scholarly journals TEMPORAL VARIATION IN THE RED GROUPER, EPINEPHELUS MORIO, DEMOGRAPHIC STRUCTURE FROM SOUTHERN GULF OF MEXICO

2010 ◽  
Vol 2 ◽  
pp. 39
Author(s):  
Doralice Caballero-Arango ◽  
Thierry Brule ◽  
Jorge L. Montero-Muño ◽  
Teresa Colás-Marrufo
Keyword(s):  
Gulf Of Mexico ◽  
Sex Ratios ◽  
Demographic Structure ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Size Frequency ◽  
Epinephelus Morio ◽  
Red Grouper ◽  
Bank Stock ◽  
Dependent Samples

Changes in the demographic structure of red grouper Epinephelus morio from the southern part of the Gulf of Mexico, were evaluated during periods when total catches, CPUE and annual yields of the specie decreased. Fishery-dependent samples (n = 1887) were obtained between August 1989 and February 2004 from the Campeche Bank, and size-frequency distributions by sex, sex ratios and sizes of sexual maturation and sex change were compared between three periods: P11989-1992 (n = 886); P21996-1998 (n = 413); and P32003-2004 (n = 588). The temporal stability of size-frequency distribution by sex, with males always being larger than females, and the sex ratios always biased towards females, were consistent with this species’ type of sexuality. Size for females and males, as well as sizes at first sexual maturity and at sex reversal all decreased from the oldest period to the more recent one and could be a consequence of the fishing intensity applied to this stock. The reductions in size of females and males associated with a relatively stable sex ratio and the lack of any drastic decrease in the number of males can be explained by this species’ reproductive ecology. Results are discussed regarding the capacity for reproductive resilience of red grouper in response to fishing pressure like that currently experienced by the Campeche Bank stock.

scholarly journals Linking population size structure, heat stress and bleaching responses in a subtropical endemic coral

Coral Reefs ◽  
2021 ◽  
Author(s):  
Liam Lachs ◽  
Brigitte Sommer ◽  
James Cant ◽  
Jessica M. Hodge ◽  
Hamish A. Malcolm ◽  
...  
Keyword(s):  
Heat Stress ◽  
Size Structure ◽  
Temporal Trends ◽  
Early Recovery ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Community Organisation ◽  
Size Frequency ◽  
Eastern Australia

AbstractAnthropocene coral reefs are faced with increasingly severe marine heatwaves and mass coral bleaching mortality events. The ensuing demographic changes to coral assemblages can have long-term impacts on reef community organisation. Thus, understanding the dynamics of subtropical scleractinian coral populations is essential to predict their recovery or extinction post-disturbance. Here we present a 10-yr demographic assessment of a subtropical endemic coral, Pocillopora aliciae (Schmidt-Roach et al. in Zootaxa 3626:576–582, 2013) from the Solitary Islands Marine Park, eastern Australia, paired with long-term temperature records. These coral populations are regularly affected by storms, undergo seasonal thermal variability, and are increasingly impacted by severe marine heatwaves. We examined the demographic processes governing the persistence of these populations using inference from size-frequency distributions based on log-transformed planar area measurements of 7196 coral colonies. Specifically, the size-frequency distribution mean, coefficient of variation, skewness, kurtosis, and coral density were applied to describe population dynamics. Generalised Linear Mixed Effects Models were used to determine temporal trends and test demographic responses to heat stress. Temporal variation in size-frequency distributions revealed various population processes, from recruitment pulses and cohort growth, to bleaching impacts and temperature dependencies. Sporadic recruitment pulses likely support population persistence, illustrated in 2010 by strong positively skewed size-frequency distributions and the highest density of juvenile corals measured during the study. Increasing mean colony size over the following 6 yr indicates further cohort growth of these recruits. Severe heat stress in 2016 resulted in mass bleaching mortality and a 51% decline in coral density. Moderate heat stress in the following years was associated with suppressed P. aliciae recruitment and a lack of early recovery, marked by an exponential decrease of juvenile density (i.e. recruitment) with increasing heat stress. Here, population reliance on sporadic recruitment and susceptibility to heat stress underpin the vulnerability of subtropical coral assemblages to climate change.

scholarly journals 2.2.2 The Size Frequency Distribution and Rate of Production of Microcraters

1976 ◽  
Vol 31 ◽  
pp. 227-231
Author(s):  
D. A. Morrison ◽  
E. Zinner
Keyword(s):  
Frequency Distribution ◽  
Lunar Surface ◽  
Particle Flux ◽  
Surface Orientation ◽  
Submicron Particle ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Crater Size ◽  
Size Frequency ◽  
Micron Diameter

AbstractCrater size frequency distributions vary to a degree which probably cannot be explained by variations in lunar surface orientation of the crater detectors or changes in micrometeoroid flux. Questions of sample representativity suggest that high ratios of small to large craters of micrometeoroids (e.g., a million 1.0 micron craters for each 500 micron crater) should be the most reliable. We obtain a flux for particles producing 0.1 micron diameter craters of approximately 300 per cm2 per steradian per year. We observe no anisotropy in the submicron particle flux between the plane of the ecliptic and the normal in the direction of lunar north. No change in flux over a 106 year period is indicated by our data.

Effect of stingray (Hemitrygon akajei) foraging on a ghost shrimp population (Nihonotrypaea harmandi) on an intertidal sandflat, western Kyushu, Japan

2020 ◽  
Vol 71 (9) ◽  
pp. 1128
Author(s):  
Akio Tamaki ◽  
Kazuyuki Harada ◽  
Yoshinobu Sogawa ◽  
Seiji Takeuchi
Keyword(s):  
Spring Tide ◽  
The Body ◽  
Gut Contents ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Size Frequency ◽  
Intertidal Sandflat ◽  
Shrimp Density ◽  
Feeding Bout ◽  
Shrimp Population

Callianassid shrimp residing in deep burrows have large bioturbating effects on marine soft-bottom communities. A few predators that excavate deep pits could have substantial effects on shrimp populations, as well as knock-on effects. Processes and consequences of such effects on shrimp populations are poorly understood. On a 300-m-wide intertidal sandflat area between tide marks in western Kyushu between 1989 and 1994, shrimp population densities were stable, reaching >1300individualsm–2. Dasyatid stingray feeding pits reaching depths up to 20cm occurred abruptly in large numbers in 1994, after which shrimp densities decreased yearly to hundreds of individuals per square metre in 2001. The densities of ray feeding pits formed per day were monitored every or every other spring tide between 2000 and 2001. Schools of rays were enclosed during submerged times and their body sizes recorded alive to determine size-frequency distribution. The body-size frequency distributions of shrimp were compared among the gut contents of several rays, ray feeding pits and intact sandflat. Reductions in the shrimp density per ray feeding bout compared with the density on the intact sandflat were recorded. A model of daily predation at different seasonal rates was used to simulate the yearly change in shrimp density. The result was consistent with the actual change.

scholarly journals Modeling Discards in Stock Assessments: Red Grouper Epinephelus morio in the U.S. Gulf of Mexico

Fishes ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 7
Author(s):  
Kyle W. Shertzer ◽  
Erik H. Williams ◽  
Skyler R. Sagarese
Keyword(s):  
Gulf Of Mexico ◽  
Stock Assessment ◽  
Time Varying ◽  
Discard Mortality ◽  
Stock Assessments ◽  
Epinephelus Morio ◽  
Red Grouper ◽  
Management Advice ◽  
The U.S

To be as accurate as possible, stock assessments should account for discard mortality in fisheries if it occurs. Three common approaches to modeling discards in assessments are to lump dead discards with landings, treat dead discards as their own fleet, or link them conversely with landings through use of a retention function. The first approach (lumping) implicitly assumes that the selectivity of landings applies also to discards. In many cases, that assumption is false, for example, if discards comprise smaller fish than do landings. The latter two approaches avoid the assumption by modeling discards explicitly with their own selectivity pattern. Here, we examine these approaches to modeling discards. Using a simulation study, we demonstrate that the two approaches to modeling discards explicitly can provide identical results under both static and time-varying conditions. Then, using a stock assessment case study of red grouper Epinephelus morio in the U.S. Gulf of Mexico, we demonstrate that in practice the approaches to modeling discards can provide different outcomes, with implications for the resultant management advice. We conclude by comparing and contrasting the different approaches, calling for more research to elucidate which approach is most suitable under various sources of error typically encountered in discard data.

Analytical thermochronometric models of Earth’s crust during the late accretionary bombardment epoch (4.5-3.5 Ga)

2020 ◽  
Author(s):  
Stephen J. Mojzsis ◽  
Oleg Abramov
Keyword(s):  
Age Distribution ◽  
Three Dimensional ◽  
Plate Boundary ◽  
Impact Angle ◽  
Asteroid Belt ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
The Earth ◽  
Size Frequency ◽  
The Impact

<p>Late accretionary bombardments in the first billion years of solar system history strongly affected the initial physical and chemical states of the Earth. Evidence of ancient impacts can be preserved in the oldest known terrestrial zircons with ages up to ca. 4.4 Ga. Here, we use the Hadean zircon record to directly assess the thermal effects of impact bombardment on the early Earth’s crust, couple the results to models of closure temperature-dependent diffusive loss and U-Pb age-resetting in zircon, derive zircon ages, and compare them to published ages.</p><p>The impact bombardment model consists of (i) a stochastic cratering model which populates the surface with craters within constraints derived from the lunar cratering record, the size/frequency distribution of the asteroid belt, and dynamical models; (ii) analytical expressions that calculate a temperature field for each crater; and (iii) a three-dimensional thermal model of the terrestrial lithosphere, where craters are allowed to cool by conduction and radiation. Equations for diffusion in zircon are coupled to these thermal models to estimate the amount of age-resetting.</p><p>We present modeling results for the Earth between 4.5 Ga and 3.5 Ga based new mass-production functions. Mean surface temperatures and geothermal gradients were assumed as 20 °C and 70 °C/km. Total delivered mass was estimated at 0.0013(M<sub>planet</sub>), or 7.8 × 10<sup>21</sup> kg. The size-frequency distributions of the impacts were derived from dynamical modeling. We begin model runs with a global magma ocean, which would have been formed by the Moon-forming impact. Mean impactor density of 3000 kg/m<sup>3</sup> and impactor velocity distribution from [1,2] was used, and impact angle of each impactor was stochastically generated from a gaussian centered at 45 degrees. The typical impact velocity of the Earth is ~21 km s<sup>-1</sup>.</p><p>It is important to note that the model age outputs we report omit normal processes of generation of zircon-saturated magmas that were operative in the Hadean. We find that as the impact flux decreases with time and becomes negligible for the purposes of thermal modeling by ca. 3.5 Ga. We find that the probability of randomly selecting a zircon of a given age increases with increasing age, predicting a large number of very old zircons. This contrasts with the actual age distribution of Hadean zircons, which, for >4 Ga, indicates the opposite case: the probability of selecting a zircon of a given age decreases with increasing age. We interpret this discrepancy to mean that impacts were not the dominant process in determining the ages of Hadean zircons. This is consistent with observations that the majority of Hadean zircons had formation temperature significantly lower than those expected for melt sheets and thermobarometry measurements suggesting formation of some Hadean zircons in a plate boundary environment.</p><p>[1] Mojzsis, S.J. et al. (2019). Astrophys. J., 881, 44. [2] Brasser, R. et al. (2020) Icarus 338, 113514. </p>

scholarly journals Age and individual growth of Mesodesma mactroides (Bivalvia) in the southernmost range of its distribution

2004 ◽  
Vol 61 (8) ◽  
pp. 1253-1259 ◽  
Author(s):  
Sandra M. Fiori ◽  
Enrique M. Morsán
Keyword(s):  
Growth Parameters ◽  
Atlantic Coast ◽  
Sandy Beaches ◽  
Growth Patterns ◽  
Individual Growth ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Growth Increments ◽  
Size Frequency ◽  
External Shell

Abstract The yellow clam, Mesodesma mactroides, is an intertidal bivalve typical from sandy beaches of the South American Atlantic coast. Growth parameters of southernmost populations of M. mactroides were studied and compared with other populations. Thin shell sections were examined to describe internal shell layers and to contrast with external shell transparency. Periodicity of deposition of external growth increments was studied recording the degree of transparency of the shell border. Growth patterns were determined using modal progression analysis from size frequency distributions, analysis of external shell increments, and size-at-age data derived from inner shell layers. Growth parameters were described using the von Bertalanffy growth model. Both internal and external patterns were coincident and exhibited a succession of one translucent and one opaque region. The transparent region was deposited during summer. Growth differences found between populations may be related to unequal size of first ring in both beaches. This feature may originate from asynchrony in spawning and recruitment. The monthly analysis of shell length size frequency distribution shows that growth of M. mactroides is seasonal. Estimations of asymptotic size of studied populations and others located at the southern (coldest) half of the geographical range of distribution suggest a negative relation with latitude.

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