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See detailDaily activity rhythms of the African catfish Heterobranchus longifilis (Clariidae) in an experimental enclosure
Anselme, Patrick ULg; Bernaerts, Pascale; Poncin, Pascal ULg

in Aquatic Living Resources (2008), 21(4), 419-422

The swimming, air-gaping, and agonistic behaviours of Heterobranchus longifilis (318 +/- 67 mm) were examined while fish were in a fasted state under 12L: 12D and variable group size ( 2, 5, 10 and 15 ... [more ▼]

The swimming, air-gaping, and agonistic behaviours of Heterobranchus longifilis (318 +/- 67 mm) were examined while fish were in a fasted state under 12L: 12D and variable group size ( 2, 5, 10 and 15 fish) in a 1000-L aquarium. Fish exhibited a predominantly nocturnal activity pattern independent of group size. A diurnal peak of activity occurred, however, at the usual feeding time. A reduction in frequency of agonistic interactions was observed in larger groups. Five fish were then observed under 72L: 0D and 0L: 72D. The nocturnal activity pattern remained, contrary to the diurnal peak, and was independent of the duration of illumination or darkness. These results suggest the absence of biological clock in H. longifilis, although fish may somehow be influenced by past feeding experience. Behavioural plasticity in this species may provide potential for aquaculture in northern latitudes. [less ▲]

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See detailMobility and home-range use of Atlantic salmon parr over short time scales
Ovidio, Michaël ULg; Enders, Eva C.; Hallot, Eric ULg et al

in Aquatic Living Resources (2007), 20(1, JAN-MAR), 95-101

This study performed in the Patapedia River (Quebec, Gaspesie) was designed to examine the space utilization and mobility patterns of individual Atlantic salmon parr over short time scales with frequent ... [more ▼]

This study performed in the Patapedia River (Quebec, Gaspesie) was designed to examine the space utilization and mobility patterns of individual Atlantic salmon parr over short time scales with frequent detections of position. In August 2004, n = 7 radio-tagged Atlantic salmon parr were located every 20 min during 10 tracking periods chosen to take into account the dawn, day, dusk and night periods. Parr showed important inter individual variability in space utilization and mobility patterns, occupying large home ranges (123 to 5602 m(2)) and sometimes migrating 2 km upstream in the river. No differences were observed in the mean distance travelled among the four daily periods by individual fish, but the estimated home ranges utilized during the four daily periods overlapped only partially, demonstrating that parr partly occupy different areas of the river during different parts of the daily cycle. The results suggest that an intense survey on a small number of fish may contribute to a complementary comprehension of space utilization and mobility patterns of Atlantic salmon parr when viewed in association with results from studies surveying larger number of fish at lower frequency. [less ▲]

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See detailInduce triploidy by heat shock in Eurasian perch, Perca fluviatilis
Rougeot, Carole ULg; Minet, Laurent; Prignon, Christian ULg et al

in Aquatic Living Resources (2003), 16(2, MAR-APR), 90-94

In Eurasian perch (Perca fluviatilis), females grow significantly faster than males. Moreover, gonadal development has a significant negative impact on somatic growth and fillet yield. In order to induce ... [more ▼]

In Eurasian perch (Perca fluviatilis), females grow significantly faster than males. Moreover, gonadal development has a significant negative impact on somatic growth and fillet yield. In order to induce sterility, triploidy induction was attempted by subjecting fertilised eggs to heat shocks. Different combinations of temperature (28, 30, 34, 35 and 36 degreesC), duration (2, 5, 10 and 25 min) and time of shock initiation (TI = 3, 5 and 7 min post-fertilisation) were tested. Flow cytometry analysis was used to assess ploidy level of control and heat-shocked larvae. Low intensity (28-30 degreesC) and long duration (10 and 25 min) shocks lead to significantly higher survival (44 +/- 26%) and triploidisation (71 +/- 26%) rates than high intensity (34-36 degreesC) and short duration (2 and 5 min) shocks (17 +/- 19% and 21 +/- 26%, respectively). The most effective conditions for efficient triploidy induction were low intensity shock of 30 degreesC, applied 5 min post-fertilisation for 25 min. This treatment led to the production of all-triploid populations (100%) with up to 43% survival rate. (C) 2003 Editions scientifiques et medicales Elsevier SAS and Ifremer/IRD/Inra/Cemagref. All rights reserved. [less ▲]

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See detailDiel activity of Sarpa salpa (Sparidae) by ultrasonic telemetry in a Posidonia oceanica meadow of Corsica (Mediterranean Sea)
Jadot, Catherine; Ovidio, Michaël ULg; Voss, Jacques ULg

in Aquatic Living Resources (2002), 15(6), 343-350

In the Mediterranean Sea, the fish Sarpa salpa (Sparidae) is the only vertebrate grazer of Posidonia oceanica meadows. In order to gain knowledge about the behaviour of S. salpa and a better understanding ... [more ▼]

In the Mediterranean Sea, the fish Sarpa salpa (Sparidae) is the only vertebrate grazer of Posidonia oceanica meadows. In order to gain knowledge about the behaviour of S. salpa and a better understanding of the meadow's primary production recycling, an original study was designed using ultrasonic telemetry to investigate activity patterns and space utilisation in the field. During June-September 2000, we compared diel movements of, six adult S. salpa (249-317 nim FL and 313-633 g) in the Bay of Calvi. These fish were tagged by intraperitoneal insertion of ultrasonic transmitters. Their positions were recorded with a directional hydrophone from a small boat with an accuracy between 10 and 50 m, depending on the local environment. The tracking duration ranged from 3 to 22 days (average 11.8 +/- 7.3). Locations were performed from at least dawn to dusk or early night, and one fish was tracked during the entire 24-h cycle. Fish were more mobile during the twilight periods, but statistical analysis indicated individual differences for the precise period of mobility. Two major behavioural patterns were observed: first, the fish remained in close vicinity of the harbour during the day and moved away to the north or the south at dusk to access nocturnal sites, occupying a home range of about 4.3 ha. The second behavioural pattern involved persistent occupation of the same sites during day and night within a relatively restricted home range (about 0.8 ha). Great variation in mobility was found and the same individual fish could show both kinds of behaviour. (C) 2002 Ifremer/CNRS/Inra/IRD/Cemagref/Editions scientifiques et medicales Elsevier SAS. All rights reserved. [less ▲]

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See detailInfluence of sexual genotype on the behaviour of females (genotype WZ) and pseudofemales (genotype ZZ) in the tilapia Oreochromis aureus
Ovidio, Michaël ULg; Desprez, Damien; Mélard, Charles ULg et al

in Aquatic Living Resources (2002), 15(3), 163-167

17alpha-ethynylestradiol sex-reversed males of Oreochromis aureus (pseudofemales, DeltaF, genotype ZZ) are used in aquaculture to produce a male monosex population by crossing with ZZ homogametic normal ... [more ▼]

17alpha-ethynylestradiol sex-reversed males of Oreochromis aureus (pseudofemales, DeltaF, genotype ZZ) are used in aquaculture to produce a male monosex population by crossing with ZZ homogametic normal males. When placed with males (M) and females (F) in the same spawning tank, the spawning rate of F is higher than for DeltaF. In order to understand this phenomenon, comparisons were made between the behaviour of 18 F (446 +/- 96 mm) and 18 DeltaF (401 +/- 59 mm). DeltaF showed a more aggressive behaviour and were significantly more dominant than normal F in fighting pair experiments (F x DeltaF) or in fighting group experiments in four different stocking densities (8, 12, 16 and 83 fish 10(-3) l with F/DeltaF ratio = 1). DeltaF were also more aggressive towards males than F were. The results support the idea that behavioural differences exist between F and DeltaF These differences are probably due to the effect of the sexual genotype on behaviour. (C) 2002 Ifremer/CNRS/Inra/IRD/Cemagref/Editions scientifiques et medicales Elsevier SAS. All rights reserved. [less ▲]

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See detailMethodological bias in home range and mobility estimates when locating radio-tagged trout, Salmo trutta, at different time intervals
Ovidio, Michaël ULg; Philippart, Jean-Claude ULg; Baras, Etienne

in Aquatic Living Resources (2000), 13(6), 449-454

Radio tracking has been extensively used to enhance our knowledge on the movement and home range of fish in general and salmonids in particular. However, the use of various temporal sampling protocols is ... [more ▼]

Radio tracking has been extensively used to enhance our knowledge on the movement and home range of fish in general and salmonids in particular. However, the use of various temporal sampling protocols is likely to overlook fish movements, and produce experimental artefacts, the amplitude of which is unknown and may compromise comparison of fish behaviours revealed by different protocols. Starting from a day-by-day tracking study of brown treat in Belgian waters (Aisne stream, nine fish, minimum 39 daily locations per fish), we re-examined their home range and mobility, through a subsampling process, as if the fish had been located at longer time intervals (2-14 days). The estimates from subsamples were compared to the original data set in order to quantify the corresponding reduction of accuracy from observed data, and how far this could be predicted on the basis of locating frequency. The results clearly indicate that all intervals longer than one day generally generate substantial biases (reduction of accuracy from 0 to 82% for home range and from 5 to 92% for mobility) but these can be partly corrected through the use of predictive models. This analysis demonstrates that any comparison between studies relying on different locating frequencies can generate some ambiguity when interpreting biological phenomena or geographical differences. (C) 2000 Ifremer/CNRS/INRA/IRD/Cemagref/Editions scientifrques et medicales Elsevier SAS. [less ▲]

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See detailFeeding in darkness alleviates density-dependent growth of juvenile vundu catfish Heterobranchus longifilis (Clariidae)
Baras, E.; Tissier, F.; Westerloppe, L. et al

in Aquatic Living Resources (1998), 11

Detailed reference viewed: 14 (3 ULg)