Do Hydropeaking Flows Alter Juvenile Fish Growth Rates? A Test with Juvenile Humpback Chub in the Colorado River

Riverine ecosystems have been altered in many large catchments by dam development to provide water, power, flood control and navigational benefits to humans. Conservation actions in these river ecosystems are commonly focused on minimum releases of water to downstream ecosystems. Increasingly minimum release approaches are being replaced with ‘experimental’ flows that mimic natural conditions in order to benefit riverine ecosystems. While these new policies are intuitive in their design, there is limited data of how riverine ecosystems actually respond to more natural flows. A test of more natural steady‐flow water release was compared with typical fluctuating hydropower flows in the adaptive management programme at Glen Canyon Dam, Arizona, during 2008–2011 to assess growth improvements of endangered juvenile humpback chub Gila cypha. Our results are counterintuitive and show that more natural steady flows reduced growth rates of juvenile humpback chub compared with fluctuating flows when both treatments occurred within the same year. Daily growth rates during steady flows of 2009 and 2010 were 0.05 and 0.07 mm day^?1 slower, respectively, than fluctuating flows those same years, despite similar water temperatures. Juvenile humpback chub also grew more slowly during steady flows that occurred in the same season. During the summer, juvenile humpback chub grew 0.12 and 0.16 mm day^?1 in fluctuating flow regimes in 2009 and 2010, respectively, and only 0.07 mm day^?1 in the experimental steady flow regime in 2011, despite higher water temperatures. Our results suggest that optimal conservation management policies for endangered species in regulated rivers may not always be achieved with more natural flows. Copyright © 2014 John Wiley & Sons, Ltd.     

Consumer‐diet discrimination of δ13C and δ15N: Source‐ and feeding‐oriented patterns based on gut content analysis in a large subtropical river of China

Understanding the trophic discrimination (?¹³C and ?¹⁵N) between consumers and diets in fluvial systems remains difficult because of the variable food sources and complex predator–prey interactions from headwaters to the estuaries. Here, stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes in fish and invertebrates from a large subtropical river in southern China were determined to explore trophic discrimination in conjunction with a gut content analysis. The ?¹³C values showed significant differences (p < .05) among functional feeding groups, with fish, shrimp, and insect scrapers presenting higher ?¹³C values (1.20 ± 0.23‰ to 1.51 ± 0.31‰) than other groups. The ?¹⁵N values varied significantly between invertebrates (0.64 ± 0.17‰ of insect collector‐gatherers to 1.63 ± 0.36‰ of shrimp predators) and fish (1.98 ± 0.19‰ of detritivores to 2.71 ± 0.43‰ of crustaceavores) and exhibited an increasing tendency from primary to secondary consumers. A linear regression analysis revealed that the longitudinal changes in ?¹³C and ?¹⁵N were closely associated with the δ¹³C of periphyton, the δ¹⁵N of particulate organic matter (POM) in water, and the relative contribution (%) of periphyton and organic detritus to the diet composition of consumers. These results indicated that discrimination factors might not only be influenced by the isotope signatures of basal food sources but also downstream shifts in dominant food items utilized by consumers. In particular, trophic discrimination between periphyton– and detritus–based food chains, such as “epilithic diatoms–shrimp scrapers–crustaceavorous fish” and “POM–bivalves–molluscivorous fish,” displayed regionally specific patterns. When back‐calculating to the diet assimilation and trophic position in subtropical streams and rivers, we suggest using the basin‐scale ?¹³C value of 0.96 ± 0.26‰ for all consumers and ?¹⁵N values of 1.07 ± 0.32‰ for invertebrates and 2.38 ± 0.37‰ for fish.     

Spatial and temporal distribution of ichthyoplankton during an unusual period of low flow in a tributary of the São Francisco River,Brazil

Flow‐dependent fish specialists require specific conditions for reproduction, so the success and reproductive intensity of these animals are determined by the flood regime. Thus, this study investigated the spatial and temporal reproductive patterns of fish, especially migratory Prochilodus species (flow‐dependent specialists) in an unusual period of low flow in the Pará River sub‐basin, one of the main tributaries of the upper São Francisco River. For this, ichthyoplankton collections were carried out between November 2013 and February 2014. Data were analysed considering the spatial and temporal variations in density of eggs and larvae for the upper, middle, and lower portions of the Pará River sub‐basin, and correlating this to some environmental variables. The results showed that the small headwater stretch of the Pará River is one relevant spawning area for migratory fish species. However, this area is isolated by the Cajuru reservoir, which makes it uncertain the recruitment of these embryos, due to interruption of natural drift between spawning/nursery areas caused for reservoirs. Larvae of newly hatched migratory species found in tributaries of the lower Pará River sub‐basin also indicate these species use these tributaries as spawning grounds and migratory routes. The period in which the research was conducted represented the most atypical low flow, one in the last 75 years, resulting in the low variability in the environmental parameters. Although few parameters increased briefly in this low flow period influenced by greater rainfall in December, this precipitation was possibly responsible for the final gonadal maturation and spawning of migratory species.     

Estrogen Receptors Mediated Negative Effects of Estrogens and Xenoestrogens in Teleost Fishes—Review

Estrogen receptors (ERs) play a key role in many biochemical and physiological processes, that are involved in maintaining organism homeostasis. At the most basic level, they can be divided into nuclear estrogen receptors and membrane estrogen receptors that imply their effect in two ways: slower genomic, and faster non-genomic. In these ways, estrogens and xenoestrogens can negatively affect animal health and welfare. Most of the available literature focuses on human and mammalian physiology, and clearly, we can observe a need for further research focusing on complex mutual interactions between different estrogens and xenoestrogens in aquatic animals, primarily fishes. Understanding the mechanisms of action of estrogenic compounds on the ERs in fishes and their negative consequences, may improve efforts in environmental protection of these animals and their environment and benefit society in return. In this review, we have summarized the ER-mediated effects of xenoestrogens and estrogens on teleost fishes metabolism, their carcinogenic potential, immune, circulatory, and reproductive systems.     

9种近海鱼重金属污染状况及食用安全性评价

为探究近海鱼重金属污染状况及其食用健康风险,采用电感耦合等离子体质谱法、液相色谱-原子荧光光谱法和原子荧光光谱法对蓝圆鲹、蓝点马鲛等9种近海鱼的头、尾、皮、骨、鱼肉和内脏中铅（Pb）、镉（Cd）、铬（Cr）、总砷（As）、无机砷和总汞（Hg）的含量进行测定,并采用污染指数法和目标危害系数法等方法进行评价。结果表明：54组样品中有9组Cr含量超过国家标准（GB 2762—2017《食品中污染物限量》）,超标率16.67%;7组样品Cd含量超标,超标率12.96%;2组样品Pb含量超标,超标率3.70%;无机As、总Hg含量均未超标。分析近海鱼不同部位重金属含量,54组样品中有7组鱼内脏重金属含量超标,超标率12.96%;鱼头、鱼尾各有3组重金属含量超标,超标率5.56%;鱼肉中重金属含量均未超标。单因子污染评价结果显示,Cr污染最为严重,Cd次之,之后是Pb。无机As及总Hg相对污染指数最低。综合污染指数评价显示,沙丁鱼内脏最高,达到3.877,处于重度污染级别。蓝圆鲹、蓝点马鲛、鲭鱼和金线鱼的内脏的综合污染指数属于中度污染级别。所有鱼肉组织的单一和多种重金属复合风险系数均小于1。由此可...     

不同解冻方式对生食鱼片解冻品质的影响

为探究不同解冻方式对生食鱼片品质的影响,以虹鳟鱼为研究对象,对冷藏室解冻、水浴解冻、微波解冻和常温空气解冻4种不同解冻方式下生食鱼片的感官、解冻速率、解冻损失率、色泽、菌落总数、挥发性盐基氮（total volatile basic nitrogen,TVB-N）含量、微观组织结构、质构特性、水分迁移和挥发性气味特征等进行测定。结果表明：冷藏室解冻的生食鱼片感官得分虽显著高于其余3种解冻方式（P<0.05）,但其解冻速率明显低于其余3种解冻方式;水浴解冻组的解冻损失率显著低于其余3种解冻方式（P<0.05）,有利于生食鱼片水分的保留,且其TVB-N含量及菌落总数仅较微波解冻组分别高1.02 mg/100 g、0.46(lg(CFU/g)),其感官得分仅较冷藏室解组冻低3.19分;微波解冻组的白度、菌落总数和TVB-N含量结果虽均优于其他3种解冻方式,能有效抑制解冻过程中色泽的改变、微生物的滋生和缓解生食鱼片中氨及胺类等碱性含氮物质的产生,但微波解冻使生食鱼片受热不均导致其部分熟化的现象明显,其感官和质构指标均较差,不适宜用于解冻生食鱼片;相较于其他3种解冻方式,常温空气解冻...     

Improved fish migration optimization method to identify PEMFC parameters

In a worldwide environment context where the emergency need to decrease pollutant emissions is an important issue, the research for solutions is increasing. Fuel cell technology is anticipated to become a practicable approach for solving the problem of pollution due to its environmentally friendly characteristics. In this work, a novel problem formulation is suggested for the efficient recognition of PEMFC parameters which the solving is by using the Improved Fish Migration Optimizer (IFMO) technique. After coding the steps of the algorithm in MATLAB, the objective function is resolved for the fuel cell. Comprehensive simulations evaluate the formulation performance with the suggested and traditional objective functions; then, the outcomes are compared. To confirm the suggested formulation ascendancy compared to the traditional curve-fitting method, a complete assessment based on convergence rate, the value of the objective function, and the value of absolute voltage error are performed. The achieved value of the objective function, absolute voltage error, and average time of computation is 0.005, 0.4, and 1.63, respectively. Environmentally, the combustion of hydrogen and its use in PEMFC produce no carbon dioxide.     

Ecological patterns of fish distribution in the Slave River Delta region,Northwest Territories,Canada, as relayed by traditional knowledge and Western science

Indigenous community members along the Slave River in Canada have voiced their concerns for the health of ecosystems under pressure from resource extraction, hydroelectric development and global climate change. We present a test case of traditional knowledge and scientific results about the spawning and migration patterns of fish in the Slave River and Delta. This dual knowledge system approach elucidates the broader connectivity of local study regions and can improve monitoring programmes by extending beyond the usual context/confines of the present or recent past, increasing the spatial and temporal range of system information.     

Biogenic amines assessment during different stages of the canning process of skipjack tuna (Katsuwonus pelamis)

The present research focused on the biogenic amines (BAs) formation in skipjack tuna (Katsuwonus pelamis) throughout the whole canning process. In agreement with its wide employment on this species, on‐board brine immersion freezing (BIF) was tested as post‐mortem processing. The study included fish samples corresponding to different stages of the canning process such as frozen, thawed, cooked and canned; after cooking, two kinds of tuna muscles were considered, that is, whole fillets (main product) and grated muscle (off‐product arising from small pieces). For the BAs (tryptamine, putrescine, cadaverine, histamine, spermidine and spermine) assessment, an HPLC‐DAD method was developed and validated in skipjack tuna samples, in agreement with different parameters such as suitability, linearity, limits of detection and quantification, precision, accuracy and robustness. Tuna submitted on‐board to BIF procedure provided low levels of spermine and spermidine (up to 27.6 mg kg^?1), while contents on the remaining BAs maintained below the limit of detection. Throughout the different stages of the canning process, skipjack tuna showed a low formation of most BAs; interestingly, histamine content was found below 10.6 mg kg^?1 level. The highest values were obtained for spermidine, these related to cooked grated tuna (from 22.6 to 66.7 mg kg^?1) and canned grated tuna (from 70.6 to 104.4 mg kg^?1). Values for pH assessment in all kinds of tuna samples corroborated the results obtained for BAs determination. BIF procedure proved to be an amenable post‐mortem processing to guarantee the quality of canned skipjack tuna.     

Three‐dimensional numerical simulations of smooth,asymmetrically roughened,and baffled culverts for upstream passage of small‐bodied fish

Traditional box culvert designs lead to development of high velocity zones in the culvert barrel that often impede upstream migration of fish. Herein, three‐dimensional Reynolds‐averaged Navier‐Stokes (RANS)‐ and Large eddy simulation (LES)‐based computational fluid dynamics (CFDs) simulations were performed to compare the effectiveness of smooth, asymmetrically roughened, and corner‐baffled barrels, in creating low‐velocity zones (LVZs) and providing opportunity for upstream passage of small‐bodied fish. The results revealed distinctive benefits provided by the asymmetrically roughened and corner‐baffled barrels relative to the smooth barrel. Cross‐sectional asymmetry, corners, and obstructions are important factors that contribute to the generation of LVZs conducive to fish passage, albeit contiguity of LVZs is required, particularly for weak swimmers. The study demonstrates the adequacy and effectiveness of CFD models to complement traditional laboratory studies in understanding basic mechanisms beneficial to fish passage and to provide insights into future designs.