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Biwa salmon Oncorhynchus sp. is endemic to Lake Biwa, Japan, where it is an important commercial and recreational fisheries species. However, no information is currently available on its population structure and migration ecology. Therefore, here we evaluated whether otolith Sr/Ca, Ba/Ca and 87Sr/86Sr ratios can be used as natural signatures in Biwa salmon and then used these to determine the natal origins of lake-migration-phase individuals and spawning adults, and the homing ability of spawning adults in the Lake Biwa water system. Quadratic discriminant function analysis demonstrated that the lake-migration school comprised individuals with multiple origins, including rivers to the east, west and north of Lake Biwa, and that the homing rate of spawning adults was low (18 out of 80 individuals), with ca. 78% of fish straying into non-natal rivers. However, this straying behaviour was not spatially random, with fish tending to migrate upstream in rivers neighbouring their natal rivers. The high rate of straying in spawning adults is considered important for establishing and maintaining this species, which is highly adapted to life in the Lake Biwa water system where environmental disturbances often occur. [ABSTRACT FROM AUTHOR]

To better understand the mechanisms that lead to marine mortality of homing adult sockeye salmon (Oncorhynchus nerka), gill and blood biopsies were used in combination with biotelemetry to demonstrate how survival to freshwater entry is related to gene expression and physiological indices of stress. Microarray analysis of gene expression indicated multiple biological processes, including immune and stress responses, protein biosynthesis, and metabolism. Quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) analysis indicated fish with upregulation of genes related to stress and infection had higher marine survival compared with fish without this genomic signature. We proposed that higher marine survival of potentially stressed and immune compromised fish can be explained by stressed and infected fish being highly motivated to enter fresh water, leading to enhanced marine survival. However, once in a river, stressed and immune compromised fish could suffer higher mortality because of premature river entry. Overall, this study supports the idea that infection and stress are important biological processes influencing behaviour and fate of sockeye salmon during homing migrations. [ABSTRACT FROM AUTHOR]

Adult coral-reef fishes display a remarkable ability to return home after being displaced. However, we know very little about homing behaviour in juvenile fishes. Homing behaviour in juvenile fishes is of interest because it will shape subsequent spatial distributions of adult fish communities. Comparing multiple species, families and functional groups allows us to distinguish between species-specific traits and more generalised, species-independent traits that may drive homing behaviour. Using displacement experiments of up to 150 m, we quantified homing behaviour of juvenile, newly recruited reef fishes of seven species in three families, including herbivorous parrotfishes and rabbitfishes, carnivorous wrasse and planktivorous damselfishes. All species showed the ability to home successfully, but success rates differed among species. Juvenile parrotfishes were the most successful (67% returning home), while return rates in the other species ranged from 10.5% ( Siganus doliatus) to 28.9% ( Coris batuensis). However, across all species body size appeared to be the main driver of homing success, rather than species-specific traits. With every cm increase in body size, odds of returning home almost tripled (170% increase) across all species. Interestingly, the probability of getting lost was not related to body size, which suggests that mortality was not a major driver of unsuccessful homing. Homing probability halved beyond displacement distances of 10 m and then remained stable. Higher likelihood of homing over short distances may suggest that different sensory cues are used to navigate. Overall, our results suggest that homing ability is a widespread trait among juvenile reef fishes. A 'sense of home' and site attachment appear to develop early during ontogeny, especially above taxon-specific size thresholds. Hence, spatial flexibility exists only in a brief window after settlement, with direct implications for subsequent patterns of connectivity and ecosystem function in adult reef fish populations. [ABSTRACT FROM AUTHOR]

Moored fish cage structures are forced to move into the offshore area due to the shrinking availability of sheltered near-shore sites and increasing environmental impacts of aquaculture, and this provokes a significant challenge for the reliability design of mooring system. The uncertainties involved in the predictions of applied loads and structural strength are analyzed for calculating the reliability level of mooring system. In this study, a probability corrosion model is used to describe the uncertainty of corrosion depth and the joint probability density of significant wave height and spectral peak period is selected to depict the randomness of sea states. The non-linear finite element model is developed to investigate the minimum breaking strength of mooring chains and is validated through comparing with the formulas providing by the International Association of Classification Societies (IACS) Unified Requirements concerning for Materials and Welding. A validated numerical model is applied to calculate the tension force of mooring system for both the single-cage system and the multi-cage system at several sea states, and the response surface method is utilized to display the limit state function to calculate the reliability level in terms of the uncertain metocean variables. The results indicate that the reliability level decreases significantly with the increasing corrosion depth and the correlation of corrosion model for mooring chains has a remarkable impact on the failure probability of mooring system. In addition, the failure probability of mooring system for the four-cage system is much higher than that for the single-cage system. [ABSTRACT FROM AUTHOR]

Analysis of otolith strontium isotope ratios (87Sr/86Sr) is an increasingly utilized approach for studying fish migration. We analysed surface and ground water from the Daly River catchment in the wet-dry tropics of northern Australia over 2 years. Analyses of otolith 87Sr/86Sr ratios were also conducted for freshwater sooty grunter ( Hephaestus fuliginosus) and the putatively diadromous diamond mullet ( Liza ordensis). Spatial variation in freshwater 87Sr/86Sr was high (range: 0.71612-0.78059), and there was strong seasonality in water 87Sr/86Sr, with highest values in the wet season. Temporal variation in water 87Sr/86Sr ratios is attributed to seasonal patterns in surface runoff from geological formations with radiogenic compositions versus input from groundwater aquifers interacting with less radiogenic formations. Temporal variation in water 87Sr/86Sr ratios precluded robust inference on movement within fresh water for both species, although movement across salinity gradients by diamond mullet was clearly identified. We conclude that temporally and spatially replicated water Sr data should be a general requisite for studies that analyse otolith Sr (87Sr/86Sr, Sr/Ca, Sr/Ba) to make inferences about fish movement and migration. [ABSTRACT FROM AUTHOR]

The ability of two common, site-attached coral-reef fishes to return to their home corals after displacement was investigated in a series of field experiments at One Tree Island, southern Great Barrier Reef. The humbug Dascyllus aruanus was displaced up to 250 m, with 42% of individuals returning home, irrespective of body size, displacement, direction (up or across currents) and route complexity, while for the lemon damselfish Pomacentrus moluccensis 35% of individuals returned overall, with 33% from the greatest displacement, 100 m along a reef edge. Given that the home range of both species is <1 m2, over their 10+ year life span, the mechanisms and motivations for such homing ability are unclear but it may allow resilience if fishes are displaced by storm events, allowing rapid return to home corals. [ABSTRACT FROM AUTHOR]

Anadromous salmon (genera Oncorhynchus and Salmo) spend much of their lives feeding in productive northern oceans and then return home to natal sites for reproduction with remarkable accuracy. The mechanisms used for navigation by individuals during migrations are thought to include geomagnetic, celestial and olfactory cues, but rarely are social interactions between individuals considered. Mounting evidence from other taxa indicates that individuals in larger groups can better sense and respond to environmental cues, thus potentially increasing their ability to navigate. Here, we propose that salmon might similarly benefit from collective navigation on their homeward journey. To explore this, we compiled data from multiple studies and found strong evidence that rates of successful homing increase with population abundance, consistent with collective navigation. We then discuss how collective navigation could benefit salmon during each stage of their seaward and homeward migrations, and complement this with a review of salmon sociality. Next, we analyse historic high-seas catch records and provide new insight into schooling structure of salmon in the marine environment. We argue that collective navigation likely represents a presently under-appreciated mechanism enhancing the navigational ability of salmon as well as other migratory species, and outline critical tests of our hypothesis. [ABSTRACT FROM AUTHOR]

Recruitment of European eels ( Anguilla anguilla) has declined to the extent that they have been added to the IUCN Red List of Threatened Species. Therefore, it is critical to ensure that eels complete their outward river migration in order to contribute to the available spawning stock. We conducted a 4-year (2007-2011) telemetry study to understand the migratory behaviour and potential impact of environmental factors on the eel during this critical life stage. Out of 399 female eels tagged with acoustic transmitters, only 28% demonstrated clear downstream migratory behaviour. Fifty-five percent were detected exhibiting no downstream migration behaviour and 17% were not detected at any monitoring station. Movement patterns of downstream-migrating (silver) eels were characterized by nocturnal activity and seasonal migration, with distinct peaks in autumn and spring. Migration was often discontinuous and exhibited phases of active locomotion and expanded stopovers. The most important determinants of movement activity were water temperature, cumulative precipitation and moonlight, although the significance varied by season and location in the river basin. Our results evidence a discontinuous, stepwise migration over an extended period. Furthermore, our findings indicate that migration success depends on holding duration prior to tagging and environmental predictors with varying importance depending on the season, as well as the locations of capture, tagging and release. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We constructed a model that predicted path selection of Atlantic salmon. Our basic assumption for the model was that Atlantic salmon optimize migration by selecting a path that minimizes water resistance. The model prediction was compared with observations in a fishway, and the results were within expectations. It appeared like the fishway design and flow configuration at our study site caused some problems for the fish to discover both of the available paths. Therefore, only 53% of female fish and 67% of male fish selected the optimal path in the beginning of the fishway, but 92% of female fish and 97% of male fish selected the optimal path at the end of the fishway. Velocity over ground was very low, which is likely because every weir in the fishway was an obstacle for the fish. This knowledge can be used to improve future fishway design, or improve flow configuration for existing fishways. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

During inshore migration, glass eels experience great environmental changes they must adapt to, but there have been few studies on the behavior of juvenile Japanese eels, Anguilla japonica, entering estuaries. To investigate the relative effects of periodic environmental changes on their inshore migration and ascending behavior from the bottom to swim with flood tidal currents, year-round collections were carried out from December 2003 to December 2005 inside Hamana Lake, Japan, where strong tidal flows occur. Glass eel collections ( N = 543) near the inlet to the lake indicated that recruitment occurred mainly in winter from November to May. Time-series autocorrelation analysis of average daily catch rates found negative autocorrelation coefficients at 16-20 days periodicities and positive ones at 30-32 days periodicities in the 2004-2005 season, suggesting that the amount of recruiting glass eels fluctuates with a lunar cycle. Abundances of glass eels showed a diel rhythm and a tidal rhythm with eels appearing only at night and catches during flood tide being higher than during ebb tide, indicating 'Selective Tidal Stream Transport' that eels utilize flood tidal-streams selectively at night to migrate inshore. The generalized additive models (GAM) for the abundance suggested that relatively long timescale factors such as 'recruitment season' and 'lunar age' could affect the abundance of glass eels. The GAM for glass eel presence/absence indicated that the timing of glass eel ascending into the water column during flood tide at night was at 150-180 min after low tide, which tended to synchronize with the rise of water temperature caused by the inflow of warm water from the Pacific coast outside the lake. Results suggested that a temperature increase at the beginning of flood tide may be a cue for the ascending behavior, or at least could be a zeitgeber of the circatidal rhythm regulating the ascending behavior. [ABSTRACT FROM AUTHOR]

Amphidromy is a distinct form of diadromy, involving a downstream migration (‘drift’) to a pelagic feeding habitat undertaken by exceptionally small, undeveloped larvae immediately after hatch. Identifying patterns of larval drift may indicate critical periods within which conservation measures can be targeted to protect migrating larvae. This study utilised diel and spatial drift sampling to examine patterns of larval drift in two of New Zealand's endemic eleotrid species, the bluegill bully (Gobiomorphus hubbsi) and the common bully (G. cotidianus) in the Waianakarua River, South Island, New Zealand. A distinct spatial and temporal window was identified within which the vast majority of larvae were migrating to sea, extending only a few hours after sunset and < 10 km inland. Similar diel patterns of larval drift have been found in other amphidromous species, suggesting this may be a widespread migratory behaviour. Managing water takes to minimise impacts on migrating larvae within this relatively small spatial and temporal window potentially represents a management strategy that could provide safe passage to the vast majority of larval fish while minimising disruption to human activities. [ABSTRACT FROM PUBLISHER]

Fish scales may be used as nonlethal alternative structures to otoliths for establishing chemical time-series that trace migration and habitat use for euryhaline species such as Atlantic tarpon ( Megalops atlanticus). We survey four decades of fish scale studies employing elemental analyses to show the wide diversity of aims, approaches and instrumentation. Analyses are mainly solution-based measurements of whole or subsampled scales or in situ solid-sampling techniques of specific growth regions. Although spot-based transects across scales have been employed for a handful of species, continuous elemental transects across scale growth increments are rare. Laser ablation based sampling methods that assay scale exteriors can be difficult to implement for species with natural topographic variations exceeding the focal range of the laser. These limitations may be overcome by performing laser ablation of scales in cross-section when scale thickness in the well-calcified external layer provides enough surface area for a laser transect. For this study, scales of Atlantic tarpon were embedded in epoxy and longitudinally cross-sectioned to expose the scale growth record of the external layer. Laser ablation ICP-MS was used to quantify continuous profiles of element:Ca ratios across scale growth increments. The analytes surveyed (Mg, P, Ca, Mn, Sr, and Ba) were consistently above the limits of detection (LODs) across each scale with the exception of Pb for one scale. Obtaining high resolution elemental life history profiles from scales will be essential for future efforts to use this structure as a non-lethal substitute for otoliths in Atlantic tarpon and other migratory fishes that possess scales with sufficiently thick calcified external layers to permit a cross-sectional approach. [ABSTRACT FROM AUTHOR]

Micropterus cataractae (Shoal Bass), an enigmatic fluvial specialist, has experienced range-wide declines because of habitat fragmentation and other negative effects of impounded rivers. In addition to these concerns, anglers often translocate Shoal Bass from riverine habitats to impoundments following tournament weigh-ins. To investigate the potential effects of this practice, we translocated adult Shoal Bass from riverine habitats to a downstream impoundment and assessed their movements, homing abilities, and eventual fates. All fish rapidly evacuated the impoundment in favor of lotic habitats, and the majority of translocated fish returned upstream within about 3 weeks. Half of our translocated fish also displayed homing to within 1 river km of their original capture site. Our results demonstrate that fluvial-specialist Shoal Bass can survive translocation into impoundments, but the differential effects of translocation associated with fishing tournaments should also be considered in the management of Shoal Bass fisheries. [ABSTRACT FROM AUTHOR]

Homing behaviors are seen across the animal kingdom, with the magnitude and scale of these movements varying to a great degree. Invertebrates, such as crayfish, prove to be excellent models for comparative research, with relatively simple nervous systems that have been extensively studied combined with a rich behavioral repertoire that has been well documented. Here we explore whether two crayfish species (a primary burrower and a tertiary burrower) can home to artificial burrows and if so, whether their homing abilities differ. The two species of crayfish, Orconectes rusticus and Fallicambarus fodiens, were examined for their ability to home to artificial burrows in a laboratory setting. Animals were placed in a homing arena, motivated to search by the presence of food, and subsequently return to the burrows. The movements of each individual crayfish were digitized and analyzed for changes in walking speed, velocity and heading angle relative to burrows, total distance travelled and path turning angles. Crayfish of both species successfully returned home, although F. fodiens had a higher homing success rate than O. rusticus. Detailed kinematic analysis showed that walking speeds almost doubled during homing to burrows and heading angles were significantly closer to zero than on the outward journeys for both species. Path turning angles were significantly lower for O. rusticus than for F. fodiens. These findings indicate that these species of crayfish can successfully home without the visual landmark of burrow chimneys and that the primary burrower ( F. fodiens) appears to be more successful with straighter return paths. The differences in these two species to home and the underlying mechanisms of homing may be due to the differences in burrow use with primary burrowers showing more efficient homing than tertiary burrowers. [ABSTRACT FROM AUTHOR]

Short-term and long-term population growth rates can differ considerably. While changes in growth rates can be driven by external factors, we consider another source for changes in growth rate. That is, changes are generated internally by gradual modification of population structure. Such a modification of population structure may take many generations, particularly when the populations are distributed spatially in heterogeneous environments. Here, the net reproductive rate R is not sufficient to characterize short-term growth. Indeed, a population with net reproductive rate greater than one could initially decline precipitously, or a population with net reproductive rate less than one could initially grow substantially. Thus, we augment the net reproductive rate with lower and upper bounds for the transient reproductive rate, R and R. We apply these measures to the study of spatially structured salmon populations and show the effect of variable homing fidelity on short-term and long-term generational growth rates. [ABSTRACT FROM AUTHOR]

White-streaked grouper ( Epinephelus ongus) is an important fishery target that forms fish spawning aggregations (FSAs) at specific spawning grounds. The aims of the present study were to investigate migration behavior and returning behavior in terms of FSA using acoustic telemetry. Among the 30 specimens tracked, three types of movement pattern were observed: type 1, high site fidelity at the release area before the spawning period, migration to the spawning ground during the spawning period and return to the release area just after the spawning period (17 specimens); type 2, high site fidelity at the release area, disappearance from the area during the spawning period but was not detected at the spawning ground and return to the release area (8 specimens); and type 3, high site fidelity at the release area was observed before, during and after the spawning period (5 specimens). For the 17 specimens that were categorized into type 1, the dates of departure from their release area and the dates of return to the release area of males were, respectively, significantly earlier and later than those of females. The duration between the departure date and the return date ('duration away') of males was significantly longer than that of females. The duration away tended to be positively related to the condition factor. All 25 specimens that were categorized as type 1 and type 2 showed returning behaviors to the release area. [ABSTRACT FROM AUTHOR]

Using a fixed-speed test, burst swimming performance was found to vary among nine populations of emergent sockeye salmon Oncorhynchus nerka fry reared in a common-garden environment. No consistent relationship was, however, detected between difficulty of fry migration (upstream v. downstream) to rearing areas and total burst swimming duration or bursting rate. [ABSTRACT FROM AUTHOR]

The theory of ecological cognition poses that the brains and behaviour of animals are shaped by the environmental challenges they face in their everyday lives. Site fidelity and homing ability was tested for five species of intertidal rock pool fish by tagging and displacing them to new rock pools at various distances from their 'home' rock pools. Three of the species were rock pool specialists whilst the remaining two spend a small proportion of their life in rock pools during early ontogeny. The three specialists showed strong site fidelity with >50 % of individuals found in the same pool 42 days after tagging. In contrast, the non-specialist species showed low fidelity and poor homing abilities. Homing success in the rock pool specialists remained relatively stable as displacement distance increased. The effect of body size on homing ability was species dependent, with only one species showing a significantly greater tendency to home with increasing size. [ABSTRACT FROM AUTHOR]

Little is known about Atlantic salmon behaviour during the last phase of the marine homing migration and subsequent river entry. In this study, 56 adult Atlantic salmon in the Alta Fjord in northern Norway were equipped with acoustic transmitters. Salmon generally followed the coastline, but their horizontal distribution was also affected by wind-induced spreading of river water across the fjord. Mean swimming depth was shallow (2.5-0.5 m), but with dives down to 30 m depth. Timing of river entry was not affected by river flow, diel periodicity, or tidal cycles. Movements during the last part of the marine migration and river entry were unidirectional and relatively fast (mean 9.7 km·day−1). However, migratory speed slowed as salmon approached the estuary, with a significantly lower speed in the innermost part of the estuary than in the open fjord. Migration behaviour seemed not to be affected by handling and tagging, as there were no behavioural differences between newly tagged fish and those captured and tagged 1 year before their homing migration. [ABSTRACT FROM AUTHOR]

Understanding patterns in site fidelity is important for defining the ecological role of species in the systems they use and for gauging the effects of human impacts on their populations. We analyzed long-term movement data of adult spottail sharks ( Carcharhinus sorrah) in Cleveland Bay, Australia, to define the degree of site fidelity this species shows to coastal areas. Individuals were monitored in the study site for 28-566 days, and residency index (i.e., proportion of days present to total monitoring period) ranged from 0.08 to 0.95. Using a randomization procedure, we determined that the movement paths for 90 % of individuals (11 female and 7 male) were more constrained than random, with individuals exhibiting a high degree of site fidelity to consistent areas within the study site. Examining distances moved revealed that individuals used the same areas repeatedly and remained in close proximity (i.e., <6 km) to their location of first detection. While some individuals consistently used and returned back to the same locations, low residency among others suggests that a portion of the population may roam more widely. Long-term site fidelity to consistent areas may be a successful behavioral strategy for C. sorrah by increasing individual fitness through spatial familiarity and knowledge of resources. [ABSTRACT FROM AUTHOR]

After several years of feeding at sea, salmonids have an amazing ability to migrate long distances from the open ocean to their natal stream to spawn. Three different research approaches from behavioural to molecular biological studies have been used to elucidate the physiological mechanisms underpinning salmonid imprinting and homing migration. The study was based on four anadromous Pacific salmon Oncorhynchus spp., pink salmon Oncorhynchus gorbuscha, chum salmon Oncorhynchus keta, sockeye salmon Oncorhynchus nerka and masu salmon Oncorhynchus masou, migrating from the North Pacific Ocean to the coast of Hokkaido, Japan, as well as lacustrine O. nerka and O. masou in Lake Toya, Hokkaido, where the lake serves as the model oceanic system. Behavioural studies using biotelemetry techniques showed swimming profiles from the Bering Sea to the coast of Hokkaido in O. keta as well as homing behaviours of lacustrine O. nerka and O. masou in Lake Toya. Endocrinological studies on hormone profiles in the brain-pituitary-gonad axis of O. keta, and lacustrine O. nerka identified the hormonal changes during homing migration. Neurophysiological studies revealed crucial roles of olfactory functions on imprinting and homing during downstream and upstream migration, respectively. These findings are discussed in relation to the physiological mechanisms of imprinting and homing migration in anadromous and lacustrine salmonids. [ABSTRACT FROM AUTHOR]

Homing behaviour and group cohesion in Atlantic cod Gadus morhua from the northern Gulf of St Lawrence were studied based on tagging-recapture data from two periods, the 1980s and a recent period from 1996 to 2008. Two or more tags from a single tagging experiment were frequently recovered together in subsequent years. The null hypothesis was tested that the frequency of matching tag recoveries occurred by chance only through random mixing of tagged G. morhua before their recapture by the commercial fishery. The alternative hypothesis was that non-random, positive association (group cohesion) existed among tagged individuals that persisted through time and during migrations. Results show that the G. morhua population exhibits a homing behaviour, with temporal stability across seasons and years: 50% of recaptured fish in the recent period were caught <34 km from their mark site, even 3 years after release. In the 1980s, G. morhua were located at <10 km from their release site 1 year after tagging during summer and at <16 km during spring and autumn combined. Despite the increasing distance between the mark and recapture sites over time, the difference was not significant. In addition, occurrences of two or more tagged fish from the same release event that were caught together indicated a non-random association among individual fish for periods of one to several years and through migrations over several hundred kilometres. Hence G. morhua showed group cohesion in addition to site fidelity. These two interacting behaviours may be fundamental for the rebuilding and conservation of depleted fish stocks. [ABSTRACT FROM AUTHOR]

Anthropogenic modifications to aquatic ecosystems have altered connecting pathways within, and in some cases, between watersheds. Human structures, such as hydroelectric facilities, often impede fish migrations and may inflict heavy mortality on fish that become impinged or entrained. Conversely, an increase in connectivity between two waterways (e.g., through the construction of shipping canals, increased boat traffic) often results in an elevated risk of invasive species introductions. Non-physical barriers, which obstruct fish from an undesirable location without influencing the waterway, are one management approach to protecting valuable fish stocks and deterring biological invasions. Because many methods of behavioral deterrence have been employed against fish, there is a need to summarize and compare existing and developing technologies. This review details the use and application of electrical, visual, acoustic, chemical, and hydrological deterrence techniques that may be used to prevent fish movements. Site requirements are discussed, and a critical assessment of benefits and limitations to each technique are given. Because no single method of fish deterrence is 'one size fits all', this review to non-physical fish barrier technology will benefit managers and researchers attempting to develop a best-fit strategy on a case-by-case basis. [ABSTRACT FROM AUTHOR]

Abstract: Information about the welfare and husbandry of pet and laboratory fish is scarce although millions of fish are sold in pet shops and used in laboratory research every year. Inadequate housing conditions can cause behavioural problems also in fish since they are complex animals with sophisticated behaviour. In this study, we investigated the influence of environmental complexity on compartment preference and behaviour in zebrafish (Danio rerio) and checker barbs (Puntius oligolepis). For the preference test, large aquaria were divided by two semi-transparent walls of Plexiglas into an empty compartment, a structured compartment enriched with plants and clay pots, and a smaller compartment in-between, where food was provided. For observation, the empty and structured compartments were divided into six zones of similar size by defining three vertical layers and two horizontal areas (back vs. front area). Seven groups of six to nine zebrafish and seven groups of seven or eight checker barbs were observed on four days each (within a time period of ten days) to assess compartment use and activity, and to assess behavioural diversity and use of zones within compartments. Both zebrafish and checker barbs showed a significant preference for the structured compartment. Nevertheless, in neither species did behavioural diversity differ between the empty and structured compartment. Zebrafish used all zones in both compartments to the same extent. Checker barbs, however, used the structured compartment more evenly than the empty compartment, where they mainly used the lower and middle zones. These results suggest that zebrafish and checker barbs have a preference for complex environments. Furthermore, they indicate that the behavioural and ecological needs of fish may vary depending on species, and recommendations for husbandry should be specified at species level. [Copyright &y& Elsevier]

Abstract: Salmon utilize olfactory cues to guide natal stream homing during spawning migrations. Both inorganic and biogenic chemicals have been proposed as odorants that might be used by salmon during homing. In this study, we used genomic DNA sequence data from nine salmonid species to compare nucleotide identities for orthologous main olfactory receptor (mOR) genes with nucleotide identities for orthologous vomeronasal type 1-like (ora) receptor genes. We found that orthologs for both classes of olfactory receptor genes (mORs and Oras) appear to be highly conserved among species. Our findings do not support the differential tuning hypothesis in Salmonidae, which predicts higher sequence conservation for mORs than ora. We did, however, find convincing evidence for site-specific positive selection acting on paralogous main olfactory receptor genes. [Copyright &y& Elsevier]

Marine reserves are perceived as a critical component in successful rebuilding of overharvested marine populations. Such efforts can be particularly successful in species with limited movement rates. However, long-term data on movement is sparse for most marine species. Here, we investigated space use in European lobster () by ultrasonic tracking in a reserve on the Norwegian Skagerrak coast from September 2006 to August 2007. Over the period, 95% of tagged lobsters remained either within the reserve or near reserve boundaries. Home range estimates based on a kernel density estimator of the 95% utilization distribution ranged from 5728 to 41 548 m2 (mean 19 879 ± 2152 m2 standard error), representing 0.57%-4.15% of the reserve area (1 km2), with no significant difference among males, non-ovigerous females, and ovigerous females for an overlapping observation period of 242 days. Logistic regression predicted average time to reach 50% and 95% of minimum convex polygon home range area at 98 and 259 days, respectively. These results show that European lobsters can be resident with limited home ranges. Small coastal reserves can be designed to afford complete or partial protection by letting boundaries engulf or intersect patches of habitat preferred by this species. [ABSTRACT FROM AUTHOR]

Abstract: The short-term movements of a small temperate fish, the annular seabream Diplodus annularis (Linnaeus 1758), were examined using standard tag-recapture and passive acoustic telemetry in Palma Bay (NW Mediterranean), a marine protected area (MPA). The study aimed to provide valuable information for assessing the recreational fishery and its results suggest that MPAs can be used to protect the adult stock of D. annularis. All the fish tagged with standard tags were recaptured near the release locations, with a maximum distance of ∼300 m. The maximum time between release and recapture was 185 d. Two different arrays of acoustic receivers were deployed, one in 2008 and another in 2009, within the MPA. Twenty adults were surgically tagged with acoustic transmitters. Fish monitored in 2008 (n = 12) were translocated from the point of capture to analyse the movement behaviour after artificial displacement. Upon release at displaced locations, 67% of the fish moved towards the original capture location using a time of return that ranged from 0.75 to 15.25 h. Fish monitored in 2009 (n = 8) were released at the point of capture. They showed high site fidelity with a maximum period of 27 d between the first time and the last time they were detected. [Copyright &y& Elsevier]

Abstract: The amazing abilities of Pacific salmon to migrate long distances from the ocean to their natal streams for spawning have been investigated intensively since 1950’s, but there are still many mysteries because of difficulties to follow their whole life cycle and to wait their sole reproductive timing for several years. In my laboratory, we have tried to clarify physiological mechanisms of homing migration in Pacific salmon, using four anadromous Pacific salmon (pink, Oncorhynchus gorbuscha; chum, Oncorhynchus keta; sockeye, Oncorhynchus nerka; masu, Oncorhynchus masou) in the north Pacific Ocean as well as two lacustrine salmon (sockeye and masu) in Lake Toya and Lake Shikotsu, Hokkaido, Japan, where the lakes serve as a model “ocean”. Three different approaches from behavioral to molecular biological researches have been conducted using these model fish. First, the homing behaviors of adult chum salmon from the Bering Sea to Hokkaido as well as lacustrine sockeye and masu salmon in Lake Toya were examined by means of physiological biotelemetry techniques, and revealed that salmon can navigate in open water using different sensory systems. Second, the hormone profiles in the brain–pituitary–gonadal (BPG) axis were investigated in chum salmon and lacustrine sockeye salmon during their homing migration by means of hormone specific time-resolved fluoroimmunoassay (TR-FIA) systems, and clarified that salmon gonadotropin-releasing hormone (sGnRH) plays leading roles on homing migration. Third, the olfactory functions of salmon were studied by means of electrophysiological, behavioral, and molecular biological techniques, and made clear that olfactory discriminating ability of natal stream odors. These results have discussed with the evolutional aspects of four Pacific salmon, sexual differences in homing profiles, and the possibility of dissolved free amino acids (DFAA) as natal stream odors for salmon. [ABSTRACT FROM AUTHOR]

Teleost fishes are capable of detecting and behaviorally responding to linearly polarized light. Fish exhibit free-swimming spatial orientation to imposed and natural polarized light fields, and the fidelity of this spatial orientation depends heavily on UV and short wavelength content of the polarization field. Fish make fine-scale behavioral discriminations between stimuli that differ in e-vector orientation, independent of brightness. The detection of polarized light by photoreceptors is based on specializations of the disk membrane in the outer segment of cones that permit preferential absorption of axial and transverse polarized light. Differential polarization detectors that have overlapping spectral sensitivity in the UV short wavelength spectrum mediate polarization sensitivity. These differential detectors are based on cone photoreceptors that share spectral sensitivity in the UV short wavelength spectrum: the α-band of UV-sensitive cone mechanism as the vertical detector, and the β-band of mid- and long-wavelength sensitive cone mechanisms as the horizontal detector. Negative feedback of horizontal cells on cones govern opponent interactions between differentially sensitive polarization detectors. Polarization opponency functions to enhance e-vector contrast under conditions that vary in degree of polarization and ambient intensity. Ontogenetic changes in the cone mosaic, resulting from programmed cell death and regeneration of UV-sensitive cones, alter the retinal location of polarization sensitivity. These developmental changes greatly influence behavioral responses to polarized light. Copyright © 2010 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Abstract: Gene expression for growth hormone (GH)/prolactin (PRL)/somatolactin (SL) family hormones in the pituitaries of homing chum salmon were examined, because gene expression for these hormones during ocean-migrating phases remains unclear. Fish were collected in the winter Gulf of Alaska, the summer Bering Sea and along homing pathway in the Ishikari River–Ishikari Bay water system in Hokkaido, Japan in autumn. The oceanic fish included maturing adults, which had developing gonads and left the Bering Sea for the natal river by the end of summer. The absolute amounts of GH, PRL and SL mRNAs in the pituitaries of the maturing adults in the summer Bering Sea were 5- to 20-fold those in the winter Gulf of Alaska. The amount of GH mRNA in the homing adults at the coastal seawater (SW) areas was smaller than that in the Bering fish, while the amount of PRL mRNA remained at the higher level until fish arrived at the Ishikari River. The gill Na+,K+-ATPase activity in the coastal SW fish and the plasma Na+ levels in the brackish water fish at the estuary were lowered to the levels that were comparable to those in the fresh water (FW) fish. In conclusion, gene expression for GH, PRL and SL was elevated in the pituitaries of chum salmon before initiation of homing behavior from the summer Bering Sea. Gene expression for GH is thereafter lowered coincidently with malfunction of SW adaptability in the breeding season, while gene expression for PRL is maintained high until forthcoming FW adaptation. [Copyright &y& Elsevier]

Two populations of homing sockeye salmon (Oncorhynchus nerka; Adams and Chilko) were intercepted in the marine approaches around the northern and southern ends of Vancouver Island (British Columbia, Canada) en route to a natal river. More than 500 salmon were nonlethally biopsied for blood plasma, gill filament tips, and gross somatic energy (GSE) and were released with either acoustic or radio transmitters. At the time of capture, GSE, body length, and circulating testosterone ([T]) differed between populations, differences that reflected known life-history variations. Within-population analyses showed that in Adams sockeye salmon, plasma glucose ([glu]), lactate ([lactate]), and ion concentrations were higher in the northern approach than in the southern approach, suggesting that the former was more stressful. GSE, [T], and gill Na+,K+ATPase activities also differed between the two locales, and each varied significantly with Julian date, suggesting seasonality. Despite these relative geographic differences, the timing of river entry and the ability to reach spawning areas were strongly correlated with energetic, reproductive, and osmoregulatory state. Salmon that delayed river entry and reached spawning areas had relatively high GSE and low [T] and gill ATPase. In contrast, salmon that entered the river directly but that ultimately failed to reach spawning areas had lower GSE and higher [T] and gill ATPase, and they also swam at significantly faster rates (failed fish ~20.0 km d-1 vs. successful fish ~15.5 km d-1). Physiologically, salmon that did not enter the river at all but that presumably died in the marine environment exhibited high stress (plasma [glu] and [lactate]) and ionoregulatory measures (plasma [Na+], [Cl-], osmolality). [ABSTRACT FROM AUTHOR]

Atlantic bluefin tuna (BFT; Thunnus thynnus) is a migrating species straddling the North Atlantic Ocean and Mediterranean Sea. It is assumed that this species is divided into a western and an eastern stock, which spawn in the Gulf of Mexico and the Mediterranean Sea, respectively. To learn more about the reproductive behavior of the eastern BFT stock, we tracked gonadal development in adult fish that were sampled between April and July during three consecutive years (2003–2005). Sampling campaigns were carried out using common fishing methods at selected locations within the Mediterranean Sea, namely Levantine Sea, Malta, and Balearic Islands. An additional sampling point, Barbate, was situated northwest of the Straits of Gibraltar along the Atlantic coast. Morphometric parameters such as the total body mass ( M B) and the weights of the gonads ( M G) were recorded, and the respective gonadosomatic index (GSI) values were calculated. The data collected revealed two important trends: (1) GSI values are higher in fish caught in the eastern rather than the western locations across the Mediterranean Sea, and (2) the GSI reaches maximum values between late May and early June in Levantine Sea (eastern Mediterranean Sea), and only 2 and 4 weeks later in the central (Malta) and western (Balearic Islands) locations, respectively. The advanced gonadal development in BFT correlates well with higher sea surface temperatures. Our findings also distinguish the northern Levantine Sea BFT population (mean M B 78.41 ± 4.13 kg), and the Barbate BFT population with the greatest M B (all fish sampled > 100 kg). These data reflect a situation in which the eastern Mediterranean basin may function as a habitat for young BFT, until they gain a larger M B and are able to move to the Atlantic Ocean. However, the existence of genetically discrete BFT populations in the Mediterranean Sea cannot be ruled out. [ABSTRACT FROM AUTHOR]

A video camera inside an underwater housing was used to record the spawning activities of lake trout, Salvelinus namaycush, in Kushog Lake, Ontario (Canada). Contrary to the commonly accepted belief describing lake trout as the only salmonine to spawn exclusively at night, the recordings were taken during the day. Lake trout spawning behaviour is described in detail and compared with other salmonine species. The loss of female “nest-building” and assumption of a novel itinerant strategy during which females travel across the breeding grounds accompanied by a group of males, is considered to be an important change in the evolution of the lake trout’s unique mode of spawning. [ABSTRACT FROM AUTHOR]

Olfaction is decisive for the homeward migration of anadromous salmonids. Two different olfactory hypotheses for explaining how this mechanism works have been proposed (the imprinting and the pheromone hypothesis), and they differ with regard to the origin of the odours that define home. The pheromone hypothesis assumes that fish respond to strain-specific pheromones and that no imprinting is necessary. The imprinting hypothesis assumes that juvenile fish become imprinted to odours of abiotic or biotic origin in natural rivers; the imprinting may be a single event or may occur sequentially during downstream migration as smolts. The two hypotheses were challenged by reciprocal transplantation of parr, residents and smolt of Arctic char ( Salvelinus alpinus) and brown trout ( Salmo trutta) between the Salangen and the Løksebotten rivers. Both rivers empty into the Salangen Fjord, Norway, about 10 km apart. Salangen Arctic char released in the Løksebotten River, and Løksebotten brown trout released in the Salangen River (parr, resident and smolt) initiated spontaneous homeward migration without preceding contact with home stream water. This indicates that site imprinting (single or sequential) could not have been involved. In the sea, the released fish apparently integrated into the migratory system of relatives from their river of origin. Recapture rates did not differ for fish allowed to receive single or sequential imprinting. [ABSTRACT FROM AUTHOR]

A specimen of the Japanese threadfin bream Nemipterus japonicus was recorded for the first time from the Mediterranean Sea. The presence of this Indo-Pacific fish in the Mediterranean is evidently due to migration from the Red Sea via the Suez Canal. [ABSTRACT FROM AUTHOR]

To analyse the effects of small-scale dams on fish communities, species diversity, population density, biomass, migration over dams and trophic relationships were investigated in the above- and below-dam sections of three Japanese streams. The dams were 1·5–3·9 m high, constructed within 400 m of the sea, and had no impoundment or fishway. Fish communities were mainly composed of diadromous fishes. Of the 17 species sampled, only a few species of gobies, Rhinogobius spp. and Gymnogobius spp. were able to climb and migrate upstream over the dams. Consequently the number of species, and total density and biomass of fishes below the dams was high, but low above the dams. One of the most dominant fish below dams, Plecoglossus altivelis altivelis, predominantly fed on benthic algae, whereas other fishes preyed on benthic invertebrates. Trophic relationships above dams were very simple, the few species of gobies preying on chironomid larvae and other aquatic invertebrates. [ABSTRACT FROM AUTHOR]

Placement of fish migration barriers (primarily of gabion construction) on select streams is one of the major recovery actions used to isolate and protect upstream populations of Apache trout Oncorhynchus gilae apache from downstream populations of nonnative salmonids. However, the effectiveness of the recovery action has not been evaluated. We evaluated the success of constructed barriers at preventing upstream movement of nonnative salmonids into areas occupied by native Apache trout. We collected and marked salmonids downstream of six barriers on six streams in the White Mountains of east-central Arizona and subsequently electrofished upstream of the barriers to determine whether marked fish had moved past them. Only 1 of 1,436 marked salmonids was collected upstream of one of the six barriers evaluated over a 3-year period. Our results showed that the barriers evaluated in our study are effective for a short term; however, long-term evaluation is needed, as these failure rates represent minimum failure rates and they could increase as the number of years since barrier construction increases. [ABSTRACT FROM AUTHOR]

Approximately three-quarters of migrating autumn (fall) chinook salmon Oncorhynchus tshawytscha smolts avoided a covered channel and selected an uncovered channel when presented with a choice in an experimental flume. Rejection of overhead cover occurred prior to, but was rare post-channel entrance. Smolts may selectively reject riparian cover as an adaptive behavioural response to minimize predation risk and enhance rates of migration. The findings have implications for fish bypass design and riparian habitat and culvert restoration. [ABSTRACT FROM AUTHOR]

The migratory history of the white-spotted charrSalvelinus leucomaeniswas examined using otolith microchemical analysis. The fish migrated between freshwater and marine environments multiple times during their life history. Some white-spotted charr used an estuarine habitat prior to smolting and repeated seaward migration within a year. [ABSTRACT FROM AUTHOR]

Some young-of-the-year Atlantic salmon (Salmo salar) have a tendency to drift soon after emergence from the gravel, whereas others, called resident fry, set up and defend territories. Little is known about the mechanisms regulating this strong tendency to drift soon after emergence, a phenomenon that can greatly influence survival within a population. This study was carried out in the Western Brook system, Gros Morne National Park, Newfoundland, Canada. The objective was to assess differences, through biometric characteristics, between drifting and resident Atlantic salmon fry by examining both groups of fish caught simultaneously in the same riverine habitat. Resident salmon fry can be up to 4.8% longer and 20.4% heavier compared with drifting fry of similar age (measured in days since emergence). Therefore, it seems that competition, more than prior residence effect, could be part of the driving forces behind this active movement and that differences between subpopulations of Atlantic salmon fry can have major repercussions on life history patterns. [ABSTRACT FROM AUTHOR]

Investigates the multiyear homing of Atlantic cod at a Bar Haven spawning ground in Placenta Bay, Newfoundland. Relocation of tagged fish; Details on the long-term-feeding migrations of cods; Management of commercial fisheries.

Discusses the ecology of fish migrations. Influence of homing on the design of studies of factors responsible for initiating and guiding fish migrations; Factors required during the open water phase of the migration; Ability of fish to utilize the sun as an aid to orientation; Ability to perceive polarized light; Sensitivity to geomagnetic and geoelectric fields.

Atlantic bluefin tuna populations are in steep decline, and an improved understanding of connectivity between individuals from eastern (Mediterranean Sea) and western (Gulf of Mexico) spawning areas is needed to manage remaining fisheries. Chemical signatures in the otoliths of yearlings from regional nurseries were distinct and served as natural tags to assess natal homing and mixing. Adults showed high rates of natal homing to both eastern and western spawning areas. Trans-Atlantic movement (east to west) was significant and size-dependent, with individuals of Mediterranean origin mixing with the western population in the U.S. Atlantic. The largest (oldest) bluefin tuna collected near the northern extent of their range in North American waters were almost exclusively of western origin, indicating that this region represents critical habitat for the western population. [ABSTRACT FROM AUTHOR]

Upstream selective movement of chum salmon (Oncorhynchus keta), which were captured in the Osaru River, Hokkaido, Japan, in late spawning season, was investigated in a two-choice test tank consisted of two water inlet arms and one pool. Artificial home stream water that was prepared based on the compositions of amino acids and related substances of the Osaru River, and natural lake water flowed in each arm. Of 44 chum salmon tested, 28 fish showed upstream movement to one of the choice arm, and 24 fish (85.7%) of those moved fish were found in the arm running the artificial home stream water. When the artificial home stream water flowed from the left and right arms, 88.9% and 80% of fish were observed in the left and right arms, respectively. These results strongly support our hypothesis that amino acids dissolved in stream waters are home stream substances for salmon homing. [ABSTRACT FROM AUTHOR]

Examines the natal homing of weakfish, an estuarine-spawning marine fish in North America. Use of natural geochemical signatures in otoliths; Range of spawning site fidelity; Comparison of data with genetic analyses of population structure; Implications for marine reserve design.

The article focuses on the threat posed by the construction at the Don Sahong Dam on the fisheries in Mekong River. Topics discussed include the negative effects of the construction on the migration and fishing sites of pa nyan catfish, the food security crisis that threaten the Mekong delta, and the efforts of Xayaburi Power Co. to outfit the dam with features that will reduce its ecological toll on the river.

Focuses on the study of the weakfish homing patterns for spawning in several estuaries in North America. Significance of the otolith concentration of fishes on homing ability; Composition of the chemical isotopes in the weakfish; Implication of the otolith analysis on tracking economically important fishes.

Corrections to the article "Homing and Straying of Atlantic Salmon in the Bidasoa River: Report of an Unusual Stray From Great Britain to the Iberian Peninsula," by Leunda P. M., Ardaiz J., Russell I. C., Toms S. and Hillman R., published in a 2013 issue of the journal is presented.