Effect of adult pheromones on the avoidance of suspended sediment by migratory banded kokopu juveniles

Migratory banded kokopu Galaxias fasciatus juveniles exhibited an attraction to adult odours and an avoidance towards suspended sediment with a turbidity of 25 nephelometric turbidity units (NTU) in a two-choice chamber apparatus. When the adult odours were mixed with suspended sediment at a turbidity of 25 or 35 NTU, an attraction towards the odour and suspended sediment chamber resulted. When adult odours were paired with turbid water at 50 NTU, juveniles would avoid the odour and suspended sediment chamber. These results demonstrate adult pheromones can increase the threshold for an avoidance response to suspended sediment in banded kokopu juveniles. This provides supporting evidence that odours released by adult conspecifics may provide an important migratory cue for juveniles in stream and habitat selection.     

The use of chemical cues in the upstream migration of coho salmon, Oncorhynchus kisutch Walbaum

The migratory behaviour of coho salmon was studied in the field. Coho salmon, Oncorhynchus kisutch , exposed to synthetic odours in a hatchery and released into Lake Michigan as juveniles, were recaptured as migrating adults 18 months later. The movements of 43 individuals were followed in experiments examining the role of imprinted chemical cues in the homing migration. Movements in relation to controlled distributions of the imprinting odours revealed that chemical cues are used by the salmon in their upstream migration. Acting with the rheotactic response, fish were guided upstream by imprinting odours simulating their home stream. Coho salmon, in the absence of their imprinting odour, respond negatively to the current. Differential responses to current appear to serve in segregating fish imprinted to odours of different home streams.     

The influence of dominance and diet on individual odours in MHC identical juvenile Arctic charr siblings

No difference in attraction was observed in sibling Artic charr Salvelinus alpinus between water scented by dominant or subordinate major histocompability complex (MHC) identical fish observed in a two-choice fluviarium. In a second experiment, MHC identical sibling donors were given different types of food pellets before the preference test. The test fish showed a significant attraction to the sibling given the same kind of food as the test fish itself during the first 6 h of the fluviarium tests. The results suggest that diet has an influence on the odours released and can, in addition to MHC related odours, be used for information relating to group member identity.     

Orientation of European corn borer first instar larvae to synthetic green leaf volatiles

European corn borer (ECB) neonate larvae are capable of orienting towards maize odours and of avoiding spinach odours. We previously reported that maize odours’ attraction was dependent on the stimulus regime. This led us to propose that maize odours could have a repellent or attractive effect depending on their concentration. In this work, we tested this hypothesis by evaluating attraction or avoidance of neonate ECB larvae to four concentrations of each of six single green leaf volatiles (GLVs); these are commonly found in maize and other plants. We found a dose‐dependent effect for all of these GLVs with the exception of 1‐hexyl acetate, which did not elicit any orientation behaviour over the range of concentrations tested. These five GLVs were repellent at high concentrations, while two of them were attractive at a lower concentration. These observations indicate for the first time that plant odours induce different behaviours in ECB neonate larvae depending not only on their chemical identity but also their concentration.     

Conventional and EMG telemetry studies of upstream migration and tailrace attraction of adult Atlantic salmon at a hydroelectric installation on the Exploits River,Newfoundland, Canada

Conventional and electromyogram (EMG) radio telemetry studies have documented occurrence of tailrace attraction and residency, and associated energy cost, for migratory wild Atlantic at a power plant on the Exploits River, insular Newfoundland, Canada. All fish demonstrated some degree of tailrace attraction and turbine discharge was the primary factor resulting in ‘false attraction’. In 2002, residency times were generally less than 1 h, although some fish demonstrated residency between 71 and 118 h. In 2004, after plant refurbishing, fish took from 6 to 11 days to reach the power plant and remained in the tailrace area from 3 to 12 days. Frequent entrances into the tailraces indicated fish were demonstrating a searching behaviour to find the upstream migration route. In 2003 and 2004, EMG data were collected from 3 fish in each year migrating to, and past, the tailraces. An Energy Index was calculated integrating EMG signal and time spent at each location to estimate potential energetic cost. Relatively high-energy expenditure was associated with tailrace attraction and residency in both years. In 2003, fish spent highest energy at the lowest tailrace (first encountered in their migration) while in 2004, there were also high-energy costs associated with a new generating unit. In both years, high EMGs both just below and above the power plant suggested these reaches were arduous and difficult to pass.     

An investigation of the possible presence of an aggregation pheromone in the milkweed bugs, Oncopeltus fasciatus and Lygaeus kalmii

ABSTRACT. The presence of an aggregation pheromone was studied in two species of milkweed bugs. The nymphs, young adults and old adults of Oncopeltus fasciatus were tested for their aggregation in response to acetone extracts of themselves and each other. The O. fasciatus nymphs were also tested for their response to odour from live O. fasciatus nymphs, as well as to Lygaeus kalmii nymphal extract, and the response of L. kalmii nymphs towards O. fasciatus nymph extract was tested. It was found that there is an aggregation pheromone in the nymphs and young adults and that there may be an alarm pheromone in the old adult O. fasciatus. A preliminary chemical analysis performed on the aggregation pheromone revealed it probably to be a polar non-aromatic compound of high molecular weight.     

Fish passage experience at small-scale hydro-electric power plants in France

There are more than 1,700 small-scale hydro-electric power stations in France today, which can be found on the majority of rivers with migratory species in them. This article gives an overview of the different types of fish facilities in use at these small-scale hydro plants. The relative advantages and drawbacks of each type of fish pass are discussed, with reference to the requirements of migratory species and the site-specific constraints. Emphasis is placed on the problems of attraction and maintenance. The article also mentions the various techniques used to evaluate existing or recently constructed fish passes. Experience in using bypass facilities combined with trashracks for downstream juvenile salmonids and eels are related. The author points out the severe cumulative impact which may occur due to the existence of several small-scale hydro projects on the same river. He presents his view on the priorities for research on fish passage facilities, especially on “fish friendly” small-scale hydropower intakes. Guest editors: R. L. Welcomme & G. Marmulla Hydropower, Flood Control and Water Abstraction: Implications for Fish and Fisheries     

Separating natural responses from experimental artefacts: habitat selection by a diadromous fish species using odours from conspecifics and natural stream water

Animals use sensory stimuli to assess and select habitats, mates and food as well as to communicate with other individuals. One way they do this is to use olfaction, whereby they identify and respond to chemical cues. All organisms release odours, which mix with other chemical substances and ambient environmental conditions. The result is that animals are frequently immersed in a complex, highly dynamic sensory environment where they must identify and respond to only some of the potential stimuli they encounter in the face of significant levels of background noise. Understanding how organisms respond to different chemical cues is therefore dependent on knowing how these responses might be influenced by potential interactions with other stimuli. To test this, we examined whether the diadromous fish Galaxias maculatus was attracted to conspecific odours and whether this response differed when cues were offered in an artificial environment lacking other potential chemical stimuli (tap water) or a more natural background environment (stream water). We found that (1) fish responded to both natural stream water odours and those from conspecifics but the response to the latter was stronger; (2) the attraction to conspecific odours was stronger in tap water than in stream water, which indicates the importance of these odours may be overestimated when they are offered in artificial media. We also conducted a brief literature review, which confirmed that artificial media are commonly used in experiments and that the background environment is often not considered. Our results show that future research testing the responses of organisms to auditory, olfactory and visual cues should carefully consider the context in which cues are presented. Without doing so, such studies may inaccurately assess the importance of sensory cues in natural situations in the wild. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Skip of the routine habitat in an amphidromous migration of ayu

Ayu Plecoglossus altivelis is a typical amphidromous fish with ontogenic requirements for habitats among lower reaches of a river, the marine coastal area, and middle reaches of a river at the immature adult stage. Mature fish that had a small body size like ordinary young were found around the spawning ground. In comparison with standard adults, the migratory histories of the dwarf adults were examined using otolith microchemistry analysis. Sr:Ca ratio estimated that the dwarf fish were exposed to saline or brackish water after once moving into the river, whereas the standard-size fish migrated upstream.     

Wind tunnel behavioural response and field trapping of the blowfly Calliphora vicina

The attraction of the blowfly Calliphora vicina Robineau‐Desvoidy, 1830 (Diptera: Calliphoridae) to single synthetic compounds, blends and authentic odours was investigated in a wind tunnel. A total of 1850 C. vicina (1750 females and 100 males) were tested. A comparison of male and female responses showed significant differences in attraction between the sexes. Females were more attracted than males to liver odour. The attraction of females lay in the ranges of 0–22% for single compounds, 26–64% for synthetic blends and 58–88% for authentic odours. Dimethyl trisulphide was the most attractive single compound. Significant improvement in attraction was achieved with blends and a three‐component lure, consisting of dimethyl trisulphide, mercaptoethanol and o‐cresol, was found to be the best solution for field trapping of C. vicina. Authentic odours from dead fish and mice were significantly more attractive than liver and the three‐component blend, and the blend and liver were similarly effective as attractants. Field tests support the results of the wind tunnel study and a high number of C. vicina were caught in funnel traps. Overall, 99.1% of the specimens caught were females.     

Sensory deficits induced by cadmium in banded kokopu, Galaxias fasciatus, juveniles

The potential for cadmium to produce sensory deficits in the mechanosensory lateral line and olfactory systems was examined in migratory Galaxias fasciatus juveniles or whitebait. Using a two-choice chamber apparatus, three groups of whitebait were tested for a known attraction to adult pheromones and then exposed to either 0.1, 0.5 or 1g Cd⁺² l^-1 for 48h and retested. The attraction to adult pheromones had been eliminated after exposure to concentrations of 0.5 and 1g Cd⁺² l^-1, indicating these levels of cadmium exposure had impaired olfactory function. Rheotaxis trials were conducted to determine the level of cadmium exposure which would inhibit lateral line function. The lateral line system was not blocked until a concentration of 2g Cd⁺² l^-1. The blocking of the lateral line and olfactory sensory systems was reversible. After 14 days recovery in clean freshwater both rheotaxis and the attraction to adult pheromones had returned. Whitebait were also tested for a preference/avoidance response at 2g Cd⁺² l^-1. Fish showed neither a preference for, or an avoidance of, a concentration which would disable both the lateral line and olfactory sensory systems. The disabling of these sensory systems may render migratory cues undetectable, affecting habitat selection by whitebait, which may ultimately affect the distribution of banded kokopu populations.     

Odour-mediated preference and prey preference of Macrolophus caliginosus between spider mites and green peach aphids

Abstract  A comparative study between direct prey preference and odour-mediated preference of the predatory mirid bug, Macrolophus caliginosus , was conducted. We used a Y-tube olfactometer to determine the attraction of the predator to herbivore-induced volatiles from Myzus persicae or Tetranychus urticae -infested sweet pepper plants over clean plants and to direct prey odours over clean air. The mirid bugs showed a stronger response to odours from infested plants than to odours from clean plants. The mirids did, however, not seem to exploit odours emitted directly from the prey themselves. Our results further demonstrated that M. caliginosus prefers M. persicae to T. urticae in a direct two-choice consumption test. This preference was, however, not reflected in a similar odour-mediated preference between plant volatiles induced by either of the two preys. Two hypotheses are suggested for this neutral response of the mirids to herbivore-induced volatiles from a preference prey or a non-preference prey.     

Sequential fishways reconnect a coastal river reflecting restored migratory pathways for an entire fish community

River regulation infrastructure has been implicated in worldwide aquatic biodiversity loss. In‐stream barriers such as weirs prevent fish migration and the impact can be particularly severe for diadromous species. Fishways are frequently installed on in‐stream barriers to reconnect migratory pathways and rehabilitate diadromous fish populations. Sequential fishways may be necessary in rivers where multiple barriers prevent migration. We monitored a coastal fish community's response to fish passage restoration at 10 predominantly low‐level weirs in the freshwater reaches of the Nepean River in southeastern Australia. Few studies have simultaneously assessed fish community passage at successive fishways within a river system. Prior to the installation of the fishways, there was a gradient of reduced species diversity in an upstream direction including the absence of many diadromous species, despite the regular inundation frequency of most weirs. Following the installation of the fishways, species diversity was still greater in the downstream monitoring sites; however, there was evidence of a positive change in fish community structure in middle and upstream sites. Most notably, three diadromous species rapidly expanded their distribution upstream and one amphidromous species expanded its downstream distribution. This study demonstrates appropriately designed successive fishways can successfully reconnect river systems for an entire fish community, encompassing species with a broad range of swimming abilities and diverse life histories.     

Activation of three species of tsetse (Glossina spp.) in response to host derived stimuli

Recordings were made of the activation of hungry Glossina morsitans morsitans Westwood, G. pallidipes Austen, and G. austeni Newstead in response to odours from ox breath and ox urine, and a moving visual stimulus, in a wind tunnel. The spontaneous activity of G.m.morsitans was very low (less than 4% of males and 2% of females active per min during control periods). That of G.austeni and G.pallidipes was in the region of 20% except for G.pallidipes females when in excess of 40% were active during control periods. Addition of ox urine odours to the airstream had no effect on activity in any of the species investigated but addition of ox breath odours to the airstream significantly increased activity of G.pallidipes and of G.m.morsitans, although for the latter only approximately 12% of flies were active. For G.austeni the addition of ox breath odours resulted in a significant increase in activity of females but not of males. The moving visual stimulus resulted in a significant increase in the activity of both sexes of G.austeni and G.m.morsitans but no change in the activity of G.pallidipes. The low level of spontaneous activity and the low response to ox breath odours in a strain of G.m.morsitans maintained in the laboratory since 1969 was compared with a new colony of this species which originated from puparia collected in Zimbabwe in 1991. No differences in either spontaneous activity or the response to ox breath odour was recorded, but females from the new colony were significantly more responsive to a moving visual stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Migratory patterns of lower Feather River natural and hatchery-origin Oncorhynchus mykiss

Oncorhynchus mykiss are known to exhibit variable life histories expressed under genetic control or through the influence of the environment. Altered environmental conditions and the presence of large numbers of non-indigenous hatchery fish can affect the rate of anadromy observed in California’s Central Valley O. mykiss. The lower Feather River, a large regulated river in Northern California, supports one of the largest populations of O. mykiss in the Central Valley, heavily subsidized by hatchery production. I examined downstream migratory behavior, movement rate, and success of natural-origin juveniles, natural-origin adults, and hatchery-origin fish using acoustic telemetry. I found that all three groups displayed a mix of migratory and non-migratory life histories. Hatchery-origin adults exhibited more migratory behavior (anadromy) than natural-origin juveniles and natural-origin adults, 41 %, 24 %, and 13 % respectively. Downstream migrants were also significantly larger than non-migratory fish. Migration timing was similar among the three groups, but natural-origin juveniles displayed the most rapid rate of movement. The relative success of each group was highest for fish migrating through the Sacramento-San Joaquin Delta to the Pacific Ocean. Hatchery-origin adults migrating through the lower Feather River showed the lowest relative success (33 %). The dominance of non-migratory life histories pattern among lower Feather River O. mykiss may be in response to the suitable habitat provided by hypolimnetic releases below dams and the current hydrological regime within the highly altered Sacramento-San Joaquin watershed.     

White sturgeon (Acipenser transmontanus) passage at the Dalles Dam, Columbia River, USA

White sturgeon (Acipenser transmontanus) ≥95 cm TL were monitored using acoustic and radio telemetry at a large hydroelectric dam (the Dalles Dam) on the Columbia River, during March 2004 through November 2005 to determine timing and routes of passage and to characterize general movements. Transmitters were surgically implanted into 148 fish during the study; 90 were released into the tailrace and 58 into the forebay. We documented 26 passage events by 19 tagged fish: eight upstream via fish ladders and 18 downstream, mostly through open spill gates. During the study 17 fish entered the two ladders one or more times; 11 entered only the east ladder, three entered only the north ladder, and three entered both ladders at sometime. Residence time within the ladders by individual fish was variable, ranging from about 1 min to nearly 6 months (median = 7.7 h). Only six fish successfully ascended the east ladder, one fish twice. We could not unequivocally determine which fish ladder one fish used to pass upstream. Differences in construction between the north and east fish ladders may account for the greater success of the east fish ladder in passing sturgeon upstream. Changes to operations at hydroelectric dams to benefit migrating anadromous salmonids may influence upstream or downstream passage by white sturgeon. Altering patterns and timing of spill discharge, altering fish ladder entrance attraction flows, and the use of lights, sound, and partial barriers to direct other species of fish to preferred passage routes have unknown effects on sturgeon passage. A better understanding of the consequences to the metapopulation of increasing or precluding upstream or downstream passage is needed.     

Otolith microchemistry of tropical diadromous fishes: spatial and migratory dynamics

Otolith microchemistry was applied to quantify migratory variation and the proportion of native Caribbean stream fishes that undergo full or partial marine migration. Strontium and barium water chemistry in four Puerto Rico, U.S.A., rivers was clearly related to a salinity gradient; however, variation in water barium, and thus fish otoliths, was also dependent on river basin. Strontium was the most accurate index of longitudinal migration in tropical diadromous fish otoliths. Among the four species examined, bigmouth sleeper Gobiomorus dormitor, mountain mullet Agonostomus monticola, sirajo goby Sicydium spp. and river goby Awaous banana, most individuals were fully amphidromous, but 9–12% were semi‐amphidromous as recruits, having never experienced marine or estuarine conditions in early life stages and showing no evidence of marine elemental signatures in their otolith core. Populations of one species, G. dormitor, may have contained a small contingent of semi‐amphidromous adults, migratory individuals that periodically occupied marine or estuarine habitats (4%); however, adult migratory elemental signatures may have been confounded with those related to diet and physiology. These findings indicate the plasticity of migratory strategies of tropical diadromous fishes, which may be more variable than simple categorization might suggest.     

Cadmium effects on development and reproduction of Oncopeltus fasciatus (Heteroptera: Lygaeidae)

Newly hatched nymphs of the insect Oncopeltus fasciatus were exposed to various concentrations of CdCl2 administered in drinking water until the end of adult life. Significant nymphal mortalities were observed at concentrations above 30 mg Cd/l (corresponding to the LC50). The duration of the nymphal stages increased in proportion to the Cd concentration; at the lowest Cd concentration of 10 mg Cd/l, the median duration was significantly prolonged by one day, while at the highest concentration of 100 mg Cd/l it was increased by 10 days over the control group. The weight of newly emerged adults lineally decreased with Cd concentration, being reduced to half the weight of controls at 100 mg Cd/l. In addition, a proportionality between delay in development and weight reduction was found in Cd-treated adults. Survival of adult females was decreased at concentrations higher than 10 mg Cd/l, while males were only affected at 30 mg Cd/l or higher doses. Reproduction was the most affected parameter. Oviposition rate, fecundity and fertility of females exposed to 10 mg Cd/l were significantly lower than controls (73%, 58% and 55% relative to controls, respectively). Hatchability of the eggs laid by treated females was also reduced. These results show that development and reproduction of O. fasciatus are seriously impaired at sublethal Cd concentrations.     

A Numerical Taxonomic Study of Pseudomonas-like Bacteria Isolated from Fish in Southeastern Queensland and their Association with Spoilage

Pseudomonas -like bacteria isolated from fresh and spoiling fish in southeastern Queensland were subjected to a wide range of physiological and nutritional tests. The results of these tests, together with those of 20 named strains, were analysed numerically, resulting in the formation of 11 groups. Most of the isolates clustered into group 1 and group 2 which also contained the bulk of the strains able to produce spoilage odours when grown in a tryptic digest of fish muscle at 2°C. Almost all of the group 1 organisms produced sulphydryl type odours, had only 50 mol % G + C and were identified as strains of Alteromonas putrefaciens which were deficient in the ability to produce H₂S detectable in Peptone Iron Agar. Certain of the group 2 strains produced fruity and sulphydryl type odours, but these organisms were not distinguishable from other strains in this group not producing odours. Group 2 strains were highly related to Pseudomonas fragi and were intermediate in properties between Ps. fluorescens and Ps. putida. The remaining nine minor groups contained few organisms able to produce spoilage odours.     

Juvenile current response, growth and maturity of above and below waterfall stocks of rainbow trout, Salmo gairdneri

Young rainbow trout were propagated from adults collected from above and below a water-fall, impassable to upstream fish migration on Kokanee Creek, tributary to Kootenay Lake, British Columbia. The two stocks of young (above and below waterfall) were reared in a hatchery under identical temperature, light and food conditions. Their directional response to water current was tested in a laboratory migration channel during their first summer and autumn. as well as the following spring. During tests in light, both stocks of young trout showed similar current responses, but in darkness the below falls stock showed much more downstream movement in the autumn than than did the above falls stock. In addition, below falls trout had a higher growth rate. were slightly heavier at the same length and matured earlier than the above falls stock. The adaptive significance of these differences are discussed in relation to maintenance of trout populations above waterfalls and to selective pressures faced by migratory below waterfall populations.