scholarly journals A “feet digging” swash zone sampling method for the sandy beach bivalve Donax deltoides (Bivalvia: Donacidae)

2019 ◽  
Author(s):  
Stephen Totterman
Keyword(s):  
Sampling Method ◽  
Sandy Beach ◽  
Low Cost ◽  
Sampling Unit ◽  
Recreational Fishing ◽  
Swash Zone ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Eastern Australia ◽  
Zone Sampling

ABSTRACTA “feet digging” method for sampling the sandy beach bivalve Donax deltoides was evaluated by comparison to quadrat-based results from eleven beaches in subtropical eastern Australia. The method was developed from a recreational fishing technique that involves twisting one’s feet into the thixotropic sand to dislodge buried clams which are then recovered by hand. Several plots are sampled across the swash zone in one five-minute sampling unit and the process is replicated at several locations along the beach. Mean feet digging clam counts were proportional to mean transect linear clam densities (r = 0.98). Clam length-frequency distributions from feet digging were similar to those from quadrat sampling except that feet digging was not effective for clams < 16 mm. Feet digging counts are sensitive to both across shore (tidal) and alongshore variation in clam abundance and were less precise than those from quadrat-based methods (CV 1.2× larger). However, feet digging is fast and the method should be useful for low cost surveys of Donax deltoides and similar “surf clams”.

scholarly journals Seasonal zonation patterns of the sandy beach bivalveDonax deltoides(Bivalvia: Donacidae) in subtropical eastern Australia

2019 ◽  
Author(s):  
Stephen Totterman
Keyword(s):  
Thermal Stress ◽  
Intertidal Zone ◽  
Sandy Beach ◽  
Seasonal Pattern ◽  
High Tide ◽  
Swash Zone ◽  
Eastern Australia ◽  
Zonation Patterns

ABSTRACTSeasonal low tide zonation patterns of the sandy beach bivalveDonax deltoidesare described from eleven beaches in subtropical eastern Australia. Ten low tide transects were sampled at equal along shore intervals along the length of each beach. Three quadrats were sampled at each of seven across shore levels on each transect, from the high tide drift line, across the intertidal zone and to the bottom of the low tide swash zone. Zone counts showed thatD. deltoidesshifted towards the low tide swash zone in summer and buried in the intertidal zone in winter. It is proposed thatD. deltoidesmoves down shore in summer to avoid thermal stress in the intertidal zone. This seasonal pattern is important when planning surveys for this species.

scholarly journals Linking population size structure, heat stress and bleaching responses in a subtropical endemic coral

Coral Reefs ◽  
2021 ◽  
Author(s):  
Liam Lachs ◽  
Brigitte Sommer ◽  
James Cant ◽  
Jessica M. Hodge ◽  
Hamish A. Malcolm ◽  
...  
Keyword(s):  
Heat Stress ◽  
Size Structure ◽  
Temporal Trends ◽  
Early Recovery ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Community Organisation ◽  
Size Frequency ◽  
Eastern Australia

AbstractAnthropocene coral reefs are faced with increasingly severe marine heatwaves and mass coral bleaching mortality events. The ensuing demographic changes to coral assemblages can have long-term impacts on reef community organisation. Thus, understanding the dynamics of subtropical scleractinian coral populations is essential to predict their recovery or extinction post-disturbance. Here we present a 10-yr demographic assessment of a subtropical endemic coral, Pocillopora aliciae (Schmidt-Roach et al. in Zootaxa 3626:576–582, 2013) from the Solitary Islands Marine Park, eastern Australia, paired with long-term temperature records. These coral populations are regularly affected by storms, undergo seasonal thermal variability, and are increasingly impacted by severe marine heatwaves. We examined the demographic processes governing the persistence of these populations using inference from size-frequency distributions based on log-transformed planar area measurements of 7196 coral colonies. Specifically, the size-frequency distribution mean, coefficient of variation, skewness, kurtosis, and coral density were applied to describe population dynamics. Generalised Linear Mixed Effects Models were used to determine temporal trends and test demographic responses to heat stress. Temporal variation in size-frequency distributions revealed various population processes, from recruitment pulses and cohort growth, to bleaching impacts and temperature dependencies. Sporadic recruitment pulses likely support population persistence, illustrated in 2010 by strong positively skewed size-frequency distributions and the highest density of juvenile corals measured during the study. Increasing mean colony size over the following 6 yr indicates further cohort growth of these recruits. Severe heat stress in 2016 resulted in mass bleaching mortality and a 51% decline in coral density. Moderate heat stress in the following years was associated with suppressed P. aliciae recruitment and a lack of early recovery, marked by an exponential decrease of juvenile density (i.e. recruitment) with increasing heat stress. Here, population reliance on sporadic recruitment and susceptibility to heat stress underpin the vulnerability of subtropical coral assemblages to climate change.

Reference points for the length-based indicator Lmax5% for use in the assessment of data-limited stocks

2019 ◽  
Vol 76 (7) ◽  
pp. 2125-2139 ◽  
Author(s):  
Tanja Miethe ◽  
Yves Reecht ◽  
Helen Dobby
Keyword(s):  
Life Histories ◽  
Stock Assessment ◽  
Reference Points ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Simulation Tools ◽  
Spawning Potential Ratio ◽  
The Mean ◽  
Commercial Sources ◽  
Length Frequency Data

Abstract In the absence of abundance indices from scientific surveys or commercial sources, reliable length frequency data from sampled commercial catches can be used to provide an indirect assessment of fishing mortality. Length-based indicators are simple metrics which describe length frequency distributions. The length-based indicator Lmax5%, the mean length of the largest 5% of individuals in the catch, combined with appropriately selected reference points, can be used to evaluate the presence of very large individuals in the catch and hence determine exploitation level. Using analytical per-recruit models, we derive reference points consistent with a spawning potential ratio of 40%. The reference points depend on the life history parameters for natural mortality, maturity, and growth (M, Lmat, L∞, k, CVL∞). Using available simulation tools, we investigate the sensitivity of the reference points to errors in these parameters and explore the usefulness of particular reference points for management purposes for stocks with different life histories. The proposed reference points are robust to uncertainty in length at first capture, Lc, and take into account the maturation schedule of a species. For those stocks with high M/k ratios (&gt;1), Lmax5%, combined with the appropriate reference point, can be used to provide a data-limited stock assessment.

Size Distributions and Growth of the Fan-shell Pinna bicolor Gmelin (Mollusca : Eulamellibranchia) in South Australia

1979 ◽  
Vol 30 (1) ◽  
pp. 25 ◽  
Author(s):  
AJ Butler ◽  
FJ Brewster
Keyword(s):  
South Australia ◽  
Adductor Muscle ◽  
Size Distributions ◽  
Limited Data ◽  
Length Frequency ◽  
Age Classes ◽  
Frequency Distributions ◽  
Growth And Survival ◽  
Random Samples ◽  
Variable Success

Fourteen random samples of Pinna bicolor were collected over a period of 31 months from 6 m depth in Gulf St Vincent off Edithburgh, South Australia. The length-frequency distributions suggest that: P. bicolor larvae settle in spring but with variable success; growth of newly settled young is rapid over summer; by age 1 year their modal shell length is about 20 cm; by age 2 it is about 26 cm; they may survive substantially longer than 3 years so that a length-class of mode c. 35 cm is always present and is composed of several age-classes not necessarily equally represented. These suggestions are corroborated by limited data on adductor muscle scars, the development of epibiota on the shells, and the growth and survival of tagged animals over 9 months.

Application of the otolith weight – age relationship for the pilchard, Sardinops sagax neopilchardus

1995 ◽  
Vol 52 (4) ◽  
pp. 657-664 ◽  
Author(s):  
W. J. Fletcher
Keyword(s):  
Maximum Size ◽  
Steady Increase ◽  
Average Weight ◽  
Fish Length ◽  
Natural Mortality ◽  
Length Frequency ◽  
Age Classes ◽  
Frequency Distributions ◽  
Southwestern Australia ◽  
Sardinops Sagax

Adult pilchard (Sardinops sagax neopilchardus) from southwestern Australia held in fish cages for 1 year showed minimal increase in mean length but a steady increase in mean otolith weight (1.61–1.83 mg); this increase (0.22 mg) closely parallels the previously calculated mean difference between adjacent age classes (0.24 mg). Modes in otolith weight frequency distributions of fishery-caught pilchards, previously suggested as corresponding with separate year classes, generally persisted and progressed through subsequent samples. By contrast, fish length frequency distributions of these samples showed no consistent modal progression. The average weight of otoliths for year classes 2–8 were used to calculate growth rates: following sexual maturity, at age 2, males grew to a significantly smaller maximum size than females (L∞ = 162 and 172 mm respectively). The otolith weight – age relationship, validated by following a cohort of unusually low abundance as it moved through the fishery, indicated that recruitment to the fishery generally began at age 2 but was not complete until age 4. These data have been successfully used in forecasting the catch rate of the fishery up to 2 years in advance and providing an estimate of the rate for natural mortality of 0.43.

Age, stucture, growth rates and movements of sea mullet, Mugil cephalus L., and Yellow-eye Mullet, Aldrichetta forsteri (Valenciennes), in the Swan-Avon river system, Western Australia

1981 ◽  
Vol 32 (4) ◽  
pp. 605 ◽  
Author(s):  
CF Chubb ◽  
IC Potter ◽  
CJ Grant ◽  
RCJ Lenanton ◽  
J Wallace
Keyword(s):  
Growth Rates ◽  
River System ◽  
First Year ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Using Data ◽  
The Times ◽  
First Year Of Life ◽  
Breeding Seasons ◽  
System 1

The age structure, growth rates and movements of M. cephalus and A forsteri in the Swan-Avon river system have been investigated using data obtained from beach seining and gill netting carried out between February 1977 and June 1980. Length-frequency data and scale readings show that the populations of both species consist predominantly of 0+ and 1 + fish. From the times when the smallest fry (20-30 mm) were present in the lower part of the river system, and from the condition of the gonads of older fish, the breeding seasons of the sea and yellow-eye mullets have been estimated as extending from March to September and from March to August respectively. The bimodality or polymodality exhibited by the length-frequency distributions for the 0 + year classes suggest that in both species groups of individuals spawn at slightly different times. The range of mean total lengths and weights of animals caught in May near the end of the first year of life was 178-222 mm and 64-119 gin M. cephalus and 136-154 mm and 19-30 g in A. forsteri, which shows that the growth of each of these two species of mullet is relatively very rapid in the Swan-Avon river system. 1 + and 2 + fish tend to leave the estuary for varying periods. Although 0+ fish of both species utilized the shallow banks of the estuary throughout the year. the sea mullet moved further upstream and were not as consistently abundant in the lower estuary. Since 0+ yellow-eye mullet 40-100 mm long were also abundant in marine coastal waters between January and May. and sea mullet of comparable age were rarely observed in these regions, it would appear that M. cephalus is the more estuarine-dependent of the two species. Commercial catches of M. cephalus were greater than those of A. forsteri. This feature can be related in part to the much faster growth rate of M. cephalus, which results in a larger proportion of its youngest year classes reaching the minimum legal size for capture prior to the time when they leave the estuary in large numbers.

scholarly journals EFFECTS OF SEASONAL VARIATIONS ON SANDY BEACH GROUNDWATER TABLE AND SWASH ZONE SEDIMENT TRANSPORT

2014 ◽  
Vol 1 (34) ◽  
pp. 59
Author(s):  
Norasman Othman ◽  
Ahmad Khairi Abd Wahab ◽  
Mohamad Hidayat Jamal
Keyword(s):  
Sediment Transport ◽  
Seasonal Variations ◽  
Sandy Beach ◽  
Groundwater Table ◽  
Swash Zone

scholarly journals ASSESSMENT OF COASTAL VULNERABILITY BASED ON THE USE OF INTEGRATED LOW-COST MONITORING APPROACH AND BEACH MODELLING: TWO ITALIAN STUDY

2020 ◽  
pp. 13
Author(s):  
Renata Archetti ◽  
Maria Gabriella Gaeta ◽  
Fabio Addona ◽  
Leonardo Damiani ◽  
Alessandra Saponieri ◽  
...  
Keyword(s):  
Low Cost ◽  
Integrated Approach ◽  
Video Monitoring ◽  
Monitoring Systems ◽  
Swash Zone ◽  
Coastal Vulnerability ◽  
Italian Study ◽  
Shoreline Evolution ◽  
Low Costs ◽  
Run Up

The use of video-monitoring techniques is significantly increased due to the diffusion of high-resolution cameras at relatively low-costs and they are largely used to estimate the shoreline evolution and wave run-up, as important coastal state indicators to be monitored and predicted for the assessment of flooding and erosion risks. In this work, we present an integrated approach based on the results from the low-cost video monitoring systems and the numerical modeling chain by means of SWAN and XBeach to accurately simulate and predict the swash zone processes.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/nLGNneJzmIU

Some Uses of Probability Paper in the Analysis of Size Frequency Distributions

1954 ◽  
Vol 5 (3) ◽  
pp. 513 ◽  
Author(s):  
RM Cassie
Keyword(s):  
Frequency Analysis ◽  
Length Frequency ◽  
Scale Reading ◽  
Frequency Distributions ◽  
Probability Paper ◽  
Size Frequency ◽  
Graph Paper ◽  
Probability Graph ◽  
Age Determinations ◽  
Length Frequency Analysis

Methods are described by which the component groups may be extracted from polymodal size frequency samples by the use of probability graph paper. Four examples are given illustrating: the solution of a distribution with more than two modes and with only one exposed flank; the coordination of fish age determinations by the two methods, length frequency analysis and scale reading; a bivariate sample where the two means coincide though the standard deviations are different; a method of correcting for truncation.

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