Multiscale Habitat Use and Selection in Cooperatively Breeding Micronesian Kingfishers

Abstract: Information about the interaction between behavior and landscape resources is key to directing conservation management for endangered species. We studied multi-scale occurrence, habitat use, and selection in a cooperatively breeding population of Micronesian kingfishers (Todiramphus cinnamominus) on the island of Pohnpei, Federated States of Micronesia. At the landscape level, point-transect surveys resulted in kingfisher detection frequencies that were higher than those reported in 1994, although they remained 15-40% lower than 1983 indices. Integration of spatially explicit vegetation information with survey results indicated that kingfisher detections were positively associated with the amount of wet forest and grass-urban vegetative cover, and they were negatively associated with agricultural forest, secondary vegetation, and upland forest cover types. We used radiotelemetry and remote sensing to evaluate habitat use by individual kingfishers at the home-range scale. A comparison of habitats in Micronesian kingfisher home ranges with those in randomly placed polygons illustrated that birds used more forested areas than were randomly available in the immediate surrounding area. Further, members of cooperatively breeding groups included more forest in their home ranges than birds in pair-breeding territories, and forested portions of study areas appeared to be saturated with territories. Together, these results suggested that forest habitats were limited for Micronesian kingfishers. Thus, protecting and managing forests is important for the restoration of Micronesian kingfishers to the island of Guam (United States Territory), where they are currently extirpated, as well as to maintaining kingfisher populations on the islands of Pohnpei and Palau. Results further indicated that limited forest resources may restrict dispersal opportunities and, therefore, play a role in delayed dispersal and cooperative behaviors in Micronesian kingfishers.     

Conservation prioritization through combined approach of umbrella species selection,occupancy estimation,habitat suitability and connectivity analysis of kingfisher: A study from an internationally important wetland complex (Ramsar site) in India

Assessment of occupancy status, as well as projection of suitable habitats and connectivity of wetland indicator species, and thereby identification of potential conservation umbrella and projection of conservation priority areas are often considered important for wetland conservation. Kingfishers are wetland indicators and suffer from habitat degradation due to world-wide destruction of wetlands. Therefore, they can be considered potential candidates for conservation intervention. The present knowledge about the spatial distribution of suitable areas and habitat connectivity of kingfishers at a landscape level is non-existent. We conducted extensive surveys and recorded four kingfisher species in East Kolkata Wetlands (EKW; Ramsar site No. 1208; ∼125 km²). The occupancy estimates were highest for White-throated kingfisher (Halcyon smyrnensis, WTK), followed by common kingfisher (Alcedo atthis, CK), stork-billed kingfisher (Pelargopsis capensis, SBK) and lowest for pied kingfisher (Ceryle rudis, PK). WTK has the highest amount of suitable areas followed by CK, PK and SBK. The spatial overlap of suitable habitats showed that SBK is the potential umbrella species and therefore provides conservation benefits to other kingfisher species and eventually to the EKW. In addition to water areas, emergent vegetation, crop lands and tree cover are other important habitats for kingfishers. The connectivity analyses revealed that suitable habitats were disjunct and are under various anthropogenic threats. Therefore, we need to protect suitable habitats and connectivity between them. Finally, we identified conservation priority areas. Conservation intervention on these high priority zones will not only be beneficial for kingfishers, but also for other avifauna having similar resource requirements as well as the wetland parse.     

Impact of food abundance, diet and food quality on the breeding of the fruit pigeon, Parea Hemiphaga novaeseelandiae chathamensis, on Chatham Island, New Zealand

Breeding and diet of Parea Hemiphaga novaeseelandiae chathamensis were studied in relation to food abundance and quality on Chatham Island from 1991 to 1994. Although pairs were found breeding in all months, they nested predominantly during winter and spring (June-November). The timing of the nesting season, the proportion of pairs that bred and the number of chicks reared per pair varied between nesting seasons. During the 1992–1993 and 1994–1995 nesting seasons, all pairs nested, and many pairs reared two chicks, often involving clutch overlap (58% of 12 cases in 1992–1993, 37% of eight cases in 1994–1995). In 1993–1994, when fruit was scarce, nesting began 2 months later, only 44% of pairs nested and no pairs attempted to rear a second chick. Prior to and during the productive nesting seasons (1992–1993, 1994–1995), the diet of Parea consisted mainly of fruit, particularly that of Matipo Myrsine chathamica in autumn (March-May) and Hoho Pseudopanax chathamicus in winter and spring. Nutrient analyses of the main Parea foods showed that the pulp of these fruit were rich in lipids and available carbohydrates compared with those in foliage foods. Heavy fruiting of Matipo and Hoho promoted early nesting and prolonged nesting for 6 months, including nesting during winter.     

Spatial scaling and transition in pneumatophore arthropod communities

Although most ecological variables are scale-dependent, few studies cover a broad range of spatial scales. Here, we consider South African mangrove pneumatophore arthropod communities (mites, crustaceans and insects), across seven spatial scales (from 10  cm to 100  km). We plot spatial autocorrelation in individual species, evaluate if resource and habitat availability determine spatial patterning, and identify the scales of community transition. Spatial autocorrelation in most ecological variables decreased with increasing spatial scale, with notable exceptions for the larger scales. Negative abundance autocorrelation was stronger at 10  km than at 100  km for common species, while the opposite was true for rare species. Spatial autocorrelation in species richness decreased from 1  m (strong positive) to 10  km (strong negative), but was not significant at the 100  km scale. These patterns reflect the patchy distribution of pneumatophores within mangrove forests, that of the forests along the coast, and the poor dispersal abilities of most of the arthropods sampled, in a highly dynamic environment. Although resource and habitat availability exhibited a similar autocorrelation pattern to that of the community, the total mass of pneumatophores did not appear to be an important determinant of community structure. Variations in the abundance of common species, as well as the restricted distribution of rare species caused assemblage structure to change gradually with increasing distance from 10 cm to 100 km, but only marginally from 10 to 100  km. We highlight the need for cross-scale studies in bridging the gap between two key ecological concepts: potential ecological niche and realized geographic range.     

Landscape‐scale habitat availability,and not local geography,predicts migratory landbird stopover across the Gulf of Maine

While it is clear that many migratory behaviors are shared across taxa, generalizable models that predict the distribution and abundance of migrating taxa at the landscape scale are rare. In migratory landbirds, ephemeral concentrations of refueling birds indicate that individual behaviors sometimes produce large epiphenomena in particular geographic locations. Identifying landscape factors that predict the distribution and abundance of birds during migratory stopover will both improve our understanding of the migratory process and assist in broad, regionally relevant conservation. In this study we used autumnal passerine stopover data from a five‐year period and eleven stopover sites across coastal Maine, USA, to test four broad hypotheses of migrant distribution and abundance that have been supported in other regions: a) the community characteristics of the pool of potential migrants, b) a site's local geography, c) landscape composition and configuration measured at different spatial scales, and d) interactions between these factors. Our final model revealed that birds concentrate at ‘habitat islands’, sites that possess a disproportionate percentage of the vegetated habitat in the 4‐km surrounding landscape. The strength of this pattern, however, was inversely proportional to a species' remaining migratory distance. Our results corroborate several studies that emphasize the importance of land cover composition at finer spatial scales (< 80 km²) for predicting the stopover distribution and abundances of migratory birds. This suggests that different migrants likely assess stopover sites with similar mechanisms along their migratory route, and these commonalities may be broadly applied to identify stopover locations of conservation importance across the continent.     

Sea ice meiofauna distribution on local to pan‐Arctic scales

Arctic sea ice provides microhabitats for biota that inhabit the liquid‐filled network of brine channels and the ice–water interface. We used meta‐analysis of 23 published and unpublished datasets comprising 721 ice cores to synthesize the variability in composition and abundance of sea ice meiofauna at spatial scales ranging from within a single ice core to pan‐Arctic and seasonal scales. Two‐thirds of meiofauna individuals occurred in the bottom 10 cm of the ice. Locally, replicate cores taken within meters of each other were broadly similar in meiofauna composition and abundance, while those a few km apart varied more; 75% of variation was explained by station. At the regional scale (Bering Sea first‐year ice), meiofauna abundance varied over two orders of magnitude. At the pan‐Arctic scale, the same phyla were found across the region, with taxa that have resting stages or tolerance to extreme conditions (e.g., nematodes and rotifers) dominating abundances. Meroplankton, however, was restricted to nearshore locations and landfast sea ice. Light availability, ice thickness, and distance from land were significant predictor variables for community composition on different scales. On a seasonal scale, abundances varied broadly for all taxa and in relation to the annual ice algal bloom cycle in both landfast and pack ice. Documentation of ice biota composition, abundance, and natural variability is critical for evaluating responses to decline in Arctic sea ice. Consistent methodology and protocols must be established for comparability of meiofauna monitoring across the Arctic. We recommend to (1) increase taxonomic resolution of sea ice meiofauna, (2) focus sampling on times of peak abundance when seasonal sampling is impossible, (3) include the bottom 30 cm of ice cores rather than only bottom 10 cm, (4) preserve specimens for molecular analysis to improve taxonomic resolution, and (5) formulate a trait‐based framework that relates to ecosystem functioning.     

Eimeria galateai sp. n. from the Paradise Kingfisher, and Eimeria duncani sp. n. from the Sacred Kingfisher in Papua New Guinea

SYNOPSIS. Eimeria galateai sp. n. from the paradise kingfisher ( Tanysiptera galatea Gray) and Eimeria duncani sp. n. from the sacred kingfisher ( Halcyon sancta Vigors & Horsfield) have been described from Papua New Guinea. Four of 11 paradise kingfishers were infected with E. galateai oocysts, measuring 13 (11–16) × 9 (8–11) μm. The oocysts were ovoid with nipple-like protrusion at one pole. Micropyle and polar granule were absent, while oocyst residuum (5 × 4 μm) was present. Sporocysts, measuring 5 (4–6) × 2 μm, were elongate-ovoid, and had a distinct convex Stieda body; the sporocyst residuum was absent. Two of 9 sacred kingfishers were infected with ovoid-truncated, 22 (19–25) × 16 (12–18) μm oocysts of E. duncani . Polar granule (5 × 2) was present in the oocysts, but there was no micropyle or oocyst residuum. Sporocysts were ovoid, measuring 9 (8–10) × 5 (4–6) μm, with a prominent Stieda body, and granular sporocyst residuum. Eimeria galateai and E. duncani are the first species of this genus to be described from birds of the order Coraciiformes.     

GRAY WHALE CALF PRODUCTION 1994–2000: ARE OBSERVED FLUCTUATIONS RELATED TO CHANGES IN SEASONAL ICE COVER?

We conducted shore-based sighting surveys to estimate the number of northbound migrating gray whale calves passing Piedras Blancas, California, for seven consecutive years (1994–2000). In addition, we conducted aerial surveys to determine offshore distribution of the migration in 1994 and 1995, measured day/night migration rates with thermal sensors in 1994–1996, and maintained concurrent replicate watches near the peak of each migration to estimate the proportion of the cow/calf pairs missed by the standard watch team. During good weather, we counted 325, 194, 407, 501, 440, 141, and 96 calves during 1994–2000, respectively. Correcting these counts for periods not on watch and for calves missed, produced final estimates of 945 calves (SE = 68.21) for 1994, 619 calves (SE = 67.19) for 1995, 1,146 calves (SE = 70.67) for 1996, 1,431 calves (SE = 82.02) for 1997, 1,388 calves (SE = 91.84) for 1998, 427 calves (SE = 41.10) for 1999, and 279 calves (SE = 34.79) for 2000. Calf production indices (calf estimate/total population estimate) are 4.2%, 2.7%, 4.8%, 5.8%, 5.5%, 1.7%, and 1.1% for the years 1994–2000, respectively. Fluctuations in calf production over this time period were positively correlated with the length of time that primary feeding habitat was free of seasonal ice during the previous year.     

Distribution of forest dwelling carabids (Coleoptera): spatial scale and the concept of communities

Associations between spatial distribution of ground-beetles (Carabidae) and environmental variables were studied over three hierarchical scales in deciduous forest in central Alberta, Canada We also examined the relationship between species abundance and distribution on several scales ranging from the local scale of our study to that of the North American temperate deciduous forest Understorey plant cover, tree cover, and occurrence of other carabids were associated with distribution of particular species at the smallest ecological scales within populations However, great differences in population sues of carabid species among five distinct sites several kilometres apart were not correlated with variation in the same environmental variables In central Alberta, abundance and extent of distribution were correlated positively among the 30 carabid species collected, and distributions of the ten species classified as 'core' species were generally aggregated at all spatial scales On the continental scale, there was a significant positive correlation between abundance and distribution for the 114 species of the entire data set, and the six species meeting the criteria of 'core' taxa on this scale, were also 'core' elements in central Alberta Further analysis of covariance of core elements of species assemblages across different taxa provides a sound empirical approach for understanding community organization     

Climate-driven changes in abundance and distribution of larvae of oceanic fishes in the southern California region

We examined climatic effects on the geographic distribution and abundance of 34 dominant oceanic fishes in the southern California region using larval fish data collected from the 50‐year long California Cooperative Oceanic Fisheries Investigations (CalCOFI) surveys. The oceanic species responses to environmental changes in their geographic distributions were not very pronounced, perhaps because they lived in the deep layer where temperature change was relatively small or because the environmental variation of the CalCOFI region is not strong enough (with an average temperature gradient of the upper 100 m around 91 km °C^?1). Among the 34 taxa, 16 showed a significant distributional shift (median latitude or boundaries) in relation to environmental variables, and eight species significantly shifted their geographic distribution from the 1951–1976 cold period to the 1977–1998 warm period. Interestingly, the vertically migrating taxa more often showed a significant response to environmental variables than the nonmigrating mesopelagic taxa, reflecting the more significant increase in heat content of the upper ocean (<200 m), compared with the deeper zone (300–500 m) where the mesopelagic fishes typically remain. Climate change has significant effects on the abundances of oceanic fishes. Twenty‐four taxa exhibited a significant change in abundance in relation to environmental variables, and 25 taxa, including both warm and cold‐water taxa, showed a significant increase in abundance from the cold to warm period. Analysis of physical data indicated that the surface‐layer (20–200 m) warmed significantly and the isotherms approached shoreward from the cold to the warm period. We further show that the spatial distribution of coastal–neritic fish retreated shoreward and oceanic fish extended shoreward from the cold to warm period. Our results suggest intensified stratification of the southern California region during the warm period may create a suitable habitat for the oceanic species. Moreover, such an unfavorable condition (e.g. changes in food habitat) for coastal–neritic species might result in competitive release for the oceanic fishes to flourish.     

Foraging areas of breeding blue-footed boobies Sula nebouxii in northern Peru, as determined by direction recorders

The association between the distribution of blue-footed boobies Sula nebouxii (BFB) and marine productivity around their breeding grounds is unclear. In Peru, they breed in a region seasonally influenced by the cold, nutrient rich Humboldt Current, and by warm, nutrient poor oceanic waters. The foraging range of BFB in Peru is unknown, although some evidence suggest that they may feed in warm offshore waters. During the austral winter 2002 and summer 2003, we tracked 26 BFBs breeding on Isla Lobos de Tierra, Peru (located approximately 15 km west of the mainland), during 59 feeding trips using small direction recorders to determine their marine habitat use. BFBs preferentially moved to the east of the island and foraged over the continental shelf in cold water masses where marine productivity and the abundance of the main prey, the Peruvian anchovy Engraulis ringens , are usually higher than in other areas. Overall, the median maximum foraging distance from the colony was 39 km (range 3–109 km), with 90% of all trips located within 30 km from the mainland, and enclosed in an area of 13,113 km². These results reveal that BFBs exploit the productive waters of the Peruvian Coastal Upwelling System, rather than open oceanic waters as previously suggested. BFBs travelled a greater distance, dispersed in a broader area, and visited more offshore waters during the winter 2002, than during the summer 2003, following the typical seasonal horizontal dispersion of the Peruvian anchovy.     

Significance of the White Sea as a stopover for Bewick's Swans Cygnus columbianus bewickii in spring

We searched for a major stopover site of Bewick's Swans Cygnus columbianus bewickii in the White Sea following the suggestion that one should exist on the stretch between Estonia and the breeding grounds (1750 km). We discovered 733 Swans in Dvina Bay during a late aerial survey in spring 1993. Subsequently, ground-based research was carried out in May 1994, 1995 and 1996 in the Dry Sea, a tidal, shallow bay with fresh to brackish water just north of the Dvina Delta. The total number of passing Bewick's Swans was estimated at 10974 (1994), 9593 (1995) and 17 972 (1996) (32–60% of the flyway population). Estimated peak numbers staging were 1500–2000 (9 May 1994), 4937 (17 May 1995) and 4457 (24 May 1996) (> 5–16% of the flyway population). The Swans foraged almost exclusively on submerged water plants apart from some supplemental feeding on emerged food plants around high tide. Stoneworts Chara spp. were an important food in the late spring of 1996, because they grew in places where bog streams quickly melted the ice. At this latitude (65̀N) food alternatives to the submerged macrophytes are rare in spring, but we cannot rule out the possibility that the Swans forage on grass rhizomes on inundated pastures. One bird tracked by satellite staged 15 days in Dvina Bay, of which four days were spent in the Dry Sea, in accordance with other indications that the Dry Sea is part of a larger stopover site within Dvina Bay. Recent evidence shows that the Swans largely skip the White Sea during autumn migration. However, in spring the birds probably need this stopover to be able to carry reserves to the breeding grounds. At present, the preservation of the submerged vegetation in Dvina Bay seems to be crucial to the conservation of this Bewick's Swan population.     

Pelagic larvae of benthic gastropods from shallow Antarctic waters of Admiralty Bay,King George Island

The occurrence, distribution and summer variation of pelagic larvae of benthic gastropods in the shallow coastal area of Admiralty Bay were determined for the summers of 1993/1994, 1994/1995 and 1996/1997 from plankton samples taken at 15- to 30-m depths in 12 stations. Significant differences were found among years at the end of January and February. Results of Principal Component Analysis showed the inverse relation of high wind speed and abundance of gastropod larvae in the three austral summers sampled, and suggested that environmental conditions prevalent during 1994/1995 and 1995/1997 were similar and differed from those of 1993/1994, which may have influenced the number of larvae observed.     

Contemporary Land Change Alters Fish Communities in a San Francisco Bay Watershed,California, U.S.A.

Urbanization is one of the leading threats to freshwater biodiversity, and urban regions continue to expand globally. Here we examined the relationship between recent urbanization and shifts in stream fish communities. We sampled fishes at 32 sites in the Alameda Creek Watershed, near San Francisco, California, in 1993–1994 and again in 2009, and we quantified univariate and multivariate changes in fish communities between the sampling periods. Sampling sites were classified into those downstream of a rapidly urbanizing area (“urbanized sites”), and those found in less impacted areas (“low-impacted sites”). We calculated the change from non-urban to urban land cover between 1993 and 2009 at two scales for each site (the total watershed and a 3km buffer zone immediately upstream of each site). Neither the mean relative abundance of native fish nor nonnative species richness changed significantly between the survey periods. However, we observed significant changes in fish community composition (as measured by Bray-Curtis dissimilarity) and a decrease in native species richness between the sampling periods at urbanized sites, but not at low-impacted sites. Moreover, the relative abundance of one native cyprinid (Lavinia symmetricus) decreased at the urbanized sites but not at low-impacted sites. Increased urbanization was associated with changes in the fish community, and this relationship was strongest at the smaller (3km buffer) scale. Our results suggest that ongoing land change alters fish communities and that contemporary resurveys are an important tool for examining how freshwater taxa are responding to recent environmental change.     

Identifying spatial relationships at multiple scales: principal coordinates of neighbour matrices (PCNM) and geostatistical approaches

We compared two methodological approaches – principal coordinate analysis of neighbour matrices (PCNM) and geostatistics – that both aim at extracting several spatial scales in order to identify spatial relationships between organisms and environmental variables at multiple scales. From a statistical point of view, PCNM analysis and geostatistics come from "two different worlds"– PCNM is based on classical "data analysis" while geostatistical modelling is developed in a probabilistic context. These two methods were used to investigate the spatial relationships between defoliation caused by spruce budworm Choristoneura fumiferana and bioclimatic conditions in Ontario since 1941 through a wide range of scales. On the one hand, PCNM variables related to defoliation frequency were partitioned into four spatial submodels representing respectively four spatial scales: very broad scale (ca>300 km), broad scale (ca 180 km), fine (ca 100 km), and very fine (<80 km). On the other hand, nested variogram modelling was used to identify the relevant scales. The nested variogram model was composed of four variograms with different characteristic scales close to those of the PCNM spatial submodels. Maps of PCNM submodels and kriging components revealed similar spatial patterns of defoliation frequency at very broad and broad scales while spatial patterns at fine and very fine scales looked quite different. Both methods showed that defoliation by spruce budworm occurs at the broader spatial scales but may be explained by fluctuations at the smaller scales. Finally, results based on geostatistics using a Linear Model of Coregionalisation suggested that climatic conditions can be considered to act at the level of outbreak dynamics while the tree community of spruce budworm's principal hosts controls local population dynamics.     

Local abundance and regional distribution of tree species of forest fragments in Brazil: a test of models

Patterns of local abundance and regional distribution of tree species were analyzed on three spatial scales and compared with those predicted by Hanski's 1982 original core-satellite model, Brown's 1984 niche-based model, and Tokeshi's 1992 model. Data were collected in seven forest fragments dispersed over approximately 7200 km2, remnants of a former continuous forest in the south of Mato Grosso do Sul state, southwestern Brazil. Fifty-six east-west-oriented 10 m yen 150 m plots were randomly demarcated in those fragments from 1994 to 1996. In each plot all trees having DBH > or = 0.15 m were recorded and measured. The smallest scale was that of the fragments themselves and the greatest was that of the entire region. No evidence was found of the bimodality predicted by Hanski's 1982 model on any scale. On all scales, an unimodal pattern was found whose mode was on the left side (satellite mode) of the distribution. This pattern was in best agreement with the predictions of Tokeshi's 1992 model.     

Covariation of stream community structure and biomass of algae, invertebrates and fish with forest cover at multiple spatial scales

1. To evaluate the spatial extent of the effects of forest cover on stream ecosystems, we measured algae, invertebrate, and fish biomass and invertebrate and fish community structure in 38 small first- to third-order streams in the National Capital Region of Canada along with forest cover at different spatial scales.
2. We considered 55 spatial scales of forest cover including several buffer widths (doubling 10–320 m) and lengths (doubling 10–1280 m, entire riparian distance upstream from sampling area) and entire catchments to determine which spatial scale maximized the correlation with biomass and metrics of community structure.
3. The proportion of variability in biomass and structural metrics explained by forest cover generally increased with increasing scale, suggesting that catchment-wide disturbances are the most influential determinants of benthic and fish communities.
4. Catchment forest cover explained more variation in algal (adjusted r ²   =   0.54), invertebrate (adjusted r ²   =   0.51) and fish (adjusted r ²   =   0.33) biomass than structural metrics of invertebrates and fish (adjusted r ²   =   0.08–0.27).
5. Analyses of the partial effects of forest cover at three scales (reach, riparian and the entire catchment) on biomass and community structure metrics identified catchment and reach scales as being most influential and never detected a significant partial effect of forest cover at the riparian scale.
6. These results suggest that maintenance or protection of reach and riparian buffers alone will not sufficiently protect stream function and structure from catchment-wide impacts.     

An integrated study of the temporal and spatial variation in the supply of propagules, recruitment and assemblages of intertidal macroalgae on a wave-exposed rocky coast, Victoria, Australia

Recruitment is known to influence distributions and abundances of benthic marine organisms. It is therefore important to document patterns of variability in recruitment and how these relate to patterns in established assemblages. This study provides an integrated assessment of the temporal and spatial variation in supply and recruitment of propagules and established populations of several macroalgae. Propagules in water samples from two stages of the incoming tide, recruitment to artificial substrata and percentage cover of species established on the shore were recorded every 2 months from December 1994 to October 1995, in two zones of an intertidal, wave-exposed rocky shore. Variability in recruitment was measured at three spatial scales: 10s cm, 100s cm and 100s m. Availability and recruitment of most taxa were greatest between April and August, although many species had available propagules and recruited throughout the year. Temporal variation in the established assemblages was, however, more species-specific. Differences in established assemblages between zones were reflected in differences in availability and recruitment of propagules between zones. Recruitment could not be predicted directly from supply of propagules, but the two processes were linked. For most species, the greatest variation in recruitment occurred at the smallest spatial scale of 10s cm, although there was also considerable large-scale (between site) variation in recruitment of several species. Results indicate that while pre-and post-settlement mortality are likely to influence macroalgal distribution and abundance, the temporal and spatial variability in supply and recruitment of propagules can explain much of the patchiness in macroalgal assemblages.     

Fish Communities of the Lower Fraser River (Canada) and a 21-year Contrast

Fish communities were sampled at 14 sites along the lower 120km of the Fraser River, British Columbia by beach seine four times in 1972–1973 and three times in 1993–1994. Of the 37 species collected, peamouth chub, largescale sucker, starry flounder, and northern squawfish were predominant in either density or biomass. Densities and biomass of most species and all fish combined were higher in 1993–1994. Strong rank correlations of species abundance or biomass indicated that the overall fish community structure was very similar in both periods. At smaller spatial scales (reaches of 2–3 sites) and shorter time scales (by season), less than half the comparisons showed any significant correlation indicating changes in community composition. Largescale sucker, one of the largest contributors to biomass in both periods, showed decreased abundance, i.e., lower density, lower biomass, and large differences in the size-frequency distribution, specifically very low representation of small size classes. Other species, especially small-bodied forms, generally increased in numbers. Despite large changes in the lower Fraser River ecosystem in the past 21 years, the overall fish community has shown remarkably little change over that interval.     

Scales of spatiotemporal variability in macroinvertebrate abundance and diversity in monsoonal streams: detecting environmental change

1. We quantified spatial and temporal variability in benthic macroinvertebrate species richness, diversity and abundance in six unpolluted streams in monsoonal Hong Kong at different scales using a nested sampling design. The spatial scales were regions, stream sites and stream sections within sites; temporal scales were years (1997–99), seasons (dry versus wet seasons) and days within seasons. 2. Spatiotemporal variability in total abundance and species richness was greater during the wet season, especially at small scales, and tended to obscure site‐ and region‐scale differences, which were more conspicuous during the dry season. Total abundance and richness were greater in the dry season, reflecting the effects of spate‐induced disturbance during the wet season. Species diversity showed little variation at the seasonal scale, but variability at the site scale was apparent during both seasons. 3. Despite marked variations in monsoonal rainfall, inter‐year differences in macroinvertebrate richness and abundance at the site scale during the wet season were minor. Inter‐year differences were only evident during the dry season when streams were at base flow and biotic interactions may structure assemblages. 4. Small‐scale patchiness within riffles was the dominant spatial scale of variation in macroinvertebrate richness, total abundance and densities of common species, although site or region was important for some species. The proportion of total variance contributed by small‐scale spatial variability increased during the dry season, whereas temporal variability associated with days was greater during the wet season. 5. The observed patterns of spatiotemporal variation have implications for detection of environmental change or biomonitoring using macroinvertebrate indicators in streams in monsoonal regions. Sampling should be confined to the dry season or, in cases where more resources are available, make use of data from both dry and wet seasons. Sampling in more than one dry season is required to avoid the potentially confounding effects of inter‐year variation, although variability at that scale was relatively small.