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Low Tide (low + tide)
Selected AbstractsMicrohabitat and rhythmic behavior of tiger beetle Callytron yuasai okinawense larvae in a mangrove forest in JapanENTOMOLOGICAL SCIENCE, Issue 3 2007Aya SATOH Abstract Mangrove forests are regularly flooded by tides at intervals of approximately 12.4 h (tidal rhythm). Larvae of the tiger beetle Callytron yuasai okinawense in a mangrove forest made shallow burrows in mounds up to 1 m in height constructed by the mud lobster Thalassina anomala. No larval burrows were observed on the forest floor, which was very muddy even during low tide. Some larvae plugged the burrow openings before they were submerged at high tide. The mean interval between consecutive burrow plugging events was 12.37 h, which is similar to the period of tidal cycles. Nine out of 30 larvae plugged the burrow openings even when the burrows did not become submerged. Plugging behavior may be governed by an endogenous biological clock, or may be a response to exogenous information about tidal level (e.g. moisture seeping through the ground). [source] Population trends and habitat use of Harlequin Ducks in Rhode IslandJOURNAL OF FIELD ORNITHOLOGY, Issue 3 2007Christine M. Caron ABSTRACT To assess population trends of Harlequin Ducks (Histrionicus histrionicus) in Rhode Island (U.S.A.), we analyzed Christmas Bird Counts and other historical surveys and also conducted surveys during the winter of 2005,2006. We estimated sex and age ratios, evaluated the effects of tidal regime and time of day on survey precision, and quantified habitat use. The population in Rhode Island experienced logistic growth from 1976 to 2004, with approximately 150 birds now wintering at three primary sites in the state. We estimated that the current ratio of males to females in the region was 1.6:1 (62% males) and that 13% of males were first-winter birds. Most Harlequin Ducks were observed in rocky habitats within 50 m of the shore or offshore islands. We detected the greatest numbers of birds, with the least amount of variation, during morning surveys at low tide, suggesting that this may be the most appropriate time for population monitoring. Increases in the Rhode Island population and male-biased sex ratios may indicate a local population recovery resulting from a hunting ban initiated in 1990. Although most Harlequin Ducks in eastern North America winter in Maine, the population in Rhode Island represents one of the largest in the southern part of their range. SINOPSIS Para determinar las tendencias poblacionales de arlequines (Histrionicus histrionicus), en Rhode Island, analizamos los conteos navideños, otros censos históricos y además llevamos a cabos censos durante el invierno de 2005,2006. Cuantificamos el uso de habitat, estimamos la tasa de edad y sexos y evaluamos el efecto del régimen de mareas y la hora del dia en la presición de los censos. La población de patos arlequines experimentó un crecimiento logístico de 1976,2004, con unos 150 patos pasando el invierno en tres localidades primarias, del estado. Estimamos una tasa de 1.6:1 de machos a hembras (62% de machos), siendo un 13% de los machos individuos de primer invierno. La mayoría de las aves fueron observadas en hábitats rocosos a unos 50 m de la playa o en islas cerca de la playa. Detectamos el mayor número de aves, con la menor variación, en los censos que se llevaron a cabo durante la marea baja, lo que sugiere que este es el momento más apropiado para monitorear sus poblaciones. El aumento de estas aves en Rhode Island, el sesgo en su sexo, hacia mayor cantidad de machos, pudiera indicar, de un recobro poblacional como resultado la prohibición de su cacería a partir de 1990. Aunque la mayoría de los arlequines de la parte este de los EUA pasan el invierno en Maine, la población de Rhode Island representa una de las mayores en la parte sur de su distribución. [source] A novel artificial habitat collection device for studying resettlement patterns in anguillid glass eelsJOURNAL OF FISH BIOLOGY, Issue 5 2001V. Silberschneider The number of glass eels Anguilla australis and A. reinhardtii caught in artificial habitat collectors, made from a PVC base and polyethylene split rope fibres, was related to the number of rope fibre tufts attached to each collector rather than collector area directly. Ageing of collectors in situ to promote algal growth enhanced the catch of glass eels. Glass eels entered the collectors at night primarily during the flood tide, and did not move into the collectors during daylight hours. Glass eel abundance increased with increasing distance from the freshwater drain located in the causeway. The artificial habitat collectors are effective for assessing relative numbers of resettling glass eels and may be useful for studying recruitment and settlement patterns of other anguillid eel species, as well as identifying areas and habitats within a catchment that provide important shelter for glass eels. Sampling glass eels can be carried out with maximum effect and minimum effort using compact, aged artificial habitat collectors on the night time flood tide when low tide coincides with dusk. [source] HABITAT DIFFERENCES IN THE TIMING OF REPRODUCTION OF THE INVASIVE ALGA SARGASSUM MUTICUM (PHAEOPHYTA, SARGASSACEAE) OVER TIDAL AND LUNAR CYCLES,JOURNAL OF PHYCOLOGY, Issue 1 2009Carla Monteiro Sargassum muticum (Yendo) Fensholt is an invasive species that is firmly established on intertidal and subtidal rocky shores of Europe and the Pacific coast of North America. Local success and spread of S. muticum is thought to rely on its reproductive potential that seems dependent on exogenous factors like tidal and lunar cycles. This study is the first to compare the reproductive patterns (periodicity of egg expulsion and embryo settlement) of this invader in two different habitats: the middle and low intertidal. The combination of monthly, daily, and tidal samples at triplicate sites within each habitat showed a semilunar periodicity of egg expulsion and embryo settlement coincident with increasing tidal amplitude just before full and new moons. In both habitats, duration of each egg expulsion event was ,1 week, and embryo settlement occurred during the first daily low tide and with the incoming high tide during spring tides. However, both expulsion and settlement started 1,2 d earlier, expulsion saturation was faster, and settlement was higher in the mid- compared to the low intertidal. Our results suggest that the exact timing of gamete expulsion and embryo release of S. muticum responds to local factors, including tidal cues, which result in differences between mid- and low-intertidal habitats. [source] Effects of the Cardiff Bay tidal barrage on the abundance, ecology and behaviour of shelducks Tadorna tadornaAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 4 2009Peter N. Ferns Abstract 1.Closure of the Taff/Ely Estuary by the Cardiff Bay barrage in 1999 resulted in the replacement of intertidal mudflats by a permanent freshwater lake. This led to an 89% reduction in the population of shelducks Tadorna tadorna. 2.The birds switched from foraging mainly for Nereis diversicolor and Hydrobia ulvae by scything with the bill as they walked across the mudflats at low tide, to feeding on benthic chironomid midge larvae while swimming in shallow water around the margins of the lake. 3.The population decline occurred as a consequence of a decrease in the area available for foraging,,,from about 1,km2 of mudflats to about 0.1,km2 of water shallow enough for shelducks to reach the bottom when dabbling, head dipping and upending. 4.Contrary to expectation, the amount of time shelducks spent feeding was similar pre- and post-barrage, and their body and plumage condition improved. 5.A tidal rhythm in activity persisted, with a reduced amount of feeding at high tide, probably because of the slight rise in water levels that sometimes occurred at this time. Copyright © 2008 John Wiley & Sons, Ltd. [source] Determinants of preferred intertidal feeding habitat for Eastern Curlew: A study at two spatial scalesAUSTRAL ECOLOGY, Issue 2 2007PAUL G. FINN Abstract Broadscale habitat use by Eastern Curlews (Numenius madagascariensis) in their non-breeding range in eastern Australia was assessed using low tide surveys on feeding grounds, where 60 skilled volunteers made repeated counts of the birds on intertidal flats, across 41% (9500 ha) of the intertidal habitat within Moreton Bay, Australia. We analysed 32 defined sections of intertidal flat, of roughly equal area (mostly 200,400 ha), which varied greatly in their curlew density (2,47 birds per 100 ha) and also in substrate and other environmental features. Sites with the least resistant substrates had densities three times those with the most resistant substrates. Of 10 environmental characteristics measured for each site, substrate resistance was the best predictor of curlew density (r2 = 0.45). Characteristics that were poor predictors included distance to the nearest roost, level of human disturbance and distance to urban settlement. For a finer-scale assessment, microhabitat use and feeding behaviour were recorded during low tide within 12 intertidal flats, which varied in size (23,97 ha), substrate, topography and other features. Across all flats, curlews strongly preferred to feed relatively close (0,50 m) to the low-water line. They fed on a variety of substrates (including sand, sandy-mud, mud and seagrass) in broadly similar proportions to their occurrence in the habitat. There was a statistically significant preference for sand, although its magnitude was not strong. These results indicate that curlews select habitat most strongly at a between-flat rather than within-flat scale. [source] EFFECT OF TEMPERATURE AND DESICCATION ON THE PHOTOSYNTHETIC PERFORMANCE OF PORPHYRA PERFORATAJOURNAL OF PHYCOLOGY, Issue 2000A. Cabello-Pasini Porphyra perforata is a common seaweed inhabiting the upper intertidal zone, and as a consequence it experiences great fluctuations in tissue temperature and desiccation. The objective of this work was to evaluate the effect of ambient temperature and the tissue desiccation status on the photosynthetic performance of P. perforata. Photosynthetic performance was evaluated polarographically after the temperature or desiccation treatments. Maximum photosynthesis (Pmax) occurred between 25 and 30° C and decreased at higher and lower temperatures, however, no significant differences were observed in the initial slope of photosynthesis (,) from 10 to 30° C. This suggests that the photosynthetic efficiency of this species does not decrease as a result of fluctuating temperatures during tidal emergence/submergence. Pmax and , were relatively constant in tissue of P. perforata with 5 to 100% relative water content. This also suggests that natural desiccation rates during low tides do not decrease photosynthetic rates in this species. Variations in the synthesis of specific proteins as a result of fluctuations in temperature and relative water content in the tissue of P. perforata are being studied. [source] | ||||||||||