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Indexation 578 : Histoire naturelle des organismes vivants
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Affiner la rechercheAbnormal periostracum secretion during the mineralization process of the pearl in the blacklip pearl oyster Pinctada margaritifera / Comps, Michel
Titre : Abnormal periostracum secretion during the mineralization process of the pearl in the blacklip pearl oyster Pinctada margaritifera Type de document : texte imprimé Auteurs : Comps, Michel, Auteur Importance : pp. 49-55 Langues : Anglais (eng) Index. décimale : 578 Histoire naturelle des organismes vivants Résumé : Whitish parasite-like bodies (PLBs), 0.5-2 [tm in size, were detected within the pearl bag of some grafted pearl oysters, Pinctada margaritifera, from Takapoto island (French Polynesia). Histological and ultrastructural investigations have revealed that these bodies consisted of lamellar organic material locally secreted by some epithelial cells of the pearl bag. The fine structure and the formation of these bodies are described. The causes of this abnormal secretion of organic mater, which actually corresponds to periostracum, are not presently known. No parasite nor infectious micro-organism was found associated with the PLBs. Abnormal periostracum secretion during the mineralization process of the pearl in the blacklip pearl oyster Pinctada margaritifera [texte imprimé] / Comps, Michel, Auteur . - [s.d.] . - pp. 49-55.
Langues : Anglais (eng)
Index. décimale : 578 Histoire naturelle des organismes vivants Résumé : Whitish parasite-like bodies (PLBs), 0.5-2 [tm in size, were detected within the pearl bag of some grafted pearl oysters, Pinctada margaritifera, from Takapoto island (French Polynesia). Histological and ultrastructural investigations have revealed that these bodies consisted of lamellar organic material locally secreted by some epithelial cells of the pearl bag. The fine structure and the formation of these bodies are described. The causes of this abnormal secretion of organic mater, which actually corresponds to periostracum, are not presently known. No parasite nor infectious micro-organism was found associated with the PLBs. Exemplaires(0)
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Titre : Abundance estimation of fish schools based on a relationship between school area and school biomass Type de document : texte imprimé Auteurs : Misund, Ole Arve, Auteur Importance : pp. 235-241 Langues : Anglais (eng) Index. décimale : 578 Histoire naturelle des organismes vivants Résumé : A method for acoustic abundance estimation by horizontal guided sonar of fish schooling close to surface is presented. The basic principle is to measure the horizontal area of schools in situ, and derive the school biomass subsequently through a school area to school biomass relationship. The application of the method is exemplified through a sonar survey in the eastern North Sea-Skagerrak in September 1990. The areas of recorded schools were measured by the estimate function of a Furuno CSH-70 sonar, and selected schools were captured by purse seine to establish a school-area to school-biomass relationship. In the actual region, the biomass of herring (Clupea harengus) and mackerel (Scomber scombrus) was estimated to about 90000 and 430000 tons, respectively. The accuracy of the method is discussed and improvements are suggested. Abundance estimation of fish schools based on a relationship between school area and school biomass [texte imprimé] / Misund, Ole Arve, Auteur . - [s.d.] . - pp. 235-241.
Langues : Anglais (eng)
Index. décimale : 578 Histoire naturelle des organismes vivants Résumé : A method for acoustic abundance estimation by horizontal guided sonar of fish schooling close to surface is presented. The basic principle is to measure the horizontal area of schools in situ, and derive the school biomass subsequently through a school area to school biomass relationship. The application of the method is exemplified through a sonar survey in the eastern North Sea-Skagerrak in September 1990. The areas of recorded schools were measured by the estimate function of a Furuno CSH-70 sonar, and selected schools were captured by purse seine to establish a school-area to school-biomass relationship. In the actual region, the biomass of herring (Clupea harengus) and mackerel (Scomber scombrus) was estimated to about 90000 and 430000 tons, respectively. The accuracy of the method is discussed and improvements are suggested. Exemplaires(0)
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Titre : Acomprehensive assessment of the failure of barbus barbus spawning migrations through a fish pass in the canalized river meuse (Belgium) Type de document : texte imprimé Auteurs : Baras, Etienne, Auteur Importance : pp. 181-189 Langues : Anglais (eng) Index. décimale : 578 Histoire naturelle des organismes vivants Résumé : This paper presents a comprehensive study of the impact of damming on the spawning migrations of Barbus barbus in the canalized River Meuse (Southern Belgium). A Denil fish pass on the Ampsin-Neuville dam was controlled 251 times in 1989-1993. The most striking feature is the almost complete absence of barbel in 1990-1993 (15 fishes in 4 years). Most captures of barbel in the fish pass in 1989 were clumped within a few days (mid-May) and related with spawning migrations. Stepwise multiple regression analyses revealed that attractivity was the major condition set allowing barbel to migrate successfully through the pass, while feasibility parameters (water velocity) were found not to be relevant. The variables involved in the attractivity condition set refer indirectly to the influence of water catchment by a hydroelectric plant and to the relative importance of the flow in the pass. The study concludes that this additional condition set significantly interferes with the natural environmental stimuli triggering spawning migrations in barbel and questions the effectiveness of the thermally-related reproductive strategy of the species in an environment with restricted longitudinal connectivity. This statement is discussed in parallel with the recent evolution of barbel populations in canalized rivers. Acomprehensive assessment of the failure of barbus barbus spawning migrations through a fish pass in the canalized river meuse (Belgium) [texte imprimé] / Baras, Etienne, Auteur . - [s.d.] . - pp. 181-189.
Langues : Anglais (eng)
Index. décimale : 578 Histoire naturelle des organismes vivants Résumé : This paper presents a comprehensive study of the impact of damming on the spawning migrations of Barbus barbus in the canalized River Meuse (Southern Belgium). A Denil fish pass on the Ampsin-Neuville dam was controlled 251 times in 1989-1993. The most striking feature is the almost complete absence of barbel in 1990-1993 (15 fishes in 4 years). Most captures of barbel in the fish pass in 1989 were clumped within a few days (mid-May) and related with spawning migrations. Stepwise multiple regression analyses revealed that attractivity was the major condition set allowing barbel to migrate successfully through the pass, while feasibility parameters (water velocity) were found not to be relevant. The variables involved in the attractivity condition set refer indirectly to the influence of water catchment by a hydroelectric plant and to the relative importance of the flow in the pass. The study concludes that this additional condition set significantly interferes with the natural environmental stimuli triggering spawning migrations in barbel and questions the effectiveness of the thermally-related reproductive strategy of the species in an environment with restricted longitudinal connectivity. This statement is discussed in parallel with the recent evolution of barbel populations in canalized rivers. Exemplaires(0)
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Titre : Acoustic detection of the spacial and temporal distribution of fish shoals in the bay of Biscay Type de document : texte imprimé Auteurs : Scalabrin, Carla, Auteur Importance : pp. 269-283 Langues : Anglais (eng) Index. décimale : 578 Histoire naturelle des organismes vivants Résumé : Echo sounder data were used to investigate the spatio-te'rrfporal variability of shoal behaviour in the Bay of Biscay. Data collected from annual surveys were processed using MOVIES-B software in order to measure this variability. The software was designed to measure morphological, energetic and space-time distribution descriptors from the acoustic signal received from fish shoals. Two surveys, DAAG 90 and DAAG 91, provided the appropriate characteristics for such an analysis. The survey's objective was to obtain relative abundance indices for the anchovy (Engraulis encrasicolus) biomass in the Bay of Biscay. The surveys were carried out in the same area (southern Bay of Biscay), at the same period (April) within one year interval (1990 and 1991), using the same equipment (vessel, acoustic system, fishing gear) in a multispecies environment. Frequency distributions for every descriptor were obtained and used to describe the acoustic detection of fish shoals. The analysis of frequency distributions of space-time descriptors (year, day-hour and bottom depth) allowed the construction of derived discrete variables, which defined new subsets of detections. The subsets were then described by the continuous variables. A principal components analysis was used to describe the multidimensional data structure and to describe behaviour patterns. The size and external outline unevenness are correlated groups of shoal descriptors, but are independent of the water column shoal position and the degree of internal shoal structure. An important feature is shoal size variability between years. Significant differences in shoal characteristics were found between bathymetric zones of the same region and the pattern was similar between years. This spatial wariability is related to the distribution of different species between bathymetric zones. Although it was not possible to explain size variability between years, this will be necessary to improve shoal characterization. More knowledge about oceanographic conditions, the productivity level and availability of food, predator pressure and accurate identification of shoal species is required, in order to study the spatial or temporal variability in size and behaviour of shoals. Acoustic detection of the spacial and temporal distribution of fish shoals in the bay of Biscay [texte imprimé] / Scalabrin, Carla, Auteur . - [s.d.] . - pp. 269-283.
Langues : Anglais (eng)
Index. décimale : 578 Histoire naturelle des organismes vivants Résumé : Echo sounder data were used to investigate the spatio-te'rrfporal variability of shoal behaviour in the Bay of Biscay. Data collected from annual surveys were processed using MOVIES-B software in order to measure this variability. The software was designed to measure morphological, energetic and space-time distribution descriptors from the acoustic signal received from fish shoals. Two surveys, DAAG 90 and DAAG 91, provided the appropriate characteristics for such an analysis. The survey's objective was to obtain relative abundance indices for the anchovy (Engraulis encrasicolus) biomass in the Bay of Biscay. The surveys were carried out in the same area (southern Bay of Biscay), at the same period (April) within one year interval (1990 and 1991), using the same equipment (vessel, acoustic system, fishing gear) in a multispecies environment. Frequency distributions for every descriptor were obtained and used to describe the acoustic detection of fish shoals. The analysis of frequency distributions of space-time descriptors (year, day-hour and bottom depth) allowed the construction of derived discrete variables, which defined new subsets of detections. The subsets were then described by the continuous variables. A principal components analysis was used to describe the multidimensional data structure and to describe behaviour patterns. The size and external outline unevenness are correlated groups of shoal descriptors, but are independent of the water column shoal position and the degree of internal shoal structure. An important feature is shoal size variability between years. Significant differences in shoal characteristics were found between bathymetric zones of the same region and the pattern was similar between years. This spatial wariability is related to the distribution of different species between bathymetric zones. Although it was not possible to explain size variability between years, this will be necessary to improve shoal characterization. More knowledge about oceanographic conditions, the productivity level and availability of food, predator pressure and accurate identification of shoal species is required, in order to study the spatial or temporal variability in size and behaviour of shoals. Exemplaires(0)
Disponibilité aucun exemplaire
Titre : Acoustic study of fish and invertebrate behavior in a tropical reservoir Type de document : texte imprimé Auteurs : Prchalova, Marie, Auteur Importance : pp. 325-331 Langues : Anglais (eng) Index. décimale : 578 Histoire naturelle des organismes vivants Résumé : The fish and invertebrate behavior of the Ubol Ratana Reservoir, Thailand, were monitored using up- and downlooking split beam sonar located at a fixed location. In the same area and period, ichthyoplankton nets and multimesh gillnets were used. The bulk of targets, recorded by acoustics and direct capture, consisted both of fish 3-4 cm long and insect larvae 0.2-1 cm long. Diurnal patterns of behavior were very distinct: during the daytime, invertebrates were hidden in the bottom and most fish stayed in compact shoals. Time course of acoustic fish biomass and abundance was very variable due to shoaling. Only the largest fish were recorded as solitary targets. At night, the whole acoustic range was filled with targets and the time course of fish biomass (5-15 kg ha"1) and abundance (20-45 thousand individuals ha"1) were more constant. The biomass increased mostly at surface layers. Fish appeared in the evening in the water column 1 h earlier and stayed there in the morning 1 h longer than invertebrates. Dawn and dusk are good periods for studying fish before invertebrates outnumber them. Apart from fish, according to the target strength, swimming speed and depth distribution, at least four groups of water invertebrates were distinguished acoustically, some with extremely fast vertical movement (7-9 cm s"' vertical speed). Comparison of up- and downlooking observations gave comparable results in midwater layer outside the near-field of the transducer. The uplooking approach can be more suitable for night records; downlooking for the day. Acoustic study of fish and invertebrate behavior in a tropical reservoir [texte imprimé] / Prchalova, Marie, Auteur . - [s.d.] . - pp. 325-331.
Langues : Anglais (eng)
Index. décimale : 578 Histoire naturelle des organismes vivants Résumé : The fish and invertebrate behavior of the Ubol Ratana Reservoir, Thailand, were monitored using up- and downlooking split beam sonar located at a fixed location. In the same area and period, ichthyoplankton nets and multimesh gillnets were used. The bulk of targets, recorded by acoustics and direct capture, consisted both of fish 3-4 cm long and insect larvae 0.2-1 cm long. Diurnal patterns of behavior were very distinct: during the daytime, invertebrates were hidden in the bottom and most fish stayed in compact shoals. Time course of acoustic fish biomass and abundance was very variable due to shoaling. Only the largest fish were recorded as solitary targets. At night, the whole acoustic range was filled with targets and the time course of fish biomass (5-15 kg ha"1) and abundance (20-45 thousand individuals ha"1) were more constant. The biomass increased mostly at surface layers. Fish appeared in the evening in the water column 1 h earlier and stayed there in the morning 1 h longer than invertebrates. Dawn and dusk are good periods for studying fish before invertebrates outnumber them. Apart from fish, according to the target strength, swimming speed and depth distribution, at least four groups of water invertebrates were distinguished acoustically, some with extremely fast vertical movement (7-9 cm s"' vertical speed). Comparison of up- and downlooking observations gave comparable results in midwater layer outside the near-field of the transducer. The uplooking approach can be more suitable for night records; downlooking for the day. Exemplaires(0)
Disponibilité aucun exemplaire Permalink
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