scholarly journals Length-Length and Length-Weight Relationships in Nephrops norvegicus from the Aegean Sea (Linnaeus, 1758)

2011 ◽  
Vol 12 (1) ◽  
pp. 121
Author(s):  
I. AYDIN ◽  
C. AYDIN
Keyword(s):  
Carapace Length ◽  
Aegean Sea ◽  
Body Width ◽  
Nephrops Norvegicus ◽  
Frequency Distributions ◽  
Total Length ◽  
Size Frequency ◽  
Length Width

The objective of this study was to determine the length-length, length-width and length-weight relationships inNephrops norvegicus as a basis for conversions. A total of 659 specimens were collected with trawl gears from the commercial trawler “Hapuloğlu” between 17 and 21 August 2008 in international waters of the middle Aegean Sea. Morphometric equations for the conversions of length and weight were constructed for females, males, and combined sexes. Females were generally smaller than males, and size-frequency distributions total length (TL), carapace length (CL), and body width (BW) revealed significant differences between females and males

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.

SOLVING THE PUZZLE OF THE BIVALVE SHELL FRAGMENT: INFERRING THE ORIGINAL ABUNDANCE AND SIZE FREQUENCY FROM THE FRAGMENTED RECORD

Palaios ◽  
2020 ◽  
Vol 35 (10) ◽  
pp. 432-445
Author(s):  
ERIC N. POWELL
Keyword(s):  
Shell Model ◽  
Shell Length ◽  
Shell Thickness ◽  
Conservative Estimate ◽  
Potential Donor ◽  
Size Frequency ◽  
Shell Fragment ◽  
Length Width ◽  
Bivalve Shell ◽  
Original Size

ABSTRACT Much of the contribution of bivalves to paleoecology is based on the fraction preserved whole. The use of fragments has been limited by the inability to reconstruct the whole shell. For this study, shells of selected species were broken, metrics obtained for shell reconstruction, and a stepwise model developed and tested to evaluate the potential of reconstructing whole shells from fragments. The model is based on the facts that shell thickness is well correlated with shell length, width, and weight, that fragments can be assigned to shell areas, and that each shell area can be matched to a potential donor shell by combinations of length, width, and weight. Simulations using the model show that shell reconstructions are feasible and that the size frequency can be reconstructed more accurately than the number of shells. If all fragments are preserved, shell number tends to be modestly overestimated. Assuming fragment loss, the shell number estimated will be a conservative estimate of original abundance. Reconstructed size frequencies did not differ significantly from the original size frequencies of the whole shells even if 40% of the fragments were not preserved. Biovolume, consequently, may also be estimable. Standardly, bivalve fragments are enumerated by counting intact umbos. If all fragments are preserved, this approach is preferable, as shell model reconstructions overestimate abundance under that circumstance. However, the expectation that fragments with intact umbos are uniquely well preserved is unrealistic and if fragment loss has occurred, relying on all fragments may provide an improved estimate of the original abundance and, in addition, an estimate of the size frequency and the latter proves to be robust even with 40% of the fragments lost.

Determinacy of fecundity in sole (Solea solea) from the Bristol Channel

1990 ◽  
Vol 70 (4) ◽  
pp. 803-813 ◽  
Author(s):  
J. W. Horwood ◽  
M. Greer Walker
Keyword(s):  
Bay Of Biscay ◽  
English Channel ◽  
Potential Fecundity ◽  
Frequency Distributions ◽  
The North ◽  
Size Frequency ◽  
Solea Solea ◽  
The North Sea ◽  
The Common ◽  
Common Sole

Ovaries of the common sole (Solea solea (Linnaeus)) were collected prior to, or at the beginning of, spawning from the spawning grounds in the Bristol Channel. Size frequency distributions of oocytes over 100 μm are presented. They clearly show a break in the size frequency distributions, at about 170 μm, indicating that the production of new oocytes to be spawned that season had ceased. It indicates that the sole is a determinate spawner and that, at least for this population, an annual potential fecundity can be measured. Estimated annual fecundity at length of Bristol Channel sole is calculated, and values are compared with those found for sole from the North Sea, eastern English Channel and the Bay of Biscay.

scholarly journals Nonparametric Assessment of Multimodality for Size Frequency Distributions

2002 ◽  
Vol 15 (4) ◽  
Author(s):  
I.H. SALGADO-UGARTE ◽  
M. SHIMIZU ◽  
T. TANIUCHI ◽  
K. MATSUSHITA
Keyword(s):  
Frequency Distributions ◽  
Size Frequency
Sign in / Sign up

Export Citation Format

Share Document