scholarly journals Evidence for rapid avoidance of rockfish habitat under reduced quota and comprehensive at-sea monitoring in the British Columbia Pacific halibut fishery

2020 ◽  
Vol 77 (8) ◽  
pp. 1409-1420
Author(s):  
Robyn E. Forrest ◽  
Ian J. Stewart ◽  
Cole C. Monnahan ◽  
Katherine H. Bannar-Martin ◽  
Lisa C. Lacko
Keyword(s):  
British Columbia ◽  
Spatial Clustering ◽  
Clustering Methods ◽  
Quota System ◽  
Encounter Rates ◽  
System A ◽  
Pacific Halibut ◽  
Hippoglossus Stenolepis ◽  
Footprint Area ◽  
Management Changes

The British Columbia longline fishery for Pacific halibut (Hippoglossus stenolepis) has experienced important recent management changes, including the introduction of comprehensive electronic catch monitoring on all vessels; an integrated transferable quota system; a reduction in Pacific halibut quotas; and, beginning in 2016, sharp decreases in quota for yelloweye rockfish (Sebastes ruberrimus, an incidentally caught species). We describe this fishery before integration, after integration, and after the yelloweye rockfish quota reduction using spatial clustering methods to define discrete fishing opportunities. We calculate the relative utilization of these fishing opportunities and their overlap with areas with high encounter rates of yelloweye rockfish during each of the three periods. The spatial footprint (area fished) increased before integration, then decreased after integration. Each period showed shifts in utilization among four large fishing areas. Immediately after the reductions in yelloweye rockfish quota, fishing opportunities with high encounter rates of yelloweye rockfish had significantly lower utilization than areas with low encounter rates, implying rapid avoidance behaviour.

Environmental Effects on the Distributions of Groundfish in Hecate Strait, British Columbia

1994 ◽  
Vol 51 (6) ◽  
pp. 1401-1409 ◽  
Author(s):  
R. Ian Perry ◽  
Max Stocker ◽  
Jeff Fargo
Keyword(s):  
British Columbia ◽  
Early Summer ◽  
Sediment Type ◽  
Depth Range ◽  
Pacific Halibut ◽  
Gadus Macrocephalus ◽  
Hippoglossus Stenolepis ◽  
By Catch ◽  
Groundfish Fishery ◽  
Variable Condition

Hecate Strait, British Columbia, is an area of variable topography with a variety of bottom habitats, which supports an important mixed-species groundfish fishery. A previous analysis identified three characteristic assemblages of groundfish species. In the present study, we identify relationships between the dominant species of these assemblages and environmental conditions in early summer 1989 and 1991: bottom type and depth (invariant conditions) and temperature (a variable condition). Three categories of species were identified: (i) those consistently associated with particular depths and temperatures between years, (ii) those with variable depth and temperature associations, and (iii) those with no apparent relationships to depth, temperature, or sediment type. Category (i) was dominated by flatfishes and could be further separated into groups associated with deep and cool, shallow and warm, and intermediate depth and temperature conditions. Category (ii) included roundfishes plus Pacific halibut (Hippoglossus stenolepis) and were widely distributed. At least one species (Pacific cod (Gadus macrocephalus)) tended to maintain a particular temperature range while changing its depth range between years. Identification of significant associations between fish species and habitat conditions is the first step towards incorporating environmental information into survey abundance indices and reducing by-catch problems.

scholarly journals Applicability Evaluation of Several Spatial Clustering Methods in Spatiotemporal Data Mining of Floating Car Trajectory

2021 ◽  
Vol 10 (3) ◽  
pp. 161
Author(s):  
Hao-xuan Chen ◽  
Fei Tao ◽  
Pei-long Ma ◽  
Li-na Gao ◽  
Tong Zhou
Keyword(s):  
Spatial Analysis ◽  
Spatial Clustering ◽  
Heat Index ◽  
Operating Efficiency ◽  
Clustering Methods ◽  
Clustering Method ◽  
Trajectory Mining ◽  
Density Peaks ◽  
Analysis Methods ◽  
Taxi Trajectory

Spatial analysis is an important means of mining floating car trajectory information, and clustering method and density analysis are common methods among them. The choice of the clustering method affects the accuracy and time efficiency of the analysis results. Therefore, clarifying the principles and characteristics of each method is the primary prerequisite for problem solving. Taking four representative spatial analysis methods—KMeans, Density-Based Spatial Clustering of Applications with Noise (DBSCAN), Clustering by Fast Search and Find of Density Peaks (CFSFDP), and Kernel Density Estimation (KDE)—as examples, combined with the hotspot spatiotemporal mining problem of taxi trajectory, through quantitative analysis and experimental verification, it is found that DBSCAN and KDE algorithms have strong hotspot discovery capabilities, but the heat regions’ shape of DBSCAN is found to be relatively more robust. DBSCAN and CFSFDP can achieve high spatial accuracy in calculating the entrance and exit position of a Point of Interest (POI). KDE and DBSCAN are more suitable for the classification of heat index. When the dataset scale is similar, KMeans has the highest operating efficiency, while CFSFDP and KDE are inferior. This paper resolves to a certain extent the lack of scientific basis for selecting spatial analysis methods in current research. The conclusions drawn in this paper can provide technical support and act as a reference for the selection of methods to solve the taxi trajectory mining problem.

scholarly journals Snake mortality and cover board effectiveness along exclusion fencing in British Columbia, Canada

2018 ◽  
Vol 132 (1) ◽  
pp. 30-35 ◽  
Author(s):  
Dana M. Eye ◽  
Jared R. Maida ◽  
Owain M. McKibbin ◽  
Karl W. Larsen ◽  
Christine A. Bishop
Keyword(s):  
British Columbia ◽  
Great Basin ◽  
Natural Vegetation ◽  
Board Effectiveness ◽  
Encounter Rates ◽  
Snake Species ◽  
Coluber Constrictor ◽  
Northern Pacific

We report on snake mortalities along exclusion fencing in southern British Columbia, showing Western Yellow-bellied Racer (Coluber constrictor mormon) deaths were disproportionately higher than our encounter rates with the species within the snake community. This suggests racers were susceptible to fence mortality more so than Northern Pacific Rattlesnakes (Crotalus o. oreganus) or Great Basin Gophersnakes (Pituouphis catenifer deserticola). Datalogger recordings revealed temperatures under cover boards were well above the tolerable temperatures of the three snake species, although the boards appeared to temper ambient heat more efficiently than natural vegetation. We caution that the effects of fencing and cover boards may vary across ecosystems and snake species.

Abstract MP41: Comparisons of Built Environment Characteristics Inside and Outside of Spatial Clusters of Physical Activity and Obesity in Older U.S. Women

Circulation ◽  
2013 ◽  
Vol 127 (suppl_12) ◽  
Author(s):  
Kosuke Tamura ◽  
Robin C Puett ◽  
Jaime E Hart ◽  
Heather A Starnes ◽  
Francine Laden ◽  
...  
Keyword(s):  
Physical Activity ◽  
Built Environment ◽  
Spatial Clustering ◽  
Health Study ◽  
Clustering Methods ◽  
Spatial Clusters ◽  
Spatial Scan Statistic ◽  
Complex Picture ◽  
Intersection Density ◽  
Study Participants

Introduction: Spatial clustering methods have been applied to cancer for over a decade. These methods have been used in studies on physical activity (PA) and obesity. One recent study examined differences in built environment attributes inside and outside PA clusters. We tested two hypotheses: 1) PA and obesity would spatially cluster in older women; and 2) built environment attributes typically related to higher walkability would be found in high PA clusters, while attributes related to lower walkability would appear in high obesity clusters. Methods: We used data from 22,589 Nurses’ Health Study participants (mean age = 69.9 ± 6.8y) in California, Massachusetts, and Pennsylvania. Two outcomes were examined: meeting PA guidelines via self-reported walking (≥ 500 MET-min/week) and obesity (BMI ≥ 30.0). Objective built environment variables were created: population and intersection density, diversity of facilities, and facility density. We used a spatial scan statistic to detect clusters (i.e., areas with high or low rates) of the two outcomes. Built environment attributes were compared inside and outside clusters. Results: Six spatial clusters of PA were found in California and Massachusetts. Two obesity clusters were found in Pennsylvania. Overall there were significant differences (p<0.05) in population and intersection density, and diversity and density of facilities inside and outside clusters. In some cases, built environment attributes related to higher walkability appeared in high PA clusters, while in other PA clusters we did not find this pattern. Differences in built environment attributes inside and outside obesity clusters showed inconsistent patterns. Conclusion: Although PA and obesity clusters emerged, the comparison of built environment attributes inside and outside clusters revealed a complex picture not fully consistent with existing literature. Further examination of PA and obesity clusters in older adults should include other built environment factors that may be related to these outcomes.

scholarly journals Assessing the relationship between diet and size-at-age in Pacific halibut (Hippoglossus stenolepis) using δ13C and δ15N analysis

2019 ◽  
Vol 76 (12) ◽  
pp. 2326-2331
Author(s):  
Nathan Wolf ◽  
Sarah R. Webster ◽  
Jeffery M. Welker ◽  
Bradley P. Harris
Keyword(s):  
North Pacific Ocean ◽  
Isotope Analysis ◽  
Δ13c And Δ15n ◽  
Pacific Halibut ◽  
Hippoglossus Stenolepis ◽  
Dietary Strategy ◽  
Mean Size ◽  
Intermediate Size ◽  
Size At Age ◽  
The Relationship

The ecological mechanisms driving an observed decline in the mean size-at-age of adult Pacific halibut (Hippoglossus stenolepis) in the eastern North Pacific Ocean have yet to be defined. Here, we present the results of a study designed to investigate the relationship between one potential mechanism — diet — and size-at-age using carbon and nitrogen stable isotope analysis. Our results indicate significant differences in the skeletal muscle δ13C and δ15N values between size-at-age categories for each sex, with larger-size-at-age fish consuming diets with higher δ15N values, indicating higher trophic level feeding. Analysis of Bayesian standard ellipse areas showed that for females, intermediate size-at-age categories have the largest dietary range. For males, the largest dietary range was observed in the largest size-at-age category. Our results suggest a size-based stratification in dietary strategy for Pacific halibut with implications for observed declines in size-at-age.

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