Multiple challenges confront a high-effort inland recreational fishery in decline

2018 ◽  
Vol 75 (9) ◽  
pp. 1357-1368 ◽  
Author(s):  
Christopher L. Cahill ◽  
Stephanie Mogensen ◽  
Kyle L. Wilson ◽  
Ariane Cantin ◽  
R. Nilo Sinnatamby ◽  
...  
Keyword(s):  
Multiple Stressors ◽  
Fishing Effort ◽  
Population Declines ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Abundance Estimates ◽  
Sampling Locations ◽  
Management Perspective ◽  
Capture Recapture ◽  
Multiple Challenges ◽  
High Effort

Catch-and-release regulations designed to protect fisheries may fail to halt population declines, particularly in situations where fishing effort is high and when multiple stressors threaten a population. We demonstrate this claim using Alberta’s Bow River, which supports a high-effort rainbow trout (Oncorhynchus mykiss) fishery where anglers voluntarily release >99% of their catch. We examined the population trend of adult trout, which were tagged and recaptured using electrofishing surveys conducted intermittently during 2003–2013. We constructed Bayesian multisession capture–recapture models in Stan to obtain abundance estimates for trout and regressed trend during two periods to account for variation in sampling locations. General patterns from all models indicated the population declined throughout the study. Potential stressors to this system that may have contributed to the decline include whirling disease (Myxobolus cerebralis), which was detected for the first time in 2016, notable floods, and release mortality. Because disease and floods are largely uncontrollable from a management perspective, we suggest that stringent tactics such as angler effort restrictions may be necessary to maintain similar fisheries.

Temporal and spatial patterns of angler effort across lake districts and policy options to sustain recreational fisheries

2012 ◽  
Vol 69 (2) ◽  
pp. 321-329 ◽  
Author(s):  
John. R. Post ◽  
Eric A. Parkinson
Keyword(s):  
Urban Areas ◽  
Fishing Effort ◽  
Lake District ◽  
Large Cities ◽  
Catch And Release ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Explicit Consideration ◽  
Management Approaches ◽  
High Effort ◽  
Proportional Reduction

Studies suggest anglers allocate fishing effort across lakes districts based on fishing quality and travel time resulting in high effort near urban areas, which declines with distance. This results in quality fisheries in remote areas and poorer quality near population centres. In this paper we explore the effectiveness of harvest and effort regulations to counter this tendency for overfishing and stock collapse for a rainbow trout ( Oncorhynchus mykiss ) fishery from a lake district in British Columbia, Canada. Our results suggest that daily bag limits can improve fishing quality if the effort is not too high, but fail to prevent collapse close to population centres. The ability of complete catch-and-release regulations to maintain quality fisheries is inversely related to the rate of release mortality. Catch-and-release fisheries with low mortality can maintain quality close to large cities, whereas higher release mortality does not prevent collapse. Direct fishing effort limitation can maintain quality fisheries, but a high proportional reduction in effort is required to maintain quality near population centres. Explicit consideration of the location of fisheries within lake districts is necessary to design effective management approaches and will likely require a mixed strategy with substantial spatial variation in harvest control.

scholarly journals On the Estimation of Dispersal and Movement of Birds

The Condor ◽  
2004 ◽  
Vol 106 (4) ◽  
pp. 720-731 ◽  
Author(s):  
William L. Kendall ◽  
James D. Nichols
Keyword(s):  
Robust Design ◽  
Nonlinear Dynamic ◽  
Detection Probability ◽  
Cross Correlation ◽  
Statistical Methodology ◽  
Open Population ◽  
Abundance Estimates ◽  
Capture Recapture ◽  
Over Time

Abstract The estimation of dispersal and movement is important to evolutionary and population ecologists, as well as to wildlife managers. We review statistical methodology available to estimate movement probabilities. We begin with cases where individual birds can be marked and their movements estimated with the use of multisite capture-recapture methods. Movements can be monitored either directly, using telemetry, or by accounting for detection probability when conventional marks are used. When one or more sites are unobservable, telemetry, band recoveries, incidental observations, a closed- or open-population robust design, or partial determinism in movements can be used to estimate movement. When individuals cannot be marked, presence-absence data can be used to model changes in occupancy over time, providing indirect inferences about movement. Where abundance estimates over time are available for multiple sites, potential coupling of their dynamics can be investigated using linear cross-correlation or nonlinear dynamic tools. Sobre la Estimación de la Dispersión y el Movimiento de las Aves Resumen. La estimación de la dispersión y el movimiento es importante para los ecó logos evolutivos y de poblaciones, así como también para los encargados del manejo de vida silvestre. Revisamos la metodología estadística disponible para estimar probabilidades de movimiento. Empezamos con casos donde aves individuales pueden ser marcadas y sus movimientos estimados con el uso de métodos de captura-repactura para múltiples sitios. Los movimientos pueden ser monitoreados ya sea directamente, usando telemetría o teniendo en cuenta las probabilidades de detección cuando se usan marcas convencionales. Cuando uno o más sitios no pueden ser observados, se puede estimar el movimiento usando telemetría, recuperación de anillos, observaciones circunstanciales, un diseño poblacional robusto cerrado o abierto, o determinismo parcial de los movimientos. Cuando los individuos no pueden ser marcados, se pueden usar datos de presencia-ausencia para modelar los cambios en el tiempo de la ocupación, brindando inferencias indirectas sobre los movimientos. Cuando las estimaciones de abundancia a lo largo del tiempo están disponibles para varios sitios, se puede investigar la interrelación potencial de sus dinámicas usando correlaciones cruzadas lineales o herramientas para dinámica no lineal.

scholarly journals Interacting stressors matter: diet quality and virus infection in honeybee health

2019 ◽  
Vol 6 (2) ◽  
pp. 181803 ◽  
Author(s):  
Adam G. Dolezal ◽  
Jimena Carrillo-Tripp ◽  
Timothy M. Judd ◽  
W. Allen Miller ◽  
Bryony C. Bonning ◽  
...  
Keyword(s):  
Virus Infection ◽  
Multiple Stressors ◽  
Experimental Studies ◽  
Calcium Content ◽  
Micronutrient Deficiencies ◽  
Population Declines ◽  
High Quality ◽  
Diet Diversity ◽  
Extreme Stress ◽  
High Virus

Honeybee population declines have been linked to multiple stressors, including reduced diet diversity and increased exposure to understudied viral pathogens. Despite interest in these factors, few experimental studies have explored the interaction between diet diversity and viral infection in honeybees. Here, we used a mixture of laboratory cage and small semi-field nucleus hive experiments to determine how these factors interact. In laboratory experiments, we found that high-quality diets (polyfloral pollen and high-quality single-source pollen) have the potential to reduce mortality in the face of infection with Israeli acute paralysis virus (IAPV). There was a significant interaction between diet and virus infection on mortality, even in the presence of high virus titres, suggesting that good diets can help bees tolerate virus infection. Further, we found that extreme stress in the form of pollen starvation in conjunction with IAPV infection increase exiting behaviour from small experimental hives. Finally, we showed that higher-quality pollen diets have significantly higher iron and calcium content, suggesting micronutrient deficiencies could be an under-explored area of bee nutrition.

scholarly journals Abundance, survival and temporary emigration of bottlenose dolphins (Tursiops sp.) off Useless Loop in the western gulf of Shark Bay, Western Australia

2012 ◽  
Vol 63 (11) ◽  
pp. 1059 ◽  
Author(s):  
Krista Nicholson ◽  
Lars Bejder ◽  
Simon J. Allen ◽  
Michael Krützen ◽  
Kenneth H. Pollock
Keyword(s):  
Western Australia ◽  
Bottlenose Dolphins ◽  
Early Spring ◽  
Anthropogenic Activity ◽  
Apparent Survival ◽  
Photo Identification ◽  
Temporary Emigration ◽  
Shark Bay ◽  
Abundance Estimates ◽  
Capture Recapture

Capture–recapture models were used to provide estimates of abundance, apparent survival and temporary emigration of Indo-Pacific bottlenose dolphins (Tursiops sp.) in a 226-km2 study area off Useless Loop in the western gulf of Shark Bay, Western Australia. Photo-identification data were collected during boat-based surveys in Austral autumn to early spring (April–September) from 2007 to 2011. Abundance estimates varied from 115 (s.e. 5.2, 95% CI 105–126) individuals in 2008 to 208 (s.e. 17.3, 95% CI 177–245) individuals in 2010. The variability in abundance estimates is likely to be a reflection of how individuals used the study area, rather than fluctuations in true population size. The best fitting capture–recapture model suggested a random temporary emigration pattern and, when coupled with relatively high temporary emigration rates (0.33 (s.e. 0.07) – 0.66 (s.e. 0.05)) indicated that the study area did not cover the entire ranges of the photo-identified dolphins. Apparent survival rate is a product of true survival and permanent emigration and was estimated annually at 0.95 (s.e. 0.02). Since permanent emigration from the study area is unlikely, true survival was estimated to be close to 0.95. This study provides a robust baseline for future comparisons of dolphin demographics, which may be of importance should climate change or increasing anthropogenic activity affect this population.

scholarly journals Behavioural adjustment of fish to temporal variation in fishing pressure affects catchability: an experiment with angled trout

2020 ◽  
Vol 77 (1) ◽  
pp. 188-193 ◽  
Author(s):  
Barbara Koeck ◽  
Magnus Lovén Wallerius ◽  
Robert Arlinghaus ◽  
Jörgen I. Johnsson
Keyword(s):  
Temporal Variation ◽  
Internal State ◽  
Empirical Support ◽  
Population Level ◽  
Theoretical Models ◽  
Fishing Effort ◽  
Threat Perception ◽  
Fishing Pressure ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Catch Rates

In passive fisheries, such as angling, the fishing success depends on the ultimate decision of a fish to ingest the bait, based on an individual’s internal state, previous experience, and threat perception. Fish surviving capture by anglers are known to be less vulnerable, and catch rates usually quickly decline with increasing fishing effort. Previous theoretical models have thus suggested fishing closures as a means to recover responsiveness of fish to angling gear and maintain catch rates, yet empirical support remains limited. In a controlled replicated pond experiment, we evaluated the effects of temporal variation in fishing pressure on catch rates of rainbow trout (Oncorhynchus mykiss) by simulating short-term fishing closures. Fishing closures increased catch rates and population-level catchability by reducing threat perception at the population level and allowing released individuals to return to a vulnerable state. Our experimental results show that periodic fishing closures benefit catch rates but at the risk of aggravating the likelihood of overharvesting.

Errors in identification using natural markings: rates, sources, and effects on capture–recapture estimates of abundance

2001 ◽  
Vol 58 (9) ◽  
pp. 1861-1870 ◽  
Author(s):  
Peter T Stevick ◽  
Per J Palsbøll ◽  
Tim D Smith ◽  
Mark V Bravington ◽  
Philip S Hammond
Keyword(s):  
Error Rate ◽  
Large Scale ◽  
False Negative ◽  
Parametric Bootstrap ◽  
Humpback Whales ◽  
The North ◽  
Abundance Estimates ◽  
Capture Recapture ◽  
Quality Rating ◽  
Estimation Of Variance

The results of a double-marking experiment using natural markings and microsatellite genetic markers to identify humpback whales (Megaptera novaeangliae) confirm that natural markings are a reliable means of identifying individuals on a large scale. Of 1410 instances of double tagging, there were 414 resightings. No false positive and 14 false negative errors were identified. The rate of error increased with decreasing photographic quality; no errors were observed among photographs of the highest quality rating, whereas an error rate of 0.125 was identified in sightings for which only part of the area used for identification was visible. There was also a weaker relationship between error rate and the distinctiveness of markings, which may result from non-independence in coding for image quality and distinctiveness. A correction is developed for the Petersen two-sample abundance estimator to account for false negative errors in identification, and a parametric bootstrap procedure for estimation of variance is also developed. In application to abundance estimates from the North Atlantic, the correction reduces the bias in estimates made using poorer quality photographs to a negligible level while maintaining comparable precision.

scholarly journals First estimation of Eurasian lynx (Lynx lynx) abundance and density using digital cameras and capture–recapture techniques in a German national park

2012 ◽  
Vol 35 (2) ◽  
pp. 197-207 ◽  
Author(s):  
K. Weingarth ◽  
◽  
C. Heibl ◽  
F. Knauer ◽  
F. Zimmermann ◽  
...  
Keyword(s):  
National Park ◽  
Large Scale ◽  
Lynx Lynx ◽  
Digital Cameras ◽  
The European Union ◽  
Eurasian Lynx ◽  
Habitat Directive ◽  
Abundance Estimates ◽  
Capture Recapture

Eurasian lynx are individually identifiable by their unique coat markings, making them ideal candidates for capture–recapture (CMR) surveys. We evaluated the use of digital photography to estimate Eurasian lynx population abundance and density within the Bavarian Forest National Park. From November 2008 to January 2009 we placed 24 camera trap sites, each with two cameras facing each other on well–used walking tracks). The units were placed based on a systematic grid of 2.7 km. We captured five independent and three juvenile lynx and calculated abundance estimates using Program Mark. We also compared density estimates based on the MMDM method (Mean Maximum Distance Moved) from telemetry data (½MMDMGPS) and from camera trapping data (½MMDMCAM). We estimated that in an effectively sampled area of 664 km2 the Eurasian lynx density was 0.9 individuals/100 km2 with ½MMDMCAM. The Eurasian lynx density calculated with ½MMDMGPS was 0.4 individuals/100 km2 in an effectively sampled area of 1,381 km2. Our results suggest that long–term photographic CMR sampling on a large scale may be a useful tool to monitor population trends of Eurasian lynx in accordance with the Fauna–Flora–Habitat Directive of the European Union.

scholarly journals Bycatch mitigation could prevent strong changes in the ecological strategies of seabird communities across the globe

2021 ◽  
Author(s):  
Cerren Richards ◽  
Robert S. C. Cooke ◽  
Diana E. Bowler ◽  
Kristina Boerder ◽  
Amanda E. Bates
Keyword(s):  
Spatial Variation ◽  
Ecosystem Functioning ◽  
Species Traits ◽  
Fishing Effort ◽  
Population Declines ◽  
Ecological Strategies ◽  
Mass Generation ◽  
Management Actions ◽  
Distribution Ranges ◽  
Fisheries Bycatch

Fisheries bycatch, the incidental mortality of non-target species, is a major threat to seabirds worldwide. Mitigating bycatch is an important factor to reduce seabird population declines and consequent changes in ocean trophic dynamics and ecosystem functioning. However, it remains an open question how and where mitigating bycatch at a global scale may conserve seabird traits and the ecological strategies that traits represent. Here we combine a dataset of species traits and distribution ranges for 341 seabirds with spatially resolved fishing effort data for gillnet, longline, trawl, and purse seine gears to: (1) understand spatial variation in seabird community traits; and (2) test whether mitigating fisheries bycatch may prevent shifts in traits of seabird communities and loss of ecological strategies. We find distinct spatial variation in the community weighted mean of five seabird traits (clutch size, body mass, generation length, foraging guild, and diet guild). Furthermore, our analysis suggests that successful bycatch mitigation could prevent strong shifts in the traits of seabird communities across the globe particularly in the North Atlantic and Southern Oceans. Specifically, changes in dominant foraging and diet guilds, and shifts towards communities with faster reproductive speeds (larger clutch sizes and shorter generation lengths) and smaller body masses could be avoided. Therefore, bycatch mitigation may have important indirect benefits for sustaining ecosystem functioning, as mediated by species traits. Incorporating species traits into management actions will provide valuable tools for marine spatial planning and when evaluating the success of conservation initiatives.

scholarly journals Abundance of East coast Australian humpback whales (Megaptera novaeangliae) in 2005 estimated using multi-point sampling and capture-recapture analysis

2020 ◽  
pp. 253-259
Author(s):  
David A. Paton ◽  
Lyndon Brooks ◽  
Daniel Burns ◽  
Trish Franklin ◽  
Wally Franklin ◽  
...  
Keyword(s):  
East Coast ◽  
Megaptera Novaeangliae ◽  
Humpback Whales ◽  
Migration Route ◽  
Closed Population ◽  
Breeding Stock ◽  
Abundance Estimate ◽  
Abundance Estimates ◽  
Capture Recapture ◽  
Near Extinction

The humpback whales (Megaptera novaeangliae) that migrate along the east coast of Australia were hunted to near extinction during the lastcentury. This remnant population is part of Breeding Stock E. Previous abundance estimates for the east Australian portion of Breeding Stock Ehave been based mainly on land-based counts. Here we present a capture-recapture abundance estimate for this population using photo-identificationdata. These data were collected at three locations on the migration route (Byron Bay – northern migration, Hervey Bay and Ballina – southernmigration) in order to estimate the population of humpback whales that migrated along the east coast of Australia in 2005. The capture-recapturedata were analysed using a variety of closed population models with a model-averaged estimate of 7,041 (95% CI 4,075–10,008) whales.

scholarly journals Trade-Offs Underwater: Physiological Plasticity of Rainbow Trout (Oncorhynchus mykiss) Confronted by Multiple Stressors

Fishes ◽  
2018 ◽  
Vol 3 (4) ◽  
pp. 49 ◽  
Author(s):  
Elena Wernicke von Siebenthal ◽  
Kristina Rehberger ◽  
Christyn Bailey ◽  
Albert Ros ◽  
Elio Herzog ◽  
...  
Keyword(s):  
Resource Allocation ◽  
Rainbow Trout ◽  
Phenotypic Plasticity ◽  
Oncorhynchus Mykiss ◽  
Multiple Stressors ◽  
Parasitic Infection ◽  
Phenotypic Flexibility ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Trade Offs ◽  
The Individual

Organisms have evolved mechanisms to partition the available resources between fitness-relevant physiological functions. Organisms possess phenotypic plasticity to acclimate to changing environmental conditions. However, this comes at a cost that can cause negative correlations or “trade-offs”, whereby increasing investments in one function lead to decreased investments in another function. The aim of the present study was to investigate the prioritization of resource allocation between growth, pathogen defense, and contaminant response in juvenile rainbow trout (Oncorhynchus mykiss) exposed to changes of resource income or expenditure. We performed a multifactorial experiment with three resource-impacting stressors—limited food availability, a parasitic infection, exposure to a vitellogenesis-inducing contaminant—and combinations thereof. Treatment with the individual stressors evoked the expected responses in the respective physiological target systems—body growth, immune system, and hepatic vitellogenin transcription—but we found little evidence for significant negative relations (trade-offs) between the three systems. This also applied to fish exposed to combinations of the stressors. This high phenotypic flexibility of trout in their resource allocation suggests that linear resource allocations as mechanisms of phenotypic plasticity may be too simplistic, but it also may point to a greater capacity of ectothermic than endothermic vertebrates to maintain key physiological processes under competing resource needs due to lower maintenance costs.

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