Density of fishers and the efficacy of relative abundance indices and small-scale occupancy estimation to detect a population decline on the Hoopa Valley Indian Reservation, California

2011 ◽  
Vol 35 (2) ◽  
pp. 69-75 ◽  
Author(s):  
Sean M. Matthews ◽  
J. Mark Higley ◽  
J. Scott Yaeger ◽  
Todd K. Fuller
Keyword(s):  
Relative Abundance ◽  
Population Decline ◽  
Small Scale ◽  
Indian Reservation ◽  
Occupancy Estimation ◽  
Abundance Indices

scholarly journals THE INFLUENCE OF THE COASTAL CURRENT ON THE ESTIMATION OF RELATIVE ABUNDANCE INDICES IN SMALL-SCALE SHRIMP FISHERY

2021 ◽  
Vol 47 ◽  
pp. e665
Author(s):  
Paulo Victor do Nascimento ARAÚJO ◽  
Alex Barbosa de MORAES ◽  
Flávia LUCENA FRÉDOU ◽  
Fúlvio Aurélio de Morais FREIRE
Keyword(s):  
Relative Abundance ◽  
Stock Assessment ◽  
Northeastern Brazil ◽  
Small Scale ◽  
Coastal Current ◽  
Sampling Effort ◽  
Catch Per Unit Effort ◽  
Abundance Index ◽  
Shrimp Fishery ◽  
Abundance Indices

The aim of this scientific note was to evaluate the influence of the coastal current on the estimation of relative abundance indices for small-scale marine shrimp trawling to indicate the best relative abundance index to be used for stock assessment and conservation. Georeferenced experimental trawls were carried out with standardized equipment and capture time on the coast of Rio Grande do Norte, northeastern Brazil. Drags followed convergent and divergent orientations in relation to the flow of the local coastal current. The results showed that the direction of the coastal current flow directly influences the distances and drag shifts, generating variations in the sampling effort and, consequently, bias when using Catch per Unit Effort (CPUE) as a relative abundance index. Conversely, the adoption of Catch per Unit of Swept Area (CPUA) as an index of relative abundance for shrimp trawling becomes more suitable since the variations in the distances of trawl shifts are perceptible through this index.

scholarly journals Integrating spatial synchrony/asynchrony of population distribution into stock assessment models: a spatial hierarchical Bayesian statistical catch-at-age approach

2016 ◽  
Vol 73 (7) ◽  
pp. 1725-1738 ◽  
Author(s):  
Yan Jiao ◽  
Rob O'Reilly ◽  
Eric Smith ◽  
Don Orth ◽  
Keyword(s):  
Relative Abundance ◽  
Bayesian Model ◽  
Population Distribution ◽  
Stock Assessment ◽  
Spatial Models ◽  
Reference Points ◽  
Hierarchical Bayesian ◽  
Hierarchical Bayesian Model ◽  
Spatial Synchrony ◽  
Abundance Indices

Abstract In many marine fisheries assessments, population abundance indices from surveys collected by different states and agencies do not always agree with each other. This phenomenon is often due to the spatial synchrony/asynchrony. Those indices that are asynchronous may result in discrepancies in the assessment of temporal trends. In addition, commonly employed stock assessment models, such as the statistical catch-at-age (SCA) models, do not account for spatial synchrony/asynchrony associated with spatial autocorrelation, dispersal, and environmental noise. This limits the value of statistical inference on key parameters associated with population dynamics and management reference points. To address this problem, a set of geospatial analyses of relative abundance indices is proposed to model the indices from different surveys using spatial hierarchical Bayesian models. This approach allows better integration of different surveys with spatial synchrony and asynchrony. We used Atlantic weakfish (Cynoscion regalis) as an example for which there are state-wide surveys and expansive coastal surveys. We further compared the performance of the proposed spatially structured hierarchical Bayesian SCA models with a commonly used Bayesian SCA model that assumes relative abundance indices are spatially independent. Three spatial models developed to mimic different potential spatial patterns were compared. The random effect spatially structured hierarchical Bayesian model was found to be better than the commonly used SCA model and the other two spatial models. A simulation study was conducted to evaluate the uncertainty resulting from model selection and the robustness of the recommended model. The spatially structured hierarchical Bayesian model was shown to be able to integrate different survey indices with/without spatial synchrony. It is suggested as a useful tool when there are surveys with different spatial characteristics that need to be combined in a fisheries stock assessment.

Comparison of odontocete populations of the Marquesas and Society Islands (French Polynesia)

2008 ◽  
Vol 89 (5) ◽  
pp. 931-941 ◽  
Author(s):  
Alexandre Gannier
Keyword(s):  
Relative Abundance ◽  
Bottlenose Dolphin ◽  
Bottlenose Dolphins ◽  
Sperm Whale ◽  
French Polynesia ◽  
Society Islands ◽  
Spotted Dolphin ◽  
Abundance Indices ◽  
Beaked Whales ◽  
Using Data

Small boat surveys were organized to study cetaceans of the Marquesas (9°S and 140°W) and the Society Islands (17°S and 150°W) in French Polynesia. Prospecting took place from 12–15 m sailboats, between 1996 and 2001 with systematic visual searching. Boats moved according to sea conditions, at a mean speed of 10 km/h. Effective effort of 4856 km in the Marquesas and 10,127 km in the Societies were logged. Relative abundance indices were processed for odontocetes using data obtained with Beaufort 4 or less. In the Marquesas, 153 on-effort sightings were obtained on 10 delphinids species including the spotted dolphin, spinner dolphin, bottlenose dolphin, melon-headed whale and rough-toothed dolphin. In the Societies, 153 sightings of 12 odontocetes included delphinids (spinner, rough-toothed and bottlenose dolphins, short-finned pilot and melon-headed whales, Fraser's dolphin, Risso's dolphin and pygmy killer whale) and two species of beaked whales, the sperm whale and dwarf sperm whale. Relative abundance indices were higher in the Marquesas than in the Societies both inshore (0.93 ind/km2 against 0.36 ind/km2) and offshore (0.28 ind/km2 against 0.14 ind/km2). Differences in remote-sensed primary production were equally important, the Marquesas waters featuring an annual average of 409 mgC.m−2 · day−1 and the Societies of only 171 mgC · m−2 · day−1. The presence of a narrow shelf around the Marquesas also accounted for differences in odontocete populations, in particular the delphinids.

scholarly journals Friendly Communities and Outdoor Spaces in Contexts of Urban Population Decline

Land ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 439
Author(s):  
M. Francisca Lima ◽  
Catharine Ward Thompson ◽  
Peter Aspinall
Keyword(s):  
Green Infrastructure ◽  
Urban Population ◽  
Social Connectedness ◽  
Population Decline ◽  
Urban Ecosystems ◽  
Capital City ◽  
Metropolitan Region ◽  
Small Scale ◽  
Public Parks ◽  
Outdoor Spaces

Urban population decline has been extensively described as a triggering factor for community segregation and fragmentation, as well as for land use vacancy and house/flat vacancies, resulting in rising interest in strategies of green infrastructure expansion aimed at citizens’ wellbeing and urban ecosystems. However, city-scaled green infrastructures can be formed by different typologies of outdoor spaces, providing diverse social affordances that can impact community cohesion and resilience differently. This study focuses on the relationship between preferences for particular outdoor space typologies and for community friendliness, under contexts of urban population decline as a migratory process. In the context of Lisbon, a European capital-city experiencing migration and immigration but also urban population shrinkage in some areas of its metropolitan region, the study used conjoint analysis to test participants’ preference for different attributes of their urban environment. The results showed a significant positive correlation, in the sample living in depopulating neighbourhoods, between preferences for friendlier communities and for outdoor spaces of an enclosed and protected character (r = 0.34), compared with no significant correlation in the studied non-depopulating neighbourhoods. These results do not deny the importance of public parks of wide dimensions as a strategy for shrinking cities’ green infrastructures but suggest that urban citizens living in depopulating neighbourhoods have a higher awareness of the importance of small-scale, enclosed outdoor/green spaces to give a stronger sense of social connectedness. This study contributes to the general literature on urban shrinkage by showing that these sensitive conditions can potentially change behaviour and use of public spaces in urban contexts.

Evaluation of three relative abundance indices for assessing dingo populations

1996 ◽  
Vol 23 (2) ◽  
pp. 197 ◽  
Author(s):  
L Allen ◽  
R Engeman ◽  
H Krupa
Keyword(s):  
Relative Abundance ◽  
Canis Lupus ◽  
Activity Index ◽  
Correlation Coefficients ◽  
Target Species ◽  
Wild Canids ◽  
Population Reduction ◽  
Abundance Indices ◽  
High Level ◽  
Level Of Agreement

Three methods of assessing relative abundance of wild canids were evaluated on a population of dingoes, Canis lupus dingo (Corbett), on a cattle station in south-westem Queensland. The tested indices relied on measurements of activity based on spoor. Two of the techniques attracted the target species to tracking stations through the use of a novel (fatty acid scent) or food-based (buried meat) attractant. The third index (activity) measured the number of dingo tracks crossing tracking stations placed at 1-km intervals along a road transect. All three indices had a high level of agreement for detecting differences in relative abundance, with correlation coefficients exceeding 0.85. When the stations were analysed in 1-km segments, the activity index proved the most sensitive, producing proportionally more positive responses than either of the other two indices irrespective of whether the tracking stations were assessed at 1-, 2-, 3- or 4-day intervals. Inconsistencies between indices existed, with the derived abundance indices not showing the anticipated reduction following population reduction. The effect of season and the interaction between dingo activity and index methodology are discussed.

scholarly journals Distinctive patterns and signals at major environmental events and collapse zone boundaries

2021 ◽  
Vol 193 (10) ◽  
Author(s):  
Melinda Pálinkás ◽  
Levente Hufnagel
Keyword(s):  
Climate Change ◽  
Cluster Analysis ◽  
Species Richness ◽  
Relative Abundance ◽  
Large Scale ◽  
Hierarchical Cluster ◽  
Small Scale ◽  
Total Abundance ◽  
First Order ◽  
Environmental Events

AbstractWe studied the patterns of pre-collapse communities, the small-scale and the large-scale signals of collapses, and the environmental events before the collapses using four paleoecological and one modern data series. We applied and evaluated eight indicators in our analysis: the relative abundance of species, hierarchical cluster analysis, principal component analysis, total abundance, species richness, standard deviation (without a rolling window), first-order autoregression, and the relative abundance of the dominant species. We investigated the signals at the probable collapse triggering unusual environmental events and at the collapse zone boundaries, respectively. We also distinguished between pulse and step environmental events to see what signals the indicators give at these two different types of events. Our results show that first-order autoregression is not a good environmental event indicator, but it can forecast or indicate the collapse zones in climate change. The rest of the indicators are more sensitive to the pulse events than to the step events. Step events during climate change might have an essential role in initiating collapses. These events probably push the communities with low resilience beyond a critical threshold, so it is crucial to detect them. Before collapses, the total abundance and the species richness increase, the relative abundance of the species decreases. The hierarchical cluster analysis and the relative abundance of species together designate the collapse zone boundaries. We suggest that small-scale signals should be involved in analyses because they are often earlier than large-scale signals.

scholarly journals Evaluation of Potential Overwinter Mortality of Age-0 Walleye and Appropriate Age-1 Sampling Gear

2018 ◽  
Vol 9 (1) ◽  
pp. 65-74 ◽  
Author(s):  
Jeffrey D. Grote ◽  
Melissa R. Wuellner ◽  
Brian G. Blackwell ◽  
David O. Lucchesi
Keyword(s):  
South Dakota ◽  
Body Condition ◽  
Relative Abundance ◽  
Coefficient Of Variation ◽  
First Year ◽  
Selective Mortality ◽  
Frequency Distributions ◽  
Abundance Indices ◽  
Overwinter Mortality ◽  
First Year Of Life

Abstract Potential recruitment of age-0 Walleye Sander vitreus to adults is often indexed by the relative abundance of age-0 individuals during their first summer or fall. However, relationships between age-0 and adult Walleye abundance are often weak or nonsignificant in many waters. Overwinter mortality during the first year of life has been hypothesized as an important limitation to Walleye recruitment in lakes, but limited evidence of such mortality exists, likely due to difficulties in sampling age-1 Walleye during spring. The objectives of this study were to: 1) compare results from nighttime electrofishing to index relative abundance of age-1 Walleyes with relative abundance indices of minifyke nets in four eastern South Dakota lakes; 2) determine whether size-selective mortality was occurring in those four lakes; and 3) if size-selective mortality was occurring in these lakes, determine whether that mortality was attributed to body condition. We sampled four natural lakes in eastern South Dakota 2 wk after ice-off in 2013 and 2014. Precision of nighttime electrofishing (coefficient of variation = 216.6) was greater than that estimated for minifyke nets (coefficient of variation = 338.5) across both years. We detected no differences in length-frequency distributions of collected spring age-1 Walleye between the two gears. Age-0 fall relative abundance indices from electrofishing were significantly greater (P < 0.01) than spring age-1 nighttime electrofishing indices of relative abundance at three of the four study lakes, indicating that overwinter mortality may occur at a substantial rate during the first year of life for Walleye in these systems. Quantile–quantile regression plots showed evidence of size-selective mortality in three of four lakes sampled. However, body condition of age-0 Walleye appeared to have little to no influence on overwinter mortality. Instead, we suggest that smaller-sized walleye may be more vulnerable to overwinter predation. Collectively, these results provide evidence of previously hypothesized overwinter mortality within the first year for Walleye and indicate possibilities for indexing potential adult recruitment of Walleye just after this critical period.

scholarly journals Grazing Altered the Pattern of Woody Plants and Shrub Encroachment in a Temperate Savanna Ecosystem

2019 ◽  
Vol 16 (3) ◽  
pp. 330 ◽  
Author(s):  
Zhiyong Zhang ◽  
Bo Zhang ◽  
Xiao Zhang ◽  
Xiaohui Yang ◽  
Zhongjie Shi ◽  
...  
Keyword(s):  
Spatial Patterns ◽  
Woody Plants ◽  
Large Scale ◽  
Population Decline ◽  
Grazing Pressure ◽  
Shrub Encroachment ◽  
Small Scale ◽  
Adult Trees ◽  
Aggregated Distribution ◽  
Grazing Pressures

Ulmus pumila-dominated temperate savanna is an important tree-grass complex ecosystem in the Otindag sand land, northern China. To date, few investigations have been undertaken on the spatial patterns and structure of this ecosystem and its driving factors under different grazing pressures. The objective of our study therefore is to explore whether grazing has affected the population structure/pattern of woody plants and shrub encroachment in a temperate savanna ecosystem. Results indicate that species richness and seedlings decreased with increasing grazing pressure. An increase in grazing pressure did not significantly affect adult-tree density, but it hindered the normal regeneration of U. pumila seedlings, further inducing population decline. U. pumila seedlings had a more significant aggregated distribution than juvenile or adult trees. The adult and juvenile trees had an aggregated distribution at the small scale and a random distribution at the large scale. Shrubs also showed a significant aggregated distribution. No clear effect on the spatial patterns of adult trees was observed; however, there was a noticeable effect for juveniles and seedlings under different grazing pressures. U. pumila seedlings had a positive association with their juveniles and Spiraea aquilegifolia, but a negative association with Caragana microphylla. Shrub encroachment occurred with decreasing grazing pressures. In conclusion, overgrazing led to the decline of U. pumila population, but the decrease in grazing pressure increased shrub encroachment in the temperate savanna ecosystem. Moderate grazing management may be a better way to enhance the stability of U. pumila population and reduce shrub encroachment.

scholarly journals The geometric mean of relative abundance indices: a biodiversity measure with a difference

Ecosphere ◽  
2011 ◽  
Vol 2 (9) ◽  
pp. art100 ◽  
Author(s):  
Stephen T. Buckland ◽  
Angelika C. Studeny ◽  
Anne E. Magurran ◽  
Janine B. Illian ◽  
Stuart E. Newson
Keyword(s):  
Relative Abundance ◽  
Geometric Mean ◽  
Abundance Indices

Seasonal variation of striped dolphins, fin- and sperm whales' abundance in the Ligurian Sea (Mediterranean Sea)

2007 ◽  
Vol 87 (1) ◽  
pp. 345-352 ◽  
Author(s):  
Sophie Laran ◽  
Violaine Drouot-Dulau
Keyword(s):  
Relative Abundance ◽  
Sperm Whale ◽  
Line Transect ◽  
Physeter Macrocephalus ◽  
Monthly Basis ◽  
Ligurian Sea ◽  
Stenella Coeruleoalba ◽  
Abundance Indices ◽  
Fin Whales ◽  
Acoustic Sampling

In order to investigate seasonal changes in cetacean relative abundance, a series of surveys were conducted between the French mainland and Corsica. From February 2001 to February 2004, thirty similar transects were conducted monthly, using the same dedicated boat and a consistent sampling protocol, including visual observation and passive acoustic sampling. A total effort of 5759 km was sampled, conducted at the same speed and in good sighting conditions. Relative abundances of striped dolphins (Stenella coeruleoalba) and fin whales (Balaenoptera physalus) were determined using standard line-transect methodology. The relative abundance of striped dolphins peaked in May and September (>1.3×10-2 ind.km-1), while a consistent minimum value (<0.6×10-2 ind.km-1) was obtained from December to April. A maximum relative abundance of fin whales occurred in August with 5.6×10-2 ind.km-1 and decreased to almost zero from November to January. For sperm whale (Physeter macrocephalus), a long diver species, frequency and abundance indices were determined using acoustic sampling. The highest acoustic relative abundance was observed from August to October, with more than 2×10-2 ind.km-1. Environmental parameters (sea surface temperature and chlorophyll) were computed for the sampling area from remote sensing imagery and pooled on a monthly basis, to correlate with relative abundance indices of the three species.

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