Production at the Cohort and Population Levels

2020 ◽  
pp. 149-168
Author(s):  
Michael J. Fogarty ◽  
Jeremy S. Collie
Keyword(s):  
Population Ecology ◽  
Life Stage ◽  
Population Level ◽  
Fish Population ◽  
Individual Growth ◽  
Relative Importance ◽  
Compensatory Mechanisms ◽  
Fisheries Science ◽  
Dominant Component ◽  
Time Period

The dominant focus on production processes in fisheries science sets it apart from other areas of population ecology in which population numbers are the principal currency for analysis. This chapter extends consideration of individual growth and mortality rates provided in earlier chapters to broaden the context for understanding cohort and population processes. A cohort is a group of organisms born within a given time period (e.g. year). How a fish population will respond to harvesting requires not only accurate accounting of its effective reproductive output but an understanding of the relative importance of compensatory mechanisms operating at different points in the life cycle. Recruitment (the number in a cohort surviving to a specified life stage or age) emerges as a dominant component of production at the population level. A dominant theme in this chapter concerns population regulation as embodied in the recruitment process and the high variability in this process.

scholarly journals Image-based, unsupervised estimation of fish size from commercial landings using deep learning

2019 ◽  
Vol 77 (4) ◽  
pp. 1330-1339 ◽  
Author(s):  
Amaya Álvarez-Ellacuría ◽  
Miquel Palmer ◽  
Ignacio A Catalán ◽  
Jose-Luis Lisani
Keyword(s):  
Length Distribution ◽  
Population Level ◽  
Fish Population ◽  
Maximum Deviation ◽  
Fish Length ◽  
Convolutional Network ◽  
Fisheries Science ◽  
Length Estimation ◽  
Challenges And Opportunities ◽  
European Hake

Abstract The dynamics of fish length distribution is a key input for understanding the fish population dynamics and taking informed management decisions on exploited stocks. Nevertheless, in most fisheries, the length of landed fish is still made by hand. As a result, length estimation is precise at fish level, but due to the inherent high costs of manual sampling, the sample size tends to be small. Accordingly, the precision of population-level estimates is often suboptimal and prone to bias when properly stratified sampling programmes are not affordable. Recent applications of artificial intelligence to fisheries science are opening a promising opportunity for the massive sampling of fish catches. Here, we present the results obtained using a deep convolutional network (Mask R-CNN) for unsupervised (i.e. fully automatic) European hake length estimation from images of fish boxes automatically collected at the auction centre. The estimated mean of fish lengths at the box level is accurate; for average lengths ranging 20–40 cm, the root-mean-square deviation was 1.9 cm, and maximum deviation between the estimated and the measured mean body length was 4.0 cm. We discuss the challenges and opportunities that arise with the use of this technology to improve data acquisition in fisheries.

scholarly journals Resource partitioning between kit foxes (Vulpes macrotis) and coyotes (Canis latrans): a comparison of historical and contemporary dietary overlap

2018 ◽  
Vol 96 (5) ◽  
pp. 497-504 ◽  
Author(s):  
P.A. Byerly ◽  
R.C. Lonsinger ◽  
E.M. Gese ◽  
A.J. Kozlowski ◽  
L.P. Waits
Keyword(s):  
Great Basin ◽  
Native Species ◽  
Dietary Diversity ◽  
Canis Latrans ◽  
Population Level ◽  
Relative Importance ◽  
Dietary Overlap ◽  
Kit Fox ◽  
Prey Diversity ◽  
Vulpes Macrotis

Range expansions by generalists can alter communities and introduce competitive pressures on native species. In the Great Basin Desert, USA, coyotes (Canis latrans Say, 1823) have colonized and are now sympatric with native kit foxes (Vulpes macrotis Merriam, 1888). Since both species have similar diets, dietary partitioning may facilitate coexistence. We analyzed coyote and kit fox diets, then compared our results to an earlier study. Because populations are dynamic, we expected that decreases in prey or increases in predator abundance could alter dietary patterns. We found no significant changes in population-level prey diversity for kit foxes or coyotes, but found high levels of dietary overlap between species. We did detect a significant decrease in the relative importance of leporids (family Leporidae) in the diets of both canids, but they remained important for coyotes. The relative importance of small mammals was greater for kit foxes than coyotes, but their importance had not changed significantly over time. We detected significant declines in prey diversity per sample (scat-level dietary diversity) for both canids, suggesting that during a foraging event, individuals may encounter less diverse prey now than historically. These findings suggested that kit foxes and coyotes were not limited by prey, despite high dietary overlap.

scholarly journals Impact of Rotavirus Vaccine Introduction in Children Less Than 2 Years of Age Presenting for Medical Care With Diarrhea in Rural Matlab, Bangladesh

2019 ◽  
Vol 69 (12) ◽  
pp. 2059-2070 ◽  
Author(s):  
Lauren M Schwartz ◽  
K Zaman ◽  
Md Yunus ◽  
Ahasan-ul H Basunia ◽  
Abu Syed Golam Faruque ◽  
...  
Keyword(s):  
Vaccine Coverage ◽  
Controlled Trial ◽  
Population Level ◽  
Diarrhoeal Disease ◽  
Incidence Rates ◽  
Service Area ◽  
Rotavirus Vaccine ◽  
Rotavirus Vaccines ◽  
Time Period ◽  
The Impact

Abstract Background Following the conclusion of a human rotavirus vaccine (HRV) cluster-randomized, controlled trial (CRT) in Matlab, Bangladesh, HRV was included in Matlab’s routine immunization program. We describe the population-level impact of programmatic rotavirus vaccination in Bangladesh in children <2 years of age. Methods Interrupted time series were used to estimate the impact of HRV introduction. We used diarrheal surveillance collected between 2000 and 2014 within the 2 service delivery areas (International Centre for Diarrhoeal Disease Research, Bangladesh [icddr,b] service area [ISA] and government service area [GSA]) of the Matlab Health and Demographic Surveillance System, administered by icddr,b. Age group–specific incidence rates were calculated for both rotavirus-positive (RV+) and rotavirus-negative (RV–) diarrhea diagnoses of any severity presenting to the hospital. We used 2 models to assess the impact within each service area: Model 1 used the pre-vaccine time period in all villages (HRV– and control-only) and Model 2 combined the pre-vaccine time period and the CRT time period, using outcomes from control-only villages. Results Both models demonstrated a downward trend in RV+ diarrheal incidences in the ISA villages during 3.5 years of routine HRV use, though only Model 2 was statistically significant. Significant impacts of HRV on RV+ diarrhea incidences in GSA villages were not observed in either model. Differences in population-level impacts between the 2 delivery areas may be due to the varied rotavirus vaccine coverage and presentation rates to the hospital. Conclusions This study provides initial evidence of the population-level impact of rotavirus vaccines in children <2 years of age in Matlab, Bangladesh. Further studies are needed of the rotavirus vaccine impact after the nationwide introduction in Bangladesh.

Environmental and geospatial factors drive juvenile Chinook salmon distribution during early ocean migration

2013 ◽  
Vol 70 (8) ◽  
pp. 1167-1177 ◽  
Author(s):  
Brian J. Burke ◽  
Martin C. Liermann ◽  
David J. Teel ◽  
James J. Anderson
Keyword(s):  
Chinook Salmon ◽  
Selection Criteria ◽  
Climate Changes ◽  
Sublethal Effects ◽  
Life Stage ◽  
Migration Route ◽  
Relative Importance ◽  
Patchy Distribution ◽  
Multiple Cues ◽  
Fish Distributions

Migrating animals rely on a variety of cues to guide them, but the relative importance of those signals may vary with size, life stage, or location. During their initial ocean migration, yearling Chinook salmon (Oncorhynchus tshawytcha) from the Columbia River have stock-specific spatial distributions that shift through time. We used a two-process mixture model to examine how the distribution of yearling migrants from three Chinook salmon stocks varies as a function of geospatial (e.g., latitude and distance from shore) and environmental (e.g., chlorophyll a and temperature) covariates. In this framework, one process described the probability of being inside the spatial, temporal, and environmental boundaries of the migration route, and one process described the patchy distribution of salmon abundance within that route. We found that both environmental and geospatial covariates explained substantial portions of observed spatial patterns in abundance, suggesting that these stocks responded to multiple cues during migration. However, model selection criteria indicated that fish distributions were more affected by geospatial than by environmental covariates. We conclude that during migration, behavioral responses to environmental variation are secondary to responses to geospatial variation, sometimes resulting in suboptimal environmental conditions. This may have sublethal effects on growth and could ultimately influence stock-specific responses to broad-scale climate changes.

scholarly journals Growth, death, and resource competition in sessile organisms

2021 ◽  
Vol 118 (15) ◽  
pp. e2020424118
Author(s):  
Edward D. Lee ◽  
Christopher P. Kempes ◽  
Geoffrey B. West
Keyword(s):  
Evolutionary Dynamics ◽  
Resource Competition ◽  
Temporal Dynamics ◽  
Population Level ◽  
Individual Growth ◽  
Local Competition ◽  
Large Colony ◽  
Rates Of Growth ◽  
Sessile Organisms

Population-level scaling in ecological systems arises from individual growth and death with competitive constraints. We build on a minimal dynamical model of metabolic growth where the tension between individual growth and mortality determines population size distribution. We then separately include resource competition based on shared capture area. By varying rates of growth, death, and competitive attrition, we connect regular and random spatial patterns across sessile organisms from forests to ants, termites, and fairy circles. Then, we consider transient temporal dynamics in the context of asymmetric competition, such as canopy shading or large colony dominance, whose effects primarily weaken the smaller of two competitors. When such competition couples slow timescales of growth to fast competitive death, it generates population shocks and demographic oscillations similar to those observed in forest data. Our minimal quantitative theory unifies spatiotemporal patterns across sessile organisms through local competition mediated by the laws of metabolic growth, which in turn, are the result of long-term evolutionary dynamics.

scholarly journals Long time frames to detect the impact of changing COVID-19 measures, Canada, March to July 2020

2021 ◽  
Vol 26 (40) ◽  
Author(s):  
Jessica E Stockdale ◽  
Renny Doig ◽  
Joosung Min ◽  
Nicola Mulberry ◽  
Liangliang Wang ◽  
...  
Keyword(s):  
Population Level ◽  
Time Frame ◽  
Control Measures ◽  
Type Model ◽  
Time Period ◽  
Long Time ◽  
The Mean ◽  
Reported Data ◽  
Time Frames ◽  
The Impact

Background Many countries have implemented population-wide interventions to control COVID-19, with varying extent and success. Many jurisdictions have moved to relax measures, while others have intensified efforts to reduce transmission. Aim We aimed to determine the time frame between a population-level change in COVID-19 measures and its impact on the number of cases. Methods We examined how long it takes for there to be a substantial difference between the number of cases that occur following a change in COVID-19 physical distancing measures and those that would have occurred at baseline. We then examined how long it takes to observe this difference, given delays and noise in reported cases. We used a susceptible-exposed-infectious-removed (SEIR)-type model and publicly available data from British Columbia, Canada, collected between March and July 2020. Results It takes 10 days or more before we expect a substantial difference in the number of cases following a change in COVID-19 control measures, but 20–26 days to detect the impact of the change in reported data. The time frames are longer for smaller changes in control measures and are impacted by testing and reporting processes, with delays reaching ≥ 30 days. Conclusion The time until a change in control measures has an observed impact is longer than the mean incubation period of COVID-19 and the commonly used 14-day time period. Policymakers and practitioners should consider this when assessing the impact of policy changes. Rapid, consistent and real-time COVID-19 surveillance is important to minimise these time frames.

scholarly journals Modelling annual mass balances of eight Scandinavian glaciers using statistical models

2015 ◽  
Vol 9 (1) ◽  
pp. 383-415 ◽  
Author(s):  
M. Trachsel ◽  
A. Nesje
Keyword(s):  
North Atlantic ◽  
Statistical Models ◽  
Atlantic Multidecadal Oscillation ◽  
Relative Importance ◽  
Mass Balances ◽  
Average Mass ◽  
The North ◽  
Nao Index ◽  
Time Period ◽  
The North Atlantic Oscillation

Abstract. Glacier mass balances are mainly influenced by accumulation-season precipitation and ablation-season temperature. We use a suite of statistical models to determine the influence of accumulation-season precipitation and ablation-season temperature on annual mass balances of eight Scandinavian glaciers, ranging from near coastal, maritime glaciers to inland, continental glaciers. Accumulation-season precipitation is more important for maritime glaciers, whereas ablation-season temperature is more important for annual balances of continental glaciers. However, the importances are not stable in time. For instance, accumulation-season precipitation is more important than ablation-season temperature for all glaciers in the 30 year period 1968–1997. In this time period the Atlantic Multidecadal Oscillation (AMO) index was consistently negative and the North Atlantic Oscillation (NAO) Index was consistently positive between 1987 and 1995, both being favourable for glacier growth. Hence, the relative importance of precipitation and temperature for mass balances is possibly influenced by the AMO and the NAO. Climate sensitivities estimated by statistical models are similar to climate sensitivities based on degree-day models, but are lower than climate sensitivities of energy balance models. Hence, future projections of mass balances found with our models seem rather optimistic. Still, all average mass balances found for the years 2050 and 2100 are negative.

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