Growth and Mortality in an Arctic Intertidal Population of Macoma balthica (Pelecypoda, Tellinidae)

1973 ◽  
Vol 30 (9) ◽  
pp. 1345-1348 ◽  
Author(s):  
Roger H. Green
Keyword(s):  
Growth Rates ◽  
Macoma Balthica ◽  
Dry Weight ◽  
Hudson Bay ◽  
Intertidal Environment ◽  
Air Temperatures ◽  
Proximate Factor ◽  
The Mean ◽  
Intertidal Population ◽  
Annual Mortality

In an arctic intertidal environment on Hudson Bay, Macoma balthica have a higher growth rate at a tidal level of 1.1 m above mean low water than at the mean low water level, in terms of both length and dry weight. Temperature, rather than food, appears to be the primary proximate factor involved, and summer air temperatures play a major role. The estimated growth rates are comparable to reported growth rates for intertidal Macoma populations in Scotland and the Netherlands. A partial life table calculated from the death assemblage indicates that Macoma at 1.1 m above mean low water have an annual mortality which increases from about 20% at age 2 to about 50% at age 7 years.

Establishment in Australia of two insects for biological control of the floating weed Salvinia molesta

1984 ◽  
Vol 74 (3) ◽  
pp. 505-516 ◽  
Author(s):  
P. M. Room ◽  
I. W. Forno ◽  
M. F. J. Taylor
Keyword(s):  
Biological Control ◽  
Nitrogen Concentration ◽  
Dry Weight ◽  
Salvinia Molesta ◽  
Air Temperatures ◽  
Present Distribution ◽  
The Mean ◽  
Maximum Temperatures ◽  
North And South ◽  
Extensive Damage

AbstractIn attempts at the biological control of Salvinia molesta in Australia, the curculionid Cyrtobagous sp. was released at eight sites and became established at seven of them. At these seven sites, air temperatures ranged from less than 0°C to more than 45°C and the mean concentration of nitrogen in S. molesta ranged from 1·18 to 1·82% of dry weight. Establishment was effected by releasing 200 adults, and the shortest time for extensive damage to be caused to the weed was four months. Cyrtobagous sp. dispersed in undamaged S. molesta at rates of a few metres per month. The pyralid Samea multiplicalis Gn. was released, and became established, at three sites and spread at least 170 km north and south in 20 months. At the sites colonised, air temperatures ranged from less than 0°C to more than 45°C and the mean nitrogen concentration in Salvinia molesta ranged from 1·34 to 3·30% of dry weight. Establishment was effected by releasing 800 larvae, and the shortest time for extensive damage to be caused to S. molesta was three months. Contrasts in the biology and ecology of the two species of insects are discussed briefly as is competition between them for food. In late 1983, Cyrtobagous sp. had achieved control of S. molesta at five sites, while Samea multiplicalis had achieved control at none. It is suggested that S. multiplicalis might perform better in locations which experience maximum temperatures lower than those in the present distribution.

scholarly journals Producción secundaria de una población de Chione cancellata (Bivalvia: Veneridae) de la costa sur del Golfo de Cariaco, Venezuela

2015 ◽  
pp. 913-919
Author(s):  
Antulio S Prieto A ◽  
Cenia Ramos ◽  
Dwight Arrieche
Keyword(s):  
Growth Rates ◽  
Population Distribution ◽  
Dry Weight ◽  
Abundant Species ◽  
Thalassia Testudinum ◽  
Age Classes ◽  
Production Values ◽  
Distribution Ranges ◽  
The Mean ◽  
Continuous Reproduction

Production and biomass of Chione cancellata, an abundant species in Thalassia testudinum sea beds, were studied from March, 1984 to May, 1985 in Guaracayal, Cariaco Gulf, Venezuela. The population distribution ranges were stable. Many individuals were 20-30 mm long (80%) and recruitment was low. The mean density was 45.54 ind m' with a mean standing dry weight biomass of 7.37 g m', both changed significantly with time. Growth rates in marked bivalves of different size classes was maximum in the period between 14-X- 1984 and 10-V-1985. A production of 17 .34 g m' year' was obtained using a method designed to study populations with continuous reproduction and indistinguishable age classes. The greatest production values were obtained for cockles 20 to 30 mm in length. Highest production was between 28-Il-1985 and 27-IV-1985. The annual tumover rate (PIB) was 2.65 year'.

Moisture, its accumulation and site of evaporation in the coats of sweating cattle

1970 ◽  
Vol 74 (2) ◽  
pp. 247-258 ◽  
Author(s):  
T. E. Allen ◽  
J. W. Bennettf ◽  
Susan M. Donegan ◽  
J. C. D. Hutchinson
Keyword(s):  
Moisture Content ◽  
Unit Area ◽  
Outer Part ◽  
Dry Weight ◽  
Indoor Environments ◽  
Air Temperatures ◽  
Free Moisture ◽  
Saturated Atmosphere ◽  
The Mean ◽  
Sun And Shade

SUMMARYMoisture content of the coats of cattle, expressed as the percentage of the dry weight of hair, has been measured in a wide variety of environmental conditions in summer, springand winter. Strips of coat were clipped from 25 Jersey, 15 Zebu x Jersey crossbred and 9 Hereford heifers in a shed, in a climate room under warm, hot dry and hot humid conditions and outdoors both in sun and shade. Moisture content, weight of coat per unit area, depth of coat, skin and rectal temperatures, sweating and respiratory rates, air temperatures and vapour pressures were measured.The mean moisture content of the coats varied in the different environments from 5·8 to 27·5 % and mean sweating rates from 28 to 438 g m-2 h-1. Moisturein summer coats out of doors in the sun averaged 11·2% and was about the same as that outof doors in the shade. In the shed, coat moisture was also low (average 11·8%) and amounted to less than half of the moisture content of clipped hair in equilibrium with a near saturated atmosphere. Herefords that had been fed a low plane ration from winter to summer, retained their long winter coats and these, in summer, had only half the moisture content of the short coats of normally fed Herefords. In the hot room, the moisture content of summer coats was usually higher than out of doors and varied around 18%.The inner part of the coat had more moisture than the outer part and estimates of moisture gradients were made. Calculation of the contribution of sweating to total moisture in indoor environments showed that, at rapid rates of sweating, it was about 8% and was higher in winter andspring coats than in summer coats (Fig. 3). It was estimated that sun and wind reduced the moisture content of summer coats by about 3% in outdoor summer environments. The effect of sun and wind on moisture content of winter coats in the same environment was estimated at nearly 9%.The results suggest that the site of evaporation was at the skin except in very hot humid indoor environments when some free moisture may have been present in the hair.

The Seasonal Growth of Eucalyptus regnans F. Muell

1975 ◽  
Vol 23 (2) ◽  
pp. 239 ◽  
Author(s):  
DH Ashton
Keyword(s):  
Growth Rates ◽  
Late Summer ◽  
Growing Season ◽  
Day Length ◽  
Maximum Diameter ◽  
Main Peak ◽  
Daily Maximum ◽  
Eucalyptus Regnans ◽  
Air Temperatures ◽  
The Mean

At Wallaby Creek, Vic. (altitude 670 m), Eucalyptus regnans seedlings 1-6 m in height usually commence growth in early September, reach maximum growth in midsummer and cease growing in late May. The active growing season when shoot growth exceeds 12 mm per month is 7-9½. months. Slow growth occurs in midwinter in Melbourne (altitude 47 m) and is not affected by day length. The growth rates of seedlings of associated understorey species are, in descending order of magnitude: Acacia dealbata, E. vegnans, Prostantheva lasianthos, Pomadevvis aspeva, Acacia melanoxylon. Their growth periods are similar, except for that of A. melanoxylon which is much shorter. Leaves of E. regnans mature in 2½-3½ months. In larger seedlings some of the leaves produced are initiated during the growing season. The size of the mature leaf depends partly on the season of its emergence. In winter and spring, die-back of apical shoots occurs in most seedlings owing to weevil attack and fungal infection. Insects may severely damage young leaves, but rapid recovery in full light takes place by the development of axillary and accessory buds. Maximum diameter growth rates tend to occur in November just prior to the main peak of shoot extension. Further increases in diameter may occur in April, and slight shrinkage may take place in late summer and midwinter. The period of active growth can be correlated with the period over which the air temperatures at 1.3 m above ground exceed a daily mean of 5.0-7.5°C, a daily maximum of 12.8° and a weekly maximum exceeding 15.5°. Growth,resumption may be delayed until weekly minimum air tempera- tures rise above - 2°. The mean temperatures at 1.3 m are roughly the mean of air temperatures from the top and base of the shoot. The mean temperatures at the mean commencement and cessation of growth differ by only 0.6-1.6°C, whereas the day length differs by 1½ hr. Growth rates correlate strongly with mean temperatures (particularly mean maximum tempera- tures) in spring and early summer. The wide deviations which occur in late summer and early autumn may be attributable to depletion of soil water reserves.

scholarly journals Growth rate and haploidization of Aspergillus niger on medium containing p-fluorophenylalanine

1968 ◽  
Vol 12 (3) ◽  
pp. 305-315 ◽  
Author(s):  
Pol Lhoas
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Growth Curves ◽  
Dry Weight ◽  
Maximum Growth ◽  
Maximum Growth Rate ◽  
Complete Medium ◽  
Acid Analogue ◽  
Mean Size ◽  
The Mean

1. The comparison of the dry weight of thin layer haploid and diploid colonies of A. niger on complete medium and complete medium supplemented with p-fluoro-phenylalanine led to the conclusion that there is a difference in growth rates of hyphae under these different conditions.2. The growth curves of the same strains on both media were established. On complete medium, haploids and diploid show a growth rate increasing linearly for about 20 h after germination and reaching a maximum which is then maintained. On p-fluorophenylalanine, the haploids show a similar curve, although the maximum growth rate reached and maintained is about half that on complete medium; for the diploid, however, the maximum is less than the corresponding one in the haploid and, once this maximum has been reached, the growth rate goes down linearly to a very low value which is then maintained.3. The cytological study of the hyphal tip cell showed, in the presence of the amino acid analogue, a reduction of the mean size of the diploid nuclei together with an increase of the number of nuclear fragments. This explains the growth rates observed and is accepted as a confirmation that p-fluorophenylalanine, by its action on the mitosis, favours chromosome losses which lead finally to the production of haploid nuclei.

An Arctic Intertidal Population of Macoma balthica (Mollusca, Pelecypoda): Genotypic and Phenotypic Components of Population Structure

1983 ◽  
Vol 40 (9) ◽  
pp. 1360-1371 ◽  
Author(s):  
Roger H. Green ◽  
Shiva M. Singh ◽  
Beverly Hicks ◽  
Janet M. McCuaig
Keyword(s):  
Growth Rate ◽  
Macoma Balthica ◽  
Electrophoretic Analysis ◽  
Annual Rings ◽  
Lethal Temperature ◽  
Tidal Level ◽  
Tide Level ◽  
The Mean ◽  
Intertidal Population ◽  
Lower Tolerance

In July 1980 we collected live Macoma balthica from populations at two tide levels near Fort Churchill, Man., Canada. Upper lethal temperature tolerances were determined for clams from the mean low water (MLW) tidal level and from 1.1 m above MLW tidal level, after which all specimens were hard frozen for later electrophoretic analysis. Of 22 loci evaluated, the following were polymorphic: AKP, ACP, EST, LAP, MDH, and ME. Genotypes at these loci were related to tide level, growth rate, tolerance to high temperature, and age. Analysis of shell annual rings verified an earlier report of much faster growth in the higher tide level population. Growth rate and degree of heterozygosity are both higher at 1.1 m than at MLW. Degree of heterozygosity increases with age, suggesting selection against homozygotes. At 1.1 m, but not at MLW, individuals with higher growth rates have lower tolerance to high temperatures and a higher degree of heterozygosity. Similar patterns are described for the six individual loci.

Naturally occurring activity variation of an alkaline phosphatase isozyme associated with physiological fitness in an intertidal population of Macoma balthica

1986 ◽  
Vol 28 (2) ◽  
pp. 282-285 ◽  
Author(s):  
Shiva M. Singh ◽  
Roger H. Green
Keyword(s):  
Alkaline Phosphatase ◽  
Macoma Balthica ◽  
High Tide ◽  
Activity Level ◽  
Hudson Bay ◽  
Biochemical Basis ◽  
Physiological Fitness ◽  
Naturally Occurring ◽  
Intertidal Population ◽  
Enzyme Alkaline Phosphatase

We observed variability in the level of an isozyme for the enzyme alkaline phosphatase (AKP, EC 3.1.3.1) in a Macoma balthica population from Hudson Bay. The distribution of "high" and "no" activity AKP-2 variants were different in samples from "high" tide as compared with "low" tide areas. Furthermore, the AKP-2 activity level is associated with survival at high temperature (32 °C), but in the "high" tide subpopulation only. Although this striking association between the activity level of an isozyme and an environmental parameter in a natural population is one of the very few in the literature, further studies are required to establish the genetic basis for the level of the enzyme activity and the biochemical basis for this relationship.Key words: isozyme, alkaline phosphatase, natural selection, evolution.

Biology and Management of Inland Striped Bass and Hybrid Striped Bass

2013 ◽  
Keyword(s):  
Striped Bass ◽  
Growth Rates ◽  
Morone Saxatilis ◽  
Mortality Rates ◽  
Minimum Length ◽  
Hybrid Striped Bass ◽  
White Bass ◽  
Management Objectives ◽  
The Mean ◽  
Annual Mortality

Abstract.— Total annual mortality and mortality caps (maximum mortality thresholds) were estimated for hybrid striped bass (striped bass <em>Morone saxatilis</em> × white bass <em>M. chrysops</em>) populations sampled in six large Kansas reservoirs spanning 1995–2001; all reservoirs lacked a minimum length limit but had a 2/d creel limit. Total annual mortality of age-1 and older hybrid striped bass was estimated using a weighted catch curve. Mortality caps were modeled by varying growth rates and management objectives. Mortality rates that approach the cap signal the need for increased monitoring to determine what additional management action should be taken (e.g., harvest regulations to reduce mortality) or to reevaluate the size objective (targeted mean length of harvested fish) for the fishery. Estimated mortality caps were then compared with observed growth and mortality rates. Total annual mortality rates for all reservoirs varied from 22% to 52% (mean = 38%; SE = 4.9). All but two reservoirs had total annual mortality rates greater than 40%. Analysis of mortality caps indicated that when the objective was to maintain the mean length of harvested hybrid striped bass at current levels, total annual mortality was lower than the mortality cap for most reservoirs if a 381 mm total length (TL) minimum length limit (i.e., preferred length) were to be imposed. A management objective of 500 mm TL for the mean length of harvested hybrid striped bass was realistic for all reservoirs modeled with a 457-mm-TL length limit (special regulation available to managers) but only for two reservoirs with a 381-mm-TL length limit. Likewise, only two of the study reservoirs could support a management objective of 550 mm TL (herein defined as trophy length) for mean length of harvested hybrid striped bass when modeled with a 457-mm-TL length limit. Our analysis illustrates the potential of mortality caps for monitoring and establishing realistic management goals for hybrid striped bass fisheries.

scholarly journals Admixing Chaff with Straw Increased the Residues Collected without Compromising Machinery Efficiencies

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1766 ◽  
Author(s):  
Alessandro Suardi ◽  
Sergio Saia ◽  
Walter Stefanoni ◽  
Carina Gunnarsson ◽  
Martin Sundberg ◽  
...  
Keyword(s):  
Energy Production ◽  
Dry Weight ◽  
Global Scale ◽  
Unit Weight ◽  
Residual Biomass ◽  
Energy Needs ◽  
The Mean ◽  
Field Efficiency ◽  
The One ◽  
Staple Crop

The collection of residues from staple crop may contribute to meet EU regulations in renewable energy production without harming soil quality. At a global scale, chaff may have great potential to be used as a bioenergy source. However, chaff is not usually collected, and its loss can consist of up to one-fifth of the residual biomass harvestable. In the present work, a spreader able to manage the chaff (either spreading [SPR] on the soil aside to the straw swath or admixed [ADM] with the straw) at varying threshing conditions (with either 1 or 2 threshing rotors [1R and 2R, respectively] in the combine, which affects the mean length of the straw pieces). The fractions of the biomass available in field (grain, chaff, straw, and stubble) were measured, along with the performances of both grain harvesting and baling operations. Admixing chaff allowed for a slightly higher amount of straw fresh weight baled compared to SPR (+336 kg straw ha−1), but such result was not evident on a dry weight basis. At the one time, admixing chaff reduced the material capacity of the combine by 12.9%. Using 2R compared to 1R strongly reduced the length of the straw pieces, and increased the bale unit weight; however, it reduced the field efficiency of the grain harvesting operations by 11.9%. On average, the straw loss did not vary by the treatments applied and was 44% of the total residues available (computed excluding the stubble). In conclusion, admixing of chaff with straw is an option to increase the residues collected without compromising grain harvesting and straw baling efficiencies; in addition, it can reduce the energy needs for the bale logistics. According to the present data, improving the chaff collection can allow halving the loss of residues. However, further studies are needed to optimise both the chaff and the straw recoveries.

Distribution and abundance of ringed (Phoca hispida) and bearded seals (Erignathus barbatus) in western Hudson Bay

1997 ◽  
Vol 54 (4) ◽  
pp. 914-921 ◽  
Author(s):  
N J Lunn ◽  
I Stirling ◽  
S N Nowicki
Keyword(s):  
Polar Bear ◽  
Hudson Bay ◽  
Phoca Hispida ◽  
Current Estimate ◽  
Ringed Seals ◽  
Erignathus Barbatus ◽  
The Mean ◽  
Western Hudson Bay ◽  
The Relationship ◽  
Bearded Seals

We flew a medium-altitude, systematic, strip-transect survey for ringed (Phoca hispida) and bearded seals (Erignathus barbatus) over western Hudson Bay in early June 1994 and 1995. The mean density (per square kilometre) of ringed seals hauled out on the ice was four times higher in 1995 (1.690) than in 1994 (0.380). The 1994 survey appeared to underestimate seal abundance because it was flown too late. Ringed seals preferred high ice cover habitat (6 + /8 ice) and, within this habitat, favoured cracking ice and large floes. We found no consistent effect of either wind or cloud cover on habitat preference. We estimated a total of 1980 bearded seals and 140<|>880 ringed seals hauled out on the sea ice in June 1995. A recent review of the relationship between ringed seal and polar bear (Ursus maritimus) populations suggests that a visible population of this size should support a population of up to 1300 polar bears, which is in general agreement with the current estimate of 1250-1300 bears in western Hudson Bay.

Sign in / Sign up

Export Citation Format

Share Document