scholarly journals Connectivity of nekton assemblages along artificial reefs and adjacent waters in Haizhou Bay

2021 ◽  
Author(s):  
Shike Gao ◽  
Bin Xie ◽  
Wenwen Yu ◽  
Chengyu Huang ◽  
Xiao Zhang ◽  
...  
Keyword(s):  
Habitat Preferences ◽  
Artificial Reef ◽  
Artificial Reefs ◽  
Natural Area ◽  
Density Estimates ◽  
Community Patterns ◽  
Haizhou Bay ◽  
Kernel Density Estimates ◽  
Aquaculture Area ◽  
And Diffusion

Abstract The successful construction of marine protected areas (MPAs) in temperate waters largely depends on our understanding of the distribution and coexistence of organisms with varying habitat preferences, which helps us to better understand the community patterns mediated by connectivity in coastal areas. This study was conducted to examine the connectivity of nekton assemblages in artificial reefs and adjacent waters, which included five habitats: the artificial reef area (AR), aquaculture area (AA), natural area (NA), estuary area (EA) and comprehensive effect area (CEA), in Haizhou Bay in October 2020. Analysis of variance (ANOVA) showed that there were significant differences in the characteristics and abundances of nekton in each habitat (P<0.05). Approximately 38.2% of the individuals were found in at least three habitats, and very few species were present in only a single habitat. Several highly abundant nekton species were selected according to the kernel density estimates (KDEs), and their body lengths varied gradationally among habitats, potentially indicating migration and diffusion during their life history. The results showed that artificial reefs and adjacent waters in Haizhou Bay are related by similar nekton assemblages and ontogenetic variation. Finally, this study has implications for the conservation and monitoring of nekton assemblages in artificial reefs and adjacent waters, highlighting that the principle of connectivity should be taken into consideration in the design of MPAs and MPA networks that can be applied in different stages of implementation and in different combinations of scenarios.

Nesting habitat of the broad-shelled turtle (Chelodina expansa)

2018 ◽  
Vol 66 (1) ◽  
pp. 4 ◽  
Author(s):  
Kristen Petrov ◽  
Heidi Stricker ◽  
James U. Van Dyke ◽  
Graham Stockfeld ◽  
Peter West ◽  
...  
Keyword(s):  
Habitat Preferences ◽  
Kernel Density ◽  
Life History Stage ◽  
Nesting Habitat ◽  
Density Estimates ◽  
Nest Sites ◽  
Kernel Density Estimates ◽  
Turtle Conservation ◽  
Murray River ◽  
Nesting Preferences

Turtles have persisted for over 220 million years, despite facing threats at every life-history stage. In Australia, nest predation by introduced foxes has driven severe declines in some populations. Our project quantified the nesting habitat of the endangered broad-shelled turtle (Chelodina expansa) to facilitate protection of critical nesting grounds. We determined the nesting preferences of C. expansa at five distinct wetlands on the Murray River from 2011 to 2014. We identified environmental variables associated with nest sites in different habitats and compared those at nests and non-nest sites to determine nesting preferences. Kernel density estimates were used to identify important nesting grounds. Our study has important implications for conservation of C. expansa. Habitat preferences for nest sites of C. expansa are predictable both within and across sites, with females preferring to nest ~50 m from shore (~4 m elevation), in open habitat with little vegetation. Based on these habitat preferences, kernel density estimates showed that C. expansa may select the same nesting beaches in subsequent years. Fox depredation of nests (and nesting adults) drives turtle declines in Australia, so identifying nesting areas for protection is a first step in turtle conservation.

scholarly journals Foraging range and habitat use by Cape Vulture Gyps coprotheres from the Msikaba colony, Eastern Cape province, South Africa

Koedoe ◽  
2015 ◽  
Vol 57 (1) ◽  
Author(s):  
Morgan B. Pfeiffer ◽  
Jan A. Venter ◽  
Colleen T. Downs
Keyword(s):  
South Africa ◽  
Protected Areas ◽  
Breeding Season ◽  
Movement Ecology ◽  
Kernel Density ◽  
Eastern Cape Province ◽  
Eastern Cape ◽  
Convex Polygons ◽  
Density Estimates ◽  
Kernel Density Estimates

Despite the extent of subsistence farmland in Africa, little is known about endangered species that persist within them. The Cape Vulture (Gyps coprotheres) is regionally endangered in southern Africa and at least 20% of the population breeds in the subsistence farmland area previously known as the Transkei in the Eastern Cape province of South Africa. To understand their movement ecology, adult Cape Vultures (n = 9) were captured and fitted with global positioning system/global system for mobile transmitters. Minimum convex polygons (MCPs),and 99% and 50% kernel density estimates (KDEs) were calculated for the breeding and non breeding seasons of the Cape Vulture. Land use maps were constructed for each 99% KDE and vulture locations were overlaid. During the non-breeding season, ranges were slightly larger(mean [± SE] MCP = 16 887 km2 ± 366 km2) than the breeding season (MCP = 14 707 km2 ± 2155 km2). Breeding and non-breeding season MCPs overlapped by a total of 92%. Kernel density estimates showed seasonal variability. During the breeding season, Cape Vultures used subsistence farmland, natural woodland and protected areas more than expected. In the non-breeding season, vultures used natural woodland and subsistence farmland more than expected, and protected areas less than expected. In both seasons, human-altered landscapes were used less, except for subsistence farmland.Conservation implications: These results highlight the importance of subsistence farm land to the survival of the Cape Vulture. Efforts should be made to minimise potential threats to vultures in the core areas outlined, through outreach programmes and mitigation measures.The conservation buffer of 40 km around Cape Vulture breeding colonies should be increased to 50 km.

scholarly journals REDUCTION OF WAVE OVERTOPPING RATE BY THE USE OF ARTIFICIAL REEFS

1988 ◽  
Vol 1 (21) ◽  
pp. 23
Author(s):  
Toru Sawaragi ◽  
Ichiro Deguchi ◽  
San-Kil Park
Keyword(s):  
Wave Breaking ◽  
Artificial Reef ◽  
Numerical Procedure ◽  
Artificial Reefs ◽  
Irregular Waves ◽  
Analysis Method ◽  
Wave Analysis ◽  
Wave Overtopping ◽  
Unidirectional Flow ◽  
Individual Wave

A wave overtopping rate from a sea dike of various toe depths is formulated based on a weir model in an unidirectional flow. To evaluated the wave overtopping rate from a seadike on an artificial reef by the weir model, a numerical procedure for predicting wave transformations including the effect of forced wave breaking on the reef is constructed. After confirming the applicability of the model through experiments with regular and irregular waves, the effect of artificial reef on wave overtopping is discussed. So-called individual wave analysis method is shown to he applicable to the wave overtopping caused by irregular waves.

scholarly journals Gender differences in income distributions in Poland

2020 ◽  
Vol 63 (3) ◽  
pp. 210-232
Author(s):  
Julia Włodarczyk ◽  
Keyword(s):  
Income Inequality ◽  
Descriptive Analysis ◽  
Theil Index ◽  
Median Income ◽  
Quantile Regressions ◽  
Density Estimates ◽  
Income Distributions ◽  
The Past ◽  
Social Monitoring ◽  
Kernel Density Estimates

The paper presents results of a descriptive analysis of income distributions as well as top income inequality among women and men in Poland. The analysis is based on the dataset provided by the Council for Social Monitoring (2019). Throughout 2003–2015 their panel survey included, for example, a question on individual net monthly income in the past three months. In order to reduce differences associated with the age of entering and exiting the labour market on declared income levels (especially pensions), the calculations include only women and men aged 25–60 years. The analysis of income distributions of women and men in Poland is based on standard measures such as mean income, median income and related measures, as well as the Gini coefficient, Theil index and entropy index. It is supplemented by kernel density estimates and results of simultaneous quantile regressions that demonstrate differences between women and men across income groups. The analysis of top income inequality includes comparisons of subsamples consisting of top 3% earners in each group. The share of women in the top percentiles is then calculated and discussed. The analysis shows different dynamics related to the incomes of women and men, which provides support for including business cycle considerations in the analysis of income inequalities and their gender aspects.

Dispersal of yellowtail kingfish (Seriola lalandi) from a coastal embayment following a recreational fisheries enhancement stocking program: attempts to integrate aquaculture and habitat-based initiatives

2021 ◽  
Author(s):  
Alistair Becker ◽  
Michael B Lowry ◽  
D Stewart Fielder ◽  
Matthew D Taylor
Keyword(s):  
Artificial Reef ◽  
Artificial Reefs ◽  
Recreational Fisheries ◽  
Dispersal Patterns ◽  
The North ◽  
Sea Ranching ◽  
In The Wild ◽  
Yellowtail Kingfish ◽  
Seriola Lalandi ◽  
Fisheries Enhancement

Fisheries enhancement initiatives including marine stocking and artificial reef deployments are becoming increasingly common in many parts of the world. Combining the two by releasing hatchery reared fish onto artificial reefs is used in sea-ranching operations but is an approach rarely adopted for recreational fisheries. Yellowtail kingfish (Seriola lalandi) form a valuable recreational fishery in Australia and in 2018 a pilot stocking program was initiated to enhance this fishery. Fish were released onto estuarine artificial reefs in Botany Bay to evaluate if estuarine artificial reefs are suitable release habitat for juvenile yellowtail kingfish and to monitor their dispersal patterns using acoustic telemetry and a tag-recapture program. Both approaches showed similar patterns, indicating juvenile yellowtail kingfish rapidly dispersed from the release location and can travel at least 60 km during their first weeks in the wild. Twenty percent of the acoustically tagged fish entered nearby estuaries to the north and south and tagged fish were also recaptured in these estuaries, indicating that the estuaries provide habitat for juveniles. There was little interaction between stocked fish and two large coastal artificial reefs positioned near Botany Bay. Stocked yellowtail kingfish will likely disperse rapidly from release locations which is consistent with their pelagic life history. While this may present challenges to fisheries managers, increasing release numbers to maintain stocking densities over a broader area may provide a solution. Future releases of fish on coastal natural and artificial reefs are an important next step in refining stocking practices for this species and will help further identify key juvenile habitats.

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