Home About us Contact
|
Home About us Contact | ||
|
|
||
Egg Survival (egg + survival)
Selected AbstractsCreation of artificial upwelling areas for brown trout, Salmo trutta, spawning in still water bodiesFISHERIES MANAGEMENT & ECOLOGY, Issue 5 2006Å. BRABRAND Abstract, Brown trout, Salmo trutta L., spawning sites were constructed by creating areas of artificial upwelling water, 252 ± 37 mL m,2 min,1 (95% CL), through appropriately sized spawning gravel substrate in 3 m2 vessels buried in the bottom of a 150-m2 pond. Natural spawning occurred in the vessels during autumn 2001,2004, with hatching and alevin swim up the following spring. In areas of upwelling, egg survival was 85,95%, while no live eggs were observed in areas without upwelling. In areas with upwelling, the maximum density of live eggs at the eyed stage was 570,1510 eggs m,2. In spring 2004 and 2005, the density of alevins was estimated at 322 (±187) m,2 and 567 (±217) m,2, respectively, in areas with upwelling water, compared with 35.2 ± 25.4 m,2 in areas without upwelling water in 2004. [source] Process-based model for direct and indirect effects of hydrographic conditions on Central Baltic cod (Gadus morhua) egg mortalityFISHERIES OCEANOGRAPHY, Issue 2 2008K. H. ANDERSEN Abstract A process-oriented model for the mortality of eggs of cod Gadus morhua in the Central Baltic Sea is developed, based on a synthesis of existing knowledge of the effects of salinity, oxygen and predation by sprat Sprattus sprattus. The models show the importance of the vertical and temporal overlap between eggs and predations. Effects related to the changing buoyancy of the eggs due to age and size of the mother fish, batch number and stock structure are not of major importance for the egg survival of this stock. It is demonstrated that under the present high sprat predation pressure, the observed delay in spawning time has increased egg survival. [source] Lagged effects of North Atlantic Oscillation on spittlebug Philaenus spumarius (Homoptera) abundance and survivalGLOBAL CHANGE BIOLOGY, Issue 12 2006ANTTI HALKKA Abstract The North Atlantic Oscillation (NAO) is a large-scale pattern of climate variability that has been shown to have important ecological effects on a wide spectrum of taxa. Studies on terrestrial invertebrates are, however, lacking. We studied climate-connected causes of changes in population sizes in island populations of the spittlebug Philaenus spumarius (L.) (Homoptera). Three populations living in meadows on small Baltic Sea islands were investigated during the years 1970,2005 in Tvärminne archipelago, southern Finland. A separate analysis was done on the effects of NAO and local climate variables on spittlebug survival in 1969,1978, for which survival data existed for two islands. We studied survival at two stages of the life cycle: growth rate from females to next year's instars (probably mostly related to overwintering egg survival), and survival from third instar stage to adult. The latter is connected to mortality caused by desiccation of plants and spittle masses. Higher winter NAO values were consistently associated with smaller population sizes on all three islands. Local climate variables entering the most parsimonious autoregressive models of population abundance were April and May mean temperature, May precipitation, an index of May humidity, and mean temperature of the coldest month of the previous winter. High winter NAO values had a clear negative effect on late instar survival in 1969,1978. Even May,June humidity and mean temperature of the coldest month were associated with late instar survival. The climate variables studied (including NAO) had no effect on the growth rate from females to next year's instars. NAO probably affected the populations primarily in late spring. Cold and snowy winters contribute to later snow melt and greater spring humidity in the meadows. We show that winter NAO has a considerable lagged effect on April and May temperature; even this second lagged effect contributes to differences in humidity. The lagged effect of the winter NAO to spring temperatures covers a large area in northern Europe and has been relatively stationary for 100 years at least in the Baltic area. [source] Sediment infiltration traps: their use to monitor salmonid spawning habitat in headwater tributaries of the Cascapédia River, QuébecHYDROLOGICAL PROCESSES, Issue 20 2005André E. Zimmermann Abstract Sediment infiltration can clog salmon nests and reduce egg survival. As a countermeasure, environmental managers often deploy infiltration traps to monitor sediment infiltration. Traps provide a repeatable means of measuring infiltration and enable comparisons to be made between sites. Results from infiltration rates measured with traps have also been used to estimate infilling rates into salmon nests. Application of these data is questionable, as the composition of the bed and the amount of fine sediment within the bed is known to affect infiltration rates. Thus, infiltration rates measured with infiltration traps may differ from the infiltration rates occurring in redd and riffle gravels. To examine how relationships between sediment infiltration rates varied between four watersheds, we continuously monitored suspended sediment transport, shear stress and infiltration rates at four sites over 5 months. We also compared infiltration rates measured with infiltration traps with changes in the hydraulic conductivity and subsurface grain size distribution of adjacent artificially constructed salmon nests and natural riffle gravels. Among the four watersheds, clear differences in sediment infiltration rates were observed. The differences correlated with the subsurface silt content but no strong relationship existed between land-use or basin physiography/geology. Despite observing an average of 30 kg m,2 of sediment finer than 2 mm being deposited in the infiltration traps during the study, no change in redd or riffle substrate was observed. If the deposition rates measured with the traps reflect the processes in redds, enough sediment would have been deposited to inhibit egg emergence. However, no reduction in egg survival to the eyed stage was observed. In summary, our results show that infiltration traps with clean gravels can be used to detect intersite differences in sediment transport regimes. Extrapolations of sediment infiltration rates measured with such collectors to estimate infiltration rates in redds or riffles is, however, flawed. Copyright © 2005 John Wiley & Sons, Ltd. [source] Hydrological influences on hyporheic water quality: implications for salmon egg survivalHYDROLOGICAL PROCESSES, Issue 9 2004I. A. Malcolm Abstract The spatial and temporal variability of groundwater,surface-water (GW,SW) interactions was investigated in an intensively utilized salmon spawning riffle. Hydrochemical tracers, were used along with high-resolution hydraulic head and temperature data to assess hyporheic dynamics. Surface and subsurface hydrochemistry were monitored at three locations where salmon spawning had been observed in previous years. Temperature and hydraulic head were monitored in three nests of three piezometers located to characterize the head, the run and the tail-out of the riffle feature. Hydrochemical gradients between surface and subsurface water indicated increasing GW influence with depth into the hyporheic zone. Surface water was characterized by high dissolved oxygen (DO) concentrations, low alkalinity and conductivity. Hyporheic water was generally characterized by high levels of alkalinity and conductivity indicative of longer residence times, and low DO, indicative of reducing conditions. Hydrochemical and temperature gradients varied spatially over the riffle in response to changes in local GW,SW interactions at the depths investigated. Groundwater inputs dominated the head and tail of the riffle. The influence of SW increased in the area of accelerating flow and decreasing water depth through the run of the riffle. Temporal GW,SW interactions also varied in response to changing hydrological conditions. Gross changes in hyporheic hydrochemistry were observed at the weekly scale in response to changing flow conditions and surface water inputs to the hyporheic zone. During low flows, caused by freezing or dry weather, hyporheic hydrochemistry was dominated by GW inputs. During higher flows hyporheic hydrochemistry indicated that SW contributions increased. In addition, high-resolution hydraulic head data indicated that rapid changes in GW,SW interactions occurred during hydrological events. The spatial, and possibly the temporal, variability of GW,SW interactions had a marked effect on the survival of salmon ova. It is concluded that hyporheic dynamics and their effect on stream ecology should be given increased consideration by fisheries and water resource managers. Copyright © 2004 John Wiley & Sons, Ltd. [source] Combined effects of climate and biotic interactions on the elevational range of a phytophagous insectJOURNAL OF ANIMAL ECOLOGY, Issue 1 2008Richard M. Merrill Summary 1The ranges of many species have expanded in cool regions but contracted at warm margins in response to recent climate warming, but the mechanisms behind such changes remain unclear. Particular debate concerns the roles of direct climatic limitation vs. the effects of interacting species in explaining the location of low latitude or low elevation range margins. 2The mountains of the Sierra de Guadarrama (central Spain) include both cool and warm range margins for the black-veined white butterfly, Aporia crataegi, which has disappeared from low elevations since the 1970s without colonizing the highest elevations. 3We found that the current upper elevation limit to A. crataegi's distribution coincided closely with that of its host plants, but that the species was absent from elevations below 900 m, even where host plants were present. The density of A. crataegi per host plant increased with elevation, but overall abundance of the species declined at high elevations where host plants were rare. 4The flight period of A. crataegi was later at higher elevations, meaning that butterflies in higher populations flew at hotter times of year; nevertheless, daytime temperatures for the month of peak flight decreased by 6·2 °C per 1 km increase in elevation. 5At higher elevations A. crataegi eggs were laid on the south side of host plants (expected to correspond to hotter microclimates), whereas at lower sites the (cooler) north side of plants was selected. Field transplant experiments showed that egg survival increased with elevation. 6Climatic limitation is the most likely explanation for the low elevation range margin of A. crataegi, whereas the absence of host plants from high elevations sets the upper limit. This contrasts with the frequent assumption that biotic interactions typically determine warm range margins, and thermal limitation cool margins. 7Studies that have modelled distribution changes in response to climate change may have underestimated declines for many specialist species, because range contractions will be exacerbated by mismatch between the future distribution of suitable climate space and the availability of resources such as host plants. [source] The importance of measuring biotic and abiotic factors in the lower egg pocket to predict coho salmon egg survivalJOURNAL OF FISH BIOLOGY, Issue 3 2003C. B. Meyer Based on results from simulated redds of coho salmon Oncorhynchus kisutch, the amount of fine sediment <0·5 mm in the lower half of the egg pocket, rather than the entire egg pocket of the redd, was a strong predictor of egg survival to hatching ( r2 = 0·62). The relationship was much stronger than observed in other studies, which typically ignore egg pocket structure. Abundance of a fish egg-eating worm, Haplotaxis ichthyophagous, an oligochaete that may have been attracted to fine sediment and dead eggs in the egg pocket, was also associated with a decrease in egg survival. The worm, however, accounted for little of the variance in survival compared to fine sediment. Only 10% fine sediment (<0·5 mm) in the lower pocket was required to decrease survival from 100 to 5%. Other abiotic factors had weaker (gravel permeability) or non-existent (dissolved oxygen) correlations with survival. [source] Environment and host-plant genotype effects on the seasonal dynamics of a predatory mite on cassava in sub-humid tropical AfricaAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2009Christine Zundel Abstract 1,In tropical dry seasons, survival of small arthropods such as predatory mites is often negatively affected by low relative humidity (RH). For species that do not diapause or migrate to refuges, the ability of the habitat to mitigate climatic conditions becomes crucial. 2,The relative effect of macro-habitat (dry grassland hill, humid multiple cropping area, humid riparian forest) and microhabitat (host-plant genotypes with hairy, semi-hairy and glabrous apices) on the seasonal dynamics of the phytoseiid mite Typhlodromalus aripo, a predator of Mononychellus tanajoa on cassava, was examined in a field experiment during a dry season. The effect of RH and plant genotype on T. aripo egg survival was determined in an environment control chamber. 3,Predator abundance was higher in humid multiple cropping areas and on hairy cassava compared with the other habitat types and cassava genotypes. 4,Discriminant and regression analyses showed that the predator's dry season persistence was related to high RH, high plant vigour and hairy apices, but not to prey abundance. 5,In the controlled climate experiment, the effect of host-plant morphology was evident only at the intermediate RH level of 55%. An effect of apex hairiness was not found. 6,It is concluded that the effect of genotype on T. aripo persistence diminishes under low RH conditions, and that supportive effects of apex hairs become effective only in the field, probably through protection from wind and/or intraguild predation. Humid multiple cropping areas planted with hairy and vigorous cassava genotypes are suitable dry season reservoirs for T. aripo. [source] Maternal care in a neotropical jumping spider (Salticidae)JOURNAL OF ZOOLOGY, Issue 3 2008C. Vieira Abstract Although female jumping spiders (Salticidae) often stay with their egg sacs, little is known about whether this behaviour is effective in improving offspring survival. Females of the jumping spider Psecas chapoda (Salticidae) typically stay above their egg sacs and under a plain silk cover, spun from edge to edge of bromeliad leaves. The objective of this paper is to test the hypothesis that the presence of the females above the egg sac increases egg survival. We experimentally manipulated females and silk cover in P. chapoda using three treatments: female and silk cover present (control), female removed and silk cover present and female and silk cover removed. The number and area of holes in the egg sac walls, which are likely to be damage caused by egg predators, were higher in the absence of spiders and spiders+silk cover than in controls. Additionally, the number of spiderlings and exuvia was lower in the absence of females and female+silk cover than in the control treatment. The number of important specialized predators of spider eggs (i.e. mantipids) that develop inside P. chapoda egg sacs did not differ among the treatments. To our knowledge, this is the first experimental study that effectively demonstrates maternal care in spiders of the family Salticidae. [source] Egg performance on an egg-carrying bug.OIKOS, Issue 2 2001Experiments in the field Selection of oviposition sites has direct influence on female fitness. Differences in offspring survival among sites should favour females to select oviposition sites with the highest survival. Golden egg bug females (Phyllomorpha laciniata; Coreidae, Heteroptera) use conspecifics as oviposition substrates. Most eggs are laid on the back of the bug but they can be found on all body parts. Females never carry their own eggs, and males commonly carry eggs received without copulation with the donor. We examined differences in egg survival relative to paternity to the egg, host sex and body size and attachment of an egg on a host's body in the field. We also studied which bugs received eggs. Egg loss was surprisingly common: 30,80% of recaptured individuals lost eggs during a six-day period. Unexpectedly, host's paternity to the eggs did not affect egg survival. Also, egg loss did not differ among hosts in respect to other parameters studied. Males received more eggs than females, but survival of the eggs was not better on a male's back than on a female's back. Since egg loss is common in the golden egg bug, we suggest that female oviposition strategy to lay eggs on conspecifics is not perfect. This is due to active behaviour of potential hosts (for example, rejected oviposition attempts) or lack of suitable oviposition substrates (conspecifics) in the field. Since eggs do not survive unless carried, females may be acting opportunistically, doing the best job possible by laying eggs on available conspecifics. [source] U.K. winter egg survival in the field and laboratory diapause of Typhlodromips montdorensisPHYSIOLOGICAL ENTOMOLOGY, Issue 1 2005Ian S. Hatherly Abstract.,Typhlodromips montdorensis has potential for release as a glasshouse biological control agent in the U.K. against thrips and spider mites. This study investigates the field survival in the U.K. of T. montdorensis when released as eggs, and the diapause response when reared in a regime related to its location of origin. All acclimated and nonacclimated eggs of T. montdorensis die in the field within 7 days of exposure. It is not possible to induce diapause in T. montdorensis reared at 21 °C under a LD 11 : 13 h photoperiod. The results presented here support the view that T. montdorensis is unlikely to survive a U.K. winter outside of the glasshouse environment, and contribute to the understanding of the biology of this little known species. [source] Nesting in a thermally challenging environment: nest-site selection in a rock-dwelling gecko, Oedura lesueurii (Reptilia: Gekkonidae)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010DAVID A. PIKE In egg-laying species, maternal oviposition choice can influence egg survival and offspring phenotypes. According to the maternal-preference offspring-performance hypothesis, females should choose oviposition sites that are optimal for offspring fitness. However, in thermally challenging environments, maternal oviposition behaviour may be constrained by the limited availability of suitable oviposition sites. We investigated nest-site selection in a nocturnal lizard [velvet gecko Oedura lesueurii (Duméril and Bibron)] that inhabits a thermally challenging environment in south-eastern Australia. The viability of these gecko populations is critical for the persistence of an endangered snake species (Hoplocephalus bungaroides Wagler) that feeds heavily on velvet geckos. Female geckos chose nest sites nonrandomly, with 87% of nests (N = 30) being laid in deep crevices. By contrast, only 13% of clutches were laid under rocks, which were the most readily available potential nest sites. Nest success in crevices was high (100%), but no eggs hatched from nests under rocks. Temperatures in nest crevices remained relatively low and constant throughout the incubation period (mean = 22.7 °C, range 21.0,24.5 °C), whereas thermal regimes under rocks showed large diurnal fluctuations. Geckos selected crevices that were deeper, had less canopy cover, and were warmer than most available crevices; in 85% of cases, such crevices were used simultaneously by more than one female. The thermally distinctive attributes of nest sites, and their frequent communal use, suggest that nest sites are a scarce resource for female velvet geckos, and that the shading of rock outcrops through vegetation encroachment may influence nest success in this species. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99, 250,259. [source] | |||||||||||||