Aroma profiles of five basil (Ocimum basilicum L.) cultivars grown under conventional and organic conditions

A headspace solid-phase microextraction (HS-SPME) method coupled to gas chromatography–ion trap mass spectrometry (GC–ITMS) has been developed and applied for profiling of volatile compounds released from five Ocimum basilicum L. cultivars grown under both organic and conventional conditions. Comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC–TOFMS) was employed for confirmation of identity of volatiles extracted from the basil headspace by SPME.     

Flow and spawning habitat relationships for Dolly Varden: Understanding habitat–population dynamics in the Canadian Western Arctic

Northern form Dolly Varden (Salvelinus malma malma) have been designated as a species of Special Concern in Canada due to declines in population abundance and potential threats. Concern over detrimental effects of low flows on population abundance prompted research on how variability in discharge regimes influence habitat availability. Habitat suitability indices for prespawning and spawning adult anadromous Dolly Varden from two streams were integrated into a two‐dimensional hydrodynamic habitat model to assess the effect of flow variability on usable habitat. Regional hydrographs were used to identify an ecologically relevant range of flows that provided optimal spawning habitat for these populations and examine the relationship between abundance and discharge. Adults spawned in the tail end of pools at moderate water depths and water velocities, and used pebble‐ to cobble‐sized substrate for building redds; whereas, prespawning adults occupied deeper pools with moderate velocities and used cobble for cover. Model outputs showed that spawning habitat availability was optimized at flow rates between 1.6 and 3.0 m³/s and between 1.0 and 6.0 m³/s in Fish Hole Creek (FHC) and Little Fish Creek, respectively. A positive relationship between flows during the fall spawning period and abundance of the FHC population suggests that higher flows coinciding with optimal habitat availability may have contributed to positive recruitment. To strengthen and refine this habitat–population relationship for Dolly Varden in this area requires investigation of a broader suite of variables associated with environmental regimes and physical habitat in reaches used for spawning.     

Habitat diversity and fish assemblage structure in local river widenings: A case study on a swiss river

We investigated habitat availability and fish assemblage structure in three local river widenings, completed 3–14 years ago, and five adjacent canalized reaches on the river Thur, a seventh‐order river in Switzerland. To account for seasonal variability, surveys were repeated in winter and summer 2005. Results were compared with historical pre‐disturbance data to evaluate whether the current abiotic and biotic conditions in the study reaches have attained historic near‐natural levels. Hydro‐physical habitat diversity (depth, flow velocity, cover availability) was considerably greater in the two longer widenings (>900 m length) than in the canalized reaches and in the shortest widening (300 m length), with higher proportions of shallow or deep areas of different flow velocities. However, the comparison of current and historical near‐natural shoreline lengths indicated that the current geomorphological complexity is still considerably impaired in all reaches. No overall significant relationship was found between the reach type (canalized or rehabilitated) and the number of species or the total fish abundance which were strongly correlated with the availability of suitable cover and moderate flow velocity. However, highest winter abundances were observed in deep, well‐structured backwaters of the rehabilitated reaches, documenting their significance as wintering habitats. Assemblage structure and composition were similar in canalized and rehabilitated reaches. Compared to the historical data, however, fewer and different dominant species were found, and guild composition changed towards a higher representation of generalists and tolerant species. Copyright © 2008 John Wiley & Sons, Ltd.     

Enhanced bactericidal effect of enterocin AS-48 in combination with high-intensity pulsed-electric field treatment against Salmonella enterica in apple juice

The effect of the broad spectrum cyclic antimicrobial peptide enterocin AS-48 combination with high-intensity pulsed-electric field (HIPEF) treatment (35 kV/cm, 150 Hz, 4 micros and bipolar mode) was tested on Salmonella enterica CECT 915 in apple juice. A response surface methodology was applied to study the bactericidal effects of the combined treatment. The process variables were AS-48 concentration, temperature, and HIPEF treatment time. While treatment with enterocin AS-48 alone up to 60 microg/ml had no effect on the viability of S. enterica in apple juice, an increased bactericidal activity was observed in combination with HIPEF treatments. Survival fraction was affected by treatment time, enterocin AS48 concentration and treatment temperature. The combination of 100 micros of HIPEF treatment, 30 microg/ml of AS-48, and temperature of 20 degrees C resulted in the lowest inactivation, with only a 1.2-log reduction. The maximum inactivation of 4.5-log cycles was achieved with HIPEF treatment for 1000 micros in combination with 60 microg/ml of AS-48 and a treatment temperature of 40 degrees C. Synergism between enterocin AS-48 and HIPEF treatment depended on the sequence order application, since it was observed only when HIPEF was applied in the presence of previously-added bacteriocin. The combined treatment could improve the safety of freshly-made apple juice against S. enterica transmission.     

Heat transfer model with two heat transfer coefficients along a multiperforated plate — Application to combustion chamber wall cooling

Walls‘ cooling of aeronautic propeller combustion chamber is performed with the injection, through the combustion chamber wall, of a part of the air coming from compressors placed upstream. Measurements of the wall thermal fields are made by infrared thermography along the injection wall. This injection wall is pierced by 9 rows of 8 holes (α=90°) in staggered configuration (p/D=s/D=6). We propose a model using two heat transfer coefficients to represent the convective exchanges. The results are non-dimensioned and presented in comparison with the case without holes. The use of this model allows us to define 4 zones. Those 4 zones exist for the 5 blowing rates.     

Limited evidence of zebra mussel (Dreissena polymorpha) consumption by freshwater drum (Aplodinotus grunniens) in Lake Winnipeg

Freshwater drum (Aplodinotus grunniens) may be a predator of the invasive zebra mussel (Dreissena polymorpha), which established in Lake Winnipeg in 2013. In this study, the diets, trophic position, and growth of 51 freshwater drum collected in 2019 (six years post-zebra mussel invasion) were compared to 64 freshwater drum sampled in 2000. Benthic insect larvae were the dominant food items in both years. Although mollusks occur in high densities in Lake Winnipeg, they were only consumed by a few freshwater drum in either sample year. Zebra mussels were not a frequent prey item in 2019 as they were only consumed by four of the sampled freshwater drum. Stable isotope analysis of white muscle tissue yielded similar δ¹³C and δ¹⁵N values in both years and were consistent with a benthic, insectivorous diet. Length-at-age data derived from otoliths revealed that the 2019 population had at least an equal growth rate to the 2000 population. Weight-at-length data suggested that fish condition was greater in 2019 than in 2000, which coincided with increased benthic macroinvertebrate density in Lake Winnipeg. Based on these findings, Lake Winnipeg freshwater drum continue to feed predominantly on insect larvae and not zebra mussels.     

The distribution,density, and biomass of the zebra mussel (Dreissena polymorpha) on natural substrates in Lake Winnipeg 2017–2019

The distribution, density, biomass and size-structure of the zebra mussel (Dreissena polymorpha) population in Lake Winnipeg were examined between 2017 and 2019. Zebra mussels have colonized most of the available hard substrate in the south basin and Narrows region, but colonization of the north basin remains low at present, even on suitable substrate. Numerical densities and shell free biomass peaked at 5530 ± 953 m^?2 and 64.7 ± 57.9 g shell free dry mass m^?2 respectively. The distribution appeared to be strongly limited by substrate type and availability, with further limitations on the distribution imposed by physical disturbance in shallow waters and unsuitable substrate in deeper areas of the lake. Zebra mussels <1 year old dominated the populations, and individuals >18 mm were exceedingly rare. Poor recruitment was observed at sites along the eastern side of the south basin compared to elsewhere in the lake. The proximate causes of these differences in colonization success and recruitment are not clear, but may be in part due to heterogeneous patterns of key physico-chemical environmental conditions such as calcium concentrations required for successful development of juvenile mussels and colder water temperatures in the north basin. This study provides a baseline of information on which to track further expansion of zebra mussels in Lake Winnipeg and assist efforts to develop an understanding of how zebra mussels may affect the ecology of Lake Winnipeg.     

Historical and contemporary movement and survival rates of walleye (Sander vitreus) in Lake Winnipeg,Canada

Understanding patterns of fish movement in large lake ecosystems is essential for determining appropriate management actions as differences in movement behaviour can influence life history traits such as growth and survival. Lake Winnipeg in Manitoba, Canada supports the 2nd largest walleye (Sander vitreus) commercial fishery in North America. We used mark-recapture models to determine movement and estimate survival of walleye between basins of Lake Winnipeg in historical and contemporary contexts, comparing a tag-recovery study completed historically during 1974–1977 with a contemporary (2017–2019) acoustic telemetry study. Mark-recapture models revealed comparably low but detectable annual transitions between basins from historical (0.3–1.2%) and contemporary datasets (7–8.5%). Historically, fish > 300 mm more frequently moved in a south to north direction. Contemporary estimates suggest similar length-based directionality in that fish > 350 mm were always more likely to move in a south-north direction. Contemporary annual survival derived from mark-recapture models ranged between 27 and 45% and 64.3% when derived from catch curve analysis, while independently derived annual historical survival estimates ranged between 50 and 69% and 45.5% from catch curve analysis. Using the contemporary dataset, we also observed seasonal variation in movement and survival between basins, with the greatest movement across the lake occurring during the fall. Our results demonstrate a persisting pattern of low but measurable movement, suggesting between basin movement is not unusual for Lake Winnipeg. Further, low walleye survival rates reported here for the two time periods studied, support recent management actions to reduce fishing pressure across the lake.     

Developing habitat associations for fishes in Lake Winnipeg by linking large scale bathymetric and substrate data with fish telemetry detections

Understanding relationships between freshwater fishes and habitat is critical for effective fisheries and habitat management. Habitat suitability indices (HSI) are commonly used to describe fish–habitat associations in rivers and other freshwater ecosystems. When applied to large lakes however, standard sampling procedures are inadequate because of larger sampling areas and an increased risk of fish collection bias through one-time observations. Here, we use lake bathymetry, substrate, and multiple fish telemetry detections collected from a systematically deployed receiver grid to develop HSI for four fish species (lake sturgeon, freshwater drum, common carp, and walleye) in Lake Winnipeg. Seasonal variations in habitat use based on water depth and substrate were observed in three of four species. Lake sturgeon remained in shallow locations with predominantly gravel substrate near the mouth of the Winnipeg River regardless of season. Freshwater drum persisted over fine substrate in both summer and winter but had a broader depth range in the summer compared to winter. Common carp shifted from mid-range depths and silt substrate in the summer to shallow depths and gravel substrate in the winter. Walleye showed an unchanging association to fine substrate but expanded from primarily mid-range depths in the summer to include shallower depths in the winter. These findings show how multiple telemetry detections per fish can be combined with hydroacoustic data to provide informative habitat associations for fishes in a large lacustrine ecosystem.     

Spatial ecology of common carp (Cyprinus carpio) in Lake Winnipeg and its potential for management actions

Common carp feeding and spawning behaviours negatively impact the functioning of marsh ecosystems. In the Netley-Libau Marsh, situated on the southern end of Lake Winnipeg, water level regulations, nonpoint source nutrient pollution, and the non-native common carp are thought to be the main contributors to the degradation of the marsh habitat. Using acoustic telemetry, we analysed the movement rate, frequency and timing of suspected spawning migrations, spatial ecology, and aggregation of common carp in the Lake Winnipeg drainage over a three year time period. Common carp moved the farthest during the open water period when water temperature was >5 °C. Their annual migration into Netley-Libau Marsh was correlated to ordinal date. Common carp left the marsh in late spring/early summer, presumably feeding in Lake Winnipeg, before moving to overwintering sites situated in Traverse Bay and Lake Winnipeg, where they arrived typically by October and formed aggregations. These findings will inform habitat and fisheries managers in the effort to undertake evidence-based management actions. The predictability of the movements and the tendency for common carp to aggregate indicates that exclusion techniques and commercial fishing may represent viable management solutions.