First documentation of detailed behaviors of endangered adult Sakhalin taimen <Emphasis Type="Italic">Parahucho perryi</Emphasis> in the Bekanbeushi River system,eastern Hokkaido,Japan, using bio-logging and acoustic telemetry concurrently

Behavior of adult Parahucho perryi was examined using bio-logging and acoustic telemetry concurrently in the Bekanbeushi River system, eastern Hokkaido, Japan, in 2009 and 2010. Based on 46.1–87.9 h data from five P. perryi (69.0–80.0 cm fork length) caught from Lake Akkeshi, they used upstream (n = 2), midstream (n = 3), and downstream (n = 4) habitats. Large variability in diel activity and depth occupation existed in each stream habitat; however, fish in the downstream habitat tended to be more active than those in the upper habitats and mainly occupied shallower depths than mean bottom depth in this habitat.     

Habitat utilization, movement and use of groundwater seepages by larval and juvenile Black Redhorse, Moxostoma duquesnei

Black Redhorse (Moxostoma duquesnei) larval and juvenile habitat was characterized in the Grand River, Ontario from June to September 2007–2012. Similar to adult Black Redhorse and their congeners, larval Black Redhorse were most likely to be located in clean, clear, stable runs with low to moderate flow, over pebble, gravel and cobble substrate, mixed with sand. Areas (n?=?22) where 0+ Black Redhorse were observed and collected were 1.4?±?0.2 m from shore, with a mean water temperature of 22.0?±?0.5 °C, mean depth of 0.20?±?0.02 m and mean water velocity of 0.12?±?0.05 m/s. Larval and juvenile Black Redhorse occupied riffles, runs, pools and backwater areas; however, there was a strong preference for runs. Juvenile Black Redhorse moved upstream in the early evening and at night to overwintering areas in the Grand River in November when water temperature approached 5 °C. The persistence of Black Redhorse populations in the Grand River may be related to the presence of groundwater, which provides refuge from extreme temperature and poor water quality during the summer.     

Depth distribution and abundance of a coral-associated reef fish: roles of recruitment and post-recruitment processes

The abundance of many reef fish species varies with depth, but the demographic processes influencing this pattern remain unclear. Furthermore, while the distribution of highly specialized reef fish often closely matches that of their habitat, it is unclear whether changes in distribution patterns over depth are the result of changes in habitat availability or independent depth-related changes in population parameters such as recruitment and mortality. Here, we show that depth-related patterns in the distribution of the coral-associated goby, Paragobiodon xanthosoma, are strongly related to changes in recruitment and performance (growth and survival). Depth-stratified surveys showed that while the coral host, Seriatopora hystrix, extended into deeper water (>20 m), habitat use by P. xanthosoma declined with depth and both adult and juvenile P. xanthosoma were absent below 20 m. Standardization of S. hystrix abundance at three depths (5, 15 and 30 m) demonstrated that recruitment of P. xanthosoma was not determined by the availability of its habitat. Reciprocal transplantation of P. xanthosoma to S. hystrix colonies among three depths (5, 15 and 30 m) then established that individual performance (survival and growth) was lowest in deeper water; mortality was three times higher and growth greatly reduced in individuals transplanted to 30 m. Individuals collected from 15 m also exhibited growth rates 50% lower than fish from shallow depths. These results indicate that the depth distribution of this species is limited not by the availability of its coral habitat, but by demographic costs associated with living in deeper water.     

Seasonal movements of striped bass <Emphasis Type="Italic">Morone saxatilis</Emphasis> in a large tidal and hydropower regulated river

Following a failed spawning event in 1975 and the suspected absence of recent spawning by Striped Bass Morone saxatilis in the Saint John River, New Brunswick, the native Striped Bass population has been considered extirpated. Non-native migratory Striped Bass, however, still frequent the river, and a remnant, likely native, population may still exist. To characterize the movements and habitat use of adult Striped Bass still arriving to, and possibly residing within the Saint John River, Striped Bass (n?=?40, size range, 40.5–90.9 cm FL) were captured throughout 2010–13 in the lower Saint John River, and surgically implanted with multi-year acoustic transmitters. Striped Bass were passively tracked using an array of 5–33 project specific receivers between 2010 and 14 and augmented by detections from the Ocean Tracking Network from 2011 to 13. Most tag detections recorded during the predicted spawning period occurred near locations suspected to have supported Striped Bass spawning historically. Only six tagged fish (15% of total) were detected outside of the river, five of which only left the river briefly during the spawning period and then returned. Tagged Striped Bass used four overwintering sites within the Saint John River to which individuals demonstrated annual fidelity. Our findings suggest the presence of a local, possibly reproducing Striped Bass population that exhibits multi-annual residency within the river; however, successful spawning remains to be confirmed.     

Effects of habitat features on size-biased predation on salmon by bears

Predators can drive trait divergence among populations of prey by imposing differential selection on prey traits. Habitat characteristics can mediate predator selectivity by providing refuge for prey. We quantified the effects of stream characteristics on biases in the sizes of spawning salmon caught by bears (Ursus arctos and U. americanus) on the central coast of British Columbia, Canada by measuring size-biased predation on spawning chum (Oncorhynchus keta) and pink (O. gorbuscha) salmon in 12 streams with varying habitat characteristics. We tested the hypotheses that bears would catch larger than average salmon (size-biased predation) and that this bias toward larger fish would be higher in streams that provide less protection to spawning salmon from predation (e.g., less pools, wood, undercut banks). We then we tested for how such size biases in turn translate into differences among populations in the sizes of the fish. Bears caught larger-than-average salmon as the spawning season progressed and as predicted, this was most pronounced in streams with fewer refugia for the fish (i.e., wood and undercut banks). Salmon were marginally smaller in streams with more pronounced size-biased predation but this predictor was less reliable than physical characteristics of streams, with larger fish in wider, deeper streams. These results support the hypothesis that selective forces imposed by predators can be mediated by habitat characteristics, with potential consequences for physical traits of prey.     

Evidence of Segregated Spawning in a Single Marine Fish Stock: Sympatric Divergence of Ecotypes in Icelandic Cod?

There is increasing recognition of intraspecific diversity and population structure within marine fish species, yet there is little direct evidence of the isolating mechanisms that maintain it or documentation of its ecological extent. We analyzed depth and temperature histories collected by electronic data storage tags retrieved from 104 Atlantic cod at liberty ≥1 year to evaluate a possible isolating mechanisms maintaining population structure within the Icelandic cod stock. This stock consists of two distinct behavioral types, resident coastal cod and migratory frontal cod, each occurring within two geographically distinct populations. Despite being captured together on the same spawning grounds, we show the behavioral types seem reproductively isolated by fine-scale differences in spawning habitat selection, primarily depth. Additionally, the different groups occupied distinct seasonal thermal and bathymetric niches that generally demonstrated low levels of overlap throughout the year. Our results indicate that isolating mechanisms, such as differential habitat selection during spawning, might contribute to maintaining diversity and fine-scale population structure in broadcast-spawning marine fishes.     

Spawning habitat in the spined loach, <Emphasis Type="Italic">Cobitis taenia</Emphasis> (Cypriniformes: Cobitidae)

Spawning habitat of the endangered spined loach Cobitis taenia was studied in northwestern Germany. The distribution of eggs of the loach in the field was best correlated with the density of vegetation but had little correlation with current velocity, water depth, or bottom substrate. In the aquarium, the loach chose dense vegetation for an oviposition site, as inferred by the direct observations of spawning and the location of spawned eggs. It is concluded that such habitat specialization is an important element in the autecology of the endangered fish and a critical stage in the habitat requirements of its populations.     

Photosynthetic light requirements and vertical distribution of macroalgae in newly ice-free areas in Potter Cove,South Shetland Islands,Antarctica

In Potter Cove, Antarctica, newly ice-free areas appeared due to glacial retreat. Simultaneously, the inflow of sediment increased, reducing underwater photosynthetically active radiation (PAR, 400–700 nm). The aim of this study was to determine the photosynthetic characteristics of two macroalgal species colonizing three newly ice-free areas, A1, A2 and A3, with increasing degree of glacial influence from A1 to A3. Turbidity, salinity and temperature were measured, and light attenuation coefficients (K _d) calculated and considered as a proxy for glacial sediment input. The lower depth distribution of the red alga Palmaria decipiens and the brown alga Himantothallus grandifolius was 10 m in A3, 20 m in A2 and 30 m in A1. Both species were then collected, at 5 and 10 m at all areas. Photosynthetic parameters and the daily metabolic carbon balance (CB) were determined. K _d was significantly higher in A3 compared with A1 and A2. The CB of P. decipiens was significantly higher in A1 followed by A2 and A3, and significantly higher at shallower than at greater depth. For H. grandifolius CB was significantly lower in A3 and in A2 at deeper depths compared with the rest of areas and depths. The lower distribution limit of the algae was positively correlated to the light penetration. An increase in the sediment run-off due to global warming might lead to an elevation of the lower depth distribution limit but retreating glaciers can open new space for macroalgal colonization. These changes will probably affect macroalgal primary productivity in Potter Cove with consequences for the coastal ecosystem.     

Deepwater broadcast spawning by Montastraea cavernosa, Montastraea franksi, and Diploria strigosa at the Flower Garden Banks, Gulf of Mexico

Broadcast spawning by corals is a tightly synchronized process characterized by co-ordinated gamete release within 30–60 min time windows once per year. In shallow water corals, annual water temperature cycles set the month, lunar periodicity the day, and sunset time the hour of spawning. This tight temporal regulation is critical for achieving high fertilization rates in a pelagic environment. Given the differences in light and temperature that occur with depth and the importance of these parameters in regulating spawn timing, it has been unclear whether deeper coral can respond to the same environmental cues that regulate spawning behaviour in shallower coral. In this report, a remotely operated vehicle was used to monitor coral spawning activity at the Flower Garden Banks at depths from 33 to 45 m. Three species Montastraea cavernosa, Montastraea franksi, and Diploria strigosa were documented spawning within this depth range. All recorded spawning events were within the same temporal windows as shallower conspecifics. These data indicate that deep corals at this location either sense the same environmental parameters, despite local attenuation, or communicate with shallower colonies that can sense such spawning cues.     

Seasonal and daily movements of the bluntnose sixgill shark (<Emphasis Type="Italic">Hexanchus griseus</Emphasis>) in the strait of Georgia from satellite tag data

The bluntnose sixgill shark (Hexanchus griseus Bonnaterre 1788) is a large, deepwater apex predator that, in a few unique locations such as the Strait of Georgia, Canada, occupies shallow, inshore waters as juveniles. The occurrence of pregnant females in the Strait of Georgia suggests that this is an important area for parturition and juvenile rearing. Bluntnose sixgill sharks are listed under the Canadian Species at Risk Act, and an understanding of their behaviour in habitat selection during important life stages is an important component for conservation measures. We employed satellite tags to identify the daily and seasonal depth and thermal habitats of juvenile bluntnose sixgill sharks in the Strait of Georgia. Tag release and depth information suggests that juvenile bluntnose sixgill sharks within the Strait of Georgia remain there until they mature and migrate to offshore deepwaters. The dominant depth habitat utilized by the juvenile sharks in our study was deepwater (>200 m), with only occasional occupation of depths <100 m, indicating that even within coastal areas, juveniles still prefer deepwater. Overall the sharks occupied shallower depths at night than during the day with increased vertical activity in both the day and night compared to crepuscular periods. Seasonally, the sharks occupied shallower depths in the summer than in winter, but inconsistency in the temperatures with which those depths were associated suggests that their vertical behaviour is influenced by local foraging opportunities and not by thermoregulation.     

Factors influencing the spatial ecology of Lake Sturgeon and Walleye within an impounded reach of the Winnipeg River

Impoundments of free-flowing rivers for hydropower generation often confine fish to relatively small reaches that can restrict movement, limit habitat availability, and alter life history strategies. Here, acoustic telemetry was used to describe the seasonal habitat use, locomotory activity, and depth use for Lake Sturgeon (Acipenser fulvescens) and Walleye (Sander vitreus) within an impounded reach on the Winnipeg River, Manitoba, Canada. Lake Sturgeon foraged and overwintered in the riverine-lacustrine transitionary habitat as well as immediately below the tailrace of the upstream run-of-river facility. Walleye demonstrated high site fidelity to the upstream habitat situated near the tailrace of a hydropower facility. Contrary to Lake Sturgeon, that used multiple habitat types, Walleye used the tailrace for spawning, foraging, and overwintering, given their high residency rates throughout all months at this location. Activity for both species increased with water temperature and when residing in habitat types located farther upstream, but were minimally active during the winter season throughout the impounded reach. On average, Lake Sturgeon utilized 73% of the available depth while Walleye utilized 62% of the available depth across habitat types and months. Overall, the habitat located within the tailrace and below run-of-river facilities should be a conservation priority for both Lake Sturgeon and Walleye populations. There was persistent presence of Lake Sturgeon and Walleye throughout the spawning, foraging, and overwintering periods in the SSGS tailrace and within the first rkm downstream of the tailrace. The habitat proximal to run-of-river facilities generally encompasses small areas of the total potential habitat within impoundments, yet is important to both species studied here. The results provide information on the seasonal habitat use and biological responses to environmental cues for Lake Sturgeon and Walleye that will enhance management and ecological understanding for populations that are confined to impounded reaches.     

Morphogenetic diversity of the ectomycorrhizal genus <Emphasis Type="Italic">Cortinarius</Emphasis> section <Emphasis Type="Italic">Calochroi</Emphasis> in the Iberian Peninsula

The taxonomic and genetic diversity of Cortinarius section Calochroi in one of the most biodiversity-rich regions in Europe, the Iberian Peninsula, was investigated through morphological and phylogenetic methods. This combined methodological approach allowed the identification of 15 known species and one new species, Cortinarius ortegae, which is described here. A dichotomous key is provided for field recognition of Calochroi species inhabiting different Iberian and Balearic Island woodlands. Polymorphism analyses within some studied species showed that the distribution of intraspecific lineages is dependent on geography and, in some cases, tree host. Furthermore, the dating analysis suggested that diversification within Calochroi started in the Pliocene and most of the current genetic diversity originated in the Pleistocene. This temporal scenario supports hypotheses in which climatic oscillations in the Quaternary may have been driving the evolution of this group of ectomycorrhizal fungi.     

Inconsistency between salinity preference and habitat salinity in euryhaline gobiid fishes in the Isazu River,northern Kyoto Prefecture

Adults of three amphidromous gobiid fishes, Tridentiger brevispinis, Rhinogobius similis, and Gymnogobius petschiliensis, are euryhaline and generally found in both freshwater (FW) and brackish water (BW) areas. The determining factors for their choice of habitat with different salinity have never been explored. In this study, a salinity-choice experiment was conducted using the above species captured in the FW region of the Isazu River, northern Kyoto Prefecture. For comparison, the fluvial goby Rhinogobius flumineus and BW-acclimated G. petschiliensis were also tested. We found that the three euryhaline species, including BW-acclimated G. petschiliensis, preferred BW to FW, whereas R. flumineus preferred FW. These results suggest that salinity preference did not determine habitat in these euryhaline gobiids, which were found in FW. Surveys were also conducted focusing on competitors and predators in their potential habitats. Thus, net sampling captured many other gobiid species, and an environmental DNA method detected Japanese temperate bass, a voracious predator, in the estuarine areas, suggesting that biotic factors are major determinants in the distribution of euryhaline species.     

Vertical migration in streams: seasonal use of the hyporheic zone by the spinous loach <Emphasis Type="Italic">Cobitis shikokuensis</Emphasis>

Vertical hydrological connectivity between the surface stream and benthic and hyporheic zones plays a key ecological role in the biodiversity of lotic ecosystems because it allows surface and benthic organisms to use the hyporheic zone as a seasonal habitat and refuge. Use of the hyporheic zone by surface/benthic organisms has been well studied in invertebrates, but little is known about the importance of this connectivity for fishes. We investigated streambed surface and hyporheic densities (5–10, 15–20 and 20–25 cm below the streambed surface) of a stream fish, Cobitis shikokuensis, over a 20-month period in the Shigenobu River, southwestern Japan, to test the hypothesis that it uses the hyporheic zone for spawning and overwintering. In total, 1,804 individuals (13–58 mm total length) were captured from 33 streambed surface samplings and 102 individuals (10–46 mm total length) were present in 1,147 samples of 57 hyporheic samplings. Population densities in both zones peaked in late summer–early autumn due to the recruitment of age 0+ fish and a female with eggs was found in the hyporheic zone during the reproductive season. Both 0+ and older fish were absent from the streambed surface during winter, and fish densities were also lower in the hyporheic zone at this time. However, the vertical distribution of the fish tended to be skewed towards the deeper hyporheic layers from autumn to spring. These findings indicate that C. shikokuensis vertically migrates between the streambed surface and the hyporheic zone for spawning, rearing and overwintering, suggesting that the integrity of vertical hydrological connectivity in lotic systems is crucial for certain fish species.     

The effect of bloom of filamentous green algae on the reproduction of yellowfin sculpin <Emphasis Type="Italic">Cottocomephorus grewingkii</Emphasis> (Dybowski, 1874) (Cottoidae) during ecological crisis in Lake Baikal

In shallow water areas of open Lake Baikal, filamentous green alga of the genus Spirogyra grows abundantly. Together with alga of the genus Ulothrix, it forms algal mats. According to our observations from 2010 to 2013, the spawning habitat conditions for the yellowfin sculpin Cottocomephorus grewingkii (Dybowski, 1874) (Cottidae) proved to be significantly disturbed in the littoral zone of Listvennichnyi Bay (southern Baikal), which, in turn, reduced the number of egg layings. With a 100% projective cover of the floor and a high density of green filamentous algae, the shallow-water stony substrate becomes completely inaccessible for spawning of the August population.     

Assessment of the Feasibility of Preventing Reproduction of Lake Charr, Salvelinus Namaycush, in Shallow Areas of Reservoirs Affected by Drawdowns

Lake charr, Salvelinus namaycush, spawn almost exclusively in lakes, in the fall. Spawning sites in inland lakes are generally located close to the shore in areas with coarse-textured substrate, and in depths of less than 2m. Because of the type of water management system applied in reservoirs where water levels are lowered during the winter, eggs deposited during the fall around the shallow shoreline of reservoirs can be exposed. The depth of spawning sites relative to drawdowns may be a limiting factor for lake charr survival in reservoirs. In 1995 and 1996, we evaluated the ability to induce lake charr reproduction in deeper water, below the range of fluctuating water levels by the sequential construction of artificial reefs and limiting access to natural spawning habitat. The creation of artificial deeper water spawning areas, adjacent to natural sites, produced a partial transfer of reproduction. However when natural spawning sites were covered with tarpaulins almost all the eggs were laid in the artificial deeper water spawning areas. Complete or partial transfer of reproduction activities to sites below the depth not affected by water level fluctuations is therefore a potential way of alleviating the effects of hydroelectric reservoir management.     

Intra- and interspecific hybridization in invasive Siberian elm

Hybridization creates unique allele combinations which can facilitate the evolution of invasiveness. Frequent interspecific hybridization between the Siberian elm, Ulmus pumila, and native elm species has been detected in the Midwestern United States, Italy and Spain. However, Ulmus pumila also occurs in the western United States and Argentina, regions where no native elm species capable of hybridizing with it occurs. We examined whether inter- or intraspecific hybridization could be detected in these regions. Nuclear markers and the program STRUCTURE helped detect interspecific hybridization and determine the population genetic structure in both the native and the two non-native ranges. Chloroplast markers identified sources of introduction into these two non-native ranges. No significant interspecific hybridization was detected between U. pumila and U. rubra in the western United States or between U. pumila and U. minor in Argentina and vice versa. However, the genetic findings supported the presence of intraspecific hybridization and high levels of genetic diversity in both non-native ranges. The evidence presented for intraspecific hybridization in the current study, combined with reports of interspecific hybridization from previous studies, identifies elm as a genus where both inter- and intraspecific hybridization may occur and help maintain high levels of genetic diversity potentially associated with invasiveness.     

The distribution of salmonids in upland streams in relation to depth and gradient

The distribution of various age classes of salmon and trout was assessed in upland streams by electrofishing. Water depths and site gradients were measured and correlated to fish densities. The fry of both species were significantly more abundant in shallow water; up to 75·3% of salmon fry and 72·2% of trout fry were captured in sites of mean depth < 20 cm. Older trout were found mainly in the deeper areas, with a maximum of 7·4% captured in sites < 20 cm mean depth. Yearling fish were found in all the depth-ranges sampled, but with a tendency for higher numbers in mid-range depths. There were similar correlations in the abundance of each age class with the actual areas of shallow, mid-range and deep water habitat available within sites. Correlations of fish density with gradient indicated that trout were limited in their distribution to areas of lower flow, whereas salmon were not. Since depth and gradient were significantly negatively correlated, there was an apparent preference of trout for slightly deeper habitats than the equivalent year classes of salmon. The observed habitat segregation is discussed in terms of competition and selection.     

Unionid mussel composition and ditch environments in floodplain and alluvial fan geomorphic types: a case study of a Lake Biwa river basin

To determine the differences in the ditch environments and mussel composition between floodplains and alluvial fans, two geomorphic types in a Lake Biwa river basin were surveyed. An intrinsic Gaussian conditional autoregressive (CAR) model was applied to assess the relationship between the density of Nodularia douglasiae biwae, the dominant species in the floodplain area, and ditch environment. Relative to the alluvial fan area, ditches in the floodplain area had higher percentages of muddy and sandy substrates, a lower percentage of pebble substrates, greater sediment softness, faster flow velocity, and deeper water depth. N. d. biwae and Pronodularia japanensis were collected in both the floodplain and alluvial fan areas. Lanceolaria grayana and Sinanodonta japonica were captured only in the floodplain area, and Sinanodonta lauta was found only in the alluvial fan area. The differences in the ditch environments between the two geomorphic types and the drought tolerance of the mussel species may explain why the mussel composition differs between the two geomorphic types. The CAR model indicated that N. d. biwae was more abundant in ditches with sandy and soft sediment and with deeper water. It also points to the importance of microhabitat-scale sampling to determine the relationship between unionid density and ditch environment.