Habitat requirements and spawning strategy of an estuarine-dependent fish, Percalates colonorum

2014 ◽  
Vol 65 (3) ◽  
pp. 218 ◽  
Author(s):  
Dylan E. van der Meulen ◽  
Chris T. Walsh ◽  
Matthew D. Taylor ◽  
Charles A. Gray
Keyword(s):  
Deep Water ◽  
Habitat Requirements ◽  
Fine Scale ◽  
Spatial And Temporal Patterns ◽  
Spawning Activity ◽  
Eastern Australia ◽  
Close Proximity ◽  
Prey Items ◽  
Spawning Habitats ◽  
Timing Of Spawning

Determining the links among estuarine hydrography, habitat and spawning of estuarine-dependent fish is essential for understanding reproductive dynamics, recruitment processes and directing conservation efforts. Acoustic tracking was used to evaluate fine-scale spatial and temporal patterns in spawning activity of Percalates colonorum (estuary perch) within the Shoalhaven River, south-eastern Australia. Plankton tows were used to determine the timing of spawning events. Tagged P. colonorum exhibited movements restricted to areas of structurally complex large wooden debris and a concrete ferry landing. Egg counts confirmed that spawning events coincided with adult aggregations, whereas egg abundances peaked at night during the first 2 h of the run-out tide. We postulate that spawning and recruitment success of P. colonorum is attributable to its selective spawning habitats that are (1) structurally complex to provide refuge and protection from predation, as well as congregate prey items, (2) adjacent to deep water of high velocities to maximise egg dispersal and (3) in close proximity to river entrance to facilitate coastal dispersal of eggs and inter-estuarine connectivity of larvae.

Conodont Biostratigraphy of Ordovician Deep-Water Turbiditic Sequences in Eastern Australia—A New Biozonal Scheme for the Open-Sea Realm

2021 ◽  
Vol 32 (3) ◽  
pp. 486-500
Author(s):  
Yong Yi Zhen ◽  
Ian G. Percival ◽  
Phil Gilmore ◽  
Jodie Rutledge ◽  
Liann Deyssing
Keyword(s):  
Deep Water ◽  
Conodont Biostratigraphy ◽  
Open Sea ◽  
Eastern Australia

Effective Power and Speed Loss of Underwater Vehicles in Close Proximity to Regular Waves

2017 ◽  
Author(s):  
Stefan Daum ◽  
Martin Greve ◽  
Renato Skejic
Keyword(s):  
Free Surface ◽  
Deep Water ◽  
Water Waves ◽  
Underwater Vehicles ◽  
Total Resistance ◽  
Wave Load ◽  
Regular Waves ◽  
Effective Power ◽  
Close Proximity ◽  
Deep Water Waves

The present study is focused on performance issues of underwater vehicles near the free surface and gives insight into the analysis of a speed loss in regular deep water waves. Predictions of the speed loss are based on the evaluation of the total resistance and effective power in calm water and preselected regular wave fields w.r.t. the non-dimensional wave to body length ratio. It has been assumed that the water is sufficiently deep and that the vehicle is operating in a range of small to moderate Froude numbers by moving forward on a straight-line course with a defined encounter angle of incident regular waves. A modified version of the Doctors & Days [1] method as presented in Skejic and Jullumstrø [2] is used for the determination of the total resistance and consequently the effective power. In particular, the wave-making resistance is estimated by using different approaches covering simplified methods, i.e. Michell’s thin ship theory with the inclusion of viscosity effects Tuck [3] and Lazauskas [4] as well as boundary element methods, i.e. 3D Rankine source calculations according to Hess and Smith [5]. These methods are based on the linear potential fluid flow and are compared to fully viscous finite volume methods for selected geometries. The wave resistance models are verified and validated by published data of a prolate spheroid and one appropriate axisymmetric submarine model. Added resistance in regular deep water waves is obtained through evaluation of the surge mean second-order wave load. For this purpose, two different theoretical models based on potential flow theory are used: Loukakis and Sclavounos [6] and Salvesen et. al. [7]. The considered theories cover the whole range of important wavelengths for an underwater vehicle advancing in close proximity to the free surface. Comparisons between the outlined wave load theories and available theoretical and experimental data were carried out for a submerged submarine and a horizontal cylinder. Finally, the effective power and speed loss are discussed from a submarine operational point of view where the mentioned parameters directly influence mission requirements in a seaway. All presented results are carried out from the perspective of accuracy and efficiency within common engineering practice. By concluding current investigations in regular waves an outlook will be drawn to the application of advancing underwater vehicles in more realistic sea conditions.

Plasticity in sexual size dimorphism and Rensch’s rule in Mediterranean blennies (Blenniidae)

2008 ◽  
Vol 86 (10) ◽  
pp. 1173-1178 ◽  
Author(s):  
W. Lengkeek ◽  
K. Didderen ◽  
I. M. Côté ◽  
E. M. van der Zee ◽  
R. C. Snoek ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Sexual Size Dimorphism ◽  
Fine Scale ◽  
Evolutionary Patterns ◽  
Rensch’S Rule ◽  
Size Dimorphism ◽  
Rensch's Rule ◽  
Close Proximity ◽  
Species Comparisons ◽  
Aidablennius Sphynx

Comparative analyses of sexual size dimorphism (SSD) across species have led to the discovery of Rensch’s rule. This rule states that SSD increases with body size when males are the largest sex, but decreases with increasing size when females are larger. Within-species comparisons of SSD in fish are rare, yet these may be a valuable tool to investigate evolutionary patterns on a fine scale. This study compares SSD among closely related populations of three species of Mediterranean blennies (Blenniidae): Microlipophrys canevae (Vinciguerra, 1880), Parablennius incognitus (Bath 1968), and Aidablennius sphynx (Valenciennes, 1836). SSD varied more among populations than among species and Rensch’s rule was confirmed within two species. It is not likely that the variation among populations in SSD mirrors genetic variation, as many of the populations were in close proximity of one another, with a high potential for genetic exchange. This study complements larger scale analyses of other taxa and demonstrates the fine scale on which evolutionary processes responsible for Rensch’s rule may be operating.

scholarly journals Fine-scale dietary changes between the breeding and non-breeding diet of a resident seabird

2015 ◽  
Vol 2 (4) ◽  
pp. 140291 ◽  
Author(s):  
Nicole D. Kowalczyk ◽  
André Chiaradia ◽  
Tiana J. Preston ◽  
Richard D. Reina
Keyword(s):  
Prey Availability ◽  
Juvenile Fish ◽  
Fish Communities ◽  
Small Range ◽  
Isotopic Niche ◽  
Fine Scale ◽  
Close Proximity ◽  
Isotope Analyses ◽  
Little Penguin ◽  
Foraging Ranges

Unlike migratory seabirds with wide foraging ranges, resident seabirds forage in a relatively small range year-round and are thus particularly vulnerable to local shifts in prey availability. In order to manage their populations effectively, it is necessary to identify their key prey across and within years. Here, stomach content and stable isotope analyses were used to reconstruct the diet and isotopic niche of the little penguin ( Eudyptula minor ). Across years, the diet of penguins was dominated by anchovy ( Engraulis australis ). Within years, during winter, penguins were consistently enriched in δ 15 N and δ 13 C levels relative to pre-moult penguins. This was probably due to their increased reliance on juvenile anchovies, which dominate prey biomass in winter months. Following winter and during breeding, the δ 13 C values of penguins declined. We suggest this subtle shift was in response to the increased consumption of prey that enter the bay from offshore regions to spawn. Our findings highlight that penguins have access to both juvenile fish communities and spawning migrants across the year, enabling these seabirds to remain in close proximity to their colony. However, annual fluctuations in penguin isotopic niche suggest that the recruitment success and abundance of fish communities fluctuate dramatically between years. As such, the continued monitoring of penguin diet will be central to their ongoing management.

scholarly journals Unique fine scale village spatial-temporal distributions of Anopheles farauti differ by physiological state and sex

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Edgar J. M. Pollard ◽  
Tanya L. Russell ◽  
Allan Apairamo ◽  
Thomas R. Burkot
Keyword(s):  
Solomon Island ◽  
Solomon Islands ◽  
Physiological State ◽  
Fine Scale ◽  
Peak Activity ◽  
Spatial And Temporal Patterns ◽  
Anopheles Farauti ◽  
Mosquito Collection ◽  
Human Landing ◽  
Gravid Females

Abstract Background The ecology of many mosquitoes, including Anopheles farauti, the dominant malaria vector in the southwest Pacific including the Solomon Islands, remains inadequately understood. Studies to map fine scale vector distributions are biased when trapping techniques use lures that will influence the natural movements of mosquitoes by attracting them to traps. However, passive collection methods allow the detailed natural distributions of vector populations by sex and physiological states to be revealed. Methods The barrier screen, a passive mosquito collection method along with human landing catches were used to record An. farauti distributions over time and space in two Solomon Island villages from May 2016 to July 2017. Results Temporal and spatial distributions of over 15,000 mosquitoes, including males as well as unfed, host seeking, blood-fed, non-blood fed and gravid females were mapped. These spatial and temporal patterns varied by species, sex and physiological state. Sugar-fed An. farauti were mostly collected between 10–20 m away from houses with peak activity from 18:00 to 19:00 h. Male An. farauti were mostly collected greater than 20 m from houses with peak activity from 19:00 to 20:00 h. Conclusions Anopheles farauti subpopulations, as defined by physiological state and sex, are heterogeneously distributed in Solomon Island villages. Understanding the basis for these observed heterogeneities will lead to more accurate surveillance of mosquitoes and will enable spatial targeting of interventions for greater efficiency and effectiveness of vector control.

scholarly journals Contrasting effects of mangroves and armoured shorelines on fish assemblages in tropical estuarine seascapes

2019 ◽  
Vol 76 (4) ◽  
pp. 1052-1061 ◽  
Author(s):  
Christopher J Henderson ◽  
Ben L Gilby ◽  
Thomas A Schlacher ◽  
Rod M Connolly ◽  
Marcus Sheaves ◽  
...  
Keyword(s):  
Fish Assemblages ◽  
Urban Expansion ◽  
Ecological Impacts ◽  
Spatial Context ◽  
Fish Diversity ◽  
Mangrove Forests ◽  
Habitat Types ◽  
Tropical Estuarine ◽  
Eastern Australia ◽  
Close Proximity

Abstract Coastal seascapes are composed of a diversity of habitats that are linked in space and time by the movement of organisms. The context and configuration of coastal ecosystems shapes many important properties of animal assemblages, but potential seascape effects of natural and artificial habitats on nearby habitats are typically considered in isolation. We test whether, and how, the seascape context of natural and urban habitats modified fish assemblages across estuaries. Fish were sampled with underwater videos in five habitat types (mangroves, rock bars, log snags, unvegetated sediments, armoured shorelines) in 17 estuaries in eastern Australia. Different habitats supported distinct fish assemblages, but the spatial context of mangroves and armoured shorelines had pervasive ecological effects that extended across entire estuaries. In most estuarine habitats, fish diversity and abundance was greatest when they were in close proximity of mangroves, and decreased due to the proximity of armoured shorelines. Many cities are centred on estuaries, and urban expansion is often associated with the fragmentation of mangrove forests. Our findings emphasize that these transformations of urban estuarine landscapes are likely to propagate to broader ecological impacts detectable in multiple habitats beyond mangrove forests.

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