Differential behavioural responses of mayflies from streams with and without fish to trout odour

1. In streams, mayflies (Order Ephemeroptera) are at risk from fish feeding visually in the water column. The effect of fish odour on the behaviour of Baetis bicaudatus from a fishless stream and a trout stream was investigated in four large oval tanks supplied with water from the fishless stream.
2. For each mayfly population, mayfly positioning on the substratum and movement in the water column (drift) were measured during the day and night, over 3 days. Brook trout ( Salvelinus fontinalis ) odour was added to two tanks to test the effect of a threat from fish.
3. Throughout the experiment more mayflies from the trout stream were observed on the substratum surface and in the water column during the night than the day, but the magnitude of night drift was less in tanks with fish odour.
4. Baetis from the fishless stream also displayed a nocturnal periodicity in drift and positioning, but their night-time drift was not affected by the presence of fish odour. On the first day of the experiment, however, more mayflies were observed on the substratum surface and drifting in tanks without fish odour during the day.
5. Sensitivity to fish odour may enable mayflies to alter their behaviour according to the risk of predation from fish.     

Differential behavioural responses of mayflies from streams with and without fish to trout odour

1. In streams, mayflies (Order Ephemeroptera) are at risk from fish feeding visually in the water column. The effect of fish odour on the behaviour of Baetis bicaudatus from a fishless stream and a trout stream was investigated in four large oval tanks supplied with water from the fishless stream.
2. For each mayfly population, mayfly positioning on the substratum and movement in the water column (drift) were measured during the day and night, over 3 days. Brook trout ( Salvelinus fontinalis ) odour was added to two tanks to test the effect of a threat from fish.
3. Throughout the experiment more mayflies from the trout stream were observed on the substratum surface and in the water column during the night than the day, but the magnitude of night drift was less in tanks with fish odour.
4. Baetis from the fishless stream also displayed a nocturnal periodicity in drift and positioning, but their night-time drift was not affected by the presence of fish odour. On the first day of the experiment, however, more mayflies were observed on the substratum surface and drifting in tanks without fish odour during the day.
5. Sensitivity to fish odour may enable mayflies to alter their behaviour according to the risk of predation from fish.     

Prevalence of kairomone-induced diapause in Daphnia magna from habitats with and without fish

The prevalence of the diapause response of the freshwater crustacean Daphnia magna to chemical cues on fish predation was evaluated in 35 clones originating from 14 European water bodies—inhabited or not inhabited by fish. Clonal lineages of experimental animals were cultured for 4 weeks in the presence or absence of water to which an extract of faeces of crucian carps (Carassius carassius), that were fed with Daphnia, was added. The proportion of females producing diapausing forms during the experimental period was used as a measure of the diapause response. A positive diapause response to fish predation cues was observed in 43% of investigated clones that originated from 71% of the water bodies tested. This indicated that the diapause response to fish scent is a common phenomenon in Daphnia magna from various locations in Europe. Surprisingly, no signs of a stronger diapause reaction to the tested cues were found in Daphnia originating from water bodies inhabited by fish compared with those from fish-free habitats.     

Use of water flow direction to provide spatial information in a small-scale orientation task

Experiments were designed to investigate whether three-spined sticklebacks Gasterosteus aculeatus can use direction of water flow as an orientation cue. The fish had to learn the location of a food patch in a channel where water flow direction was the only reliable indicator of the food patch position. Fish from two ponds and two rivers were trained and tested in the spatial task to determine whether river three-spined sticklebacks are more adept at using water flow as a spatial cue than fish from ponds. All fish were able to use water flow to locate the food patch but one of the two river groups was significantly faster at learning the patch location. When the task was reversed so that fish that had formerly been trained to swim downstream now had to learn to swim upstream and vice versa both river groups learned the reversed task faster than the two pond groups. In a second experiment, to investigate whether fish from ponds or rivers vary in the type of spatial cue that they prefer to use, fish from one pond and one river were given a choice between two different types of spatial cue: flow direction or visual landmarks. A test trial in which these two cues were put into conflict revealed that the river population showed a strong preference for flow direction whilst the pond population preferred to use visual landmarks.     

Biochemical changes in the lateral muscles of roach, Rutilus rutilus from two habitats following exercise

Batches of roach from two contrasting habitats were exercised in a flume at various water velocities for 1 h, and muscle metabolite levels were determined. It was found that the percentage change in lactate was greater in fish from the still water habitat than that in their running water counterparts, and it is proposed that natural conditioning of fish to water flow may be one of the main factors responsible.     

Acoustic assessment of the fish spatio‐temporal distribution during the initial filling of the Three Gorges Reservoir,Yangtze River (China), from 2006 to 2010

The aim of this study was to quantify the fish fauna in the Three Gorges Dam (TGD) and assess the tendency for change as well as for any spatial and temporal distribution. Two types of echo‐sounder equipment (HTI Model 241 and Simrad EY60) were used to detect the fish density and fish spatio‐temporal distribution. Eight surveys were conducted between 2006 and 2010, with the results showing that fish abundance in the Three Gorges Reservoir (TGR) increased yearly from 15.5 to 123 ind./1000 m³, a change apparently correlated with the corresponding increase in the reservoir water level. Horizontally, fish density increased from the lower reaches to the upper reaches. Fish preferred inhabiting the area around the Zhongxian section during winter and the Chongqing section in spring. Vertically, fish density was highest in the lower layer, followed by the middle layer. The difference in fish density in different water layers observed in spring was not as evident as in the winter. Fish target strength throughout the eight investigations showed a skewed distribution with respect to fish size. The overall increasing tendency of fish density and the spatio‐temporal distribution of fish species were closely related to the water level of the TGR during the impounding period. Other influencing factors included water flow rate, water depth, reservoir shape, habitat type, and protection policy.     

Seasonal variation in diel behaviour and habitat use by age 1+ Steelhead (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>) in Coast and Cascade Range streams in Oregon,U.S.A.

The seasonal diel behaviour of age 1+ steelhead from Coast and Cascade Range streams in Oregon was examined in the field and in laboratory streams. During the summer, fish from both areas were active during the day in natural streams: they held position in the water column in moderate velocities and depths. At night, fish were in slower water, closer to the bottom above smaller substrates. In winter, diel behaviour differed between the two groups. Coastal fish exhibited behaviour similar to that observed in the summer. Cascade Range fish were not observed during the day, but were found at night, holding positions close to the bottom in slower water. In laboratory streams, fish from both regions were subjected to a decreasing temperature regime from 16°C to 2°C. Use of cover for concealment during the day was negatively correlated with water temperatures for both groups. However, the shelter-seeking response to declining water temperatures was significantly greater for Cascade fish than it was for coastal fish. Field and laboratory observations of diel behaviour support the hypothesis that steelhead from the two geographic regions have different adaptive strategies for winter conditions and that these differences, because they persisted even in laboratory conditions, are probably genetically based.     

Salinity tolerance of the guppy, Poecilia reticulata Peters

Experiments were conducted to determine the adaptability of the guppy to various salt concentrations. The guppy, Poecilia reticulata , (total length 11–40 mm) were subjected to abrupt and gradual changes from fresh water (salinity=0.1%) to various salinities (%). No mortality occurred when the fish were transferred from fresh water to 50% sea water (19.5%). Through gradual adaptation from 50% sea water to 80% of the fish were able to tolerate 100% (39%) sea water for 7 days. After a 7 day stay in sea water, fish were readapted to fresh water during a 3 h period. Through gradual adaptation fish were also able to tolerate salinities ranging from 39.0% (100% sea water) to 58.5%. After a 30 day stay in 150% sea water (58.5%), fish were readapted to fresh water over a 5 h period. The results indicate that they were well able to tolerate the abrupt change from 100 or 150% sea water to fresh water. Females that stayed in 150% sea water (58.5%) for 30 days had embryos in their gonads.     

鱼体(去鳃)和鱼鳃对不同形态铜的积累特征

在实验室条件下研究实验鱼Ｐａｒａｃｈｅｉｒｏｄｏｎ对人工河水中不同形态的积累特征,对比了鱼体（去鳃）和鱼鳃对铜吸收量的差异,并探讨了鱼对铜的吸收机理。研究结果表明,实验鱼鳃部和体内铜积累量均随水相游离铜浓度增高,暴露时间增长而增加,但鳃部积累浓度较鱼体其余部分高一个数量级,其从水相富集铜的速率显著高于鱼体。     

Salinity tolerance of the mosquito fish, Gambusia affinis (Baird and Girard)

Experiments were conducted to determine the adaptability of mosquito fish to various salt concentrations. Mosquito fish, Gambusia affinis , (total length (T.L.) 27–37 mm) were subjected to abrupt and gradual changes from fresh water to various salinities (S). Low mortality (10%) occurred when the fish were transferred from fresh water (S = 0·5‰) to 50% sea water (S = 19·5‰ Through gradual adaptation 65·0% of the fish were able to tolerate 100% sea water for 7 days. After a 7 -day stay in sea water, fish were readapted to fresh water during a 3-h period. The results indicate that they were well able to tolerate the abrupt change. Through a gradual adaptation fish were also able to tolerate salinities ranging from 39·0‰ (100% sea water) to 58·8‰     

The intestinal microflora of farmed Dover sole (Solea solea) at different stages of fish development

The bacterial flora in the intestines of farmed Dover sole ( Solea solea L.) was investigated at different stages of fish development in relation to different diets fed under farming conditions. The flora of water and diets were also analyzed. The dominant generic group isolated from all water samples examined was Pseudomonas Gp IV/ Alcaligenes. The same generic group was dominant in homogenized pelagic larvae indicating a relationship between the microflora of those young fish and that of tank water. In older fish a steady increase in the percentage incidence of Vibrio / anaerogenic Aeromonas was observed in the intestines as fish grew and diets changed. The Vibrio /anaerogenic Aeromonas group was dominant in Lumbricillus rivalis used as an intermediate diet and the increased incidence of this group in fish intestines occurred after fish were fed this diet. The composite pellet used for ongrowing carried a high percentage of Gram positive micro-organisms and there was no relationship between the pellet microflora and that found in the fish intestines.     

Surveillance of fish species composition using environmental DNA

Prompt and accurate methods for assessing the species composition of given areas are indispensable in addressing the rapid loss of biodiversity. Here, we propose a method for the surveillance of fish species composition in freshwater using environmental DNA as species markers. First, the applicability of the method was demonstrated through aquarium experiments. DNA was extracted from 120?ml aquarium water, and the degenerated primers targeting the fish mitochondrial cytochrome b gene were used for amplification. PCR-amplified fragments were analysed by random cloning, and all species reared in the aquarium were detected. Next, this method was applied to natural freshwater environments. Water samples were collected from three sites in the Yura River, Japan; DNA was concentrated from 2?l of environmental water, and then amplified and cloned. Up to four species of fish were detected by sequencing 47 randomly selected clones from a single water sample. Overall, the results were consistent with previous knowledge of fish habitat utilisation. Using this method, the surveillance of fish species composition can be conducted less laboriously than with traditional methods.     

Isolation of Laribacter hongkongensis, a novel bacterium associated with gastroenteritis, from drinking water reservoirs in Hong Kong

AIMS: Freshwater fish has been found to be the reservoir of Laribacter hongkongensis, a recently discovered bacterium associated with community-acquired gastroenteritis. However, little is known about the ecology of this bacterium in the aquatic environment. We carried out a surveillance study to investigate the presence of L. hongkongensis in water and freshwater fish from 10 drinking water reservoirs in Hong Kong. METHODS AND RESULTS: Using membrane filtration, L. hongkongensis was isolated from the waters of six reservoirs, with numbers ranging from 1 to 12 CFU l(-1). Higher recovery rates were observed in summer and during days of higher water and ambient temperatures. Of 27 freshwater fish collected from the reservoirs, L. hongkongensis was recovered from the intestines of two fish, a Goldfish and a Nile tilapia. Overall, 35 different pulsed-field gel electrophoresis patterns are found among the 59 isolates recovered from water and the two isolates from freshwater fish. CONCLUSIONS: The present report represents the first to demonstrate the presence of L. hongkongensis in natural water environments. SIGNIFICANCE AND IMPACT OF THE STUDY: Although it is unlikely that treated, drinking water is an important source of L. hongkongensis-associated gastroenteritis, one should be aware of the possibility of other contaminated water as a source of human infection.     

Flexible antipredator behavior in a dragonfly species that coexists with different predator types

Two of the main predators of dragonfly larvae, insectivorous fish in communities with fish and large dragonfly species in communities without fish, differ markedly in their mode of predation. In general, dragonfly species coexist successfully with one predator or the other, but larvae of the dragonfly Pachydiplax longipennis can coexist successfully with both. I examined the behavioral response of these larvae to a simulated predator attack to determine whether their response (1) differs between the two communities, and (2) is sensitive to waterborne cues about the type of predator present. I compared larvae from two different communities: fish ponds where insectivorous fish were the top predators, and fish-free ponds where large dragonflies were the top predators. Larvae from fish-free ponds actively moved away from an attack significantly more than did larvae from fish ponds, provided each was attacked in its native pond water. Larvae collected from a fish-free pond but then attacked in fish water moved less than did controls (larvae attacked in fish-free water). Likewise, larvae collected from a fish pond but attacked in fish-free water moved more than did controls (larvae attacked in fish water). Larvae attacked first in water from their native pond and then in water from the contrasting pond changed their response in the expected direction. These results indicate that escape behavior in P. longipennis differs between communities with different predator types and is sensitive to waterborne cues in a manner consistent with the mode of predation employed by each predator.     

The pathology and seawater performance of farmed Atlantic salmon infected with glochidia of Margaritifera margaritifera

The pathology of glochidial infection of the freshwater mussel Margaritifera margaritifera was examined in farmed Atlantic salmon Salmo salar in fresh water and for 150 days after transfer of salmon to sea water. Prevalence of infection in fresh water was 95%, mean abundance 134 per fish and mean infection intensity 140. Prevalence in sea water was 80–94% in the first 7 weeks after transfer but glochidia were absent, apart from remains, after 50 days in sea water. Glochidia on salmon in fresh water were associated with localized hyperplasia and fusion of secondary gill lamellae. Focally extensive epithelial hyperplasia and fusion of secondary lamellae were present 4–10 days after transfer to sea water. Twenty-three days after transfer, small nodules with a more discrete appearance were present suggesting partial resolution of tissue response; hyperplastic responses associated with glochidia were much reduced after 50 days. Plasma chloride in infected fish 10 days after transfer was 153 mmol. 1⁻¹, significantly higher than fish without infection, suggesting poorer adaptation to sea water. No mortalities due to glochidial infection in sea water were recorded and there was no significant difference in mean weight between infected and control fish.     

Factors affecting river entry of adult Atlantic salmon in a small river

In this study, effects of stock origin, fish size, water flow and temperature on time of river ascent of adult Atlantic salmon Salmo salar were tested. Brood stocks were collected in eight Norwegian rivers situated between 59 and 69° N. The fish were reared to smolts, individually tagged and released in the River Imsa, south-west Norway (59° N). Adults from all stocks approached the Norwegian coast concurrently, but Atlantic salmon ≥70 cm in natural tip length entered coastal water slightly earlier during summer than smaller fish. Atlantic salmon <70 cm, however, ascended the river significantly earlier and at lower water flow and higher water temperature than larger fish. Although largest in size, the fish from the northern populations (62–69° N) ascended the River Imsa almost 1 month earlier than those from the south (59–60° N). They seemed less restricted by the environmental factors than the fish originating from the more southern rivers. There was no apparent trend among years in time of river ascent. Maximum ascent per day occurred at water discharges between 12·5 and 15 m³ s⁻¹ and at water temperatures between 10 and 12·5° C. There was a significant positive correlation between water flow and river ascent during the first part of the upstream run from July to September with best correlation for September, when multiple regression analysis indicated that water temperature had an additional positive effect. Stock origin, fish size and water discharge were important variables influencing the upstream migration of Atlantic salmon in small rivers.     

Evaluation of a water concentration method for the detection of infectious pancreatic necrosis virus in a fish hatchery

A virus-adsorption-elution (viradel) method using electropositive microporous filters (Virosorb 1-MDS) was used for the concentration and détéction of infectious pancreatic necrosis virus (IPNV) at a hatchery with a past history of IPNV infection. Samples of fish tissue and unconcentrated water were also examined for the presence of IPNV. Virus was isolated from three of the nine concentrated water samples taken from various locations at the hatchery. Virus was also isolated from pooled fish tissues, but not from unconcentrated water samples. Representative numbers of viruses isolated from water and fish tissues were examined for virus neutralization in the presence of anti-IPNV amiserum; resistance to acid, ether, and heat; and replication in the presence of 5-bromo-2'-deoxyuridine (BUDR). When tested by dot-immunobinding assay using a panel of monoclonal antibodies (MABs), the viral isolates were found to belong to the West Buxton serotype of IPNV.     

净化养殖水体紫色非硫光合细菌的筛选与鉴定

本研究从杭州养鱼塘水样及底泥样品中富集分离得到三株紫色非硫光合细菌,分别命名为HZ-3,HZ-4,HZ-5。 通过比较这三株菌对鱼、虾养殖水体的净化效果,筛选出菌株HZ-5 净化能力较强 ,经过5天的处理,该菌株使养鱼塘水样的COD 降低24.87%;使养虾池塘水样的COD 降低 36.99%;使养鱼塘水样的亚硝态氮的降解率达到97.79%。对菌株HZ-5进行了形态学观察、生理生化鉴定、活细胞吸收光谱以及16S rDNA序列分析。16S rDNA序列分析结果表明该菌株与沼泽红假单胞菌的16S rDNA序列有高达99％的同源性,结合形态特征和生理生化特性以及活细胞吸收光谱特征等,将其鉴定为沼泽红假单胞菌（Rhodopseudomonas palustris）。     

A comparison of plasma vitamin C and E levels in two Antarctic and two temperate water fish species

Antarctic fish have a high polyunsaturated lipid content and their muscle cells have a high mitochondria density suggesting that Antarctic fish are under greater oxidative stress than temperate water fish. To test this hypothesis, the plasma concentrations of the antioxidant vitamins E and C were measured in two Antarctic fish species, Pagothenia borchgrevinki and Trematomus bernacchii, and compared with the plasma concentrations of these vitamins in two New Zealand temperate water fish species, blue cod (Parapercis colias) and banded wrasse (Notolabrus fucicola). Neither vitamin is known to be synthesised in fish and so must be obtained from the diet. The plasma from both Antarctic fish species had vitamin E concentrations five to six times higher than those found in the two temperate water fish species. However, significantly higher levels of vitamin C were only found in the plasma of T. bernacchii, a benthic Antarctic fish. The average level of vitamin C in the plasma of the cryopelagic P. borchgrevinki was approximately one-third that of T. bernacchii. The T. bernacchii plasma yielded a high range of vitamin C values, possibly reflecting differences in nutritional status among the animals captured. No beta-carotene was found in any of the fish plasma samples studied. The data suggest that even though Antarctic fish live at -1.5 degrees C they may be exposed to greater metabolic stress from free radical mediated oxidation than temperate water species.     

六六六在水环境中转移、积累和归趋研究——3.六六六在鱼体的积累释放

鳃是六六六进入鱼体的主要通道,鱼体的残留水平决定于水与体脂间的分配平衡。要使背肌六六六残留低于0.5毫克/公斤,则水中六六六含量要低于0.024毫克/升。鱼体六六六残留向水体释放的速度与温度有关,温度低,释放慢;当温度低于10℃时,释放的速度极慢以至难以检出。建议采用清水寄养的方法,让鱼体释放六六六,降低残毒,提高商品质量。这种方法估计也适用于其它脂溶性的与水分配系数不是太大的污染物。