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.

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.

Plant Resistance in Some Modern Soybean Varieties May Favor Population Growth and Modify the Stylet Penetration of Bemisia tabaci (Hemiptera: Aleyrodidae)

2021 ◽  
Author(s):  
Mauricélia F Almeida ◽  
Clébson S Tavares ◽  
Euires O Araújo ◽  
Marcelo C Picanço ◽  
Eugênio E Oliveira ◽  
...  
Keyword(s):  
Population Growth ◽  
Bemisia Tabaci ◽  
Intrinsic Rate ◽  
Reproductive Rate ◽  
Genetically Engineered ◽  
Population Increase ◽  
Net Reproductive Rate ◽  
Bt Toxin ◽  
Demographic Performance

Abstract Complaints of severe damage by whiteflies in soybean fields containing genetically engineered (GE) varieties led us to investigate the role of transgenic soybean varieties expressing resistance to some insects (Cry1Ac Bt toxin) and to herbicide (glyphosate) on the population growth and feeding behavior of Bemisia tabaci (Gennadius) MEAM1 (Hemiptera: Aleyrodidae). In the laboratory, the whiteflies reared on the GE Bt soybeans had a net reproductive rate (R0) 100% higher and intrinsic rate of population increase (rm) 15% higher than those reared on non-GE soybeans. The increased demographic performance was associated with a higher lifetime fecundity. In electrical penetration graphs, the whiteflies reared on the GE soybeans had fewer probes and spent 50% less time before reaching the phloem phase from the beginning of the first successful probe, indicating a higher risk of transmission of whitefly-borne viruses. Data from Neotropical fields showed a higher population density of B. tabaci on two soybean varieties expressing glyphosate resistance and Cry1Ac Bt toxin. These results indicate that some GE soybean varieties expressing insect and herbicide resistances can be more susceptible to whiteflies than non-GE ones or those only expressing herbicide resistance. Most likely, these differences are related to varietal features that increase host-plant susceptibility to whiteflies. Appropriate pest management may be needed to deal with whiteflies in soybean fields, especially in warm regions, and breeders may want to consider the issue when developing new soybean varieties.

scholarly journals Glacial – interglacial atmospheric CO<sub>2</sub> change: a simple "hypsometric effect" on deep-ocean carbon sequestration?

2006 ◽  
Vol 2 (5) ◽  
pp. 711-743 ◽  
Author(s):  
L. C. Skinner
Keyword(s):  
Carbon Sequestration ◽  
Carbon Storage ◽  
Ocean Circulation ◽  
Deep Water ◽  
Deep Sea ◽  
Storage Capacity ◽  
Deep Ocean ◽  
Contributing Factors ◽  
Carbon Reservoir ◽  
Ocean Carbon

Abstract. Given the magnitude and dynamism of the deep marine carbon reservoir, it is almost certain that past glacial – interglacial fluctuations in atmospheric CO2 have relied at least in part on changes in the carbon storage capacity of the deep sea. To date, physical ocean circulation mechanisms that have been proposed as viable explanations for glacial – interglacial CO2 change have focussed almost exclusively on dynamical or kinetic processes. Here, a simple mechanism is proposed for increasing the carbon storage capacity of the deep sea that operates via changes in the volume of southern-sourced deep-water filling the ocean basins, as dictated by the hypsometry of the ocean floor. It is proposed that a water-mass that occupies more than the bottom 3 km of the ocean will essentially determine the carbon content of the marine reservoir. Hence by filling this interval with southern-sourced deep-water (enriched in dissolved CO2 due to its particular mode of formation) the amount of carbon sequestered in the deep sea may be greatly increased. A simple box-model is used to test this hypothesis, and to investigate its implications. It is suggested that up to 70% of the observed glacial – interglacial CO2 change might be explained by the replacement of northern-sourced deep-water below 2.5 km water depth by its southern counterpart. Most importantly, it is found that an increase in the volume of southern-sourced deep-water allows glacial CO2 levels to be simulated easily with only modest changes in Southern Ocean biological export or overturning. If incorporated into the list of contributing factors to marine carbon sequestration, this mechanism may help to significantly reduce the "deficit" of explained glacial – interglacial CO2 change.

scholarly journals The Search for Supernova-Produced Radionuclides in Terrestrial Deep-Sea Archives

2012 ◽  
Vol 29 (2) ◽  
pp. 109-114 ◽  
Author(s):  
J. Feige ◽  
A. Wallner ◽  
S. R. Winkler ◽  
S. Merchel ◽  
L. K. Fifield ◽  
...  
Keyword(s):  
Solar System ◽  
Marine Sediment ◽  
Deep Sea ◽  
Massive Stars ◽  
Sediment Cores ◽  
Deep Ocean ◽  
Transport Mechanisms ◽  
Supernova Shell ◽  
Process Element ◽  
Insight Into

AbstractAn enhanced concentration of 60Fe was found in a deep ocean crust in 2004 in a layer corresponding to an age of ∼2 Myr. The confirmation of this signal in terrestrial archives as supernova-induced and the detection of other supernova-produced radionuclides is of great interest. We have identified two suitable marine sediment cores from the South Australian Basin and estimated the intensity of a possible signal of the supernova-produced radionuclides 26Al, 53Mn, 60Fe, and the pure r-process element 244Pu in these cores. The finding of these radionuclides in a sediment core might allow us to improve the time resolution of the signal and thus to link the signal to a supernova event in the solar vicinity ∼2 Myr ago. Furthermore, it gives us an insight into nucleosynthesis scenarios in massive stars, condensation into dust grains and transport mechanisms from the supernova shell into the solar system.

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