activity, which reduces the size of fish after a few generations. In this paper, the population dynamics of the Pintado Pseudoplatystoma corruscans, one of the main commercial species of freshwater fish in Brazil, were simulated considering different scenarios of fishing mortality and different minimum and maximum lengths of capture. The results show that selective fishing based on the different proposed selectivity curves can result in an evolution-mediated increase in the growth rate of the fish, the biomass and the catch. This suggests that appropriate changes in Brazilian legislation can contribute to the sustainability of fisheries and to conservation of the fish stocks exploited by man.     

Mitochondrial DNA reveals low population differentiation in elongate loach, <Emphasis Type="Italic">Leptobotia elongata</Emphasis> (Bleeker): implications for conservation

Elongate loach (Leptobotia elongata (Bleeker)), an endemic fish species to China, is a famous ornamental freshwater fish. Here, a comparative study of mtDNA control region (D-loop) (835 bp) sequences was performed to analyze its wild population structure and evaluate the genetic diversity for 110 individuals from five locations in the upper reaches of the Yangtze River, China. A total of 49 polymorphic sites and 45 haplotypes yielded high haplotype diversity (h = 0.952), but low nucleotide diversity (π = 0.00454) as that of many fish species. Sequence divergences between haplotypes ranged from 0.0033 ± 0.0011 to 0.0050 ± 0.0012 in intra-groups, and from 0.0037 ± 0.0.0011 to 0.0050 ± 0.0012 between groups. Significant values of Tajima’s D (−1.86383, P < 0.01) and Fu’s F _S (−25.93, P < 0.01), together with uni-modal mismatch distribution, indicated a recent genetic bottleneck or population expansion of the species. Analysis of molecular variance (AMOVA) indicated a small amount of differentiation among groups (1.7%); most of the total variation occurred within groups (98.3%). Also, there was no significant population structure (F _ST = 0.017, P > 0.05), and estimates of gene flows among groups were extremely high (Nm = 28.88), suggesting low genetic divergence between populations in the species. The lack of genetic differentiation among groups is most likely due to the combined gene flow from the downstream movement of eggs and larvae with currents and the upstream or downstream migration of adults throughout the distribution. These groups of L. elongata distributed in upper reaches of the Yangtze River should be considered as a single management unit.     

Genetic differentiation of a primitive teleost,the African bonytongue Heterotis niloticus,among river basins and within a floodplain river system in Benin,West Africa

Examination of eight microsatellite DNA loci revealed high levels of genetic differentiation among populations of the African bonytongue Heterotis niloticus from three river basins that constitute important fishing areas in Benin. Low levels of population genetic differentiation were detected within the Ouemé–Sô River floodplain system. These results have important implications for conservation and management of stocks supporting important inland fisheries in West Africa.     

Population genetics of wild Siniperca knerii Garman, 1912 in China as evaluated by microsatellites

The Chinese perch Siniperca knerii Garman, 1912 is an endemic perciform freshwater fish species mainly distributed in the Yangtze River and the Pearl River of China. To evaluate their genetic diversity in these rivers, microsatellite markers were used to assess the genetic structure and genetic variability among nine wild populations of S. knerii. In this study, the 12 loci used were polymorphic, with observed heterozygosity (Ho) ranging from 0.4079 to 0.8886 and polymorphism information content (PIC) ranging from 0.4511 to 0.7146. Results showed that six populations from the Yangtze River had a higher genetic diversity than those from the three Pearl River populations. The Bayesian STRUCTURE analysis recovered genetic clusters that matched localities perfectly or the kind of ecology environment with a significant Fst between them. The findings of this research should provide useful information for management and conservation of S. knerii stocks.     

A mark-recapture population estimate for invasive silver carp (<Emphasis Type="Italic">Hypophthalmichthys molitrix</Emphasis>) in the La Grange Reach,Illinois River

Invasive silver carp (Hypophthalmichthys molitrix) populations have expanded greatly in the Upper Mississippi River System (UMRS) since their introduction in the early 1970s. We conducted a Chapman-modified, continuous Schnabel mark-recapture population and biomass estimate for silver carp (106–901 mm) in the La Grange reach, Illinois River during 2007–2008. We estimated a total of 328,192 (95% CI 231,226–484,474) silver carp (2,544 per river km 1,792–3,756) comprising 705 (95% CI; 496–1,040) metric tons of biomass (5.5 metric tons per river km 3.8–8.1). Long Term Resource Monitoring Program (LTRMP) data from the La Grange reach showed an exponential increase in silver carp catches since 1998, with an intrinsic rate of increase approaching 84%. In 2008, silver carp comprised about 51% of the total LTRMP annual fish collection. To our knowledge, this large river reach may contain the greatest ambient densities of wild silver carp in the world. Our findings provide a target for reduction efforts and also emphasize the importance of the La Grange reach as a source population for potential expansion of the species to the Laurentian Great Lakes.     

Freshwater icefishes (Salangidae) in the Yangtze River basin of China: Spatial distribution patterns and environmental determinants

Synopsis We surveyed 86 lakes affiliated to the Yangtze River to assess the status of natural freshwater icefishes, and to study their spatial distribution patterns and environmental relationships. Results showed that the spatial patterns of icefish diversity and the occupancy of each species related closely to the historical process of habitat fragmentation. Statistical analyses indicated that the spatial structure of the icefish assemblage significantly related to the area- and isolation-related environmental variables. These results illustrated the significant impacts of hydrological engineering (dykes and floodgates) on the historical dynamics of the icefish populations, and shed light on the essentiality and feasibility of conserving and wise using freshwater icefishes by managing suitable habitats and re-connecting the river-lake network in the Yangtze River basin.     

Maximum tag to body size ratios for an endangered coho salmon (<Emphasis Type="Italic">O. kisutch</Emphasis>) stock based on physiology and performance

Many coho salmon stocks (Oncorhynchus kisutch) have been in decline during the past three decades. Canada’s most endangered salmon stock, the Thompson River coho salmon, is being studied extensively as managers attempt to reverse these population declines. Investigators are using acoustic telemetry to track the migratory behaviour and survival of the Thompson River (and other) coho salmon stocks. Coho salmon pre-smolts are relatively small compared with salmonid species that are typically studied using acoustic telemetry; therefore the identification of the appropriate sizes of fish and tags to use is critical. This study tested the effects of surgically implanting the three smallest sizes of acoustic tags currently available on the growth, survival, tag retention, swimming performance and physical condition of coho salmon pre-smolts for 300 days post-surgery. Maximum tag size to body size ratios ranged from 15–17% by fork length and 7–8% by mass for the three tag sizes (11 cm fork length for a 6 × 19 mm tag, 12.5 cm for a 7 × 19 mm tag, and 14 cm for a 9 × 21 mm tag). Based on our results, it is unlikely that coho salmon pre-smolts implanted with acoustic transmitters following these size guidelines would have poor survival in studies of freshwater migratory behaviour as a result of the surgery or the tag.     

Close the High Seas to Fishing?

The world''s oceans are governed as a system of over 150 sovereign exclusive economic zones (EEZs, ∼42% of the ocean) and one large high seas (HS) commons (∼58% of ocean) with essentially open access. Many high-valued fish species such as tuna, billfish, and shark migrate around these large oceanic regions, which as a consequence of competition across EEZs and a global race-to-fish on the HS, have been over-exploited and now return far less than their economic potential. We address this global challenge by analyzing with a spatial bioeconomic model the effects of completely closing the HS to fishing. This policy both induces cooperation among countries in the exploitation of migratory stocks and provides a refuge sufficiently large to recover and maintain these stocks at levels close to those that would maximize fisheries returns. We find that completely closing the HS to fishing would simultaneously give rise to large gains in fisheries profit (>100%), fisheries yields (>30%), and fish stock conservation (>150%). We also find that changing EEZ size may benefit some fisheries; nonetheless, a complete closure of the HS still returns larger fishery and conservation outcomes than does a HS open to fishing.     

Lack of trophic competition among wild and hatchery juvenile chum salmon during early marine residence in Taku Inlet,Southeast Alaska

Early marine trophic interactions of wild and hatchery chum salmon (Oncorhynchus keta) were examined as a potential cause for the decline in harvests of adult wild chum salmon in Taku Inlet, Southeast Alaska. In 2004 and 2005, outmigrating juvenile chum salmon were sampled in nearshore habitats of the inlet (spring) and in epipelagic habitat at Icy Strait (summer) as they approached the Gulf of Alaska. Fish were frozen for energy density determination or preserved for diet analyses, and hatchery stocks were identified from the presence of thermal marks on otoliths. We compared feeding intensity, diets, energy density, and size relationships of wild and hatchery stocks (n = 3123) across locations and weeks. Only hatchery fish feeding intensity was negatively correlated with fish abundance. In both years, hatchery chum salmon were initially larger and had greater energy density than wild fish, but lost condition in early weeks after release as they adapted to feeding on wild prey assemblages. Diets differed between the stocks at all inlet locations, but did not differ for hatchery salmon between littoral and neritic habitats in the outer inlet, where the stocks overlapped most. Both diets and energy density converged by late June. Therefore, if density-dependent interactions affect wild chum salmon, these effects must be very rapid because survivors in Icy Strait showed few differences. Our study also demonstrates that hatchery release strategies used near Taku Inlet successfully promote early spatial segregation and prey partitioning, which reduce the probability of competition between wild and hatchery chum salmon stocks.     

The Transparent Goby, Aphia MinutaReview of Biology and Fisheries of a Paedomorphic European Fish

The transparent goby, Aphia minuta, is one of the few pelagic species of the family Gobiidae. Its geographic range covers the eastern Atlantic Ocean, from Gibraltar to Norway and the Mediterranean basin including the Azov and Black seas. However, it does not occur along the north African coasts. The species is characterized by a unique larval morphology and precocious sexual maturation, i.e. a type of heterochrony known as progenesis. The transparent goby is an annual species that lives less than 1 year, with a maximum size of less than 60 mm. The breeding season is quite long and spawning takes place at least twice during its short lifespan. Just after spawning, all breeders quickly die probably as a consequence of the degeneration of the intestinal epithelium by apoptosis, marking the end of the entire cohort. Spending most of its life in the water column, it is a planktotrophic feeder, relying mainly on small copepods. In turn the transparent goby is preyed on by several species of fish and larger cephalopods. During ontogenesis, t hree phases characterize the species: a “pelagic phase”, composed of larval stages hatched from demersal eggs that inhabit shallow coastal waters; an “aggregated phase”, composed of juveniles that gather in schools in shallow waters during winter; finally, a “demersal phase”, composed of adults that in spring migrate offshore with a more dispersed distribution in proximity of the bottom. Despite its small size, this species is largely exploited by local small-scale fisheries developed mainly in the western and central Mediterranean. The fishing fleets, harboured in several sites in Spain and Italy, are generally composed of small vessels. Most of them use very selective gear such as purse-seine nets to catch schools of the transparent goby during winter. For these artisanal fisheries, the transparent goby represents, although seasonally, a very important source of income, yielding locally up to more than 100 tons per fishing season and 75 kg/vessel/day. This review critically examines the published literature on the biology and fisheries of the transparent goby, aiming to provide useful tools for appropriate management and for a sustainable exploitation of this important resource.     

Population Genetic Structure of the Yangtze Finless Porpoise (Neophocaena phocaenoides asiaeorientalis): Implications for Management and Conservation

Understanding the population genetic structure is a prerequisite for conservation of a species. The degree of genetic variability characteristic of the mitochondrial DNA control region has been widely exploited in studies of population genetic structure and can be useful in identifying meaningful population subdivisions. To estimate the genetic profile of the Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis), an endangered freshwater population endemic to China, the complete mtDNA control region was examined in 39 individuals belonging to seven different stocks inhabiting the middle and lower reaches of the Yangtze River. Very low genetic diversity was found (nucleotide diversity 0.0011± 0.0002 and haplotypic diversity 0.65± 0.05). The mtDNA genetic pattern of the Yangtze population appears to indicate a founder event in its evolutionary history and to support the marine origin for this population. Analyses by F_st and Φ_st yielded statistically significant population genetic structure (F_st = 0.44, P < 0.05; Φ_st = 0.36, P < 0.05). These results may have significant implications for the management and conservation of the Yangtze finless porpoise in the future.     

Biology, fisheries, and conservation of sturgeons and paddlefish in China

This paper reviews five of the eight species of acipenseriforms that occur in China, chiefly those of the Amur and Yangtze rivers. Kaluga Huso dauricus and Amur sturgeon Acipenser schrenckii are endemic to the Amur River. Both species still support fisheries, but stocks are declining due to overfishing. Acipenseriformes of the Yangtze River are primarily threatened by hydroelectric dams that block free passage to spawning and feeding areas. The Chinese paddlefish Psephurus gladius now is rare in the Yangtze River system, and its spawning activities were severely limited by completion of the Gezhouba Dam in 1981. Since 1988, only 3–10 adult paddlefishes per year have been found below the dam. Limited spawning still exists above the dam, but when the new Three Gorges Dam is complete, it will further threaten the paddlefish. Artificial propagation appears to be the only hope for preventing extinction of P. gladius, but it has yet to be successfully bred in captivity. Dabry's sturgeon A. dabryanus is a small, exclusively freshwater sturgeon found only in the Yangtze River system. It is concentrated today in reaches of the main stream above Gezhouba Dam. The fishery has been closed since 1983, but populations continue to decline. Acipenser dabryanus has been cultured since the 1970s, and holds promise for commercial aquaculture; availability of aquacultural methods offers hope for enhancing natural populations. The Chinese sturgeon A. sinensis occurs in the Yangtze and Pearl rivers and seas of east Asia. There is still disagreement about the taxonomy of the Pearl and Yangtze River populations. The Yangtze River population is anadromous. Adults begin spawning at about age 14 years (males) and 21 years (females), and adults spend over 15 months in the river for reproduction. Spawning sites of A. sinensis were found every year since 1982 below the Gezhouba Dam, but it seems that insufficient suitable ground is available for spawning. Since 1983, commercial fishing has been prohibited but more measures need to be taken such as establishing protected areas and characterizing critical spawning, summering and wintering habitats.