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See detailEvaluation of surgery procedures for tagging eel Anguilla anguilla (L.) with biotelemetry transmitters
Baras, Etienne; Jeandrain, Denys ULiege

in Hydrobiologia (1998), 371/372

Externally attached telemetry transmitters are unsuitable to tag yellow eels Anguilla anguilla (L.), in streams where they exhibit cryptic life habits and hide in narrow cavities between rocks. We ... [more ▼]

Externally attached telemetry transmitters are unsuitable to tag yellow eels Anguilla anguilla (L.), in streams where they exhibit cryptic life habits and hide in narrow cavities between rocks. We evaluated the adequacy of surgical implantation and closing procedures for tagging eels with biotelemetry transmitters. Epoxy dummy transmitters (18_8 mm, 1.6–1.7 g) were implanted in eels anaesthetised with 2-phenoxy-ethanol (0.9 ml l−1), through a 20mm mid ventral incision made in the posterior quarter of their body cavity. The incision was either left open, or closed in different ways: stitches (absorbable or non absorbable suture material) or commercial-grade cyanoacrilate adhesive (LoctiteTM). Fish were stocked in a 4 m2 flow through tank (15–17 _C), controlled daily for mortality and weekly for evaluating the healing process. No transmitter was expelled over a 12-week period, even in eels with unclosed incisions, of which 50% healed within 28 days (t50). Regardless of the nature of the filament, suturing induced skin and muscle necrosis, caused significantly higher mortality rates (60% after 10 weeks) and paradoxically slowed down the healing rate (40 and 45 d, respectively). Cyanoacrilate suppressed the inflammatory response and granted higher survival rate (90%), but did not permit to speed up the closing process (t50 = 52 d), as eels actively bit and removed the adhesive within hours. This behaviour was suppressed when we applied a freshly cut fragment of the eel dorsal fin as a biological bandage over the drying cyanoacrilate. The adhesive remained in place for one to two days and permitted to substantially increase the healing rate (t50 = 15 d). These results substantiate the efficiency of surgery techniques for tagging eels with radio transmitters, at least for units of small weight and bulk. [less ▲]

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See detailEnvironmental unpredictability rules the autumn migration of brown trout (Salmo trutta L.) in the Belgian Ardennes
Ovidio, Michaël ULiege; Baras, Etienne; Goffaux, Delphine et al

in Hydrobiologia (1998), 372

This telemetry study aimed to document the mobility of Salmo trutta in the River Ourthe sub-basin (tributary of the River Meuse) during summer and autumn, and to analyse the environmental factors which ... [more ▼]

This telemetry study aimed to document the mobility of Salmo trutta in the River Ourthe sub-basin (tributary of the River Meuse) during summer and autumn, and to analyse the environmental factors which trigger spawning migration or limit their extension. Nine trout (233-2217 g and 26.6-55.2 cm FL) were radio-tagged with intraperitoneal radio transmitters and positioned daily, from 14 August 1996 to 15 January 1997. Until 1 October, fish showed restricted movements: daily journeys never exceeded 300 m and corresponded to displacements by high floods or to routine home range movements. From 7 October to 15 November, seven of the nine trout travelled upstream over distances from 5.6 to 22.95 km, into tributaries and sub-tributaries. Migration speed was fast during the early days, when trout could travel over more than 5 km per night, then progressively decreased as they were approaching putative spawning redds under lower temperature. Both ire the River Ourthe and in the Aisne stream, all migrations started within less than three weeks (early October) and were found to be triggered by the combination of three environmental factors: high variations of water temperature and water level between consecutive days, within a thermal range of 10-12 degrees C. From the trout point's of view, these may be signs that the environment becomes unpredictable, as its variability increases within a thermal range which no longer enables them to achieve high growth rates. These results are discussed within the context of foraging strategies, life history strategies and management of trout population. [less ▲]

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See detailCanonical variables of aquatic bryophyte combinations for predicting water trophic level
Vanderpoorten, Alain ULiege; Palm, R.

in Hydrobiologia (1998), 386(1-3), 85-93

A method for predicting water quality by linear regression using aquatic bryophy te canonical variables as predictors is presented. An example of application in the Alsatian Rhine valley is developed. The ... [more ▼]

A method for predicting water quality by linear regression using aquatic bryophy te canonical variables as predictors is presented. An example of application in the Alsatian Rhine valley is developed. The /--squared obtained before and after cross-validation reached 0.68 and 0.58 for the standard deviation of temperatures, 0.55 and 0.46 for the logarithm of the mean concentrations of N-NH4+, 0.52 and 0.43 for the logarithm of the mean concentrations of N-NO3- and 0.38 and 0.31 for the logarithm of the mean concentrations of P-PO43-. Higher r-squared were not expected due to the broad physico-chemical ranges and the low diversity of genuine aquatic bryophytes. The predicted values of the mean concentrations of N-NH4+, P-PO43- and of the standard deviation of temperatures were often greater than the measured ones. The aquatic bryophytes integrate the sudden increase of the trophic level in oligotrophic streams during the floods of the main eutrophic river and testify to a higher trophic level than expected from regular physico-chemical analyses outside the flood period. Aquatic bryophytes are also affected by water quality in the long term and indicate pollutants other than those measured in current water quality. Other factors besides trophic level might influence the aquatic bryophyte assemblages and should be monitored in order to find the precise relationships between water quality and aquatic macrophytes and in order to create a more accurate model of the effects of the flooding of disconnected streams by the Rhine waters (currently in progress in the Upper Rhine) on the aquatic macrophyte assemblages. [less ▲]

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See detailRelative importance of the trophic and direct pathways on PCB contamination in the rotifer species Brachionus calyciflorus (Pallas)
Joaquim-Justo, Célia ULiege; Gosselain, V; Descy, Jean-Pierre et al

in Hydrobiologia (1995)

To determine the contribution of food ingestion (trophic pathway) to PCB contamination of zooplankton in the river Meuse (Belgium), we used 14 C-labelled algae (Dictyosphaerium ehrenbergianum) to measure ... [more ▼]

To determine the contribution of food ingestion (trophic pathway) to PCB contamination of zooplankton in the river Meuse (Belgium), we used 14 C-labelled algae (Dictyosphaerium ehrenbergianum) to measure ingestion and assimilation rates in the rotifer species Brachionus calyciflorus . When the concentration of algae in the culture medium varied from 20 103 to 200 103 algal cells ml -1 (0.12 to 1 .18 mg C 1 - '), the Brachionus calyciflorus ingestion rate varied from 0 .25 ± 0 .12 to 1 .52 ± 0 .43 ng C ind -1 h-1 at 15 °C and from 0 .74 ± 0 .17 to 5 .93 ± 0.61 ng Cind-' h-1 at 20 °C . The assimilation efficiency (ratio of the assimilation rate to the ingestion rate) measured in a culture medium containing 200 103 algal cells ml`' was 55 .7 ± 5.8%. Since the PCB concentration measured in the phytoplankton of the river Meuse is about 3 pg PCBs g -1 D.W., the estimated PCB contamination of zooplankton ascribable to the trophic pathway ranges from 0 .22 ± 0 .17 to 1 .31 ± 0.77 jag PCBs g -1 D.W. at 15 °C and from 0.64 ± 0 .34 to 5 .10 ± 2 .10 pg PCBs g -1 D. W. at 20'C . The lower figure based on measurements effected at 20 ° C is comparable to the actual level measured in zooplankton samples collected in the river Meuse (0 .69 ± 0.20 pg PCBs g`' D.W.) . The applicability of the formula used in our estimate was checked in a 48-hour in vitro experiment in which the rotifers were fed contaminated algae . The PCB accumulation measured in the rotifers was found to coincide with the calculated PCB contamination . Additional experiments were carried out to determine the contribution of the direct pathway to PCB contamination of zooplankton living in the river Meuse (0.02 pg PCBs 1-1 of water; average dissolved organic matter : 3 mg C 1 -1 ). The PCB concentration in zooplankton resulting from direct uptake of PCBs from the water was estimated at 0 .19 ± 0.05 jug PCBs g -1 D.W. These results show that in zooplankton living in polluted ecosystems, PCBs are likely to accumulate via the trophic pathway to concentrations up to 30 times higher than by direct contamination . Furthermore, our estimates of PCB contamination via the trophic pathway coincide quite well with actual concentrations measured in situ . [less ▲]

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See detailThe phytoplankton community of the river Meuse, Belgium: seasonal dynamics (year 1992) and the possible incidence of zooplankton grazing
Gosselain, Véronique ULiege; Descy, Jean-Pierre; Everbecq, Etienne ULiege

in Hydrobiologia (1994), 289

Qualitative and quantitative aspects of the phytoplankton of the river Meuse were studied during 1992 at a point 537 km from the source. The phytoplankton was dominated by diatoms and green algae. The ... [more ▼]

Qualitative and quantitative aspects of the phytoplankton of the river Meuse were studied during 1992 at a point 537 km from the source. The phytoplankton was dominated by diatoms and green algae. The factors regulating the phytoplankton groxth were clearly physical variables : discharge, temperature and irradiance. [less ▲]

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