Characteristics of the aeropollen dynamics at several localities in Spain

In the Iberian Peninsula and Balearic Islands there are several bioclimatic regions which result in many different and fragmentary landscapes. Results obtained from monitoring 18 localities in Spain allow an outline of the aeropollen dynamics of some of these environments. The major pollen types are: I. trees: Pinus, Qvercus, Olea, Cupressaceae, 2. shrubs: Corylus, Pislacia and 3. herbs: Poaccae, Urticaceae, Chenopodiaceae-Amaranthaceae, Plantago and Asteraceae. In some locations Alnus, Artemisia, Buxus, Betula, Castanea, Eucalyptus, Populus, Ulmus, and Ephedra also have to be considered. Quantitatively, pollen from trees predominates over that from herbs and shrubs, although at some localities this trend varies. The first pollen grains found in the weekly atmospheric analyses are from trees (winter). In spring tree pollen grains share the atmosphere with herb pollen. For this reason it is usual to find peak values of pollen content in the atmosphere during this part of the year, while winter and autumn are characterized by low pollen counts.     

Assessment of airborne Asteraceae pollen in Brisbane, Australia

In the southern hemisphere, the airborne prevalence and seasonal distribution of Asteraceae pollen are poorly characterized. In this study, we assessed the longitudinal distribution of Asteraceae pollen using an historic aerobiological dataset. The influence of weather parameters on pollen derived from Asteraceae species was additionally explored. Asteraceae pollen was collected using a static Burkard 7-day spore trap during a 5-year (June 1994–May 1999) aerometric surveillance program in Brisbane, Australia. Two discrete seasonal intervals were identified each sampling year. The first interval (September and October) consisted of small quantities of unidentifiable Asteraceae pollen. The second interval (March and April) was characterized by the highest concentrations of Asteraceae pollen that were predominantly derived from Baccharis halimifolia. Associations between daily Asteraceae pollen concentrations and temperature were observed during each sampling year. The results of the study demonstrated that pollen derived from B. halimifolia, an invasive weed species introduced in the late nineteenth century, continue to be in the environment of Brisbane. Given the public health burden associated with personal Asteraceae pollen exposure in other geographic locations, future Australian-based clinical studies should characterize the contribution of Asteraceae pollen, in particular B. halimifolia, to allergic sensitization and respiratory morbidity.     

Vegetation changes and human occupation in the Patagonian steppe, Argentina, during the late Holocene

Vegetation changes during the late Holocene are interpreted from four fossil pollen sequences from two caves at the Los Toldos archaeological locality, Santa Cruz province, Argentina. Taphonomic processes are particularly taken into account in order to analyze the effects on the fossil pollen records of biotic factors such as human occupation and animals, and abiotic ones such as volcanic ash fall. Fossil pollen assemblages are interpreted using local modern pollen data. The main vegetation change occurred at ca. 3750 uncal b.p., when a shrub steppe of Asteraceae subf. Asteroideae with Schinus, Ephedra frustillata and a high proportion of grasses was replaced by a shrub steppe of Colliguaja integerrima and Asteraceae subf. Asteroideae. This change is synchronous with an archaeological record change and could be related either to moderate climatic variations or the effects of ash fall on the environment. Plant communities similar to the present-day ones were established in the Los Toldos area from ca. 3750 uncal b.p.     

Pollen analysis of Apis dorsata Fabricius honeys in Bankura and Paschim Medinipur districts,West Bengal

One-hundred-and-five species corresponding to 38 families were identified through pollen analyses of 53 Apis dorsata honeys collected from Bankura and Paschim Medinipur districts, West Bengal. The families most frequently encountered were Fabaceae, Arecaceae, Asteraceae and Myrtaceae. Fabaceae had the greatest representation in number of pollen types (18 types), followed by Asteraceae (nine types), Cucurbitaceae (seven types), Lamiaceae and Myrtaceae (each with six types) and Malvaceae and Rutaceae (each with five types). Most of the honey samples correspond to class I. The presence of dominant pollen was detected in 18 samples. The predominant pollen types were Borassus flabellifer, Sesamum indicum (during summer), Eucalyptus globulus (during late autumn), Brassica nigra, Eucalyptus globulus (during winter) and Borassus flabellifer and Lannea coromandelica (during spring). The unifloral honeys obtained mostly during late autumn and winter were dominated by Eucalyptus globulus type. In monsoon and autumn unifloral honeys containing predominant pollen types (> 45%) were not found. However, according to frequency distribution the pollen types represented as very frequent were Peltophorum pterocarpum, Tridax procumbens (in monsoon) and Acacia auriculiformis, Cocos nucifera, Eucalyptus globulus, Tridax procumbens and Ziziphus mauritiana (in autumn). The seasonal diversity of pollen types obtained was at a maximum during spring (36 types) and minimum during late autumn (14 types). Seasonal variation in the number of pollen types per sample range from 5.86 ± 1.87 (during late autumn) to 6.86 ± 1.95 (during autumn) and exhibit low correlation (r = 0.31) with floral diversity. The diversity of pollen types per unifloral honey sample remains lower than multifloral honeys.     

Airborne pollen of Brisbane,Australia: A five-year record, 1994 - 1999

The seasonal incidence of pollen in the atmosphere of Brisbane has been established from a near-continuous, volumetric trapping program over the five-year period, July 1994-June 1999. Grass pollen accounts for 71.6% of the average annual pollen load with highest densities (up to 150 grains/m 3 ) recorded in summer and autumn. Significant contributions were also made by taxa of the Cupressaceae (8.7%) and Urticaceae (1.8%) during spring and of the Pinaceae (4.5%) during winter. Pollen seasons of the Casuarinaceae (6.5%) and Myrtaceae (3.2%) are more extended, the former peaking in late winter and the latter in late spring. The onset and duration of the Poaceae and Urticaceae seasons varied from year to year, being later when precipitation levels were low in the late spring-early summer months. Total pollen numbers and grass pollen densities are substantially less than those recorded from southern Australia. Nevertheless, respiratory disease in Brisbane affects up to 10% of the population, and airborne pollen of Poaceae, Urticaceae, Cupressaceae, Pinaceae, and Myrtaceae have been implicated in the release of allergens.     

Spatio-temporal patterns in the mortality of bay scallop recruits in North Carolina: investigation of a life history anomaly

By timing reproduction to occur when predatory mortality on progeny is minimal, organisms may maximize recruitment to adult populations. Accordingly, an hypothesis to explain the greater importance of fall than spring spawning to North Carolina populations of bay scallops (Argopecten irradians) is that predatory mortality of bay scallop recruits is lower in fall and winter than spring and summer. To test this hypothesis, we measured predatory mortality of scallop recruits monthly. To infer the identities of predators that are most important in determining patterns of mortality of bay scallop recruits in spring and in fall, predatory mortality of bay scallop recruits was compared between the edge and interior of sheltered and exposed seagrass patches during the day and at night in May and November. Consideration of predatory mortality throughout the year indicated that mortality of scallop recruits over late spring and summer approaches 100% but is negligible over late fall and winter. In May, predatory mortality of scallop recruits was similar during day and night but greater at exposed than sheltered sites. In November, predatory mortality was greater during night than day and slightly greater at sheltered than exposed sites. In neither month did position within patch influence mortality, and at all times and places, missing and crushed scallops contributed a higher proportion than drilled scallops to the total dead. These spatio-temporal patterns of mortality of scallop recruits suggest that mud crabs, Dyspanopeus sayi, which are more abundant in exposed than sheltered seagrass beds during spring and can feed by day and night, are a likely major contributor to spatio-temporal pattern in mortality of scallop recruits in North Carolina. Blue crabs, Callinectes sapidus, which are many times more abundant in summer than winter, may also contribute to observed seasonal patterns in mortality. The dramatically lower rates of predation on bay scallops over the winter months appear to provide fall settlers with a temporal window of opportunity to recruit to the adult population. Although spring spawning contributes little to adult populations in most years because of high rates of predatory mortality during summer, we hypothesize that spring spawning persists because infrequent devastating perturbations, such as hurricanes and red tides, can result in complete failure of fall recruitment.     

Airborne Pollen of Kuwait City,Kuwait, 1975–1987

The amount of airborne pollen in Kuwait was sampled daily over a twelve year period using a Hirst volumetric spore trap. The pollen was identified and expressed at the mean number m^-33 day^-1. Pollen occurs throughout the year but the concentration of the various pollen types varied from year-to-year and from season-to-season. The highest counts were in 1978, and the lowest in 1986. This latter low value is the result of prolonged drought, intensive human interference and continuous grazing. The highest counts are recorded in the spring (April-May) and the autumn (September-October). The pollen spectrum comprises mainly: Chenopodiaceae, Prosopis, Cyperus, Poaceae, Plantago and Brassicaceae. Poaceae pollen is abundant during the spring and the high valves coincide with the flowering season of the annual and perennial grass species. Cyperus is also abundant in the spring (April-May) the major source being the perennial sedge, Cyperus conglomeratus. Chenopodiaceae dominates from June to November with the highest peak in September and October. The majority of the species belonging to this family are perennials which flower during summer and autumn. Prosopis shows 2 peaks: a lower one in May-June and a higher one in October. A calendar of airborne pollen grain is presented. These results coulf be of use in allergy cases in Kuwait and possibly also in adjacent countries (S. Iraq, NE Saudi Arabia).     

Seasonal variation of collected pollen loads of honeybees (Apis mellifera L. anatoliaca)

Pollen collected by honeybees foraging in the region of Bursa, Turkey was analysed for a whole year. Pollen loads were collected from the hives of Apis mellifera anatoliaca once a week and were classified by colour. Forty‐one taxa were identified from the pollen analyses of the loads and 14 of these had percentages higher than 1%. Only 2.05% of the total pollen could not have been identified. Dominant taxa include; Brassicaceae (11.19%), Helianthus annuus L. (10.84%), Cichorioideae (8.93%) Salix spp. (7.99%), Rosaceae (7.37%), Centaurea spp. (7.56%), Papaver spp. (7.41%), Knautia spp. (6.99%), Fabaceae (6.01%), Asteraceae (5.73%), Xanthium spp. (2.65%), Chrozophora spp. (2.45%), Plantago spp. (1.56%) and Acer spp. (1.54%) representing 88.23% of the total. Distinct variations in plant usage are seen through the year with initial use of Rosaceae, Salix, and to a lesser extent Brassicaeae. As these groups finish flowering the bees move onto Helianthus annuus, Centaurea through the summer followed by Asteraceae in the late summer and Fabaceae in the autumn. There is a strong reliance on crop species for pollen forage but a number of indigenous species are also seen within the samples. The most productive period for collecting various pollen types, and the ideal period to determine pollen preferences of honey bees was June‐August.     

Aerial seed bank dynamics and seedling emergence patterns in two annual Mediterranean Asteraceae

Question: We explored the functional significance of seasonal aerial seed banks in two coexisting, heterocarpic annual Asteraceae with dormant (Chrysanthemum coronarium) and non‐dormant (Anacyclus radiatus) achenes. We hypothesised that the plant achene pool is a significant component of total seed reserves, and that within‐season seedling emergence timing is shaped by achene release patterns. Location: SW Spain. Methods: In an observational study, we established temporal achene release patterns. We also quantified the aerial and soil achene pools throughout the release season, and assessed seedling emergence timing. Sowing experiments were used to explore the influence of achene release dynamics on emergence timing, and to establish achene morph‐specific patterns of between‐year distribution of germination. Results: Achene release extended from late spring to late autumn (Chrysanthemum), or from early autumn to early winter (Anacyclus). Within species, achene morphs differed in release timing. Only in Chrysanthemum, a small achene fraction seemed to persist in the soil, and between‐year germination distribution differed among morphs. In coexisting populations, the Anacyclus plant achene pool was an order of magnitude higher than the soil pool throughout the release season, whereas in Chrysanthemum both pools were of the same magnitude during autumn. Within‐year seedling emergence was significantly staggered beneath parent plants compared with the pattern resulting solely from the germination response in soil, with the exception of Chrysanthemum in one of the two study years. Conclusions: Results suggest that seasonal aerial seed banks are effective within‐season, risk‐reducing traits in ruderal Mediterranean habitats characteristic of the study species.     

Food limitation and seasonal population declines of rotifers

Summary Keratella cochlearis exhibited consistent seasonal abundance patterns during a four-year study in Little Rock Lake, Wisconsin, U.S.A. In each year, spring population peaks were followed by strong summer reductions. Concomitant with population declines, there were reductions in rotifer egg ratios. Keratella taurocephala abundance patterns were similar to those of K. cochlearis during 1984 and 1985, but not in 1986 and 1987, when spring peaks and summer declines were not apparent. However, summer declines in the egg ratio of K. taurocephala were observed during each year. The reduction in rotifer populations simultaneously with decreased egg ratios suggested that population declines were caused by food limitation. Food-addition experiments conducted in situ in small enclosures indicated that food was limiting for K. cochlearis when its populations were declining, but not during other periods of the year. Keratella taurocephala did not show a consistent response to food addition.     

Growing or reproducing in a temperate sea: optimization of resource allocation in a colonial ascidian

Relatively little is known about the life cycles of ascidians in temperate seas. Here, we investigated the biological cycle of the colonial ascidian Didemnum fulgens, a dominant species in some shallow localities of the NW Mediterranean Sea. Growth rates and frequencies of fission/fusion events were calculated over a period of 13 months, and the reproductive cycle determined after 32 months of observation. For analyses of reproduction, zooids were dissected in the laboratory and classified into five reproductive categories; these data were used to calculate a maturity index. For growth analyses, underwater photographs of marked colonies were used to estimate the surface area of D. fulgens colonies, calculate monthly growth rates, and document fusion and fission events. Clear seasonal patterns in reproduction and growth were observed, with distinct periods of investment into each function. Gonad maturation started in winter and larval release occurred in early summer, just before maximal sea temperatures were reached. After reproducing, colonies shrank and aestivated during the warmer summer months. Growth occurred during the cooler months, with maximal and minimal growth rates observed in winter and summer, respectively. Fusions and fissions occurred year‐round, although fissions were more frequent in fall (coincident with high growth rates) and fusions in spring (coincident with reproduction). These results add to the mounting evidence that ascidian life cycles in temperate seas are characterized by a trade‐off between investment in reproduction and growth, triggered by seasonal temperature shifts and constrained by resource availability during summer.     

Airborne pollen patterns in Mar del Plata atmosphere (Argentina) and its relationship with meteorological conditions

This work is part of a series of aerobiological researches conducted in the city of Mar del Plata, Argentina. The annual, seasonal and daily features of the pollen cloud were analyzed over 2 years, together with the effects of the meteorological variables. Cupressaceae amounted to 75 and 54% of the annual total in each year, and it was analyzed separately due to its proven overrepresentation. Eighty-five pollen types were registered during the 2 years, bearing a similar annual pattern (more than 50% from August to November, December also being an important month). Arboreal pollen predominated between late winter and spring (61 and 49% of the annual total), while non-arboreal pollen did so from late spring to summer. The observed seasonality was significantly correlated with the monthly mean temperatures and associated with its effect on phenology. No significant differences along the day were detected between years and 50% of the daily total was recorded between 1000 and 1600 hours. The maximum concentration was registered at 1000 hours in spring and summer, but later in autumn and winter. Regarding the hourly scale, the significant correlation of total pollen with temperature and wind speed was positive, albeit negative with relative humidity. These effects are linked to airborne pollen release and transport. The role rainfall plays on airborne pollen is discussed. To interpret the results, it is important to consider the time scale at which the aerobiological phenomenon is analyzed.     

Temporal variation of energy reserves in mayfly nymphs (Hexagenia spp.) from Lake St Clair and western Lake Erie

1. We analysed changes in energy reserves (lipid and glycogen) and length–weight relationships of burrowing mayflies (Hexagenia spp.) in 1997–99 to compare an established population in Lake St Clair with a recovering population in western Lake Erie of the Laurentian Great Lakes. In addition, we measured changes in water temperature and potential food in both water columns and sediments. 2. Although overall mean values of lipid and glycogen levels of Hexagenia nymphs from Lake St Clair and western Lake Erie were not significantly different, there were differences in seasonal patterns between the two lakes. In Lake St Clair, levels were highest in early spring, declined throughout the year, and reached their lowest levels in fall during all 3 years of study. In contrast, levels in western Lake Erie were lower in spring, increased to a maximum in summer, then declined in fall. Seasonal patterns in length–weight relationships were similar to those for lipid and glycogen. 3. Total lipid as a percentage of dry weight did not increase with developmental stage of nymphs until just prior to metamorphosis and emergence from water. However, the major reserve lipid, triacylglycerols, increased systematically with development stage. In the final stage of development, triacylglycerols declined, probably as a result of energy consumption and its conversion to other biochemical components for metamorphosis and reproduction. 4. Indicators of potential food (algal fluorescence in the water column and chlorophyll a and chlorophyll a/phaeophytin ratio in sediments) suggest that Hexagenia in Lake St Clair have a food source that is benthic based, especially in early spring, whereas in western Lake Erie nymphs have a food source that is water column based and settles to the lake bottom during late spring and summer.     

Predicting the intensity of the birch pollen season

We present a model for the prediction of the magnitude ofBetula flowering and pollen dispersal which may be used in the management of birch pollinosis and in the planning of clinical trials. The pollen sum during the flowering season is regressed on the temperature sum from May 1st to July 20th during the initiation year, the pollen sum of the initiation year, and the temperature sum during the main pollen season in the flowering year. We suggest that the fluctuating flowering pattern inBetula alba-species is primarily determined by the availability of assimilation products during inflorescence initiation and development during the spring one year before anthesis. When inflorescences, which are initiated during the previous year, elongate in the beginning of anthesis, they act as strong sinks to stored carbohydrates, and thus compete with developing leaves and shoots. The result is an initially reduced photosynthetic capacity in years with intense flowering, and a limited potential for the initiation of new inflorescences for the following year. The ambient temperature during catkin initiation affects assimilation efficiency and is a determinant of about equal importance to flowering intensity as is the magnitude of the flowering in the initiation year. The amount of pollen dispersed is also dependent on the weather during anthesis, which is not possible to predict until about one month in advance. The two other independent variables are available during the previous summer, making it possible to give a sufficiently valid prediction to allergologists about the magnitude of the next birch pollen season, according to its botanical determinants. We suggest that the varying reproductive output inBetula alba should not be described as true masting. A more parsimonious explanation to the flowering pattern is that an individual continually maximizes reproductive effort, according to what is possible, but that reproduction is often constrained by the environment.     

Predicting the intensity of the birch pollen season

We present a model for the prediction of the magnitude ofBetula flowering and pollen dispersal which may be used in the management of birch pollinosis and in the planning of clinical trials. The pollen sum during the flowering season is regressed on the temperature sum from May 1st to July 20th during the initiation year, the pollen sum of the initiation year, and the temperature sum during the main pollen season in the flowering year. We suggest that the fluctuating flowering pattern inBetula alba-species is primarily determined by the availability of assimilation products during inflorescence initiation and development during the spring one year before anthesis. When inflorescences, which are initiated during the previous year, elongate in the beginning of anthesis, they act as strong sinks to stored carbohydrates, and thus compete with developing leaves and shoots. The result is an initially reduced photosynthetic capacity in years with intense flowering, and a limited potential for the initiation of new inflorescences for the following year. The ambient temperature during catkin initiation affects assimilation efficiency and is a determinant of about equal importance to flowering intensity as is the magnitude of the flowering in the initiation year. The amount of pollen dispersed is also dependent on the weather during anthesis, which is not possible to predict until about one month in advance. The two other independent variables are available during the previous summer, making it possible to give a sufficiently valid prediction to allergologists about the magnitude of the next birch pollen season, according to its botanical determinants. We suggest that the varying reproductive output inBetula alba should not be described as true masting. A more parsimonious explanation to the flowering pattern is that an individual continually maximizes reproductive effort, according to what is possible, but that reproduction is often constrained by the environment.     

A long-term study of winter and early spring tree pollen in the Tulsa, Oklahoma atmosphere

Since 1986 the atmosphere in Tulsa, Oklahoma has been monitored for airborne pollen and spores with a Burkard 7-day spore trap situated on the roof of a building at The University of Tulsa. The present study specifically examined the early spring tree pollen season for several local taxa and the occurrence of pre-season pollen during December and January. Knowledge of the local pollen season will help identify the presence of out-of-season pollen and possible long distance transport (LDT) events. Average daily concentrations of airborne pollen for species ofBetula, Quercus, Ulmus, and Cupressaceae were determined for each year from 1987 to 1996. The data showed that during the early spring the precise pollination periods for these allergenic tree species are highly variable. There were considerable variations in start date, season length, peak concentration, date of peak, and cumulative season total. The start dates forUlmus, Betula, andQuercus varied by 30 days or more, while the early spring Cupressaceae pollen showed the least variation in start date (only 23 days). More research is needed to understand the mechanisms which govern the onset and magnitude of pollen release. Although several reports have documented episodes of long distance transport (LDT) of pollen, the actual contribution of out-of-season or out-of-region pollen to local air spora is poorly known. The current study also re-examined the LDT ofJuniperus ashei pollen in Oklahoma.Juniperus pollen appeared in the Tulsa atmosphere on 40% of the days in December and January with concentrations as high as 2400 pollen grains/m³ of air; however, no local populations ofJuniperus pollinate at this time of the year. High concentrations occurred on days with southerly winds suggesting thatJuniperus ashei populations in southern Oklahoma and Texas were the pollen source. Since no local pollen is present in the Tulsa atmosphere in December and January, this example of LDT has been easy to document.     

A bioenergetic model for Mysis growth and consumption applied to a Baltic population of Mysis mixta

A bioenergetic model for Mysis growth and consumption is presentedand used to calculate seasonal patterns of food consumptionby Mysis mixta at two stations in a coastal area of the northernBaltic Sea. Calculated specific consumption rates ranged from19%/day in small juveniles during the spring to 2%/day in adultsduring the winter. Gross conversion efficiencies on an energybasis were 26–34% in the spring and summer, 9–10%in the fall, and negative during the winter. These values areconsistent with experimental results available in the literature.Changes in stomach content over the year and differences instomach content between the two stations were similar to theseasonal patterns of daily food intake indicated by the model.The estimated weight of the stomach content from animals caughtat night corresponded to 9% of modeled daily consumption duringthe summer and fall. This is consistent with gut passage timesreported in the literature for feeding mysids but not with gutpassage times from starving mysids.     

Annual variations of air-borne pollen in the Coastal Plain of Israel

A survey of airborne pollen was conducted during 1984 in the coastal plain of Israel. The flora of that area is continuously changing due to urbanization and agriculture, thus affecting the airborne pollen spectrum.

Significant pollen counts were monitored throughout the year, with a seasonal peak during spring. Meteorological parameters, such as wind velocity, wind direction and temperature affected pollen content of the air. Under certain conditions, even pollen of insect-pollinated plant species was found in the air.

The most conspicuous among the airborne pollen were olive, cypress and pine trees as well as pollen grains from the Poaceae, Amaranthaccae, Chenopodiaceae, Asteraceae, Brassicaceae and Urticaccae.

Results indicate that most of the airborne pollen grains were of local origin and from cultivated trees. Thus, it is possible to reduce airborne pollen contaminants around human habitations by selection of the proper non-allergenic ornamental plants.     

Pollen grain viability in Parietaria judaica L. during the long blooming period and correlation with meteorological conditions and allergic diseases

Abstract

Pollen grain viability and starch presence in pollen were followed during the long blooming period (May-November) of Parietaria judaica, the most widespread pellitory in Italy, responsible for many cases of allergic diseases. Observations were carried out near Siena (Tuscany), in the years 1978 and 1979.

Viability is high in late spring and early autumn, and pollen grains are starchy. The presence of starchless grains is always related to low viability: a production of pollen with a low viability occurs at the beginning and end of blooming, and also in summer, during drought periods. Pollen grain viability varies widely during the blooming period, and its variations are correlated to meteorological conditions, mainly rainfall and temperature.

Allergic diseases due to pellitory, however, are mainly reported between April and July, and on the other hand a small amount of patients states that they suffer all the year round. The discrepancies between the periods of viable pollen production and of declared symptoms by patients, are discussed.     

Migration and Movement Patterns of Green Sturgeon (Acipenser medirostris) in the Klamath and Trinity rivers, California, USA

Green sturgeon, Acipenser medirostris, movement and migration within the Klamath and Trinity rivers were assessed using radio and sonic telemetry. Sexually mature green sturgeon were captured with gillnets in the spring, as adults migrated upstream to spawn. In total, 49 green sturgeon were tagged with radio and/or sonic telemetry tags and tracked manually or with receiver arrays from 2002 to 2004. Tagged individuals exhibited four movement patterns: upstream spawning migration, spring outmigration to the ocean, or summer holding, and outmigration after summer holding. Spawning migrations occurred from April to June, as adults moved from the ocean upstream to spawning sites. Approximately 18% of adults, those not out mignation in the spring, made spring post-spawning outmigrations. The majority of adults, those not outmigrating in the spring, remained in discrete locations characterized as deep, low velocity pools for extended periods during the summer and early fall. Fall outmigration occurred when fish left summer holding locations, traveled rapidly downstream, and exited the river system. High river discharge due to the onset of winter rainstorms and freshets appear to be the key environmental cue instigating the fall outmigration.