Exploring the population dynamics of winter skate (Leucoraja ocellata) in the Georges Bank region using a statistical catch-at-age model incorporating length, migration, and recruitment process errors

2010 ◽  
Vol 67 (5) ◽  
pp. 774-792 ◽  
Author(s):  
M. G. Frisk ◽  
S. J.D. Martell ◽  
T. J. Miller ◽  
K. Sosebee
Keyword(s):  
Population Dynamics ◽  
Information Criterion ◽  
Adult Mortality ◽  
Population Increase ◽  
Observation Error ◽  
Georges Bank ◽  
Recruitment Process ◽  
Open Population ◽  
Age Model ◽  
Parsimonious Models

Winter skate ( Leucoraja ocellata ) of all length classes increased dramatically in abundance on Georges Bank in the 1980s following the decline of many groundfish species. We present a full population model of winter skate to better understand the population dynamics of the species and elucidate the mechanisms underlying their increase in abundance in the 1980s. Specifically, we developed four statistical catch-at-age models incorporating length-frequency data with the following model structures: (i) observation error only (base model R1); (ii) observation and recruitment process errors (model R2); (iii) adult migration modeled as a random walk in adult mortality (model R3); and (iv) observation and recruitment process errors and adult migration (model R4). Akaike’s information criterion values indicated that models R3 and R4, which both included adult migration, were the most parsimonious models. This finding strongly suggests that the winter skate population increase on Georges Bank in the 1980s was not solely a result of increases in recruitment but likely involved adult migration (i.e., it is an open population). Finally, recent predicted fishing mortalities exceeded FMSY for all models.

Population dynamics of large and small mammals: Graeme Caughley's grand vision

2009 ◽  
Vol 36 (1) ◽  
pp. 1 ◽  
Author(s):  
Charles J. Krebs
Keyword(s):  
Population Dynamics ◽  
Population Control ◽  
Population Increase ◽  
Control Mechanisms ◽  
Relative Role ◽  
Top Down ◽  
Large Herbivores ◽  
Disturbed Systems ◽  
Herbivorous Mammals ◽  
Grand Vision

Ecologists that study the population dynamics of large and small herbivorous mammals operate in two worlds that overlap only partly, and in this paper I address whether the conjecture that these worlds represent two distinct and valid paradigms is currently justified. I argue that large mammals fall into three groups depending on whether they have effective predators or not, and whether they are harvested by humans. Because of human persecution of large predators, more and more large herbivorous mammals are effectively predator-free and are controlled bottom-up by food. But in less disturbed systems, large herbivorous mammals should be controlled top-down by effective predators, and this can lead to a trophic cascade. Small herbivorous mammals have been suggested to be controlled top-down by predators but some experimental evidence has challenged this idea and replaced it with the notion that predation is one of several factors that may affect rates of population increase. Intrinsic control (territoriality, infanticide, social inhibition of breeding) appears to be common in small herbivorous mammals with altricial young but is absent in species with precocial young, in ecosystems with strong stochastic weather variation (deserts) and in areas of human-induced habitat fragmentation in agricultural monocultures. The extrinsic control of large herbivores with precocial young validates part of Graeme Caughley’s Grand Vision, but the relative role of intrinsic and extrinsic mechanisms for small herbivores with altricial young is still controversial. An improved knowledge of population control mechanisms for large and small herbivores is essential for natural resource management.

Understanding historical summer flounder (Paralichthys dentatus) abundance patterns through the incorporation of oceanography-dependent vital rates in Bayesian hierarchical models

2019 ◽  
Vol 76 (8) ◽  
pp. 1275-1294 ◽  
Author(s):  
Cecilia A. O’Leary ◽  
Timothy J. Miller ◽  
James T. Thorson ◽  
Janet A. Nye
Keyword(s):  
Population Dynamics ◽  
Gulf Stream ◽  
Stock Assessment ◽  
Deviance Information Criterion ◽  
Information Criterion ◽  
Natural Mortality ◽  
Vital Rates ◽  
Summer Flounder ◽  
Paralichthys Dentatus ◽  
Abundance Patterns

Climate can impact fish population dynamics through changes in productivity and shifts in distribution, and both responses have been observed for many fish species. However, few studies have incorporated climate into population dynamics or stock assessment models. This study aimed to uncover how past variations in population vital rates and fishing pressure account for observed abundance variation in summer flounder (Paralichthys dentatus). The influences of the Gulf Stream Index, an index of climate variability in the Northwest Atlantic, on abundance were explored through natural mortality and stock–recruitment relationships in age-structured hierarchical Bayesian models. Posterior predictive loss and deviance information criterion indicated that out of tested models, the best estimates of summer flounder abundances resulted from the climate-dependent natural mortality model that included log-quadratic responses to the Gulf Stream Index. This climate-linked population model demonstrates the role of climate responses in observed abundance patterns and emphasizes the complexities of environmental effects on populations beyond simple correlations. This approach highlights the importance of modeling the combined effect of fishing and climate simultaneously to understand population dynamics.

scholarly journals Population dynamics of five riverbed breeding bird species on the lower Drava River, NE Slovenia

Acrocephalus ◽  
2017 ◽  
Vol 38 (174-175) ◽  
pp. 85-126
Author(s):  
Luka Božič ◽  
Damijan Denac
Keyword(s):  
Population Dynamics ◽  
Bird Species ◽  
Breeding Population ◽  
Population Increase ◽  
General Situation ◽  
Breeding Bird ◽  
Main River Channel ◽  
Extreme Flood ◽  
Gravel Bars ◽  
Gravel Bar

AbstractIn 2006–2017, annual censuses of breeding bird species regarded as indicators of natural rivers were carried out on the 38.9 km long lowland stretch of the Drava riverbed between Maribor and Zavrč with altered flow regime due to the operating hydropower plants. Gravel bar habitats were surveyed in four years of the study period by combining orthophoto analysis and analysis of field photographs. Effects of gravel bar management were evaluated based at 20 locations. The Little Ringed PloverCharadrius dubiusoccurred on 39.8% of the gravel bars, but most were occupied only in a few years and held just one breeding pair. Low numbers between 2009 and 2012 (< 30 pairs) were followed by a steep population increase from 2014 onwards to a maximum of 66–73 pairs (1.7–1.9 p/km). Such population dynamics was attributed to the lack of large discharges (>500 m3/s) and consequent overgrowing of riverbed in the first part of the study period, while the increase in the second part was due to the creation of extensive shingle areas (from 20,6 ha in 2009/10 to 37,8 ha in 2014) by the extreme flood in early November 2012, subsequent regular occurrence of large discharges outside the breeding seasons and large-scale removals of woody vegetation. Breeding population of Common SandpiperActitis hypoleucosremained at a rather similar low level (<20 p) during most of the period studied after an initial decline, and did not reflect changes in the overall surface area of riverbed habitats. Contrary to the general situation, the number of breeding pairs on gravel bars subjected to management increased several-fold. Maximum number of pairs on these bars was reached up to four years after the initiation of management measures, as only then the optimal mosaic of early successional stages interspersed with shingle areas developed at main sites. The species was widespread only on lower part of the Drava. KingfisherAlcedo atthiswas fairly widely distributed along the riverbed, but occurred in rather low densities throughout (c. one pair on 2–3 km of the studied riverbed on average), probably as a result of limited bank erosion and consequent overgrowing/lack of suitable nest sites. The population was estimated as stable with effects of harsh winter conditions on breeding numbers in some years. The majority of nest holes were excavated in eroded river banks along the main river channel (77.8%), followed by similar sites located in mouth areas of small tributaries of the Drava (14.8%). Regular breeding of Sand MartinRiparia ripariasince 2012 (up to 259, mostly at only one location annually) was almost exclusively the result of the annual artificial nest site preparation programme. Fairly large gravel bar-breeding population of White WagtailMotacilla alba, monitored since 2013 and predominantly ground nesting in sparsely vegetated areas, seems unusual considering the prevalent breeding habits of the species at the European scale. Conservation implications and guidelines for future management efforts are discussed.

scholarly journals Sex‐specific population dynamics of ocelots in Belize using open population spatial capture–recapture

Ecosphere ◽  
2019 ◽  
Vol 10 (7) ◽  
Author(s):  
Christopher B. Satter ◽  
Ben C. Augustine ◽  
Bart J. Harmsen ◽  
Rebecca J. Foster ◽  
Marcella J. Kelly
Keyword(s):  
Population Dynamics ◽  
Specific Population ◽  
Open Population ◽  
Capture Recapture

Extending production models to include process error in the population dynamics

2003 ◽  
Vol 60 (10) ◽  
pp. 1217-1228 ◽  
Author(s):  
Andre E Punt
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Population Dynamics ◽  
Total Error ◽  
Error Estimator ◽  
Observation Error ◽  
Production Models ◽  
Fitting Production ◽  
Process Error ◽  
Relative Errors

Four methods for fitting production models, including three that account for the effects of error in the population dynamics equation (process error) and when indexing the population (observation error), are evaluated by means of Monte Carlo simulation. An estimator that represents the distributions of biomass explicitly and integrates over the unknown process errors numerically (the NISS estimator) performs best of the four estimators considered, never being the worst estimator and often being the best in terms of the medians of the absolute values of the relative errors. The total-error approach outperforms the observation-error estimator conventionally used to fit dynamic production models, and the performance of a Kalman filter based estimator is particularly poor. Although the NISS estimator is the best-performing estimator considered, its estimates of quantities of management interest are severely biased and highly imprecise for some of the scenarios considered.

Spatial structure of harbour seal populations and the implications thereof

2001 ◽  
Vol 79 (12) ◽  
pp. 2115-2127 ◽  
Author(s):  
T Härkönen ◽  
K C Harding
Keyword(s):  
Population Dynamics ◽  
Site Fidelity ◽  
Phoca Vitulina ◽  
Population Increase ◽  
Dynamic Processes ◽  
Term Study ◽  
Long Term Study ◽  
Harbour Seals ◽  
Age And Sex

A long-term study of freeze-branded harbour seals (Phoca vitulina) revealed explicit site fidelity. Individuals were followed up to 14 years of age and none of the 163 branded animals were observed to haul out beyond a 32-km distance from the site where they were branded as pups. Within this range, striking spatial segregation by age and sex prevailed. While females' site fidelity increased with age, males spent less time at their natal site with increasing age. These findings have consequences for understanding the population dynamics of harbour seals, since single "colonies" will act as partly isolated "subpopulations" in some contexts but not in others. The differing migration tendencies of the population segments lead to spatially segregated sex and age ratios of subpopulations and create a complex pattern of connectivity among these subpopulations. Ignoring the spatial scale will lead to severe misinterpretations of analyses of basic population-dynamic processes, especially rates of population increase, rates of gene flow, and the dynamics of the spread of diseases. We suggest that when studies have different aims, these should be addressed by encompassing different numbers of subpopulations.

Population dynamics of black spruce and white spruce near the arctic tree line in the southern Brooks Range, Alaska

2005 ◽  
Vol 35 (9) ◽  
pp. 2073-2081 ◽  
Author(s):  
Andrea H Lloyd ◽  
Alexis E Wilson ◽  
Christopher L Fastie ◽  
R Matthew Landis
Keyword(s):  
Population Dynamics ◽  
Seed Production ◽  
Matrix Model ◽  
Black Spruce ◽  
White Spruce ◽  
Adult Mortality ◽  
The Arctic ◽  
Tree Line ◽  
Northern Limit ◽  
Fire Intervals

Black spruce (Picea mariana (Mill.) BSP) is the dominant species in interior Alaska but it is largely absent from the arctic tree line. To evaluate the importance of climate and fire as controls over the species distribution, we reconstructed stand history at three sites near its northern limit in Alaska, where it grows with white spruce (Picea glauca (Moench) Voss). We developed a matrix model to explore black spruce population dynamics and response to varying fire intervals. All sites burned in the early 1900s. High recruitment of black spruce occurred for <30 years following the fire, but most current black spruce recruitment is clonal and seed viability is low. White spruce recruitment has been consistently high since the fire, and the majority of seedlings in the stands are white spruce. Despite low recruitment, the matrix model suggests that black spruce populations are nearly stable, largely because of low adult mortality rates. Although black spruce recruitment is stimulated by fire, the model indicates that fire intervals <350 years would destabilize the population, primarily because of slow growth and low seed production. Population dynamics of black spruce at its northern limit in Alaska thus appear to reflect an interaction between fire, which determines the temporal pattern of tree recruitment, and climate, which limits tree growth and, presumably, viable seed production.

scholarly journals Null controllability of a nonlinear population dynamics problem

2006 ◽  
Vol 2006 ◽  
pp. 1-20 ◽  
Author(s):  
Oumar Traore
Keyword(s):  
Population Dynamics ◽  
Internal Control ◽  
Initial Density ◽  
Adjoint System ◽  
Null Controllability ◽  
Dynamics Model ◽  
Carleman Inequality ◽  
Recruitment Process ◽  
Open Set ◽  
Population Dynamics Model

We establish a null controllability result for a nonlinear population dynamics model. In our model, the birth term is nonlocal and describes the recruitment process in newborn individuals population. Using a derivation of Leray-Schauder fixed point theorem and Carleman inequality for the adjoint system, we show that for all given initial density, there exists an internal control acting on a small open set of the domain and leading the population to extinction.

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