Assessing the production and the impact of cultivated oysters in the Thau lagoon (Mediterranee, France) with a population dynamics model

2001 ◽  
Vol 58 (5) ◽  
pp. 1012-1020 ◽  
Author(s):  
A Gangnery ◽  
C Bacher ◽  
D Buestel
Keyword(s):  
Growth Rate ◽  
Population Dynamics ◽  
Standing Stock ◽  
Individual Growth ◽  
Economic Activities ◽  
Daily Growth ◽  
Mediterranean Mussel ◽  
Thau Lagoon ◽  
The Individual ◽  
The Impact

The Thau lagoon (France) has been studied for many years because of its ecological interest related to economic activities: shellfish cultivation, tourism, and industry. The standing stock of cultivated filter feeders is around 20 000 t and consists of two main species, the Japanese oyster Crassostrea gigas and the Mediterranean mussel Mytilus galloprovincialis. To predict changes in the standing stock and the annual production, a mathematical model of the population dynamics was defined. It was based on the continuous equation of the density as a function of the mortality rate, the individual growth rate, and the interindividual variability. The daily growth rate was derived from field surveys and depended on the phytoplankton concentration and individual weight. The model also took into account the rearing strategy of the producers defined by the timetable of seeding and harvesting, obtained by an inquiry among the producers and used to simulate real cases of standing stock changes. The model was also used to assess the potential impact on the environment through the computation of the food consumption, which was compared with the residence time and the primary production.

scholarly journals The impact of non-pharmaceutical interventions on COVID-19 epidemic growth in the 37 OECD member states

2021 ◽  
Author(s):  
Francisco Pozo-Martin ◽  
Heide Weishaar ◽  
Florin Cristea ◽  
Johanna Hanefeld ◽  
Thurid Bahr ◽  
...  
Keyword(s):  
Growth Rate ◽  
Early Phase ◽  
Policy Decision ◽  
Multilevel Modelling ◽  
Daily Growth ◽  
Public Places ◽  
Member States ◽  
Unit Increase ◽  
Policy Decision Making ◽  
The Impact

AbstractWe estimated the impact of a comprehensive set of non-pharmeceutical interventions on the COVID-19 epidemic growth rate across the 37 member states of the Organisation for Economic Co-operation and Development during the early phase of the COVID-19 pandemic and between October and December 2020. For this task, we conducted a data-driven, longitudinal analysis using a multilevel modelling approach with both maximum likelihood and Bayesian estimation. We found that during the early phase of the epidemic: implementing restrictions on gatherings of more than 100 people, between 11 and 100 people, and 10 people or less was associated with a respective average reduction of 2.58%, 2.78% and 2.81% in the daily growth rate in weekly confirmed cases; requiring closing for some sectors or for all but essential workplaces with an average reduction of 1.51% and 1.78%; requiring closing of some school levels or all school levels with an average reduction of 1.12% or 1.65%; recommending mask wearing with an average reduction of 0.45%, requiring mask wearing country-wide in specific public spaces or in specific geographical areas within the country with an average reduction of 0.44%, requiring mask-wearing country-wide in all public places or all public places where social distancing is not possible with an average reduction of 0.96%; and number of tests per thousand population with an average reduction of 0.02% per unit increase. Between October and December 2020 work closing requirements and testing policy were significant predictors of the epidemic growth rate. These findings provide evidence to support policy decision-making regarding which NPIs to implement to control the spread of the COVID-19 pandemic.

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 Tree Regeneration Patterns on Contrasting Slopes at Treeline Ecotones in Eastern Tibet

Forests ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1605
Author(s):  
Lili Zheng ◽  
Peili Shi ◽  
Tiancai Zhou ◽  
Ge Hou ◽  
Minghua Song ◽  
...  
Keyword(s):  
Climate Change ◽  
Population Dynamics ◽  
Empirical Studies ◽  
Tree Regeneration ◽  
Individual Growth ◽  
Growth And Survival ◽  
Alpine Treeline ◽  
The North ◽  
Adult Trees ◽  
The Individual

Alpine treelines are projected to shift upslope in response to climate warming, but empirical studies have yielded inconsistent results, with both upshifted and stable alpine treelines. Additionally, treelines on different slope aspects of the same mountain can differ. Thus, for a better understanding of the mechanisms of treeline formation and treeline responses to climate change, we need to elucidate the population dynamics at treelines on different slope aspects. Here, we quantified the population dynamics of Balfour spruce (Picea likiangensis var. rubescens) at treeline ecotones on contrasting north- and east-facing slopes on the eastern Tibetan Plateau based on field surveys. The alpine treeline positions of Balfour spruce have not advanced toward higher altitudes on the contrasting slopes in recent decades. Compared with the east-facing slope, more recruits occurred on the north-facing slope above the present treeline, indicating a more favorable regeneration condition. However, on the north-facing slope, the individual growth rate of Balfour spruce was lower, and the number of adult trees above the present treeline was higher than that on the east-facing slope. Thus, slope aspects mediate a trade-off between the growth and survival of treeline species, explaining the absence of an impact of slope aspects on treeline responses to climate change. Our results highlight the importance of considering the effect of topography on population dynamics in predicting alpine treeline dynamics under the scenario of climate change.

scholarly journals Effect of Locally Formulated Watermelon and Moringa Syrup Booster on the Growth Performance of Heterobranchus bidorsalis Fingerlings

2019 ◽  
pp. 1-12
Author(s):  
E. C. Nwanevu ◽  
G. M. Sokari ◽  
G. N. Isitor ◽  
E. E. Orlu ◽  
S. G. Ogolo ◽  
...  
Keyword(s):  
Growth Rate ◽  
Weight Gain ◽  
Growth Performance ◽  
Citrullus Lanatus ◽  
Relative Weight ◽  
Individual Growth ◽  
Environmental Biology ◽  
Design Data ◽  
Daily Growth ◽  
Commercial Feed

Aim: Evaluation of the effectiveness of formulated Watermelon (Citrullus lanatus) and Moringa oleifera booster on the growth performance of Heterobranchus bidorsalis. Study Design: Data were subjected to statistical analysis using Duncan Multiple Range Statistics and interpretation was done using SPSS Version 22. Place and Duration of Study: The experiment was conducted in the laboratory at the Department of Applied and Environmental Biology, Rivers State University, Nigeria for a period of 12 weeks (3 months), between November, 2016 – March, 2017. Methodology: Total of 240 Heterobranchus bidorsalis fingerlings with an initial mean weight (1.61±0.23 g) and length (5.13±0.26 cm) were acclimated for one week. After acclimation, the fishes were fed twice daily (9am and 6pm) with 10% of their body weight after coating 2 ml/1 kg of the commercial feed with their individual growth booster syrup and allowed to air-dry for about 20 minutes. Heterobranchus bidorsalis fingerlings were scooped for the measurements exercise at one week interval after which they were returned to their various tanks. Results: The result of this study recorded the experimental diets with optimum growth and survivability. From the result, it was deduced that, Commercial feed coated with watermelon syrup booster recorded the best performance in the growth variables of mean weight (26.36 ±3.19 g), mean length (13.61±1.35 cm), mean weight gain (24.64±3.00 g), mean length gain (8.38±1.35 cm), relative weight gain (25.36±3.19) while Commercial feed coated with commercial syrup booster (CbCf) recorded the best performance in growth variables of Daily Growth Rate (15.15±0.55) and Specific Growth Rate (2.69±0.03%) against Moring growth booster and commercial feed (control). However, there was less mortality as the fishes in different treatment tanks survived above 90%. Conclusion: It could be summarized that Commercial feed coated with watermelon syrup booster (WbCf) had the best growth performance against the control groups although their values were not significantly impacted (p>0.05) when compared with other experimental diets.

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.

Tomatoes Remember being Brushed

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 471c-471
Author(s):  
Thomas Björkman ◽  
L.C. Garner
Keyword(s):  
Growth Rate ◽  
Avoidance Response ◽  
Growth Response ◽  
Shade Avoidance ◽  
Daily Growth Rate ◽  
Daily Growth ◽  
Tomato Seedlings ◽  
Close Proximity ◽  
The Individual ◽  
Touch Stimulus

Tomato seedlings grown in close proximity elongate rapidly in a shade-avoidance response. A daily touch stimulus can eliminate the extra growth associated with shade avoidance. Experiments to determine how the touch stimulus is integrated were performed on tomato seedlings grown in plug trays 22 mm apart, starting when two fully expanded leaves overlapped between plants to induce the shade-avoidance response. The standard touch stimulus was applied by brushing the surface of the canopy 10 times each morning with a piece of Styrofoam sheet. This treatment reduced the daily growth rate from 7.7 to 5.8 mm/day, but quadrupling the dose further reduced growth only slightly (J. Amer. Soc. Hort. Sci. 121:894). The ability of the plants to sum individual stimuli was tested by varying the interval between the individual strokes. Intervals of 0.01, 0.1, 1 and 10 min all produced the same growth response. Thus, the individual strokes were perceived as a single stimulus. Had they been perceived as separate stimuli, long intervals would have increased the response. There was no refractory period of insensitivity following the stimulus; that would have reduced the response at longer intervals. The height reduction was directly proportional to the number of days that the treatment was applied, indicating that each day of treatment reduced the growth rate for only 1 day (from 5.9 mm/day to 2.7 mm/day). Thus, brief stimuli are integrated during the day and expressed as a reduction of growth the next diurnal cycle.

scholarly journals The effect of growth rate on otolith-based discrimination of cod (Gadus morhua) ecotypes

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0247630
Author(s):  
Einar Pétur Jónsson ◽  
Steven E. Campana ◽  
Jón Sólmundsson ◽  
Klara B. Jakobsdóttir ◽  
Hlynur Bárðarson
Keyword(s):  
Growth Rate ◽  
Gadus Morhua ◽  
Sampling Period ◽  
Individual Growth ◽  
Discrete Wavelet ◽  
Shape Variation ◽  
Otolith Shape ◽  
Individual Growth Rate ◽  
The Individual ◽  
The Relationship

Otolith shape has previously been used to identify ecotypes within the Icelandic cod (Gadus morhua) stock, using DST profiles to validate the results. Fish otolith shape variation has repeatedly been found to be largely determined by growth rate. To examine the effect of growth rate on the relationship between otolith shape and cod ecotypes (using the Pan I genotype as a proxy for ecotype), 826 archived sagittal otoliths collected over a 58 year sampling period were retrieved, the individual growth rate calculated, and otolith shape described using both Normalized Elliptic Fourier transform and Discrete Wavelet transform. Discriminant functions of otolith shape successfully classified ecotype, whether using Fourier or Wavelet descriptors, but only when excluding a heterozygous genotype from the analysis. The otolith shape variability of this genotype lowered the classification success, while otolith shape, in turn, was significantly affected by growth rate and cohort. Growth rate differences previously reported for the ecotypes were present, but were less marked than expected and indeed, growth rate variance attributable to ecotype identity was dwarfed by cohort- and location-related variance in growth. Such a strong effect of growth rate suggests that cod ecotype discrimination based on otolith shape is sensitive to both temporal and spatial variations in growth, which can mask the effect of ecotype-related growth rate differences on otolith shape.

scholarly journals Aplikasi teknologi bioflok (BFT) pada kultur ikan nila, Orechromis niloticus)

2016 ◽  
Vol 4 (2) ◽  
Author(s):  
Frandy Ombong ◽  
Indra R.N Salindeho
Keyword(s):  
Growth Rate ◽  
Nile Tilapia ◽  
Quality Parameters ◽  
Total Biomass ◽  
Daily Growth ◽  
Individual Fish ◽  
Nile Tilapia Oreochromis Niloticus ◽  
Biofloc Technology ◽  
The Individual ◽  
Very High

This study was aimed to find out the growth rate of Nile Tilapia (Oreochromis niloticus) cultured with biofloc technology, and to understand the dynamic of several water quality parameters during culture period. This experiment was conducted in the Laboratory of Aquaculture Technology, FPIK, UNSRAT.  Several substances were added to stimulate the development of biofloc, which were: 0,3 mL of EM-4 containing probiotic-bacteria Lactobacillus casei dan Saccharomyces cerevisiae.; 15 mL of mollases;  0,5 g of  yeast commonly used to ferment soybean ; 12 g of dolomite.    60 seeds of  nile tilapia,  with an individual weight of 6 g, were stocked in each container.   Fish were fed at a dose of 3% of the total biomass/day at the first week, and the dose was decreased  down to 1% of the total biomass per day afterwards.  Fish were weighed at day-1, day-15 and day-30.   The change of water color and the density of the floc was consistently evaluated using imhoff-cone. The initial weight of the tested individual fish were 6,00 g. After 15 days, the weight was increased to 7,37g, and at the end of the experiment the individual fish weighed 11,47 g. Hence, the absolut growth of the tested fish was 5,47g,  the specific growth rate was 91% and the daily growth rate was 2,11%.    The density of flok reached 9,5 mL/L at the beginning of the second week, which was categorized as very high density.   The density of floc then was decreased to 4 mL/L.   The density of the floc was maintained around 5 mL/L during the experiment. The temperature of the medium was at the range of 26-300C.  The level of ammonia was 0,03mg/L and  the level of  nitrite fluctuated between 0,15-3mg/L, which is normal and safe for biofloc system.  The level of nitrate was 4-55 mg/L, which was quite high for biofloc system but not harmful for fish.   Keywords:  Biofloc, Nile-Tilapia, growth, floc-density

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