Movements of the western rock lobster (Panulirus cygnus) within shallow coastal waters using acoustic telemetry

2008 ◽  
Vol 59 (7) ◽  
pp. 603 ◽  
Author(s):  
L. D. MacArthur ◽  
R. C. Babcock ◽  
G. A. Hyndes
Keyword(s):  
Coastal Waters ◽  
Small Proportion ◽  
Acoustic Telemetry ◽  
Large Scale ◽  
Laboratory Experiments ◽  
Movement Patterns ◽  
Field Observations ◽  
Rock Lobster ◽  
Panulirus Cygnus ◽  
Shallow Coastal Waters

Understanding the residency and movement patterns of major consumers, such as lobsters, in coastal waters is important for the management of coastal habitats and their fisheries. In the present study, we tagged 34 Panulirus cygnus with acoustic transmitters on a shallow coastal reef in south-western Australia and monitored their movements using fixed and manual receivers between November and May 2005–2006 and 2006–2007. We determined the proportion of ‘white’ (migratory-phase) lobsters emigrating from the reef between November and January and also characterised the large-scale movements of ‘red’ (residential-phase) and white lobsters. We undertook tank experiments to determine the effect of tagging and handling on P. cygnus behaviour. Counter to our expectation, 50% of white lobsters were detected on the reef after the migration period, whereas only a small proportion (13.6%) of white lobsters were tracked leaving the reef and only one individual displayed directional offshore movement. This limited movement indicates that coastal no-take zones may build up legal-sized 4–5+ year old lobsters because many of these are likely to remain resident over the migration season. Laboratory experiments and field observations suggest that tagging and handling affect lobster behaviour and movement for a few days post tagging, potentially confounding conclusions on dispersal and movement patterns in some studies.

scholarly journals The orientation and migratory dynamics of the western rock lobster, Panulirus cygnus, in Western Australia

2014 ◽  
Vol 71 (5) ◽  
pp. 1052-1063 ◽  
Author(s):  
Simon de Lestang
Keyword(s):  
Large Scale ◽  
Economic Benefits ◽  
Rock Lobster ◽  
Commercial Catch ◽  
Breeding Grounds ◽  
Mean Size ◽  
Catch Rates ◽  
Panulirus Cygnus ◽  
The Impact ◽  
Oceanic Currents

Abstract Large-scale migrations are known to occur in numerous species, and in the case of the Western Rock Lobster, Panulirus cygnus, result in juveniles moving from nursery areas into deeper offshore breeding grounds. In 2008 the Western Rock Lobster fishery reduced harvest rates to increase legal and spawning biomass throughout the fishery, which also allowed greater numbers of lobsters to migrate. Increased lobster migration could potentially reduce biomass in some areas, thus adversely impacting commercial catch rates. Over 20 000 tag–recaptured lobsters were analysed to determine the dynamics underlying migration in this species and to assess the impact reduced harvest rates may have had on catches. This study showed that P. cygnus migration was associated with body size and water depth, and that magnetism and oceanic currents appear to be the most likely guideposts used for orientation. Size at migration varied in a constant fashion along the coast, being larger towards the southern end of the fishery and smallest at the offshore Abrolhos Islands. During the migration period, up to 50% of lobsters at their mean size of migration moved from coastal areas out towards deeper waters (>40 m), whereas <15% of those in deeper water at the same size moved significant distances northward. This behaviour appears to be contranatant, counteracting the downstream redistribution of larvae after their 9–11 month larval life. Reduced harvest rates and catches being focussed onto higher valued sedentary lobsters have allowed more lobsters to migrate. However, the numbers moving between management areas are relatively small, with the biological and economic benefits of fishing at a reduced exploitation rate outweighing losses to catches.

Prey preference and the consumption of sea urchins and juvenile abalone by captive rock lobsters (Jasus lalandii )

2001 ◽  
Vol 52 (5) ◽  
pp. 773 ◽  
Author(s):  
S. Mayfield ◽  
E. de Beer ◽  
G. M. Branch
Keyword(s):  
South African ◽  
Laboratory Experiments ◽  
Carapace Length ◽  
Consumption Rate ◽  
Prey Species ◽  
Sea Urchins ◽  
Fishing Ground ◽  
Field Observations ◽  
Rock Lobster ◽  
Fishing Area

Recent studies on the diet of the South African rock lobster (Jasus lalandii) have shown an increase in the consumption of sea urchins in certain areas relative to earlier assessments. Concurrent ecological surveys have demonstrated the dependence of juvenile abalone on urchins for their survival, and a radical increase in the abundance of lobsters in the area that is the main abalone fishing ground. This paper describes laboratory experiments on the consumption of urchins by lobsters, and the preferences for different prey species. Small lobsters (<68 mm carapace length) ate no urchins. Larger lobsters ate urchins of all sizes, although small urchins were preferred. The consumption rate was easily sufficient for the lobsters to have caused the documented disappearance of urchins (and juvenile abalone) in the main abalone fishing area. Lobsters showed a strong preference for mussels over all other prey offered, and for juvenile abalone over urchins, although previous field observations and laboratory experiments have shown that urchins provide shelter for juvenile abalone. However, if black mussels were available in addition to sea urchins and juvenile abalone, consumption of sea urchins and juvenile abalone declined.

The degeneration of large-scale interfacial gravity waves in lakes

2001 ◽  
Vol 434 ◽  
pp. 181-207 ◽  
Author(s):  
D. A. HORN ◽  
J. IMBERGER ◽  
G. N. IVEY
Keyword(s):  
Gravity Waves ◽  
Turbulent Mixing ◽  
Large Scale ◽  
Laboratory Experiments ◽  
Field Observations ◽  
Layer Model ◽  
Lake Ecology ◽  
Initial Wave ◽  
Basin Scale ◽  
Two Layer Model

Mechanisms for the degeneration of large-scale interfacial gravity waves are identified for lakes in which the effects of the Earth's rotation can be neglected. By assuming a simple two-layer model and comparing the timescales over which each of these degeneration mechanisms act, regimes are defined in which particular processes are expected to dominate. The boundaries of these regimes are expressed in terms of two lengthscale ratios: the ratio of the amplitude of the initial wave to the depth of the thermocline, and the ratio of the depth of the thermocline to the overall depth of the lake. Comparison of the predictions of this timescale analysis with the results from both laboratory experiments and field observations confirms its applicability. The results suggest that, for small to medium sized lakes subject to a relatively uniform windstress, an important mechanism for the degeneration of large-scale internal waves is the generation of solitons by nonlinear steepening. Since solitons are likely to break at the sloping boundaries, leading to localized turbulent mixing and enhanced dissipation, the transfer of energy from an initial basin-scale seiche to shorter solitons has important implications for the lake ecology.

THE NUMBER AND QUALITATIVE CHARACTERISTICS OF FRY FISH IN SHALLOW COASTAL WATERS OF THE VOLGA IN THE SUMMER-AUTUMN PERIOD OF 2012

2017 ◽  
pp. 65-73
Author(s):  
Edward Vladimirovich Nikitin
Keyword(s):  
Fish Species ◽  
Coastal Waters ◽  
Caspian Sea ◽  
The Caspian Sea ◽  
Volga River ◽  
Commercial Fish ◽  
Autumn Period ◽  
Fish Juveniles ◽  
Qualitative Characteristics ◽  
Shallow Coastal Waters

Shallow coastal waters of the Volga river is a flooded feeding area for fish juveniles of nonmigratory fish species. There takes place annual downstream migration of fluvial anadromous fish species from spawning grounds of the Volga river to the Northern Caspian Sea. The most important factors determining the number and qualitative characteristics of fry fishes are the level of the Caspian Sea (currently having a tendency to the lowering), hydrological and thermal regimes of the Volga river. Researches were carried out in definite periods of time. In the summer-autumn period of 2012 fry fishes were presented by 19 species (13 of them were commercial species), which belonged to 9 families. The article gives data on all the commercial fish species. In the first decade of July the maximum number of fry fish was registered in the western part of the Volga outfall offshore - in box 247 (19.86 mln specimens/km2), in the eastern part - in box 142 (20.4 mln specimens/km2). The most populous were roach, red-eye, silver bream and bream; size-weight characteristics were better in the areas remoted from the Volga delta. In the third decade of July the quantitative indicators of fry fish on these areas decreased, size-weight characteristics greatly increased. In the second decade of October in the western part of the seaside there were registered increased pre-wintering concentrations of fish juveniles, their qualitative indicators increased, which is evidence to favorable feeding conditions in 2012.

scholarly journals Fencing affects African wild dog movement patterns and population dynamics

Oryx ◽  
2021 ◽  
pp. 1-9
Author(s):  
Helen M. K. O'Neill ◽  
Sarah M. Durant ◽  
Stefanie Strebel ◽  
Rosie Woodroffe
Keyword(s):  
Population Dynamics ◽  
Large Scale ◽  
Animal Movement ◽  
Landscape Connectivity ◽  
Ecological Impact ◽  
Movement Patterns ◽  
Wrong Side ◽  
African Wild Dog ◽  
Wild Dog ◽  
Wild Dogs

Abstract Wildlife fences are often considered an important tool in conservation. Fences are used in attempts to prevent human–wildlife conflict and reduce poaching, despite known negative impacts on landscape connectivity and animal movement patterns. Such impacts are likely to be particularly important for wide-ranging species, such as the African wild dog Lycaon pictus, which requires large areas of continuous habitat to fulfil its resource requirements. Laikipia County in northern Kenya is an important area for wild dogs but new wildlife fences are increasingly being built in this ecosystem. Using a long-term dataset from the area's free-ranging wild dog population, we evaluated the effect of wildlife fence structure on the ability of wild dogs to cross them. The extent to which fences impeded wild dog movement differed between fence designs, although individuals crossed fences of all types. Purpose-built fence gaps increased passage through relatively impermeable fences. Nevertheless, low fence permeability can lead to packs, or parts of packs, becoming trapped on the wrong side of a fence, with consequences for population dynamics. Careful evaluation should be given to the necessity of erecting fences; ecological impact assessments should incorporate evaluation of impacts on animal movement patterns and should be undertaken for all large-scale fencing interventions. Where fencing is unavoidable, projects should use the most permeable fencing structures possible, both in the design of the fence and including as many purpose-built gaps as possible, to minimize impacts on wide-ranging wildlife.

scholarly journals Hydraulic transmissivity inferred from ice-sheet relaxation following Greenland supraglacial lake drainages

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ching-Yao Lai ◽  
Laura A. Stevens ◽  
Danielle L. Chase ◽  
Timothy T. Creyts ◽  
Mark D. Behn ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
Ice Sheet ◽  
Drainage System ◽  
Greenland Ice Sheet ◽  
Field Observations ◽  
Surface Uplift ◽  
Drainage Networks ◽  
Order Of Magnitude ◽  
Lake Drainage ◽  
Magnitude Increase

AbstractSurface meltwater reaching the base of the Greenland Ice Sheet transits through drainage networks, modulating the flow of the ice sheet. Dye and gas-tracing studies conducted in the western margin sector of the ice sheet have directly observed drainage efficiency to evolve seasonally along the drainage pathway. However, the local evolution of drainage systems further inland, where ice thicknesses exceed 1000 m, remains largely unknown. Here, we infer drainage system transmissivity based on surface uplift relaxation following rapid lake drainage events. Combining field observations of five lake drainage events with a mathematical model and laboratory experiments, we show that the surface uplift decreases exponentially with time, as the water in the blister formed beneath the drained lake permeates through the subglacial drainage system. This deflation obeys a universal relaxation law with a timescale that reveals hydraulic transmissivity and indicates a two-order-of-magnitude increase in subglacial transmissivity (from 0.8 ± 0.3 $${\rm{m}}{{\rm{m}}}^{3}$$ m m 3 to 215 ± 90.2 $${\rm{m}}{{\rm{m}}}^{3}$$ m m 3 ) as the melt season progresses, suggesting significant changes in basal hydrology beneath the lakes driven by seasonal meltwater input.

scholarly journals Nutrient removal from Chinese coastal waters by large-scale seaweed aquaculture

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Xi Xiao ◽  
Susana Agusti ◽  
Fang Lin ◽  
Ke Li ◽  
Yaoru Pan ◽  
...  
Keyword(s):  
Nutrient Removal ◽  
Coastal Waters ◽  
Large Scale ◽  
Seaweed Aquaculture
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