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| Registros recuperados: 12 | |
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| Rochet, Marie-joelle. |
| Density dependence means that exploited fish populations exhibit earlier maturity, a faster growth rate, increased fecundity and reduced egg size. Here, the consequences of these effects on population dynamics, the estimation of spawning biomass per recruit and associated biological reference points are examined by a simulation model. The model is a self-regenerating model in which the population parameters (age at maturity, growth, fecundity, egg size) vary according to three classes of population abundance. Early life stages are characterized by a size-dependent growth and mortality model. It is concluded that spawning per recruit is an ambiguous concept because, if density dependence occurs in the adult population, the spawning biomass of a cohort is... |
| Tipo: Text |
Palavras-chave: Teleost fishes; Population dynamics; Life history; Density dependence; Biological reference points. |
| Ano: 2000 |
URL: http://archimer.ifremer.fr/doc/2000/publication-485.pdf |
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| Djeghri, Nicolas; Pondaven, Philippe; Stockenreiter, Maria; Behl, Stephan; Huang, Jessica Y. T.; Hansen, Thomas; Patris, Sharon; Ucharm, Gerda; Stibor, Herwig. |
| Mixotrophic organisms are increasingly recognized as important components of ecosystems, but the factors controlling their nutrition pathways (in particular their autotrophy–heterotrophy balance) are little known. Both autotrophy and heterotrophy are expected to respond to density‐dependent mechanisms but not necessarily in the same direction and/or strength. We hypothesize that the autotrophy–heterotrophy balance of mixotrophic organisms might therefore be a function of population densities. To investigate this relationship, we sampled mixotrophic jellyfish holobionts (host, Mastigias papua etpisoni; symbiont, Cladocopium sp.) in a marine lake (Palau, Micronesia) on six occasions (from 2010 to 2018). Over this period, population densities varied ~100... |
| Tipo: Text |
Palavras-chave: Density dependence; Jellyfish; Marine lakes; Mixotrophy; Stable isotopes; Symbiosis; Zooxanthellae. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00663/77469/79159.pdf |
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| Royer, Francois; Fromentin, Jean-marc. |
| We present a methodology for the non-linear analysis of long-term ecological time series. Using a time-delay embedding procedure, we investigated the complexity of 1-dimensional signals and compared their structure to their stochastic counterparts. Recurrence-based statistics and surrogate testing were used for this purpose. The method was first tested on elementary models for illustrative purposes and its potentialities and limits reviewed. We then investigated the time structure of 6 Mediterranean bluefin tuna trap catches known to display long-term fluctuations. These time series showed significantly more determinism than linear stochastic processes, displaying more recurring patterns/states than stochastic surrogates. The short term structure of these... |
| Tipo: Text |
Palavras-chave: Embedding; Surrogate testing; Density dependence; Recurrence; Thunnus thynnus. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-1982.pdf |
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| Pappalardo, M.P.; Morsan, E.M.. |
| In this study we analyze growth, mortality and estimated biomass trend of purple clam, Amiantis purpurata, population placed in Playa Villarino, (Northern San Matias gulf, Argentina) in the southern most boundary of its geographical distribution. Previously, the population structure was described composed by three consecutive cohorts settled among 1978-1980, and the individual growth rate showed high spatial variability. The hypothesis to test in this study is that growth rate is regulated by local biomass. We choice four sites with different densities, to assess growth rate, natural mortality and retrospective estimated biomass trend. During February 2003, densities and growth rate (using external growth bands measurements) were analyzed matching with a... |
| Tipo: Journal Contribution |
Palavras-chave: Growth rate; Clam fisheries; Mortality; Growth curves; Density dependence; Biomass; Growth; Biomass. |
| Ano: 2005 |
URL: http://hdl.handle.net/1834/4385 |
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| Heath, Michael R.; Speirs, Douglas C.; Steele, John H.. |
| Climate fluctuations and human exploitation are causing global changes in nutrient enrichment of terrestrial and aquatic ecosystems and declining abundances of apex predators. The resulting trophic cascades have had profound effects on food webs, leading to significant economic and societal consequences. However, the strength of cascades-that is the extent to which a disturbance is diminished as it propagates through a food web-varies widely between ecosystems, and there is no formal theory as to why this should be so. Some food chain models reproduce cascade effects seen in nature, but to what extent is this dependent on their formulation? We show that inclusion of processes represented mathematically as density-dependent regulation of either consumer... |
| Tipo: Text |
Palavras-chave: Bottom-up; Density dependence; Food chain; Food web; Harvesting; Model; Predator-prey; Simulation; Top-down. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00171/28249/26505.pdf |
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| Registros recuperados: 12 | |
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