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| Registros recuperados: 145 | |
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| Ducrotoy, J; Desprez, M; Elkaim, B. |
| The recent collapse in the landings of cockles (Cerastoderma edule) from the Bay of Somme (France) required to investigate if a change in the environmental factors was liable for the drop of the bivalve populations. This project has led to a preliminary assessment of the situation and has been drawn up from the data collected by the Groupe d'Etude des Milieux Estuariens et Littoraux since 1978. It relies on the survey of the spatio-temporal changes of bio-facies. it is suggested that the impact of changes in sediment characteristics is important as well as competition with species as Pygospio elegans (Polychaeta). The above parameters are assessed as essential in the fluctuations of the cockle numbers but they do not explain entirely the collapse in the... |
| Tipo: Text |
Palavras-chave: Landing statistics; Clam fisheries; Stock assessment; Population dynamics; Marine mollusks. |
| Ano: 1985 |
URL: http://archimer.ifremer.fr/doc/1985/publication-1784.pdf |
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| Diserud, Oh. |
| In this paper, I present a method developed to detect 'extra', or novel, changes in diversity in a naturally fluctuating environment. When comparing samples in order to evaluate changes in community structure, the sampling procedure will inevitably induce randomness in observed species composition and abundance, so two samples may show considerable differences, even if they come from exactly the same community. Sometimes the effort put into the sampling varies as well, leading to the expectation of a further increase in difference. Finally, if there were a temporal distance between the samples, we would like to correct for variations in species abundance occurring naturally due to fluctuating environmental conditions. The test method presented here... |
| Tipo: Text |
Palavras-chave: Structure des communautés; Diversité; Variance environnementale; Dynamique des populations; Modèle d'abondance d'une espèce; Community structure; Diversity index; Environmental variance; Population dynamics; Species abundance model. |
| Ano: 2001 |
URL: http://archimer.ifremer.fr/doc/00322/43345/42881.pdf |
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| Ravier, Christelle; Fromentin, Jean-marc. |
| More than one hundred long-term time-series of bluefin tuna catches from the ancestral Mediterranean and Atlantic trap fisheries are used to (1) estimate historical range of BFT yields in the Mediterranean and adjacent Atlantic and (2) investigate spatial and temporal patterns of fluctuations in trap catches. Mean historical catches were around 110 000 tunas/year (± 50 000), i.e. 15 000 tons/year (∈[7 000;25 000]). Fluctuations in trap catches are of large magnitude, periods of high abundance being up to seven times higher than those of low abundance. More interesting was the occurrence of 100-year-long periodic fluctuations as well as 20-year cycles. These medium- to long-term fluctuations, representing more than 50% of the total variability in the... |
| Tipo: Text |
Palavras-chave: Thunnus thynnus; Time series analyses; Abundance; Population dynamics; Long-term changes; Trapfishing. |
| Ano: 2002 |
URL: http://archimer.ifremer.fr/doc/00194/30497/28906.pdf |
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| Heino, Mikko; Baulier, Loic; Boukal, David S.; Ernande, Bruno; Johnston, Fiona D.; Mollet, Fabian M.; Pardoe, Heidi; Therkildsen, Nina O.; Uusi-heikkila, Silva; Vainikka, Anssi; Arlinghaus, Robert; Dankel, Dorothy J.; Dunlop, Erin S.; Eikeset, Anne Maria; Enberg, Katja; Engelhard, Georg; Jorgensen, Christian; Laugen, Ane; Matsumura, Shuichi; Nussle, Sebastien; Urbach, Davnah; Whitlock, Rebecca; Rijnsdorp, Adriaan D.; Dieckmann, Ulf. |
| Biological reference points are important tools for fisheries management. Reference points are not static, butmay change when a population's environment or the population itself changes. Fisheries-induced evolution is one mechanism that can alter population characteristics, leading to "shifting" reference points by modifying the underlying biological processes or by changing the perception of a fishery system. The former causes changes in "true" reference points, whereas the latter is caused by changes in the yardsticks used to quantify a system's status. Unaccounted shifts of either kind imply that reference points gradually lose their intended meaning. This can lead to increased precaution, which is safe, but potentially costly. Shifts can also occur in... |
| Tipo: Text |
Palavras-chave: Biological reference points; Fisheries-induced evolution; Fisheries management; Population dynamics; Precautionary approach; Uncertainty. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00151/26228/24302.pdf |
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| Sergievsky, So; Granovitch, Ai; Sokolova, Im. |
| The results of a 14-year survey of the populations of L. saxatilis and L. obtusata from one locality in the Kandalaksha Bay of the White Sea are presented. The periwinkles were found to be hosts of 10 castrating trematode species. Microphallus piriformes was the most abundant species with infection prevalence often exceeding 50%. Year-to-year variation of the infection prevalence was correlated in the two host species, probably reflecting fluctuations in the influx of trematode eggs to the shore. Long-term changes in population density are associated with the variation of the age structure of the winkles, suggesting a dependence of the population density on the success of the recruitment. Fluctuations in abundance and age composition were correlated in L.... |
| Tipo: Text |
Palavras-chave: Long-term; Population dynamics; Demography; Littorina; Trematoda. |
| Ano: 1997 |
URL: http://archimer.ifremer.fr/doc/00093/20395/18062.pdf |
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| Desprez, M; Ducrotoy, J; Elkaim, B. |
| In this paper, the results collected since 1978 on the cockle (Cerastoderma edule) in the Bay of Somme have been recapitulated. A synthesis is brought up about causes of the bivalve population collapse which was portended as early as 1982 from the animal cinetics study. In order to back up the discussion, the main results dealing with the biology and ecology of the species are recalled in illustrated form. A review of the international literature leads to a comment upon the diagrams. A comparison with data from European estuaries tends to take climatic and oceanic disturbances into account as well as local pollution such as eutrophication which is probable on the littoral of Picardy. |
| Tipo: Text |
Palavras-chave: Clam fisheries; Stock assessment; Recruitment; Population dynamics; Marine mollusks. |
| Ano: 1985 |
URL: http://archimer.ifremer.fr/doc/1985/publication-1783.pdf |
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| Saraux, Claire; Van Beveren, Elisabeth; Brosset, Pablo; Queiros, Quentin; Bourdeix, Jean-herve; Dutto, Gilbert; Gasset, Eric; Jac, Cyrielle; Bonhommeau, Sylvain; Fromentin, Jean-marc. |
| Around 2008, an ecosystem shift occurred in the Gulf of Lions, highlighted by considerable changes in biomass and fish mean weight of its two main small pelagic fish stocks (European anchovy, Engraulis encrasicolus; European sardine, Sardina pilchardus). Surprisingly these changes did not appear to be mediated by a decrease in fish recruitment rates (which remained high) or by a high fishing pressure (exploitation rates being extremely low). Here, we review the current knowledge on the population's dynamics and its potential causes. We used an integrative ecosystem approach exploring alternative hypotheses, ranging from bottom-up to top-down control, not forgetting epizootic diseases. First, the study of multiple population characteristics highlighted a... |
| Tipo: Text |
Palavras-chave: Population dynamics; Top-down; Disease; Zooplankton; Exploited species; Bottom-up. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00427/53861/54903.pdf |
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| Rondelaud, D. |
| The treated habitats have not been recolonized by Lymnaea truncatula . Four aquatic snail species showed an increase in their numbers: L. glabra in the stations of Haute-Vienne, L. glabra, Physa acuta, P. hypnorum and Planorbis rotundatus in the habitats of Indre. The numbers of L. glabra and P. acuta reached their maximum on the third year and decreased thereafter; those of P. hypnorum and P. rotundatus slightly increased from the fourth or the fifth years treatment. The colonization of L. truncatula habitats was incomplete and did not reach over 50% of the surface for L. glabra and P. acuta , 20% for P. hypnorum and P. rotundatus . The bivalve Pisidium casertanum did not recolonize treated habitats. There were no modifications in the numbers of... |
| Tipo: Text |
Palavras-chave: Physa; Lymnaea; Mollusca; Biological control; Chemical control; Population density; Population dynamics; Freshwater molluscs. |
| Ano: 1991 |
URL: http://archimer.ifremer.fr/doc/1991/acte-1715.pdf |
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| Souto,KCFL; Pereira,CD; Lomônaco,C. |
| The aim of this study was to comparatively characterize the monthly variation and the sex ratio of Euxesta stigmatias (Loew) and Euxesta sororcula (Wiedermann) populations from a natural reserve and from a guava orchard. It was also investigated whether density and the climate factors affected the individuals' size and fluctuating asymmetry (FA). In both environments, E. sororcula predominated over E. stigmatias. The number of individuals of E. sororcula collected in the ecological station was significantly lower than the number of individuals caught in the orchard. However, the number of captured individuals of E. stigmatias did not differ between environments. Significant sex ratio differences were detected between the collection sites. Female's... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Fluctuating asymmetry; Morphometry; Population dynamics. |
| Ano: 2011 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1519-566X2011000600005 |
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| Registros recuperados: 145 | |
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