scholarly journals Maximum intrinsic rate of population increase in sharks, rays, and chimaeras: the importance of survival to maturity

2016 ◽  
Vol 73 (8) ◽  
pp. 1159-1163 ◽  
Author(s):  
Sebastián A. Pardo ◽  
Holly K. Kindsvater ◽  
John D. Reynolds ◽  
Nicholas K. Dulvy
Keyword(s):  
Life Span ◽  
Reproductive Output ◽  
Extinction Risk ◽  
Intrinsic Rate ◽  
Population Increase ◽  
Age At Maturity ◽  
Average Life ◽  
Demographic Parameter ◽  
Average Life Span

The maximum intrinsic rate of population increase (rmax) is a commonly estimated demographic parameter used in assessments of extinction risk. In teleosts, rmax can be calculated using an estimate of spawners per spawner, but for chondrichthyans, most studies have used annual reproductive output (b) instead. This is problematic as it effectively assumes all juveniles survive to maturity. Here, we propose an updated rmax equation that uses a simple mortality estimator that also accounts for survival to maturity: the reciprocal of average life-span. For 94 chondrichthyans, we now estimate that rmax values are on average 10% lower than previously published. Our updated rmax estimates are lower than previously published for species that mature later relative to maximum age and those with high annual fecundity. The most extreme discrepancies in rmax values occur in species with low age at maturity and low annual reproductive output. Our results indicate that chondrichthyans that mature relatively later in life, and to a lesser extent those that are highly fecund, are less resilient to fishing than previously thought.

scholarly journals Maximum intrinsic rate of population increase in sharks, rays, and chimaeras: the importance of survival to maturity

2016 ◽  
Author(s):  
Sebastián A. Pardo ◽  
Holly K. Kindsvater ◽  
John D. Reynolds ◽  
Nicholas K. Dulvy
Keyword(s):  
Reproductive Output ◽  
Extinction Risk ◽  
Intrinsic Rate ◽  
Population Increase ◽  
Age At Maturity ◽  
Demographic Parameter ◽  
Average Lifespan

AbstractThe maximum intrinsic rate of population increase rmax is a commonly estimated demographic parameter used in assessments of extinction risk. In teleosts, rmax can be calculated using an estimate of spawners per spawner, but for chondrichthyans, most studies have used annual reproductive output b instead. This is problematic as it effectively assumes all juveniles survive to maturity. Here, we propose an updated rmax equation that uses a simple mortality estimator which also accounts for survival to maturity: the reciprocal of average lifespan. For 94 chondrichthyans, we now estimate that rmax values are on average 10% lower than previously published. Our updated rmax estimates are lower than previously published for species that mature later relative to maximum age and those with high annual fecundity. The most extreme discrepancies in rmax values occur in species with low age at maturity and low annual reproductive output. Our results indicate that chondrichthyans that mature relatively later in life, and to a lesser extent those that are highly fecund, are less resilient to fishing than previously thought.

scholarly journals Diagnosing the dangerous demography of manta rays using life history theory

2013 ◽  
Author(s):  
Nicholas K Dulvy ◽  
Sebastián A. Pardo ◽  
Colin A. Simpfendorfer ◽  
John K. Carlson
Keyword(s):  
Life History ◽  
Life History Theory ◽  
Extinction Risk ◽  
Somatic Growth ◽  
Intrinsic Rate ◽  
Population Increase ◽  
Population Declines ◽  
Demographic Information ◽  
Age At Maturity ◽  
Manta Ray

The directed harvest and global trade in the gill plates of mantas, and other mobulid rays, has led to increased fishing pressure and steep population declines in some locations. The slow life history, particularly of the manta rays, is cited as a key reason why such species have little capacity to withstand directed fisheries. Here, we place their life history and demography in the context of other sharks and rays. Despite the limited availability of data, we use life history theory and comparative analysis to develop plausible ranges of somatic growth rate, annual pup production and age at maturity to estimate risk of extinction (maximum intrinsic rate of population increase rmax) using a variant of the classic Euler-Lotka model. Manta ray rmax is most sensitive to the length of the reproductive cycle, and the median rmax of 0.11 year-1(CI: 0.089-0.137) is one of the lowest known of the 106 sharks and rays for which we have comparable demographic information. In common with other unprotected, unmanaged, high-value large-bodied species with low or very low productivity, manta rays are unlikely to sustain unmonitored, unregulated exploitation and may face increasing local and regional extinction risk.

scholarly journals Diagnosing the dangerous demography of manta rays using life history theory

2013 ◽  
Author(s):  
Nicholas K Dulvy ◽  
Sebastián A. Pardo ◽  
Colin A. Simpfendorfer ◽  
John K. Carlson
Keyword(s):  
Life History ◽  
Life History Theory ◽  
Extinction Risk ◽  
Somatic Growth ◽  
Intrinsic Rate ◽  
Population Increase ◽  
Population Declines ◽  
Demographic Information ◽  
Age At Maturity ◽  
Manta Ray

The directed harvest and global trade in the gill plates of mantas, and other mobulid rays, has led to increased fishing pressure and steep population declines in some locations. The slow life history, particularly of the manta rays, is cited as a key reason why such species have little capacity to withstand directed fisheries. Here, we place their life history and demography in the context of other sharks and rays. Despite the limited availability of data, we use life history theory and comparative analysis to develop plausible ranges of somatic growth rate, annual pup production and age at maturity to estimate risk of extinction (maximum intrinsic rate of population increase rmax) using a variant of the classic Euler-Lotka model. Manta ray rmax is most sensitive to the length of the reproductive cycle, and the median rmax of 0.11 year-1(CI: 0.089-0.137) is one of the lowest known of the 106 sharks and rays for which we have comparable demographic information. In common with other unprotected, unmanaged, high-value large-bodied species with low or very low productivity, manta rays are unlikely to sustain unmonitored, unregulated exploitation and may face increasing local and regional extinction risk.

scholarly journals Quantifying the known unknowns: estimating maximum intrinsic rate of population increase in the face of uncertainty

2018 ◽  
Vol 75 (3) ◽  
pp. 953-963 ◽  
Author(s):  
Sebastián A Pardo ◽  
Andrew B Cooper ◽  
John D Reynolds ◽  
Nicholas K Dulvy
Keyword(s):  
Life History ◽  
Reproductive Output ◽  
Intrinsic Rate ◽  
Biological Information ◽  
Population Increase ◽  
Parameter Estimates ◽  
Age At Maturity ◽  
Management Options ◽  
Frequency Distributions ◽  
Life History Parameters

Abstract Sensitivity to overfishing is often estimated using simple models that depend upon life history parameters, especially for species lacking detailed biological information. Yet, there has been little exploration of how uncertainty in life history parameters can influence demographic parameter estimates and therefore fisheries management options. We estimate the maximum intrinsic rate of population increase (rmax) for ten coastal carcharhiniform shark populations using an unstructured life history model that explicitly accounts for uncertainty in life history parameters. We evaluate how the two directly estimated parameters, age at maturity αmat and annual reproductive output b, most influenced rmax estimates. Uncertainty in age at maturity values was low, but resulted in moderate uncertainty in rmax estimates. The model was sensitive to uncertainty in annual reproductive output for the least fecund species with fewer than 5 female offspring per year, which is not unusual for large elasmobranchs, marine mammals, and seabirds. Managers and policy makers should be careful to restrict mortality on species with very low annual reproductive output <2 females per year. We recommend elasmobranch biologists to measure frequency distributions of litter sizes (rather than just a range) as well as improving estimates of natural mortality of data-poor elasmobranchs.

Amalaki as a Rasayan in Geriatric Diseases

2018 ◽  
Vol 6 (06) ◽  
Author(s):  
Naina Vishwakarma
Keyword(s):  
Quality Of Life ◽  
Life Span ◽  
Old Age ◽  
Natural Process ◽  
Healthy Ageing ◽  
Average Life ◽  
Average Life Span ◽  
Medical Facilities

Geriatric problems are arising much and more in the present Era. With the increase in average life-span due to medical facilities it resulted in large number of people with old age Worldwide. To overcome this Ayurved advocates healthy ageing through Rasayan Chikitsa. By proper administration of Rasayan Therapy as a preventive tool one can prevent Jarajanit(Geriatic) vyadhis. Many herbs and techniques which provide solution to ageing and their complications are described in Ayurved. The Herbs with their properties slows down the natural process of aging and help in managing geriatric problem and improving the quality of life. Here   Amalaki an Rasayan Dravya in Geriatric diseases is brought in focus.

Longevity of exercising obese hypertensive rats

1980 ◽  
Vol 49 (4) ◽  
pp. 634-637
Author(s):  
F. W. Booth ◽  
W. F. MacKenzie ◽  
M. J. Seider ◽  
E. W. Gould
Keyword(s):  
Life Span ◽  
Myocardial Necrosis ◽  
Early Death ◽  
Early Age ◽  
Hypertensive Rats ◽  
Average Life ◽  
Average Life Span ◽  
Daily Food ◽  
Body Weights ◽  
Genetically Hypertensive

The purpose of this study was to determine whether daily running lengthens the life-span of animals dying prematurely due to cardiovascular disease. We used a strain of rat that is genetically hypertensive and obese and is reported to develop atherosclerosis (Exp. Mol. Pathol. 19: 53--60, 1973). These animals were divided into three groups consisting of runners exercised daily on treadmills from an early age life, food-restricted sedentary rats, and libitum eaters that were sedentary. This latter group had significantly higher average daily food intakes and body weights than either of the other two groups. The average life-span of both sedentary groups was significantly longer than the running group. Runners had a greater frequency of focal myocardial necrosis, but atherosclerosis was absent in all three groups. We speculate that daily running may have accentuated the development of factor s that may have contributed to the early death of runners.

Carnosine, the Protective, Anti-aging Peptide

1999 ◽  
Vol 19 (6) ◽  
pp. 581-587 ◽  
Author(s):  
Alexander A. Boldyrev ◽  
Steven Ch. Gallant ◽  
Gennady T. Sukhich
Keyword(s):  
Life Span ◽  
Standard Diet ◽  
Control Strain ◽  
Average Life ◽  
Average Life Span ◽  
Behavioral Parameters ◽  
Senescence Accelerated Mice

Carnosine attenuates the development of senile features when used as a supplement to a standard diet of senescence accelerated mice (SAM). Its effect is apparent on physical and behavioral parameters and on average life span. Carnosine has a similar effect on mice of the control strain, but this is less pronounced due to the non-accelerated character of their senescence processes.

scholarly journals Cross-fostering as a conservation tool to augment endangered carnivore populations

2018 ◽  
Vol 99 (5) ◽  
pp. 1033-1041
Author(s):  
Eric M Gese ◽  
William T Waddell ◽  
Patricia A Terletzky ◽  
Chris F Lucash ◽  
Scott R McLellan ◽  
...  
Keyword(s):  
Life Span ◽  
Litter Size ◽  
Average Life ◽  
Canis Rufus ◽  
Average Life Span ◽  
Red Wolf ◽  
In The Wild ◽  
Red Wolves ◽  
Cross Fostering

Abstract Cross-fostering offspring with nonbiological parents could prove useful to augment populations of endangered carnivores. We used cross-fostering to augment captive-born and wild-born litters for the endangered red wolf (Canis rufus). Between 1987 and 2016, 23 cross-fostering events occurred involving captive-born pups fostered into captive litters (n = 8 events) and captive-born pups fostered into wild recipient litters (n = 15 events). Percentage of pups surviving 3 and 12 months was 91.7% for captive-born pups fostered into captive recipient litters. For pups fostered into wild litters, percentage of pups surviving 5 months was > 94% among fostered pups (pups fostered into a wild red wolf litter or replaced a hybrid litter), pups in recipient litters (wild-born litters receiving fostered pups), and pups in control litters (wild-born litters not in a fostering event) when using pups with known fates. Including pups with unknown fates as deaths, percentage of pups surviving 5 months was > 54% among fostered pups, pups in recipient litters, and pups in control litters. Among wild litters, percentage of pups surviving 12 months was > 82% among fostered pups, pups in recipient litters, and pups in control litters when using pups with known fates. Including pups with unknown fates as deaths, percentage of pups surviving 12 months was > 48% among fostered pups, pups in recipient litters, and pups in control litters. Although survival to 12 months was similar among the groups, average life span was different with pups in control litters living 3.3 years, pups in recipient litters living 4.6 years, and fostered pups living 5.6 years. Of fostered pups surviving > 12 months in the wild, 9 animals whelped or sired 26 litters. Cross-fostering was successful at augmenting litter size for red wolves without any deleterious effects on recipient litters, illustrating fostering as a tool for increasing populations of endangered carnivores.

Women in the Shari῾a court records of Ottoman Damascus

2012 ◽  
Vol 3 (2) ◽  
pp. 119-142 ◽  
Author(s):  
Abdul-Karim Rafeq
Keyword(s):  
Life Span ◽  
Average Life ◽  
Christian Women ◽  
Average Life Span ◽  
Female Ratio ◽  
Court Records ◽  
Marriage Patterns ◽  
Number Of Children ◽  
Male Female Ratio ◽  
Deceased People

Qassam registers give detailed information about the estates of deceased people, the size of their households, the number of times they were married, the number of children, and the male-female ratio of minors and adults. The estates of deceased Christians in Damascus are reported more frequently in nineteenth-century qassam registers due to the application of the Tanzimat which advocated equality among all subjects and the tolerance shown towards the Christians by Egyptian rule in Syria in the 1830s. The registers indicate that monogamy was dominant in Damascus due to a low-to-average life-span. Marriage patterns and the composition of the estates of deceased women and men are examined in six qassam registers spanning a period of over a century (1750-1861). The establishment of religious endowments (vakıf) by Muslim and Christian women, and the varying titles given to these women in the court records are also discussed.

scholarly journals Body mass, temperature, and depth shape the maximum intrinsic rate of population increase in sharks and rays

2021 ◽  
Author(s):  
Sebastián A. Pardo ◽  
Nicholas K. Dulvy
Keyword(s):  
Body Mass ◽  
Deep Sea ◽  
Extinction Risk ◽  
Deep Ocean ◽  
Intrinsic Rate ◽  
Population Increase ◽  
Theoretic Approach ◽  
Mass Scaling ◽  
Mass Temperature ◽  
Recovery Potential

AbstractAn important challenge in ecology is to understand variation in species’ maximum intrinsic rate of population increase,rmax, not least becausermaxunderpins our understanding of the limits of fishing, recovery potential, and ultimately extinction risk. Across many vertebrates, terrestrial and aquatic, body mass and environmental temperature across important correlatesrmaxacross species. In sharks and rays, specifically,rmaxis known be lower in larger species, but also in deep-sea ones. We use an information-theoretic approach that accounts for phylogenetic relatedness to evaluate the relative importance of body mass, temperature and depth onrmax. We show that both temperature and depth have separate effects on shark and rayrmaxestimates, such that species living in deeper waters have lowerrmax. Furthermore, temperature also correlates with changes in the mass scaling coefficient, suggesting that as body size increases, decreases inrmaxare much steeper for species in warmer waters. These findings suggest that there (as-yet understood) depth-related processes that limit the maximum rate at which populations can grow in deep sea sharks and rays. While the deep ocean is associated with colder temperatures, other factors that are independent of temperature, such as food availability and physiological constraints, may influence the lowrmaxobserved in deep sea sharks and rays. Our study lays the foundation for predicting the intrinsic limit of fishing, recovery potential, and extinction risk species based on easily accessible environmental information such as temperature and depth, particularly for data-poor species.

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