Precipitous declines in pinto abalone (Haliotis kamtschatkana kamtschatkana) abundance in the San Juan Archipelago, Washington, USA, despite statewide fishery closure

2008 ◽  
Vol 65 (12) ◽  
pp. 2703-2711 ◽  
Author(s):  
Don P. Rothaus ◽  
Brent Vadopalas ◽  
Carolyn S. Friedman
Keyword(s):  
Shell Length ◽  
Size Class ◽  
San Juan ◽  
Population Densities ◽  
Recruitment Failure ◽  
Small Size Class ◽  
The Mean

Pinto abalone ( Haliotis kamtschatkana kamtschatkana ) index stations in the San Juan Archipelago were systematically monitored by the Washington Department of Fish and Wildlife from 1992 through 2006. During this period, abalone abundance declined by 77% and the mean shell length (SL) increased 10.4 mm. Abalone densities at all index stations are currently well below the threshold of 0.15 abalone·m–2 required for successful fertilization. From 1992 to 1996, 16% of individuals encountered measured <90 mm SL, while only 6% of the individuals from 2003 to 2006 were in this small size class. Similarly, the number of those >114 mm SL was greater in the 2000s than in the 1990s. The mean SL of all live abalone observed in the 1990s (107.62 ± 0.87 mm) was significantly different from the mean SL of empty shells (114.21 ± 2.1 mm), but no difference was detected between the mean SLs of empty shells and live abalone in the 2000s (114.97 ± 1.42 mm). Taken together, these data suggest recruitment failure from an Allee response to low population densities.

Population dynamics and production of a brine shrimp, Parartemia zietziana Sayce (Crustacea : Anostraca), in two salt lakes in westren Victoria, Australia

1977 ◽  
Vol 28 (4) ◽  
pp. 417 ◽  
Author(s):  
R Marchant ◽  
WD Williams
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Temperature Stress ◽  
Brine Shrimp ◽  
Dry Weight ◽  
Salt Lakes ◽  
Confidence Limits ◽  
Length Frequency ◽  
Population Densities ◽  
The Mean

Quantitative samples of P. zietziana were taken monthly for two years from Pink Lake and Lake Cundare. Shrimps were usually contagiously distributed. To reduce error, samples were stratified resulting in confidence limits of 40-50% for the mean population density. Despite this variability, stable trends emerged, and variation was not so great as to mask significant differences. Length-frequency analyses distinguished cohorts; a regression was established between length and dry weight, enabling growth to be estimated from samples. By combining growth with population densities in Allen curves, production was computed. In Pink Lake and Lake Cundare mean pro- duction was 11.3 and 1.0 g dry weight m-2 year-1 respectively. Generally there were two or three generations per year, but time and extent of recruitment were not predictable. Each generation suffered continuous mortality, the death of young shrimps accounting for most of the production. This mortality remains unexplained; there are no significant predators and salinity and temperature stress would occur only during summer.

scholarly journals Abundance of macrozoobenthos in relation to bottom soil textural types and water depth In aquaculture ponds

2014 ◽  
Vol 3 (2) ◽  
pp. 1-6
Author(s):  
N Nupur ◽  
M Shahjahan ◽  
MS Rahman ◽  
MK Fatema
Keyword(s):  
Water Depth ◽  
Sandy Loam ◽  
Chemical Properties ◽  
Experimental Period ◽  
Quality Parameters ◽  
Population Densities ◽  
Bottom Soil ◽  
Aquaculture Ponds ◽  
Different Depths ◽  
The Mean

The present experiment was conducted to evaluate the effects of bottom soil textural classes and different water depths on abundance of macrozoobenthos in aquaculture ponds. Three treatments, i.e., ponds bottom with sandy loam (T1), with loam (TS2) and with clay loam (T3) were considered in this experiment. Samples were collected from three different depths (60.96 cm, 106.68 cm and 152.40 cm) with three replications. The ranges of water quality parameters were suitable for the growth of macrozoobenthos during the experimental period. Similarly, chemical properties of soil were also within suitable ranges and every parameter showed comparatively higher ranges in T2. Eight genera were recorded belonging to major groups of Chironomidae, Oligochaeta, Mollusca and Ceratoponogonidae. The highest population densities of Oligochaeta (1200±4.25 per m2), Chironomidae (1422±4.88 per m2), Ceratopogonidae (399±1.56 per m2) and Mollusca (977±2.24 per m2) were found in T2. The population densities of macrozoobenthos showed fortnightly variations in all the treatments. Among the three depths, significantly highest densities of macrozoobenthos were recorded in 106.68 cm in every treatment. The mean abundance of macrozoobenthos was significantly highest in T2. The present study indicates that loamy soil pond bottom along with water depth 106.68 cm is suitable for the growth and production of macrozoobenthos in aquaculture ponds. DOI: http://dx.doi.org/10.3329/ijarit.v3i2.17811 Int. J. Agril. Res. Innov. & Tech. 3 (2): 1-6, December, 2013

The influence of population density on the number of eggs laid by females of Cardiaspina albitextura (Psyllidae)

1963 ◽  
Vol 11 (2) ◽  
pp. 190 ◽  
Author(s):  
LR Clark
Keyword(s):  
Egg Production ◽  
Adult Stage ◽  
Limiting Factor ◽  
Severe Damage ◽  
Population Densities ◽  
Experimental Conditions ◽  
Nymphal Development ◽  
The Mean ◽  
Peak Abundance ◽  
Oviposition Sites

Field observations and experiments suggest that crowding during the period of nymphal development does not greatly affect the mean number of eggs laid by Cardiaspina albitextura females. Under experimental conditions, crowding in the adult stage on foliage undamaged by nymphs resulted in reduction of the mean number of eggs laid, the supply of favourable food being probably the limiting factor. In association with increase in the number of adults per shoot, mean egg production declined at a progressively decreasing rate. At the highest population densities tested, the mean number of eggs laid per female was approximately one-third to one-fifth of the number laid by uncrowded females. Both at low and high population densities, the mean number of eggs laid per female on previously unoccupied foliage was about twice as high as on foliage which had been occupied previously by numerous other adults of the same psyllid generation. At times of peak abundance in areas of outbreak, the foliage damage caused during the period of nymphal development greatly limits both the quantity of favourable food and the number of oviposition sites available when C. albitextura reaches the adult stage. The experimental results suggest that the crowding of adults which occurs on the small amount of foliage that escapes very severe damage by nymphs contributes towards the observed limitation of egg production. However, the scattered distribution of such foliage and the poor dispersal powers of C. albitextura females probably play a more important part in determining the very low mean number of eggs laid per female reaching the adult stage. It appears that many females fail to find favourable foliage and consequently lay scarcely any eggs.

Seed size influences the coleoptile length of wheat

1988 ◽  
Vol 28 (4) ◽  
pp. 521 ◽  
Author(s):  
PS Cornish ◽  
S Hindmarsh
Keyword(s):  
Triticum Aestivum ◽  
Seed Size ◽  
Seed Weight ◽  
Size Class ◽  
Adult Plant ◽  
Coleoptile Length ◽  
Seed Width ◽  
The Mean ◽  
The Difference ◽  
Selection Of

Variation in coleoptile length within and between 2 cultivars of semidwarf wheat (Triticum aestivum) was related to seed size. Seeds of cvv. Banks and Kite were separated by sieving for width into the size classes of >2.75, 2.75-250, 2.50-2.25 and 2.25- 2.00 mm. The mean grain weights of ungraded samples were 43.1 mg (Kite) and 34.3 mg (Banks), and for the subsamples were 52.4, 37.9, 30.4 and 20.7 mg (Kite) and 41.4, 33.2, 25.8 and 19.1 mg (Banks). The effect of size class on coleoptile length was significant (P<0.01). Over both cultivars, coleoptile length declined by 0.37 mm per mg reduction in seed weight. Kite produced the longer coleoptiles overall, 87.5 mm compared with 59.0 mm for Banks. However, only 3.3 mm of this difference can be accounted for by the mean difference in seed weight (8.8 mg) and the effect of seed weight on coleoptile length (0.37 mm/mg). Genetic differences, apart from adult plant height, appear to explain most of the difference in coleoptile length between the cultivars. There was considerable genetic variability within genotypes. In Banks, with seed width >2.75 mm (41.4 mg per seed), the lengths of coleoptiles ranged from 24-89 mm (mean 65.1 mm), suggesting considerable scope for the selection of genotypes with longer coleoptiles.

A mechanism for swarming in the tunicate Salpa thompsoni (Foxton, 1961)

2001 ◽  
Vol 13 (3) ◽  
pp. 240-245 ◽  
Author(s):  
M.C. Daponte ◽  
F.L. Capitanio ◽  
G.B. Esnal
Keyword(s):  
Growth Rate ◽  
The Body ◽  
Optimal Conditions ◽  
Population Densities ◽  
Oocyte Maturity ◽  
Solitary Individual ◽  
Mean Size ◽  
The Mean ◽  
Two Populations ◽  
Parent Ratio

Two populations of Salpa thompsoni, collected from the Weddell–Scotia confluence area at the end of two summers (1994 and 1995) with contrasting densities, are compared. The present study was aimed at corroborating whether fluctuations in abundance could be related to some life history parameters considered as indicators of growth rate in salp populations, such as the body size of solitary reproductive individuals, number of buds per block or chain in the stolon, and the offspring to parent ratio. No differences were observed in the sizes reached by aggregate individuals, or in the size at which oocyte maturity was attained (moment at which the development of the embryo can be detected). There were no differences in the size reached by the embryos during their residence inside the mother's blastozooid. In 1995, the percentage of non-fecundated blastozooids (which included even the largest individuals) was higher than in 1994. The mean size of the solitary individuals was significantly higher in 1994 than in 1995. The number of buds per block was also significantly higher in most of the stages, confirming that this is the mechanism used by these organisms to produce swarms. This species eventually attains high population densities under favorable environmental conditions such as poor sea-ice cover in winter. Under optimal conditions, the number of potential descendants produced by a single solitary individual would exceed 800.

A Scheme for Population Densities for the San Juan Metropolitan Area

1952 ◽  
Vol 18 (1) ◽  
pp. 21-31
Author(s):  
Eduardo Baranano
Keyword(s):  
Metropolitan Area ◽  
San Juan ◽  
Population Densities

scholarly journals Density and Size Distribution of the Sea Cucumber, Holothuria scabra (Jaeger, 1935), at Six Exploited Sites in Mahout Bay, Sultanate of Oman

2007 ◽  
Vol 12 ◽  
pp. 43 ◽  
Author(s):  
Khalfan M. Al-Rashdi ◽  
Michel R. Claereboudt ◽  
Saud S. Al-Busaidi
Keyword(s):  
Size Distribution ◽  
Sea Cucumber ◽  
Size Distributions ◽  
Sultanate Of Oman ◽  
Population Densities ◽  
Sea Cucumbers ◽  
Holothuria Scabra ◽  
Mean Size ◽  
Males And Females ◽  
The Mean

A rapid survey of the density and size distribution of recently exploited populations of Holothuria scabra in Mahout Bay (Ghubbat Hashish Bay) was carried out at six fishing sites. The results showed that population densities varied between 1170 and 4000 individuals ha-1 and biomass ranged between 393 and 2903 kg ha-1. The mean size of sea cucumbers and population densities were much lower in populations closer to human settlements, suggestive of overfishing. The sex ratio was estimated to be 1:1 and the size distributions of males and females did not differ significantly. The length-weight relationship for both sexes was calculated as W (g) = 0.033 Length (mm) 2.178. 

scholarly journals Educational Practice for Small Size Class in Fundamental Education of Faculty of Engineering

2009 ◽  
Vol 57 (1) ◽  
pp. 84-87
Author(s):  
Mitsuhiro YOKOTA ◽  
Kimitaka HIRANO ◽  
Chikahisa HONDA
Keyword(s):  
Educational Practice ◽  
Size Class ◽  
Small Size Class ◽  
Fundamental Education

scholarly journals Resprouting Responses Dynamics of Schima superba Following a Severe Ice Storm in Early 2008 in Southern China: A Six-Year Study

Forests ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 184
Author(s):  
Yonghui Cao ◽  
Benzhi Zhou ◽  
Xiaoming Wang ◽  
Lianhong Gu
Keyword(s):  
Secondary Forest ◽  
Southern China ◽  
Size Class ◽  
Ice Storm ◽  
Basal Diameter ◽  
Schima Superba ◽  
The Mean ◽  
The Difference ◽  
Set Up ◽  
Damage Types

In 2008, an unexpected and severe ice storm affected the forest of southern China. This storm caused damage in regeneration of an important dominant tree, Schima superba (Gugertree). To study this damage, we set up permanent monitoring plots in an ice-storm-damaged subtropical evergreen broad-leaved secondary forest dominated by S.superba in Jianglang Mountains, China. We surveyed the damage to all trees with a minimum basal diameter of 4 cm and monitored their growth for 6 consecutive years. We analyzed the degrees and types of damage for S.superba and their relationships with resprouting characteristics. The results revealed that the main damage types of S.superba were decapitation (45.45%) and uprooting (28.41%). The distribution percentage for both decapitated and uprooted trees were commonly highest in the range of 10–16 cm basal diameter (BD) size class. A great number of individuals sprouted vigorously after the storm. The mean total sprout number and sprout biomass per tree for S.superba varied by tree BD size class. During the first three years after the ice storm, decapitated trees of larger BD classes produced more sprouts per tree than trees of smaller BD classes. However, the opposite trend was seen in uprooted and leaning trees. There was a trade-off between the total number and length of the sprouts. The difference of mean sprouts number and biomass per tree with size class was mainly related to the damage types. As the recovery progressed since the ice storm, the number of sprouts and sprout biomass in uprooted trees was found mainly on the middle trunk sections of uprooted trees, but in the upper sections of decapitated trees. After six years, the mean number of sprouts per tree, on different parts of the tree and for the three types of damaged trees all declined; however, sprout biomass per tree all increased. The mean number of sprout and sprout biomass per tree on different sections for decapitated trees was always highest over time since the storm. Our study will help to provide data on resprouting ability to develop a predictive model for resprouting.

scholarly journals Vachellia erioloba dynamics over 38 years in the Kalahari Gemsbok National Park, South Africa

Koedoe ◽  
2019 ◽  
Vol 61 (1) ◽  
Author(s):  
Helga Van der Merwe ◽  
Noel Van Rooyen ◽  
Hugo Bezuidenhout ◽  
Jacobus Du P. Bothma ◽  
Margaretha W. Van Rooyen
Keyword(s):  
Growth Rate ◽  
National Park ◽  
Size Class ◽  
Stem Diameter ◽  
Natural Ecosystem ◽  
Anthropogenic Influences ◽  
Conservation Area ◽  
Size Class Distribution ◽  
Class Distribution ◽  
The Mean

Vachellia erioloba is a keystone tree species in the southern Kalahari. This long-term study over nearly four decades tracks two populations in different landscapes (the interior sandy duneveld versus the clayey Nossob riverbed) of a large conservation area and offers valuable data on this species under natural soil moisture conditions and with limited anthropogenic influences. In 1978, 18 trees were permanently marked in a 1 ha plot in the interior duneveld of the Kalahari Gemsbok National Park (Dankbaar site). In the Nossob riverbed all trees in a 1 ha plot were surveyed in 1979 (Grootkolk site). At both sites, tree height and stem circumference were subsequently measured at irregular intervals until 2016 in order to investigate growth rates and population structure. Of the 18 marked trees at Dankbaar, six died and three showed coppice regrowth following substantial dieback after a fire. A mean height increase of 60 mm/year was recorded and the mean height of the remaining uncoppiced trees was 6.8 m in 2016. Stem diameter growth rate per year varied widely between trees and between years with a mean value of 2.5 mm/year over the 38-year period. Growth rate calculated for three 10-year intervals varied. Using the mean growth rate derived in the current study and stem size of the dead trees, the mean age of the trees when they died was estimated. At the Grootkolk site, the position of the centroid in relation to the midpoint of the diameter class range suggests that this population is gradually becoming a mature to old population with limited recruitment. This was supported by the size class distribution curves. However, no differences between slopes or intercepts of the stem diameter size class distributions were found.Conservation implications: This study was conducted in a large conservation area, that is, a natural ecosystem excluding most of the anthropogenic threats that are present outside of the park. The study illustrated that in the duneveld the population studied was self-sustaining, with recruitment occurring and large individuals presumably dying of old age. Although fire caused a few individuals to coppice, no fire-related deaths were reported. In the Nossob riverbed, surveys started in a stand of predominantly young trees and the size class distribution at that stage already showed a lack of recruitment. This stand is ageing and will likely disappear at this site; however, new young stands are appearing at other sites in the Nossob riverbed. Under the current conditions with negligible anthropogenic influences, it therefore appears that some V. erioloba populations in the park are increasing in size while others are decreasing, but that overall the species will persist. The impact of global climate change on this species is, however, unknown.

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