Etienne Baras

Migration of freshwater fishes

Migration And Spatial Behaviour: Introduction. The Stimulus And Capacity For Migration: Stimuli For Migration, The Capacity For Migration, Piloting, Orientation And Navigation. Types Of Migration: Migrations At The Seasonal And Ontogenetic Scale, Diel Horizontal And Vertical Migrations. Patterns Of Migratory Behaviour In Freshwater Fishes: Arctic And Subarctic Regions, Temperate Regions, Tropical Regions. Taxonomic Analysis Of Migration In Freshwater Fishes, Lampreys Through To Freshwater--Dwelling Flatfishes (In 45 Sections). Methods For Studying The Spatial Behaviour Of Fishes In Fresh--And Brackish Water: Capture Dependent Methods, Capture Independent Methods, Choice Of Methods In Fish Migration Studies. Applied Aspects Of Freshwater Fish Migration: The Impact Of Mana s Activities On Freshwater Fish Migration. Mitigation Of Hazards And Obstacles To Fish Migration, Installation, Monitoring And Efficiency Of Fish Passes. Conclusions. Indexes

Surgical implantation of telemetry transmitters in fish : how much have we learned?

Surgical implantation has become a well-established method for attaching telemetry transmitters in studies of fish behaviour. However, a rather large number of reports of transmitter expulsion, fish mortality and adverse effects on fish physiology or behaviour, suggests that refinement and evaluation of the methods is needed, especially when tagging fish species for which no protocol has ever been assayed. This paper summarizes the authors own experiences with telemetry transmitter implantation, primarily from field studies involving numerous species of fish. Where appropriate, results from existing literature are summarized and discussed. The paper focuses on how choice of surgical procedure, fish size, morphology, behaviour and environmental conditions can affect the success of telemetry transmitter implantation in fish.

Size heterogeneity, cannibalism and competition in cultured predatory fish larvae: biotic and abiotic influences

Growth heterogeneity is a central problem in larviculture and especially in predatory species. It can be influenced by a wide range of intrinsic and environmental factors, of which the respective influences are largely unknown. The role of non-interactive (temperature, day length, light intensity, food availability and composition) and interactive factors (stocking density, initial size heterogeneity, hatching time) on growth, survival and size heterogeneity was measured in larvae and post-larvae of the European seabass Dicentrarchus labrax and Eurasian perch Perca fluviatilis. Embryos hatching later than others were found less competitive than those hatching earlier in both species, but to a greater extent in perch. By contrast, the final size heterogeneity in both species was independent from the initial size heterogeneity or recurrent size sorting. High stocking density had a positive effect on perch larvae, no effect on seabass larvae and a negative impact on the post-larvae of both species, owing principally to density-dependent access to food. Day length and light intensity produced contrasting results in larvae and post-larvae. Larvae of both species performed better under bright light and continuous day length. Post-larvae of seabass performed equally well at different light levels but did better under short day lengths, whereas post-larvae of perch were unaffected by day length but performed better under reduced light levels. Increasing food availability resulted in increasing performance of perch larvae, although cannibalism was higher for submaximal than for maintenance rations. The similarity between the two species at the larval stage, and differences at the post-larval stage can be accounted for by the increasing specialisation towards specific environments and niches. Regarding the impact of rearing factors on growth, survival and size heterogeneity, interactive variables impacted essentially on growth and survival, whereas size heterogeneity was chiefly influenced by non-interactive variables, either directly or indirectly via interactive mechanisms such as cannibalism and size-dependent mortality.

The effect of PIT tags on growth and physiology of age-0 cultured Eurasian perch Perca fluviatilis of variable size.

Abstract For many biological reasons, it is often necessary to tag and monitor fish from a very early age. However, tagging can adversely affect fish, especially for high tag to body weight ratios. To determine the minimum size for passive integrated transponders (PIT) tagging in juvenile perch Perca fluviatilis , surgical implantation was evaluated in fish ranging from 1.67 to 10.62 g (55–96 mm FL). The survival, gonadal development, and capacity of tagged perch to store abdominal fat was affected neither by the tagging procedure, tag presence, nor tag to body weight ratio. Four months after tagging, no tag had caused internal damage or had been expelled, despite about 95% of them becoming encapsulated by host tissues. Negative effects from tagging were restricted to slower healing rates, and depressed growth of fish with high tag to body weight ratios during the first post-tagging days, which was compensated for by catch-up growth within less than 2 weeks. Surgical PIT tagging can be confidently applied to perch weighing less than 2 g, but the collection of biological data should be delayed by about 2 weeks after tagging. X-ray photographs revealed variable orientations of tags (95% CI: 26°) and slight (ca. 4°) changes of orientation over time. These discrepancies may affect the probability that the tag is detected by automatic data entry stations, and should be compensated for by using smaller antennas (≤87% of maximal antenna size).

EVALUATION OF IMPLANTATION PROCEDURES FOR PIT-TAGGING JUVENILE NILE TILAPIA

Abstract We evaluated three alternative procedures for tagging juvenile Nile tilapia Oreochromis niloticus (1.9–13.7 g) with passive integrated transponder (PIT) tags: injection with hypodermic syringe injectors (N = 40) and abdominal surgery with or without suturing (N = 55 and 40, respectively). The survival of Nile tilapia tagged with injectors was low (10–50% at 10 d) and proportional to fish size because of the difficulty of controlling the penetration of the syringe into the intraperitoneal cavity following the piercing of the body wall. Surgically implanted fish had much higher survival rates (78–100% at 10 d). Suturing reduced the risks of tag expulsion and protrusion of the viscera through the open incision within the first 3 d following surgery (10% risk in the nonsutured fish). Over the first 3 d after tagging, tagged fish showed depressed growth rates (to a greater extent in smaller fish and proportionally greater in sutured fish) but showed normal growth later on. These results demonstrate th...

Effect of stocking density on the dynamics of cannibalism in sibling larvae of Perca fluviatilis under controlled conditions

The effect of stocking density (10, 31.6 and 100 larvae l 1 ; three replicates per treatment) on the day-by-day dynamics of survival, growth and cannibalism was examined in sibling perch larvae reared from eyed-egg stage in 100-l cages (16L:8D, 20.0F0.5 jC, O2z6.0 mg l 1 ; feeding in excess with live Artemia nauplii during the photophase) during the first 3 weeks of exogenous feeding. Larvae unable to achieve the transition to exogenous feeding died in between 7 and 11 days post-hatch. Later, mortality from causes other than cannibalism never exceeded 1% day 1 . Cannibalism did not start before days 10–11 and first consisted in the incomplete ingestion of prey attacked tail first, exclusively. This type of cannibalism never caused losses higher than 2.0% of the initial stock, and ceased after days 16–18. From days 12–14 onwards, differential growth was apparent, and cannibals turned to complete cannibalism of small prey ingested head first, which caused greater losses (28–53% of the stock). Increasing the stocking density did not compromise growth and decreased the overall impact of cannibalism through several complementary mechanisms: (i) a postponed emergence of cannibalism, (ii) a lower proportion of cannibals in the population, and (iii) probably a lower rate of cannibalism per capita as predation was complicated and less directed at high stocking density. D 2003 Elsevier Science B.V. All rights reserved.

Evaluation of surgery procedures for tagging eel Anguilla anguilla (L.) with biotelemetry transmitters

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 20 mm 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 (tn 50). 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 (t_50 = 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 (tn 50 = 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.

Effect of water temperature on survival, growth and phenotypic sex of mixed (XX–XY) progenies of Nile tilapia Oreochromis niloticus

Abstract The ambient temperature during early ontogeny affects the phenotypic sex of various fish species, including the Nile tilapia. Forty-seven groups of Nile tilapia (220 to 350 fish each) from 11 progenies were exposed to different rearing temperatures (20.4–39.0°C) during the first 28 days of exogenous feeding (50-l aquariums, 12L:12D, feeding ad libitum) to model the relationship between ambient temperature and (a) the reversal of phenotypic sex in this species, (b) fish growth and survival rates. The efficacy of the masculinising treatment was estimated with respect to the survival rates in the treatment and control groups (i.e., T ° of circa 27°C), and to their respective sex ratios, in order to take into account the possibility that mortality affected mainly females (minimum efficacy, E m i ) or males (maximum efficacy, E M i ), depending on ambient temperature, and parental influence. Ranges of masculinising efficacy were given by log-logistic equations ln( E m i (1− E m i ) −1 )=−27.495+0.757 T ° ( R 2 =0.548) and ln( E M i (1− E M i ) −1 )=−36.707+1.050 T ° ( R 2 =0.709). The corresponding temperatures giving a masculinising efficacy of 90% were 37.8°C and 39.2°C, for E M i and E m i , respectively. As a corollary, high percentage male progenies could only be obtained at very high temperatures, close to the upper incipient lethal temperature (UILT) of juvenile tilapia (38.5–39.0°C). During the treatment period, the survival and growth of fish reared at circa 37°C averaged 41.9% and 74.5% of those of fish reared at 27–33°C, resulting in a production loss of over 70%, which was not compensated after the temperature was returned to 27°C. These results suggest that the advantage of producing faster growing males of Nile tilapia at high temperature would hardly compensate the loss of production incurred during the masculinising treatment, unless after the selection of the most thermosensitive strains or breeders.

Seasonal variations in time and space utilization by radio-tagged yellow eels Anguilla anguilla (L.) in a small stream

Seven yellow eels (572–643 mm, 318–592 g) Anguilla anguilla (L.) were tagged with surgically implanted radio transmitters (activity circuit, 1.6–1.7 g) and tracked in the Awirs stream, a small (width < 5 m, depth from 0.1 to 1.2 m), densely populated (ca. 250 kg of eel ha-1) tributary of the Belgian River Meuse. The eels were positioned daily from late April to mid-August, and their diel activity was studied during twenty four 24-h cycles. During day-time, the eels were resting in rootwads or in crevices inside stone walls or in crevices in between rocks. They became more active in the late afternoon but generally did not leave their residence before sunset, except under overcast weather. Activity peaked during the first part of the night then progressively vanished, and always ended before sunrise. The area exploited during night-time never extended over more than 40 m2, except when the eel changed its residence. The intensity and timing of nocturnal activity and the extent of the daily activity area were dependent on water temperature (respectively P < 0.0001, P < 0.05 and P < 0.0005), with eels showing little or no activity when the diurnal temperature did not exceed 13 °C. Eels showed higher agitation under full moon and maintained their activity later in the night (P < 0.05). The eels showed restricted mobility, and occupied small stream areas (from 0.01 to 0.10 ha) in a non sequential mode, except for two fish which were displaced to the River Meuse by a spate in early June and were never recovered. The length and frequency of net daily journeys were higher (P = 0.005) at water temperatures above 16 °C in late May and June, which also corresponded to the period of immigration of eels from the River Meuse. This study thus shows that large yellow eels may adopt a highly sedentary lifestyle in a continental, fast flowing and densely populated environment, even at periods of the year when these stages usually show upstream migrations.

Seasonal and diel utilisation of inshore microhabitats by larvae and juveniles of Leuciscus cephalus and Leuciscus leuciscus

From July 1995 to January 1996, we examined the seasonal variations of the diel dynamics of habitat use by young-of-the-year cyprinid fishes (chub Leuciscus cephalus and dace L. leuciscus) in a lotic stream (River Ourthe, Southern Belgium). Inshore bays and neighbouring habitats (riparian shelters, entrance of the bay and shallow riffles) were sampled every three hours from 6:00 to 22:00 h, using DC electrofishing with prepositioned frames. In early summer, chub larvae moved exclusively in between the middle of the bay and riparian shelters inside the bay. Juvenile dace and, later in the season, juvenile chub showed diel dynamics of which the amplitude was dependent on temperature and illumination: they moved into the bay in the morning, gathered in greater numbers at mid-day (up to 586 chub and 387 dace m-2), then progressively left the bay and entered neighbouring riffles in the late afternoon or evening. Small fish immigrated earlier into the bay and emigrated later than fish of larger size. By late September, most dace had left the bays, but returned there when water temperatures were <7°C. During autumn and winter, juvenile dace and chub of all sizes occupied exclusively inshore shelters with submerged riparian macrophytes or fallen tree leaves (corresponding densities of 0.7, 9.5 and 15.8 dace m-2, and of 6.8, 20.2 and 94.2 chub m-2). These results support the idea that young-of-the-year dace and chub shift from a restricted use of inshore shallow bays to a diel dynamics with alternate inshore-offshore movements at the time when they become juveniles, although the precise timings of these movements are still influenced by fish size and water temperature afterwards. The significance of these dynamics is discussed within a context of trade-off between the use of food resources and avoidance of predators.