scholarly journals Shrinking fish: comparisons of prehistoric and contemporary salmonids indicate decreasing size at age across millennia

2014 ◽  
Vol 1 (2) ◽  
pp. 140026 ◽  
Author(s):  
Pablo Turrero ◽  
Eva García-Vázquez ◽  
Carlos Garcia de Leaniz
Keyword(s):  
Body Size ◽  
Life Histories ◽  
Upper Palaeolithic ◽  
Age Classes ◽  
Mean Size ◽  
The Mean ◽  
Selection For ◽  
Dependent Growth ◽  
Size At Age ◽  
Endemic Distribution

A comparison of Upper Palaeolithic and contemporary salmonid vertebrae from the Iberian Peninsula indicates that there has been a significant decrease in the mean body size for a given age among Atlantic salmon and brown trout inhabiting the southernmost range of their endemic distribution. Mean size at age was greater in prehistoric specimens for all age classes during the freshwater phase of their life histories. Fisheries-induced evolution (selection for smaller sizes) is an obvious explanation for the observed reduction in fish body size, but recent changes in the aquatic habitat affecting density-dependent growth cannot be ruled out.

scholarly journals Selection for small body size favours contrasting sex-specific life histories, boldness and feeding in medaka, Oryzias latipes

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Beatriz Diaz Pauli ◽  
Sarah Garric ◽  
Charlotte Evangelista ◽  
L. Asbjørn Vøllestad ◽  
Eric Edeline
Keyword(s):  
Body Size ◽  
Life Histories ◽  
Small Body ◽  
Oryzias Latipes ◽  
Small Body Size ◽  
Selection For

Phenotypic correlates of mating success in the sand wasp Bembecinus quinquespinosus (Hymenoptera: Sphecidae)

1989 ◽  
Vol 67 (10) ◽  
pp. 2557-2568 ◽  
Author(s):  
Kevin M. O'Neill ◽  
Howard E. Evans ◽  
Ruth P. O'Neill
Keyword(s):  
Body Size ◽  
Mating Success ◽  
Activity Patterns ◽  
Alternative Tactics ◽  
Mating Tactics ◽  
Thermal Environments ◽  
Mean Size ◽  
Yellow Pigmentation ◽  
Selection For ◽  
Colour Patterns

Females of the sand wasp Bembecinus quinquespinosus nest in dense aggregations, the offspring emerging in great numbers the following year. Males display alternative mating tactics. Large males search and dig for females about to emerge from the ground. Mating success here is correlated with body size, primarily because larger males are better able to carry the female in flight away from the emergence area and avoid further harassment. The largest males, representing about one-quarter of the population, obtained over 90% of the matings initiated in the emergence area, whereas males below average in size were never successful there. Because some females leave the area without mating, a pool of virgins is available to small males, who patrol just outside the emergence area and intercept passing females. Males below average in size (and all females) are black with pale white bands on the abdomen. In males above mean size, the proportion of yellow pigmentation on the dorsal and lateral surfaces increases with body size. Males undertaking alternative tactics experience differing thermal environments. Yellow colouration was correlated with higher cuticular reflectance. Comparative evidence and differences in the activity patterns of males of different colour suggest that yellow pigmentation acts as a thermoregulatory mechanism allowing larger males to increase their tolerance of the high temperatures and solar radiation loads in the emergence area. We hypothesize that the mating tactics represent condition-dependent behavioural tactics, with flexibility maintained by sexual selection, and that the colour patterns represent condition-dependent morphological tactics, with the developmental response favoured by selection for thermoregulatory ability.

Effects of predation on the size structure of the gastropod Salinator solida (Martens) populations at Towra Point, NSW, Australia

1998 ◽  
Vol 49 (8) ◽  
pp. 779 ◽  
Author(s):  
A. C. Roach
Keyword(s):  
Population Size ◽  
Mangrove Forest ◽  
Size Structure ◽  
New South ◽  
New South Wales ◽  
Age Classes ◽  
South Wales ◽  
Mean Size ◽  
The Mean ◽  
Pulmonate Gastropod

The pulmonate gastropod Salinator solida inhabits intertidal mangrove and saltmarsh communities throughout New South Wales. Studies at Towra Point and elsewhere have consistently found that the mean size and range of size/age classes increases with height on shore. Afield experiment was undertaken to test the hypothesis that predation was responsible for reductions in the mean size of individuals inS. solida populations in the upper mangrove forest. Twelve months after the establishment of fenced plots, there were significantly more individuals in the fenced plots than in unfenced or partially fenced control plots; the number of snails in the 4.1–8.0 mm and > 8.1 mm size classes had increased in the fenced plots but not in the control plots. The results suggest that predation is a major factor determining variation in population size structure by acting to significantly reduce the abundance of adults in the upper mangrove forest.

Activity area during the breeding season of Varanus gouldii (Reptilia : Varanidae) in an urban environment.

1994 ◽  
Vol 21 (6) ◽  
pp. 633 ◽  
Author(s):  
G Thompson
Keyword(s):  
Body Size ◽  
Urban Environment ◽  
Leaf Litter ◽  
Breeding Season ◽  
Western Australia ◽  
Activity Area ◽  
Mean Size ◽  
The Mean ◽  
Activity Areas

The activity area of ten Varanus gouldii in Karrakatta Cemetery, Perth, Western Australia, was measured by daily locations obtained by telemetry, during the breeding season (October-December) in 1992. The mean size of activity area was 8.91 ha; activity area was positively correlated with body size. There were significant overlaps in activity areas and no evidence of territoriality for male or female V. gouldii. The animals often foraged in areas of dense leaf litter near the periphery of their activity area and retreated to burrows that were more centrally located.

Use of Size–Frequency Data to Estimate the Age Composition of Crayfish Populations

1991 ◽  
Vol 48 (12) ◽  
pp. 2324-2332 ◽  
Author(s):  
Robert France ◽  
John Holmes ◽  
Alejandro Lynch
Keyword(s):  
Frequency Data ◽  
Age Classes ◽  
Age Composition ◽  
Frequency Distributions ◽  
Limited Success ◽  
Size Frequency ◽  
Independent Analysis ◽  
Mean Size ◽  
The Mean ◽  
Rates Of Growth

Age-classes in crayfish populations can be determined from size–frequency data provided four tenets are adhered to: (1) only crayfish collected from areas of rock substrate are used; (2) trapping data are excluded; (3) species do not have longevities exceeding about 4 yr; and most importantly, (4) sample sizes are greater than about 200. Studies that have failed to follow these guidelines have met with limited success in dissecting mixed frequency distributions. Further, three validation procedures must be undertaken: (1) temporal replication within molting events to measure the precision of both data collection and size–frequency analysis; (2) corroboration with known-age crayfish from either field recaptures or laboratory molt increments; and (3) concordance with independent analysis of the mean size at onset of sexual maturity. When these checks support the size–frequency results, population age composition and analyses of rates of growth or mortality can be considered reliable.

Determination of Population Discreteness in Two Species of Shrimp, Pandalus jordani and Pandalopsis dispar, from Coastal British Columbia Using Parasite Tags and Other Population Characteristics

1987 ◽  
Vol 44 (5) ◽  
pp. 982-989 ◽  
Author(s):  
A. B. Thompson ◽  
L. Margolis
Keyword(s):  
British Columbia ◽  
Population Characteristics ◽  
Age Composition ◽  
Offshore Area ◽  
Barkley Sound ◽  
Mean Size ◽  
Imperial Eagle ◽  
The Mean ◽  
Topographic Barriers ◽  
Size At Age

Two digenean metacercariae, Neolebouria tinkerbellae and an unidentified species (Metacercaria A), parasitizing Pandalus jordani, and Metacercaria A parasitizing Pandalopsis dispar, were used as naturally occurring biological markers to determine intraspecific population discreteness. Shrimp were sampled from Imperial Eagle Channel and Trevor Channel, Barkley Sound (west coast of Vancouver Island, British Columbia), and from an adjacent offshore area. The mean size at age and the age composition of P. jordani and P. dispar were also estimated. Many differences occurred among samples in the abundances of the metacercariae, in the mean size at age, and in the age composition for each shrimp species, demonstrating that separate shrimp populations existed. In some cases, natural boundaries separated populations of shrimp, for example, the island chain and shallow waters which lie between Imperial Eagle Channel and Trevor Channel. In other cases, such as occurred for the separate populations identified within Imperial Eagle Channel, there were no apparent topographic barriers. No evidence for the occurrence of offshore or onshore migrations of P. jordani or P. dispar was obtained.

scholarly journals Temporal changes in the growth of a crustacean species, Portunus armatus, in a temperate marine embayment: evidence of density dependence

2019 ◽  
Vol 77 (2) ◽  
pp. 773-790 ◽  
Author(s):  
Rachel Marks ◽  
S Alex Hesp ◽  
Danielle Johnston ◽  
Ainslie Denham ◽  
Neil Loneragan
Keyword(s):  
Chlorophyll A ◽  
Linear Models ◽  
Mixture Distribution ◽  
Austral Summer ◽  
Growth Curves ◽  
Fisheries Science ◽  
Mean Size ◽  
The Mean ◽  
Size At Age ◽  
Marine Embayment

Abstract Growth is a key attribute influencing population dynamics and fishery production, and understanding factors that affect the growth of individuals in a population is essential in fisheries science and management. This study analyses 18 years of fishery-independent trawl data to determine the relationships among temperature, density, primary productivity and growth of the blue swimmer crab, Portunus armatus, in a temperate marine embayment. Growth was modelled using mixture distribution analyses and cohort-specific seasonal growth curves to estimate the size of crabs at the age of 0.5 and 1.5 years. Growth was highly seasonal, with size-at-age increasing during the austral summer periods and slowing/ceasing during the cooler winter months. The results from the mixture models were used to estimate the mean size of the 0.5- and 1.5-year-old crabs in each year. Linear models showed that the mean size of adult P. armatus at 1.5 years was negatively related to the density of juvenile (0.5 year) crabs in the previous year (i.e. the same cohort) and chlorophyll a concentrations in this year. Increased chlorophyll a levels may increase the survival of larval and megalopal P. armatus, leading to density-dependent effects such as increased competition among juveniles for food and spatial resources, and ultimately, reduced growth.

scholarly journals Trends in body size across an environmental gradient: A differential response in scavenging and non-scavenging demersal deep-sea fish

2005 ◽  
Vol 272 (1576) ◽  
pp. 2051-2057 ◽  
Author(s):  
M.A Collins ◽  
D.M Bailey ◽  
G.D Ruxton ◽  
I.G Priede
Keyword(s):  
Body Size ◽  
Environmental Gradient ◽  
Environmental Gradients ◽  
Food Distribution ◽  
North East ◽  
The North ◽  
Specific Effects ◽  
Mean Size ◽  
The Mean ◽  
Sea Fish

Body size trends across environmental gradients are widely reported but poorly understood. Here, we investigate contrasting relationships between size (body mass) and depth in the scavenging and predatory demersal ichthyofauna (800–4800 m) of the North-east Atlantic. The mean size of scavenging fish, identified as those regularly attracted to baited cameras, increased significantly with depth, while in non-scavengers there was a significant decline in size. The increase in scavenger size is a consequence of both intra and inter-specific effects. The observation of opposing relationships, in different functional groups, across the same environmental gradient indicates ecological rather than physiological causes. Simple energetic models indicate that the dissimilarity can be explained by different patterns of food distribution. While food availability declines with depth for both groups, the food is likely to be in large, randomly distributed packages for scavengers and as smaller but more evenly distributed items for predators. Larger size in scavengers permits higher swimming speeds, greater endurance as a consequence of larger energy reserves and lower mass specific metabolic rate, factors that are critical to survival on sporadic food items.

scholarly journals Polychaete Annelid Biomass Size Spectra: The Effects of Hypoxia Stress

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Fangyuan Qu ◽  
Clifton Nunnally ◽  
Gilbert T. Rowe
Keyword(s):  
Body Size ◽  
Continental Shelf ◽  
Large Species ◽  
Size Spectra ◽  
Entire Study ◽  
Hypoxic Conditions ◽  
Wet Weight ◽  
The Mean ◽  
Selection For ◽  
Louisiana Continental Shelf

Quantitative benthic samples were taken during spring and summer at three locations on the Louisiana continental shelf from 2004 to 2012 to assess the influence of hypoxia on the mean sizes (wet weight) of polychaete annelid worms. While the mean body size over the entire study of 64 samples was 3.99 ± 4.66 mg wet weight per individual, the mean ranged from 2.97 ± 2.87 mg during consistently hypoxic conditions (<2 mg/L) to a high of 7.13 ± 7.60 mg (p<0.01) under oxic conditions (>2 mg/L). The variations in size within assemblages were estimated from conventional biomass size spectra (BSS) and normalized biomass size spectra (NBSS) across a broad range of oxygen concentrations. The decline in size was due to the elimination of large species under hypoxic conditions (<2 mg/L), not a reduction in size within species. At “severe” levels of hypoxia (<1 mg/L), the smallest species also declined in abundance, whereas the ubiquitous “medium-sized”Paraprionospio pinnataflourished. These results suggest that there will be enhanced selection for small sizes and species with enlarged branchial palps such as those inP. pinnataif, as predicted, hypoxia becomes more commonplace in time and space worldwide.

scholarly journals Inversion heterozygosity and selection for wing length in Drosophila subobscura

1967 ◽  
Vol 10 (1) ◽  
pp. 81-93 ◽  
Author(s):  
Antonio Prevosti
Keyword(s):  
Wing Length ◽  
Chromosomal Polymorphism ◽  
Drosophila Subobscura ◽  
General Tendency ◽  
Selected Lines ◽  
Coefficient Of Variability ◽  
Specific Complex ◽  
Mean Size ◽  
The Mean ◽  
Selection For

1. Selection for long or short wings was carried out in three pairs of lines of which two were started from the same basic population. At the end of the selection experiment the frequencies of the chromosomal arrangements were determined in each line and compared with the corresponding original frequencies to see if the chromosomal polymorphism of Drosophila subobscura is related to the genetic variation of size in a regular way.2. The three pairs of lines show an asymmetrical response to selection. Selection for long wings is less effective in changing the mean of the population than selection for short wings.3. Heritability is lower in the lines selected for long wings, especially in the later generations of selection.4. Viability shows a very small decrease during selection in most selected lines.5. In no case does the coefficient of variability show statistically significant changes, but there is a general tendency for it to decrease.6. Selection for long wings favours combinations heterozygous for the standard chromosome orders and specific complex inversion orders. Selection for short wings generally fixes in homozygous combination specific complex inversion orders.7. The heterozygous combinations of the standard chromosomal orders, which are most frequent in northern populations, when combined with the complex inversion orders which are most frequent in southern populations, have a heterotic effect on size.8. The complex inversion orders usually fixed in homozygous combinations in the lines selected for short wings are those most frequent in southern populations which have a smaller mean size than northern populations.9. The blocks of genes integrated in ‘supergenes’ in the inverted segments of the chromosomes of D. subobscura differ in genetic composition with respect to the control of wing length.

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