Juvenile abundance both mirrors and masks a settlement pulse of the rock lobster Jasus edwardsii

2001 ◽  
Vol 52 (8) ◽  
pp. 1067 ◽  
Author(s):  
John D. Booth ◽  
Dean R. Stotter ◽  
Jeffrey S. Forman ◽  
Elizabeth Bradford
Keyword(s):  
Settlement Patterns ◽  
Cost Effective ◽  
The Other ◽  
Rock Lobster ◽  
Frequency Distributions ◽  
Density Dependent Mortality ◽  
Juvenile Abundance ◽  
Jasus Edwardsii ◽  
Dependent Mortality ◽  
Modal Group

Interannual changes in juvenile abundance can validate interannual changes in levels of settlement on collectors and address such postsettlement processes as density-dependent mortality. A strong pulse of postlarval Jasus edwardsii recruitment took place near Wellington in 1991–92, followed by much lower settlement. To determine whether juvenile abundances by age would reflect this pulse and so validate the collector catches, divers estimated quarterly the abundance and size of juveniles at six sites, from 1993 to 2000. Juveniles younger than 2 years were uncommon. At four sites, 2+ and 3+ lobsters were present in large proportion until March 1995. From June 1995, most were at least 3+. These data were consistent with progress of the 1991–92 modal group through the age-frequency distributions, after which juvenile abundances declined, thereby reflecting the settlement data. The other two sites differed in that 2+ and 3+ lobsters became more abundant with time. The reasons for the disparity are unknown, but clearly sufficient site replication is needed if juvenile year-class strengths are to reflect settlement patterns accurately. Where pueruli are numerous enough to register on collectors, crevice collectors appear to be more accurate and cost-effective in following recruitment highs and lows than dive surveys.

Estimating the duration of the pelagic phyllosoma phase of the southern rock lobster, Jasus edwardsii (Hutton)

2015 ◽  
Vol 66 (3) ◽  
pp. 213 ◽  
Author(s):  
R. W. Bradford ◽  
D. Griffin ◽  
B. D. Bruce
Keyword(s):  
Regression Analysis ◽  
Larval Dispersal ◽  
Settlement Patterns ◽  
Rock Lobster ◽  
Planktonic Larva ◽  
New Model ◽  
Larval Stages ◽  
Biophysical Models ◽  
Jasus Edwardsii

The phyllosoma larva of the southern rock lobster, Jasus edwardsii, is thought to be among the longest larval phases of any planktonic larva, with estimates in the literature ranging from 12 to 24 months. In the present study, we have used an extensive archive of samples (over 2800 samples with 680 phyllosoma) to refine the estimate of the duration of the pelagic phase. The distribution through the year of larval stages suggested that larvae from two separate spawning events were present in any 12-month period. Using regression analysis, we have estimated the duration of the phyllosoma phase to be 547±47.5 days (~18.2±1.6 months). A new model of J. edwardsii phyllosoma development is presented and compared with data on known hatching and settlement patterns. The new model will improve the paramiterisation of stage-specific biophysical models of larval dispersal and regional connectivity, to better inform management of the southern rock lobster fisheries.

An Experiment On Spacing-Out as a Defence Against Predation

Behaviour ◽  
1967 ◽  
Vol 28 (3-4) ◽  
pp. 307-320 ◽  
Author(s):  
D. Franck ◽  
M. Impekoven ◽  
N. Tinbergen
Keyword(s):  
Selection Pressure ◽  
Standard Sample ◽  
Direct Detection ◽  
Natural Populations ◽  
The Other ◽  
Detection Distance ◽  
Density Dependent ◽  
Density Dependent Mortality ◽  
Scattered Population ◽  
Dependent Mortality

AbstractThe paper is concerned with the tracing of a selection pressure which would account for the fact (believed to be sufficiently well established) that individuals of many well-camouflaged species live further away from other individuals of their species than the distance from which even bird predators are able to detect them. Artificially camouflaged hens' eggs were laid out in plots of different densities. Wild Carrion Crows were attracted to each plot by a standard "sample egg" which, while painted in the same way as the other eggs on the uppermost half, was laid out in a more conspicuous way. In spite of the fact that the Crows spent more time searching in the "scattered" than in the "crowded" plots, the crowded eggs suffered a much higher mortality. It is concluded that even for individuals of a well-camouflaged species it must be of advantage to live further away from others than the Direct Detection Distance of their predators. However, the experiments do not show that a crowded population as a whole suffers higher predation than a scattered population; experiments to test this and other aspects of the problem are in progress. It is argued that the absolute values of the density dependent mortality scores of the experiments cannot be applied to natural populations, because their density will in most cases be determined by other ultimate factors as well.

scholarly journals Cycles, stochasticity and density dependence in pink salmon population dynamics

2010 ◽  
Vol 278 (1714) ◽  
pp. 2060-2068 ◽  
Author(s):  
Martin Krkošek ◽  
Ray Hilborn ◽  
Randall M. Peterman ◽  
Thomas P. Quinn
Keyword(s):  
Density Dependence ◽  
Disease Transmission ◽  
Pink Salmon ◽  
The Other ◽  
Oncorhynchus Gorbuscha ◽  
Stochastic Perturbations ◽  
Density Dependent ◽  
Density Dependent Mortality ◽  
Animal Populations ◽  
Dependent Mortality

Complex dynamics of animal populations often involve deterministic and stochastic components. A fascinating example is the variation in magnitude of 2-year cycles in abundances of pink salmon ( Oncorhynchus gorbuscha ) stocks along the North Pacific rim. Pink salmon have a 2-year anadromous and semelparous life cycle, resulting in odd- and even-year lineages that occupy the same habitats but are reproductively isolated in time. One lineage is often much more abundant than the other in a given river, and there are phase switches in dominance between odd- and even-year lines. In some regions, the weak line is absent and in others both lines are abundant. Our analysis of 33 stocks indicates that these patterns probably result from stochastic perturbations of damped oscillations owing to density-dependent mortality caused by interactions between lineages. Possible mechanisms are cannibalism, disease transmission, food depletion and habitat degradation by which one lineage affects the other, although no mechanism has been well-studied. Our results provide comprehensive empirical estimates of lagged density-dependent mortality in salmon populations and suggest that a combination of stochasticity and density dependence drives cyclical dynamics of pink salmon stocks.

Two monitoring methods that assess species composition and spatio-temporal trends in bycatch from an important temperate rock lobster (Jasus edwardsii) fishery

2007 ◽  
Vol 58 (3) ◽  
pp. 273 ◽  
Author(s):  
Daniel J. Brock ◽  
Peter J. Hawthorne ◽  
Timothy M. Ward ◽  
Adrian J. Linnane
Keyword(s):  
Temporal Trends ◽  
Cost Effective ◽  
Accurate Information ◽  
Monitoring Methods ◽  
Rock Lobster ◽  
Scientific Analysis ◽  
Jasus Edwardsii ◽  
Fisheries Bycatch ◽  
Spatio Temporal

The effectiveness of two monitoring programs, designed to describe and quantify the bycatch from commercial pots, was examined in the South Australian rock lobster (Jasus edwardsii) fishery (SARLF). The first, logbook sampling, relied on information collected and recorded by fishers in logbooks. The second, bycatch sampling, required fishers to collect bycatch specimens on a nominated day for later scientific analysis. A total of 40 bycatch species were recorded during the study. Finfish, mainly blue-throat wrasse (Notolabrus tetricus) and leather jacket species (Meuschenia hippocrepis and Meushenia australis), were the major component (>90% by number). Data from the logbook program were appropriate for monitoring spatio-temporal trends in bycatch, whereas the bycatch sampling provided more accurate information on bycatch species. Each program was subject to bias when estimating total bycatch numbers and, as a result, a combination of both methods indicated a cost-effective and appropriate way with which to monitor bycatch from the fishery. In comparison with other fisheries, bycatch from the SARLF was relatively low; however, because bycatch was dominated by relatively few species, ongoing monitoring and risk assessment of these populations is needed to ensure long-term sustainability of bycatch levels.

Fluctuations of year-class strength and recruitment in the western rock lobster Panulirus longipes (Milne-Edwards).

1975 ◽  
Vol 26 (3) ◽  
pp. 317 ◽  
Author(s):  
RG Chittleborough ◽  
BF Phillips
Keyword(s):  
Food Supply ◽  
Mass Rearing ◽  
Rock Lobster ◽  
Fishing Season ◽  
Density Dependent ◽  
Density Dependent Mortality ◽  
Class Strength ◽  
Limited Food ◽  
Dependent Mortality

Settlement of puerulus larvae on collectors composed of artificial seaweed and measurements of density of young juveniles on 'nursery' reefs show wide fluctuations in year-class strength, recent settlement from the spawning crop of 1973-74 being particularly high. Owing to restricted holding capacity of the shallow 'nursery' reefs (mainly due to limited food supply), density-dependent mortality reduces most year-class strengths to similar levels by the time juveniles reach 5 years of age. Particularly weak year-classes have been shown to be associated with poor catches from the coastal 'white' fishery at the opening of a fishing season. The applications of these findings to the management of the fishery are discussed. In theory, part of the wastage resulting from excess settlement of larvae in certain areas might be saved by transplanting to less crowded reefs or by mass-rearing in ponds, without diminishing recruitment from those left on the now overstocked reefs.

scholarly journals Catchability of the southern rock lobster Jasus edwardsii. II. Effects of size

2002 ◽  
Vol 53 (8) ◽  
pp. 1149 ◽  
Author(s):  
P. E. Ziegler ◽  
C. R. Johnson ◽  
S. D. Frusher ◽  
C. Gardner
Keyword(s):  
Frequency Distribution ◽  
Rock Lobster ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Size Classes ◽  
Size Frequency ◽  
Jasus Edwardsii ◽  
Behavioural Interactions ◽  
Males And Females ◽  
Relative Selectivity

For most of the year, the size-frequency distribution of trap-caught southern rock lobster, Jasus edwardsii, reflected size-specific catchability rather than the size-frequency distribution of the population in a scientific reserve in Tasmania, Australia. The size-frequency distributions of the population on the ground and of lobsters captured in traps were similar only during a few months, typically during moulting and mating. Small males and females were usually under-represented in traps. Catchability generally increased with size, but varied with sex and season. During moulting and mating, size-specific catchability and relative selectivity of larger animals were similar to or lower than for smaller animals. The relative pattern of catchability throughout the year was similar for most size classes within each sex. Negative associations between small and large lobsters in traps were stronger in winter than in summer, indicating strong behavioural interactions. These interactions could explain the lower catchability of smaller lobsters. Relative selectivity estimates using tag–recapture and size-specific catchability data provided generally similar results.

2D Color-Intensity Representation of Ultrasonic Thickness Gauge Measurements

2020 ◽  
pp. 1192-1198
Author(s):  
M.S. Mohammad ◽  
Tibebe Tesfaye ◽  
Kim Ki-Seong
Keyword(s):  
Cost Effective ◽  
The Other ◽  
Thickness Gauge ◽  
Color Intensity ◽  
Digital Readout ◽  
Flat Surfaces ◽  
Video Cameras ◽  
Wide Range ◽  
Cost Effective Alternative ◽  
Ultrasonic Thickness

Ultrasonic thickness gauges are easy to operate and reliable, and can be used to measure a wide range of thicknesses and inspect all engineering materials. Supplementing the simple ultrasonic thickness gauges that present results in either a digital readout or as an A-scan with systems that enable correlating the measured values to their positions on the inspected surface to produce a two-dimensional (2D) thickness representation can extend their benefits and provide a cost-effective alternative to expensive advanced C-scan machines. In previous work, the authors introduced a system for the positioning and mapping of the values measured by the ultrasonic thickness gauges and flaw detectors (Tesfaye et al. 2019). The system is an alternative to the systems that use mechanical scanners, encoders, and sophisticated UT machines. It used a camera to record the probe’s movement and a projected laser grid obtained by a laser pattern generator to locate the probe on the inspected surface. In this paper, a novel system is proposed to be applied to flat surfaces, in addition to overcoming the other limitations posed due to the use of the laser projection. The proposed system uses two video cameras, one to monitor the probe’s movement on the inspected surface and the other to capture the corresponding digital readout of the thickness gauge. The acquired images of the probe’s position and thickness gauge readout are processed to plot the measured data in a 2D color-coded map. The system is meant to be simpler and more effective than the previous development.

scholarly journals Development of a Genoserotyping Method for Salmonella Infantis Detection on the Basis of Pangenome Analysis

2020 ◽  
Vol 9 (1) ◽  
pp. 67
Author(s):  
Seung-Min Yang ◽  
Jiwon Baek ◽  
Eiseul Kim ◽  
Hyeon-Be Kim ◽  
Seyoung Ko ◽  
...  
Keyword(s):  
Public Health ◽  
Polymerase Chain Reaction ◽  
Bacterial Species ◽  
Cost Effective ◽  
The Other ◽  
Gene Marker ◽  
Diagnostic Assay ◽  
Chain Reaction ◽  
Polymerase Chain ◽  
Substantial Economic Burden

In recent years, Salmonella Infantis has become a predominant serovariant in clinical and poultry isolates, thereby imposing a substantial economic burden on both public health and the livestock industry. With the aim of coping with the steep increase in serovar Infantis prevalence, a polymerase chain reaction (PCR)-based rapid and accurate diagnostic assay was developed in this study through pangenome profiling of 60 Salmonella serovars. A gene marker, SIN_02055, was identified, which is present in the S. Infantis genome but not in the pangenome of the other serovars. Primers specific to SIN_02055 were used to accurately detect serovar Infantis, and to successfully differentiate Infantis from the other 59 serovars in real-time PCR with a R2 of 0.999 and an efficiency of 95.76%. The developed method was applied to 54 Salmonella strains belonging to eight dominant serovars, and distinguished Infantis from the other seven serovars with an accuracy of 100%. The diagnostic primer set also did not show false positive amplification with 32 strains from eight non-Salmonella bacterial species. This cost-effective and rapid method can be considered an alternative to the classic serotyping using antisera.

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