Demography of an Estuarine Amphipod (Gammarus lawrencianus) Experimentally Selected for High "r": A Model of the Genetic Effects of Environmental Change

1981 ◽  
Vol 38 (9) ◽  
pp. 1120-1127 ◽  
Author(s):  
R. W. Doyle ◽  
W. Hunte
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Life History Strategy ◽  
Intrinsic Rate ◽  
Individual Growth ◽  
Population Growth Rates ◽  
Phenotypic Correlations ◽  
Demographic Traits ◽  
Marine Crustacean ◽  
Individual Growth Rate

The estuarine amphipod Gammarus lawrencianus was subjected to prolonged selection (3 years; 26 generations) for high population growth rates. The demography of the selected population was studied in detail and compared under laboratory conditions with animals derived from a control (wild) population collected in the same area 3 years later. In the lab-adapted population the intrinsic rate of population growth r increased by 72% as the result of changes in age at maturation, survivorship, and fecundity. The variance of these traits decreased and Crow's (1958) index of total selection (variance of fitness/mean fitness squared) is proposed as a quantitative and operational measure of genetic adaptation to a changed environment. Possible limitations on adaptation were investigated by examining the correlations among demographic traits within the lab-adapted population. Some phenotypic correlations were determined directly and others by an indirect technique using information from full siblings. Individual growth rate was negatively correlated both with survival and fecundity. Individual growth rate and age at sexual maturity were also negatively correlated. Negative phenotypic correlations between traits may indicate limitations on long-term adaptation. We conclude that significant evolutionary changes in the demographic traits of this (and presumably other) marine crustacean can occur within a time scale of interest to ecologists and aquaculturalists.Key words: adaptation, amphipod, aquaculture, Crustacea, evolution, Gammarus, genetics, life history, strategy

Influence of growth and survival costs of reproduction on Atlantic cod, Gadus morhua, population growth rate

1999 ◽  
Vol 56 (9) ◽  
pp. 1612-1623 ◽  
Author(s):  
Jeffrey A Hutchings
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Environmental Stochasticity ◽  
Individual Growth ◽  
Growth And Survival ◽  
Individual Growth Rate ◽  
Age Structured ◽  
Reproductive Rates

A stochastic, age-structured life history model was used to examine how age at maturity (theta), pre- (Zimm) and postreproductive (Zmat) mortality, and postreproductive growth rate can affect maximum reproductive rates of fish at low population size. Simulations suggest that annual (r) and per-generation (R0) metrics of population growth for Newfoundland's northern Grand Bank Atlantic cod, Gadus morhua, are primarily influenced by changes to mortality prior to and following reproduction. At observed weights at age and Zmat = 0.2, r ranged between 0.135 and 0.164 for cod maturing at between 4 and 7 years. Incremental increases in either Zimm or Zmat of 0.1 were associated with 0.03-0.05 reductions in r. To effect similar reductions, individual growth rate would have to decline by approximately one half. At observed weights at age, increases in Zmat from 0.20 to 0.45 increased the probability of negative per-generation growth from 3 to 26% for cod maturing at 4 years and from 6 to 46% for cod maturing at 7 years. Thus, even in the absence of fishing mortality, little or no population growth by Atlantic cod may not be unexpected in the presence of environmental stochasticity, particularly when accompanied by increases in mortality and declining individual growth.

An Evaluation of RNA–DNA Ratio as a Measure of Long-Term Growth in Fish Populations

1973 ◽  
Vol 30 (2) ◽  
pp. 195-199 ◽  
Author(s):  
Terry A. Haines
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Growth Rates ◽  
Population Growth Rate ◽  
Environmental Changes ◽  
Age Distribution ◽  
Smallmouth Bass ◽  
Fish Populations ◽  
Population Growth Rates

The value of RNA–DNA ratio as a measure of long-term growth of fish populations under semi-natural conditions and when subjected to environmental manipulations was determined. Populations of carp and smallmouth bass of known age distribution were established in artificial ponds maintained at two fertility levels. After 15 months, population growth rates (as percent increase in weight) and RNA–DNA ratios of muscle tissue from selected fish were measured. Each species exhibited a range of population growth rates. The relation between population growth rate and individual fish RNA–DNA ratio for each species was significant. When reproduction occurred, the relation was not significant unless young-of-the-year fish were excluded from population growth rate calculations. Age of fish was also found to have an important effect on RNA–DNA ratio, with the ratio being higher in younger fish.RNA–DNA ratio can be a reliable indicator of long-term population growth in fish when population age structure is known and recruitment is controlled. The method has potential for use in detecting response to environmental changes before growth rate changes become severe.

Is boldness towards predators related to growth rate in naïve captive-reared Arctic char (Salvelinus alpinus)?

2007 ◽  
Vol 64 (4) ◽  
pp. 665-671 ◽  
Author(s):  
Mika VM Laakkonen ◽  
Heikki Hirvonen
Keyword(s):  
Growth Rate ◽  
Captive Breeding ◽  
Salvelinus Alpinus ◽  
Antipredator Behavior ◽  
Underlying Mechanism ◽  
Arctic Char ◽  
Individual Growth ◽  
Detailed Knowledge ◽  
Individual Growth Rate ◽  
Slow Growing

Previous studies have shown that the antipredator responsiveness of fish degenerates through generations in captive breeding. However, detailed knowledge of the underlying mechanism is still largely lacking. We tested the hypothesis that hatchery fish supposedly selected for faster growth in the hatchery environment are bolder towards predators than their slower-growing conspecifics. This was examined by comparing the antipredator behavior of predator- naïve fast- and slow-growing individuals of a captive-bred Arctic char (Salvelinus alpinus) population to chemical cues from natural predators burbot (Lota lota) and pikeperch (Sander lucioperca). As behavioral responses depended on char body size, we compared boldness towards predators of size-matched fast- and slow-growing char. We found no differences in four behavioral antipredator traits between size-matched groups of fast- and slow-growing char. According to these results, boldness to predator cues is not related to individual growth rate in captive-bred Arctic char.

scholarly journals A POPULATION OF LYCHNOPHORA ERICOIDES MART. (ARNICA) (ASTERACEAE) IS PRONE TO EXTINCTION IN A SAVANNA OF CENTRAL BRAZIL

2017 ◽  
Vol 74 (3) ◽  
pp. 281-297 ◽  
Author(s):  
S. Ribeiro-Silva ◽  
M. B. Medeiros ◽  
V. V. F. Lima ◽  
A. B. Giroldo ◽  
S. E. de Noronha ◽  
...  
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Plant Species ◽  
Population Growth Rate ◽  
Forest Products ◽  
Life Stages ◽  
Transition Matrices ◽  
Population Growth Rates ◽  
Central Brazil ◽  
Non Timber Forest Products

Lychnophora ericoides Mart. (Asteraceae), popularly known as arnica, is a plant species subjected to non-timber forest products extraction. Evidence is mounting that some local populations are on the brink of extinction. However, demographic studies of Lychnophora ericoides are rare. Therefore, as a step towards conservation, a remnant population of Lychnophora ericoides located in an area of the Cerrado (Brazilian Savanna) in Central Brazil was evaluated from 2010 through 2014. Disturbances such as wildfires and harvesting of Lychnophora ericoides were randomly distributed throughout the study period in this area. Four annual transition matrices (A1, A2, A3 and A4) were constructed, based on life stages. The main results of studies of population dynamics for this species are as follows: 1) population growth rates (λ) with 95% confidence intervals indicated a declining population in all periods from 2010 to 2014; 2) stochastic population growth rate considering the four matrices was < 1 with value λ = 0.358 and CI95% = (0.354–0.362); 3) survival with permanence at the same stage of reproductive adult individuals (46–80%) contributed most to population growth rate, based on elasticity analysis; 4) the population is much less likely to have increases in density, compared with reduction, for all intervals from 2010 to 2014, based on transient indices; 5) the low value of λ in the high-mortality year was caused by lower stasis of individuals in the seedling or sapling and juvenile life stages, as well as fecundity in the 2011–2012 and 2012–2013 intervals, as shown by a life table response experiment; and 6) 100% of the population will probably be extinct within 15 years. There is evidence that the main cause for local extinction of Lychnophora ericoides could be the effects of frequent wildfires. Based on these results, it is suggested that the time has come for significant conservation efforts to rescue this population, including monitoring, protection and education as the first steps towards protection of this vulnerable plant species.

scholarly journals Effect of Stocking Density on Growth and Survival Rate of Giant Gouramy (Osphrenemus gouramy Lac.) Seed

2009 ◽  
Vol 8 (2) ◽  
pp. 199 ◽  
Author(s):  
S. Sarah ◽  
. Widanarni ◽  
Agus Oman Sudrajat
Keyword(s):  
Growth Rate ◽  
Survival Rate ◽  
Feed Efficiency ◽  
Stocking Density ◽  
Individual Growth ◽  
Daily Growth Rate ◽  
Daily Growth ◽  
Fish Yield ◽  
Growth And Survival ◽  
Individual Growth Rate

<p>This experiment was conducted to study the stocking density effect on growth and survival rate of giant gouramy seed in the aquarium. Fish were stocked at the density of 2.5; 5.0; 7.5 and 10 individual/l with average initial weight and length were 0.013 g and 5.56 mm, respectively. Fish were fed with silkworm (<em>Tubifex</em> sp.) <em>ad libitum</em> in the morning and evening for 22 days of experiment. Aquarium was siphoned and water was changed everyday for maintaining good water quality. Result showed that survival rate remain high in all treatment (93.5 - 95.5%). Increasing stocking density from 2.5 to 10 individual/I did not affect survival rate. On the other hand growth rate and feed efficiency decreased, while fish yield increased. Stocking density of 2,5 individual/l gave  the highest daily growth rate, individual growth rate, growth in length and feed efficiency of 12.94%, 0.0081 g/day, 16.84 mm and 12.51%; respectively. The highest value for fish yield (0,0360 g/l/day) was obtained from stocking density of 10 individual/l</p> <p>Key words: stocking density, seed, survival rate, growth rate, giant gouramy <em>Osphrenemus goramy</em></p> <p> </p> <p>ABSTRAK</p> <p>Keterbatasan pengadaan benih ikan gurame (<em>Osphronemus gourame </em>Lac.) disebabkan oleh tidak seimbangnya jumlah benih yang tersedia dengan kebutuhan usaha pembesaran. Teknik pembenihan yang digunakan sampai saat ini relatif sederhana dengan cara tradisional. Pemeliharaan gurame secara terkontrol di akuarium dapat menjawab tantangan dalam teknologi pembenihan gurame sekaligus sebagai sarana pola budidaya secara bertahap yang sedang berkembang saat ini. Produksi yang tinggi akan dicapai dengan pemeliharaan pada kepadatan yang tinggi. Pada keadaan lingkungan yang baik dan pakan yang mencukupi, peningkatan kepadatan akan disertai dengan peningkatan hasil. Jumlah ikan yang ditebar pada penelitian ini disesuaikan berdasarkan perlakuan yaitu 2,5; 5,0; 7,5 dan 10 ekor/l. Pengamatan terhadap ikan dilakukan sampai hari ke-22. Hasil pengamatan menunjukkan bahwa peningkatan kepadatan 2,5 - 10 ekor/l pada pemeliharaan benih gurame di akuarium mempengaruhi pertumbuhan, hasil dan efisiensi pakan, namun tidak berpengaruh terhadap kelangsungan hidup. Dengan meningkatnya padat penebaran, laju pertumbuhan dan efisiensi pakan semakin menurun, sedangkan hasil (<em>yield</em>) semakin meningkat. Padat penebaran 2,5 ekor/l menghasilkan laju pertumbuhan harian, laju pertumbuhan individu, pertumbuhan panjang mutlak dan efisiensi pakan tertinggi, masing-masing mencapai 12,94 %, 0,0081 g/hari, 16,84 mm dan 12,51 %. Sedangkan nilai tertinggi untuk hasil (<em>yield</em>) sebesar 0,0360 g/l/hari diperoleh pada padat penebaran 10,0 ekor/l.</p> <p>Kata kunci : padat tebar, pembenihan, gurame dan <em>Osphronemus gouramy</em></p>

scholarly journals Development and population growth of Hydra viridissima Pallas, 1766 (Cnidaria, Hydrozoa) in the laboratory

2008 ◽  
Vol 68 (2) ◽  
pp. 379-383 ◽  
Author(s):  
FC. Massaro ◽  
O. Rocha
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Generation Time ◽  
Doubling Time ◽  
Test Organism ◽  
Laboratory Culture ◽  
Individual Growth ◽  
Population Doubling ◽  
Population Doubling Time ◽  
The Individual

Hydras, the most representative freshwater Cnidaria, are of common occurrence in bodies of water in every continent except Antarctica. This study was planned with the aim of maintaining a population of Hydra viridissima in laboratory culture to enable the determination of the individual and population growth-rates of this species, as well as its population doubling time and generation time, with a view to employing these common animals as test-organisms in ecotoxicological assays. The organisms were maintained in reconstituted water at 20 ± 2 °C, illuminated at 800 lux with a photoperiod of 12 hours light: 12 hours dark, and were fed on neonates of the cladoceran Ceriodaphnia silvestrii (3 or 4 neonates per hydra, 3 times a week). The individual growth-rate (k) of the species was 0.43, the maximum length of the column 2.53 mm and the generation time 6.6 ± 1.5 days on average. The hydra population showed an intrinsic growth-rate (r) of 0.0468, according to the fitted curve, and a doubling time of 14.8 ± 2.63 days. Hydra viridissima is easy to grow in the laboratory and performs well in the conditions used in this study. It is thus a promising candidate test-organism for ecotoxicological studies.

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