Voracious invader or benign feline? A review of the environmental biology of European catfish Silurus glanis in its native and introduced ranges*

A popular species for food and sport, the European catfish (Silurus glanis) is well‐studied in its native range, but little studied in its introduced range. Silurus glanis is the largest‐bodied freshwater fish of Europe and is historically known to take a wide range of food items including human remains. As a result of its piscivorous diet, S. glanis is assumed to be an invasive fish species presenting a risk to native species and ecosystems. To assess the potential risks of S. glanis introductions, published and ‘grey’ literature on the species’ environmental biology (but not aquaculture) was extensively reviewed. Silurus glanis appears well adapted to, and sufficiently robust for, translocation and introduction outside its native range. A nest‐guarding species, S. glanis is long‐lived, rather sedentary and produces relatively fewer eggs per body mass than many fish species. It appears to establish relatively easily, although more so in warmer (i.e. Mediterranean) than in northern countries (e.g. Belgium, UK). Telemetry data suggest that dispersal is linked to flooding/spates and human translation of the species. Potential impacts in its introduced European range include disease transmission, hybridization (in Greece with native endemic Aristotle’s catfish [Silurus aristotelis]), predation on native species and possibly the modification of food web structure in some regions. However, S. glanis has also been reported (France, Spain, Turkmenistan) to prey intensively on other non‐native species and in its native Germany to be a poor biomanipulation tool for top‐down predation of zooplanktivorous fishes. As such, S. glanis is unlikely to exert trophic pressure on native fishes except in circumstances where other human impacts are already in force. In summary, virtually all aspects of the environmental biology of introduced S. glanis require further study to determine the potential risks of its introduction to novel environments.     

基于灰色关联的寒区湿地春夏季浮游植物数量与环境因子关系

根据夏季(2005年7月)和春季(2006年5月)对寒区湿地--安邦河湿地浮游植物数量及其环境因子的调查,为寒区湿地管理及以后研究提供依据和基础资料.共采到浮游植物8门92种,其中春季37种,夏季82种,数量变化呈现夏季高于春季,上游高于下游,边缘区高于核心区.环境因子除了透明度(diaphaneity,D)和pH值外,水温(water temperature,WT)、可溶性无机氮(dissolved inorganic nitrogen,DIN)、磷酸盐(PO 4-P,P)及溶解氧(dissolved oxygen,DO)都呈现明显时空规律性变化.差异度结果显示2季节P的差异度最大.灰色关联分析结果表明,P的关联度在2季节均是最大.由此表明对安邦河湿地浮游植物数量影响最大的是P,因此,控制外源性的P输入对于维持安邦河湿地生态系统的健康是非常重要的.     

海水网箱养殖中的排污收费问题研究

网箱养殖是近年来海水养殖业发展的主流趋势,在其带来巨大经济效益的同时,也对周边生态环境造成巨大的威胁和破坏。文章通过探析其经济学原因,提出通过排污收费的手段来解决高密度海水网箱养殖带来的环境问题,并建立确定排污税率标准的模型,以部分黄渤海地区的数据进行实证计算,得出各地区的排污税率以供参考。     

Aquatic dissipation of the herbicide triclopyr in Lake Minnetonka,Minnesota

A study of the aquatic fate of the triethylamine salt of triclopyr (3,5,6‐trichloro‐2‐pyridinyloxyacetic acid) was conducted in three bays of Lake Minnetonka, Minnesota. Triclopyr is under review by the US Environmental Protection Agency as a selective aquatic herbicide. The primary purpose of this study was to determine dissipation rates of the parent active ingredient, triclopyr, and its major metabolites, 3,5,6‐trichloropyridinol (TCP) and 3,5,6‐trichloro‐2‐methoxypyridine (TMP) in selected matrices including water, sediment, plants, finfish and shellfish. Two 6.5‐ha plots dominated by the weedy species Eurasian watermilfoil (Myriophyllum spicatum L) were treated with triclopyr‐triethylammonum at a rate of 2.5 mg AE liter⁻¹ (2.5 ppm) on 21–23 June 1994. A third 6.5‐ha plot was established as an untreated reference. Water and sediment samples were collected from within the plots and at selected locations up to 1600 m outside of the plots through six weeks post‐treatment for chemical residue analysis. In addition, residue samples were collected from the target and non‐target plants and other non‐target matrices, including game and rough fish, clams and crayfish. All test animals were sequestered in cages located in the center of each plot and samples were collected through four weeks post‐treatment. Half‐lives for dissipation of triclopyr and TCP in water ranged from 3.7 to 4.7 days and from 4.2 to 7.9 days, respectively, with trace amounts of TMP found. Peak triclopyr sediment values ranged from 257 to 335 ng gram⁻¹, with a mean half‐life of 5.4 days, while peak TCP sediment levels ranged from 27 to 65 ng gram⁻¹ (mean half−life = 11.0 days). Trace levels of TMP were detected at one treatment site at one sampling event. Triclopyr and TCP accumulated and cleared from animal tissues proportionately to concentrations in the water (triclopyr dissipation half‐lives <11 days, TCP < 14 days). TMP levels were two to three times higher than those of the other compounds, particularly in visceral tissue. In all cases, residues of these compounds were higher in the inedible portions of the animals, and were usually higher in bottom‐feeding fish species. © 2000 Society of Chemical Industry     

地衣芽孢杆菌De株对黄鳍鲷生长及其养殖池塘主要环境因子的影响

运用综合对比分析法,对黄鳍鲷（Sparuslatus）养殖中定期泼洒地衣芽孢杆菌（Bacillus lichenformis）De的应用效果进行了探讨。结果表明,施用地衣芽孢杆菌De可在一定程度上优化水体环境和养殖生产性能,使养殖黄鳍鲷的成活率、体长增长率和体质量增长率分别提高18．2％、21．0％和312％;显著降低水中氨氮（NH3-N）、亚硝酸盐（NO2^-N）、活性磷酸盐（PO;一一P）质量浓度及底泥中有机碳的质量分数（P〈0．05）,其中养殖前、后期的底泥有机碳质量分数分别较对照组降低49．77％和22．63％,NO2^-N、PO4^3-P质量浓度则总体较对照组降低25．82％和41．00％,NH3-N质量浓度在养殖前、中和后期较对照组降低36．33％、18．10％和14．28％;水体中弧菌数量在养殖后期较对照组降低61．76％,底泥中的总异养细菌数量在养殖中、后期较对照组提高38．61％,整个养殖期间水体及底泥中的芽孢杆菌数量分别较对照组提高15．34％和26．37％。     

基于GAM的长江口鱼类资源时空分布及影响因素

根据2006至2017年长江口及其邻近海域鱼类资源调查,运用广义加性模型研究长江口鱼类资源密度与环境因子之间的关系,并对2017年鱼类资源密度的时空分布进行预测。结果显示,春夏秋冬四个季节最佳GAM偏差解释率分别为69.6%、55.9%、51.4%和47.4%,交叉验证回归线斜率的平均效应为0.62～0.88。盐度、水温和溶解氧是影响长江口鱼类资源密度的主要环境影响因子且在不同季节对鱼类资源密度有不同的影响机制。总体上,在春、夏、秋季,盐度与鱼类资源密度之间存在正向相关性;在夏、秋、冬季,水温对鱼类资源密度有显著影响,在秋季与鱼类资源密度之间存在正向相关性;在春、秋、冬季,溶解氧对鱼类资源密度有显著影响,在冬季与鱼类资源密度之间存在正向线性相关。研究表明,2017年夏季鱼类资源密度较高;在长江口南支的自然延伸水域存在鱼类资源密度的相对低值,在崇明岛向海自然延伸方向水域存在鱼类资源密度的相对高值。后续研究将对长江口鱼类资源进行不同生态类型区分,以期更加准确地掌握影响各生态类型鱼类时空分布的环境因素及其时空分布信息。     

The dynamics of bacterial community in a polyculture aquaculture system of Penaeus chinensis,Rhopilema esculenta and Sinonovacula constricta

Polyculture with Chinese shrimp Penaeus chinensis, jellyfish Rhopilema esculenta and razor clam Sinonovacula constricta (S.J.R) is a common aquaculture system in Dandong, China. Investigation on the composition and function of microbial communities and their relationship with environmental factors in aquaculture systems have crucial implications. Therefore, the sequencing of 16S rRNA gene was applied to profile the bacterial community composition of water and sediment in S.J.R polyculture system in the present study. Proteobacteria was the dominant phylum in S.J.R polyculture ponds following with Actinobacteria and Bacteroidetes in water; in contrast, more diverse phyla were detected in sediments. Water temperature, pH and dissolved oxygen were determined the bacterial community composition in the S.J.R polyculture systems. Specially, Planktomarina, PS1 clade, Candidatus Aquiluna and Fibrobacteres, which can resist the phytoplankton blooms or degrade the cellulose, were more abundant in water at the early stage of cultivation in the S.J.R polyculture system. Moreover, the functions of bacterial communities in water were mainly associated with cell communication mediated, while the functions related to basal metabolism were enriched in sediments. The findings of this study allowed us to better understand the bacterial community in the S.J.R polyculture system and accumulated data for the improvement of cultural management.     

Dietary α‐Ketoglutarate supplementation alleviates harmful effects of high environmental ammonia on grass carp,Ctenopharyngodon idella

Current intensive fish farming usually causes high environmental ammonia (HEA) in ponds that is toxic to fish. α‐Ketoglutarate (α‐KG) can be rapidly transaminated to glutamic acid and further aminated to glutamine. Therefore, we hypothesized that dietary α‐KG supplementation would alleviate HEA toxicity to fish. To test the hypothesis, 270 healthy grass carp (Ctenopharyngodon idella) juveniles were randomly assigned to control, HEA (18.37 mg/L ammonia) and HEA + α‐KG (0.75% of α‐KG) groups. Ammonia and free amino acid content in plasma and brain, liver glutamic pyruvic transaminase and glutamic oxaloacetic transaminase activity, and urea and glycogen content were measured on the first, seventh and 42nd days. Our results showed short‐term HEA exposure (1 day) led to a significant ammonia accumulation in the brain and plasma and significantly decreased glutamic and aspartic acid content in the brain and increased glutamine content in the brain and plasma. The long‐term HEA exposure (42 days) caused significant reductions in glycine and arginine content in the brain tissue. In most cases, dietary α‐KG supplementation alleviated the fluctuations in FAA content in the brain and plasma. Our results suggested dietary α‐KG alleviated HEA toxicity to grass carp.     

Alteration of the haemocyte parameters,expression of immune‐related and neurohormone bursicon genes of giant river prawn Macrobrachium rosenbergii (de Man) in the response to salinity stress and ammonia stress

We examined the effects of salinity stress and ammonia stress on alteration of the haemocyte count, phenoloxidase activity, expressions of immune‐related genes including prophenoloxidase (proPO), crustin, heat shock protein 70 (HSP70), and expressions of stress‐responsive neurohormone (Bur‐α and Bur‐β) in the thoracic and abdominal ganglia of giant river prawn Macrobrachium. These parameters of prawn that subjected to salinity stress (transferred from 0‰ to 5‰ and 10‰), and subjected to ammonia‐nitrogen (ammonia‐N) stress (transferred from 0 to 0.262 mg/L and 0.786 mg/L) were examined after 0, 3, 6, 24, 72 and 168 hr respectively. During the initial period of 3, 6 and 24 hr, granulocyte haemocyte (granular and semi‐granular hemocyte) count and PO activity significantly decreased, while expressions of Bur‐α and Bur‐β significantly increased. After 24 hr, granulocyte haemocyte count and PO activity significantly increased, whereas expressions of Bur‐α and Bur‐β significantly decreased. The expressions of proPO, crustin and HSP70 were significantly downregulated in the prawn that subjected to salinity stress and ammonia‐N stress at all time periods of 3–168 hr. In conclusion, changes in the granulocyte haemocyte count of M. rosenbergii following salinity stress and ammonia‐N stress are closely associated with the changes of Bur‐α and Bur‐β expressions.     

Effects of acute environmental and handling exposure on physiology and fillet quality of market‐sized Channel Catfish

Catfish Ictalurus spp. are subjected to stressful conditions during harvest, which may be linked to fillet coloration and quality. Poor water quality in ponds, socks or hauling tanks, as well as handling stress, have been suggested to cause red fillets in catfish; however, chronic exposure has not resulted in red fillets. Short‐term occurrences of extreme poor water quality, particularly low dissolved oxygen, high carbon dioxide and high temperature, may occur in ponds or during harvest. Therefore, market‐sized Channel Catfish Ictalurus punctatus were acutely exposed (12 hr) to one of the three water quality treatments while confined during a simulated socking procedure and evaluated for stress responses by means of change in blood parameters and fillet quality. In fish subjected to the extreme treatment, hematocrit, plasma cortisol, glucose and lactate levels increased, with 22% mortality, indicating highly stressful conditions. In fish subjected to moderate and typical (control) treatments, cortisol increased but a lack of change or decrease in glucose and lactate indicated minimal anaerobic metabolism. Only one red fillet was produced by the extreme treatment and two by the typical treatment; therefore, the results suggest red fillets are not a product of poor water quality compounded by handling during harvest.