scholarly journals A matrix population model for the hawksbill sea turtle (Eretmochelys imbricata) in the Gulf of Paria, Venezuela

2020 ◽  
Vol 48 (5) ◽  
pp. 739-748
Author(s):  
Clemente Balladares ◽  
María Fernanda Gonzalez ◽  
Diego Rodriguez
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Population Growth Rate ◽  
Sea Turtle ◽  
Local Conservation ◽  
Eretmochelys Imbricata ◽  
Emergence Success ◽  
Stage 4 ◽  
Stage 1

Following classical literature in herpetology, we built two five-stage life tables for the endangered hawksbill sea turtle Eretmochelys imbricata in the Gulf of Paria, eastern Venezuela, using data from incidental captures by industrial trawl fisheries from 1991 until 2000, artisanal fisheries effect and regional stranding from 1999 to 2017, and a local conservation project with the nesting females from 2003 to 2018. We estimated the survivorship for the managed, translocated nests, and a portion of the natural in situ nests (≈31%). We used the resultant life graph and matrices to estimate the hawksbills population status in the region and determine differences in population growth rate and elasticity between translocated and in situ nests. Eggs/hatchlings (stage 1) and small juveniles of less than three years old (stage 2), had high mortalities. We controlled stage 1 mortality by translocating nests into a hatchery. The in situ nests suffered almost 88% predation or poaching. Conversely, these non-translocated nests' emergence success was greater than that of managed nests, but overall survivorship was the lower. We propose that fecundity could begin with sub-adults (stage 4) after the 7th year with 60 cm of curved carapace length. Finite rates of increase of both populations, managed and natural, were significantly higher than 1, and that of the managed population is significantly higher than that of the natural one, meaning that both populations would grow and that the managed one would grow faster than the natural one. Then protection of stage 1 is essential to the population of hawksbills in the region, although uncertainties of survivorship of stage 2 and fecundity of stage 4 were not properly confirmed locally. Notwithstanding, elasticity analysis indicated that the population growth rate was more affected by proportional changes in sub-adults and adults' fecundity than any other life-history element.

scholarly journals Biological scaling in green algae: the role of cell size and geometry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Helena Bestová ◽  
Jules Segrestin ◽  
Klaus von Schwartzenberg ◽  
Pavel Škaloud ◽  
Thomas Lenormand ◽  
...  
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Population Growth Rate ◽  
Internal Diffusion ◽  
Scaling Exponent ◽  
Power Scaling ◽  
Nutrient Distribution ◽  
Metabolic Scaling ◽  
Key Factor ◽  
Size And Morphology

AbstractThe Metabolic Scaling Theory (MST), hypothesizes limitations of resource-transport networks in organisms and predicts their optimization into fractal-like structures. As a result, the relationship between population growth rate and body size should follow a cross-species universal quarter-power scaling. However, the universality of metabolic scaling has been challenged, particularly across transitions from bacteria to protists to multicellulars. The population growth rate of unicellulars should be constrained by external diffusion, ruling nutrient uptake, and internal diffusion, operating nutrient distribution. Both constraints intensify with increasing size possibly leading to shifting in the scaling exponent. We focused on unicellular algae Micrasterias. Large size and fractal-like morphology make this species a transitional group between unicellular and multicellular organisms in the evolution of allometry. We tested MST predictions using measurements of growth rate, size, and morphology-related traits. We showed that growth scaling of Micrasterias follows MST predictions, reflecting constraints by internal diffusion transport. Cell fractality and density decrease led to a proportional increase in surface area with body mass relaxing external constraints. Complex allometric optimization enables to maintain quarter-power scaling of population growth rate even with a large unicellular plan. Overall, our findings support fractality as a key factor in the evolution of biological scaling.

Lessons from a century of conservation translocations

2021 ◽  
Author(s):  
Shane D Morris ◽  
Katherine E. Moseby ◽  
Barry W. Brook ◽  
Christopher N. Johnson
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Population Growth Rate ◽  
Historical Context ◽  
Extrinsic Factors ◽  
Global Database ◽  
Terrestrial Vertebrates ◽  
Failure Classification ◽  
High Population Growth ◽  
Number Of Individuals

Translocation—moving individuals for release in different locations—is among the most important conservation interventions for increasing or re-establishing populations of threatened species. However, translocations often fail. To improve their effectiveness, we need to understand the features that distinguish successful from failed translocations. Here, we assembled and analysed a global database of translocations of terrestrial vertebrates (n=514) to assess the effects of various design features and extrinsic factors on success. We analysed outcomes using standardized metrics i.e. a categorical success/failure classification, and population growth rate. Probability of categorical success and population growth rate increased with the total number of individuals released but with diminishing returns above about 20-50 individuals. There has been no increase in numbers released per translocation over time. Positive outcomes—reported success and high population growth—were less likely for translocation in Oceania, possibly because invasive species are a major threat in this region and are difficult to control at translocation sites. Increased rates of categorical reported success and population growth were found for Europe and North America, suggesting the key role of historical context in positive translocation outcomes. Categorical success has increased throughout the 20th century, but that increase may have plateaued at about 75% since about 1990. Our results suggest there is potential for further increase in the success of conservation translocations. This could be best achieved by greater investment in individual projects, as indicated by total number of animals released.

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