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  • 1
    Electronic Resource
    Electronic Resource
    Thermal related variations of seasonal and daily spawning periodicity in Barbus barbus (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 46 (1995), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In 1993, nocturnal spawning activities were observed in the diurnal spawning cyprinid Barbus barbus. This behaviour is interpreted as a response to exceptionally high daily thermal amplitudes, regarded as the sign of an unpredictable environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1995.tb01617.x
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  • 2
    Electronic Resource
    Electronic Resource
    Seasonal activities of Barbus barbus: effect of temperature on time-budgeting (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 46 (1995), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Surgically implanted activity-circuit radio transmitters (40 MHz) were used to study the seasonal activities of 21 adult (males: 23 to 35 cm f.l. and females 38 to 55 cm f.l.) Barbus barbus (Pisces, Cyprinidae) in the River Ourthe (Southern Belgium) in 1989–1991. During the autumnal thermal transition (water temperature 9 to 10° C), the typical dusk and dawn pattern observed in summer turned to a trimodal pattern with the emergence of a diurnal phase. The auroral then crepuscular and finally diurnal activity periods progressively vanished as water temperature decreased down to the thermal limit for activity (4.0° C), when barbel entered a dormancy period. An opposite progressive shift was observed during the spring thermal transition. Daily activity budgets ranged from 0 to 720 min—on the annual cycle and were significantly (r2=0.686, P〈0.05, d.f. = 36) dependent on water temperature and on morphodynamic unit size, while fish size was non-significant. Although the dusk and dawn rhythm pattern was consistent throughout summer, water temperature significantly (P〈0.05) interfered with the respective duration of crepuscular and auroral activities (r2=0.586, d.f. = 57 and r2=0.692, d.f. = 55). The precise timing of activities was also thermal-related and the activities of small male barbel were proportionally more nocturnal than those of large female barbel (ANCOVA, F=80.61, d.f. = 31 and F=4.s5, d.f. = 23, at dusk and dawn respectively), possibly due to predation pressure on small fish. It is concluded that the seasonal variations of activity budgets, rhythm patterns and timings in B. barbus correspond to a form of time-budgeting partly to achieve thermal homeostasis in a variable environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1995.tb01603.x
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  • 3
    Electronic Resource
    Electronic Resource
    Dynamics of intracohort cannibalism in cultured fish (2002)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 33 (2002), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Cannibalism is a frequent phenomenon in fish, especially in culture environments where fish are unable to escape predation via habitat segregation or migration. Not all cultured fish species start to exhibit cannibalism at the same age or size, nor is cannibalism equally intense in different species or life stages. Predator to prey size ratios vary substantially between species and life stages, chiefly because cannibalism is governed by gape size limitations and allometric growth of mouthparts. The development of sense organs, hard body parts, swimming and escape capacities in both the predator and the prey also influence prey size selectivity. The dynamics of cannibalism are influenced by these, as well as by environmental, factors that have effects on feed intake, growth depensation and facilitate or complicate the displaying of cannibalistic behaviour. Knowledge about cannibalistic behaviour and the logistics of cannibalism along with environmental enhancement are prerequisites for the mitigation of cannibalism in aquaculture. Also, within the context of strain selection, it is of importance to determine whether cannibals are natural-born killers or just lottery winners. These factors are discussed, chiefly as they apply to intracohort cannibalism. In addition, guidelines are suggested for cannibalistic risk assessment, and methods for mitigation of cannibalism are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.2002.00732.x
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  • 4
    Electronic Resource
    Electronic Resource
    Expression of myofibrillar proteins and parvalbumin isoforms in white muscle of dorada during development (2003)
    Oxford, UK : Blackwell Science Ltd
    Journal of fish biology 62 (2003), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Several polyacrylamide gel electrophoresis techniques were used to study developmental changes in myofibrillar protein composition and parvalbumin distribution in the myotomal muscle of Brycon moorei. Two myosin LC2 chains and two troponin I isoforms were successively detected. Up to four troponin T isoforms were synthesized. Slow red-muscle myofibrils from adult fish showed no common component (except actin) with larval, juvenile or adult fast white-muscle myofibrils. During growth of B. moorei, two classes of parvalbumin isoforms were sequentially expressed: larval PA I, PA IIa, and PA IIb and adult PA III. In adult fish, the content in Tn T-2 isoform decreased from the anterior to the posterior myomeres, in favour of Tn T-1 and Tn T-4. The parvalbumin content also diminished from the rostral to the caudal muscle. The fast rate of transition from larval to adult isoforms appeared to parallel the extremely fast growth of B. moorei. Sequential expression of these isoforms presumably reflected variations in the contractile properties of the muscle fibres, required by changes in physiological demands of the propulsive musculature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1095-8649.2003.00064.x
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  • 5
    Electronic Resource
    Electronic Resource
    Sibling cannibalism among juvenile vundu under controlled conditions. I. Cannibalistic behaviour, prey selection and prey size selectivity (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 54 (1999), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Sibling cannibalism among vundu Heterobranchus longifilis larvae started at the age of 4 days, with the prey caught tail-first then swallowed up to the head, which was eventually discarded (type I cannibalism). At 17 days old, this type of cannibalism vanished and was replaced by the ingestion of the whole prey (type II cannibalism), which could only be exerted by predators six times as heavy as their prey. Type II cannibalism consisted of a seemingly opportunistic ambush attack by a formerly passive predator towards a disorientated prey. It required no preliminary aggression or chase, or even contact with the prey, suggesting that the attack was not mediated by the tactile sense, and that cannibalism was independent of aggressive behaviour. When alternative food resources (formulated feed, live tilapia prey) were available, the intensity of cannibalism decreased but pellet-eaters or tilapia predators always achieved lower growth rates than those feeding on conspecifics, suggesting that cannibalism was the most advantageous foraging tactic. Losses to cannibalism among populations of 30-day old juvenile vundu with an initial ratio of 4% of cannibals were as high as 75·5–79·9% over 15 days. Predation peaked during the first days (up to 2·8 prey C−1 day−1), then vanished progressively as surviving prey grew faster than cannibals and escaped their predation. Cannibals preferred consuming the largest prey available with respect to the logistics of cannibalism (body weight ratio of 6·0). This preference for large prey was interpreted both as a foraging tactic aiming to maximize the energetic return, and as foraging strategy enabling the cannibals to exploit their prey as long as possible. Based on these data, comprehensive models of the impact of cannibalism on vundu populations were developed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1999.tb00614.x
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  • 6
    Electronic Resource
    Electronic Resource
    Ontogenetic variations of thermal optimum for growth, and its implication on thermolabile sex determination in blue tilapia (2002)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 61 (2002), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Knowledge of how the optimum temperature for growth (T°opt) varies during ontogeny, and how close it is to the temperatures that induce phenotypic masculinization is fundamental to the understanding of the evolution of thermolabile sex determinism (TSD) in fishes. In blue tilapia Oreochromis aureus, T°opt is 32·6° C at the start of exogenous feeding (10mg fish) and it decreases by c. 1° C each time that the fish body mass increases by an order of magnitude. Temperatures 〈35° C are not sufficient to induce complete phenotypic masculinization. Based on a multiple-regression model (r2=0·938) plotting growth against body mass and water temperature, genotypically female tilapia living at high temperatures during the thermosensitive period (21–28 days) and being reversed into phenotypic males would incur an initial growth disadvantage over fish living at T°opt, but not over those living at slightly colder temperatures (27–29° C). This initial disadvantage would be later compensated for by faster growth because of between-sex growth dimorphism to the detriment of phenotypic females. These arguments suggest that there is no definite pressure against the selection of TSD in blue tilapia and probably other Oreochromis spp.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2002.tb00902.x
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  • 7
    Electronic Resource
    Electronic Resource
    Phenotypic sex differentiation of blue tilapia under constant and fluctuating thermal regimes and its adaptive and evolutionary implications (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 57 (2000), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Oreochromis aureus exposed during the first 28 days of exogenous feeding to constant 35° C, or fluctuating temperatures (day at 35° C, night at 27° C, and vice versa) showed significantly (P〈0·05) faster growth, least size heterogeneity and better survival rates than siblings under constant 27° C. Constant high temperatures had a strong masculinizing effect (M: F sex ratios of 7·33–19·00: 1·00 v. 0·75–0·82: 1·00 in controls reared at 27° C). Fluctuating temperatures had less masculinizing potential but still produced sex ratios significantly skewed to the detriment of females (M: F sex ratios of 2·33–11·50: 1·00). This suggests that ambient temperature may have represented a sufficient environmental pressure for the selection of thermolabile sex-determinism in this species, and presumably in other Oreochromis spp. The evolutionary advantage of thermosensitivity in Oreochromis spp. is discussed, considering a framework where individual advantages oppose, to some degree, to the population or species interest.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2000.tb00787.x
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  • 8
    Electronic Resource
    Electronic Resource
    A preliminary investigation of spawning migrations of grayling in a small stream as determined by radio-tracking (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 55 (1999), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Adult grayling Thymallus thymallus migrated from 230 to 4980 m up the Aisne stream, Belgium, to spawn between 18 and 29 March, under decreasing floods, increasing temperature and low turbidity. Males (n=4) arrived on spawning grounds several days earlier than females (n=2), stayed there longer (10–19 v. 2–3 days), and occupied a single ground each, whereas females moved between several places. After spawning, all grayling homed precisely into the pool-riffle sequences where they were tagged in late February, and remained here until late June. These observations indicate that resident grayling are far less mobile than autumn-spawning salmonids, and that the environmental factors triggering spawning migrations resemble more closely those of spring-spawning cyprinids than of other salmonids. The implications of these restricted mobility patterns are discussed within the scope of population structure, and impact of river management.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1999.tb00666.x
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  • 9
    Electronic Resource
    Electronic Resource
    Functional implications of early sexual growth dimorphism in vundu (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 54 (1999), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Female juvenile vundu Heterobranchus longifilis outweighed males by 〉 60% (P 〈 0·0001) margins when aged 142 or 177 days. Not only did females grow faster (P=0·0494) than males during the experiment, but they also outweighed them by a 38·5% margin at the start of the experiment (86 days: P=0·0109). Sexual growth dimorphism (SGD) was estimated as having arisen at 15 ± 10 days. Vundu aquaculture could be improved substantially by monosex female rearing. Because the modelled emergence of SGD corresponded precisely with the start of type II cannibalism, it was suggested that cannibalism among juvenile vundu be exerted essentially by females, and might have different impacts on faster-growing females and slower-growing males.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1999.tb00616.x
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  • 10
    Electronic Resource
    Electronic Resource
    Postembryonic development of the cephalic region in Heterobranchus longifilis (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 50 (1997), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: At hatching, Heterobranchus longifilis does not display any primordia of the cephalic skeleton. The latter appears 12 h post–hatching and develops in three stages up to day 16. The first stage (12 h to 2 days) involves almost exclusively the development of the chondrocranium. During the second period (days 3–8), dermal elements of the splanchnocranium appear. The final stage is marked by resorption of the cartilages, progressively replaced by ossifications (days 10–16). At their appearance the elements of the splanchnocranium are fused together, as are the first neurocranial elements. Later, the splanchnocranium splits up. By the time the yolk sac is completely resorbed, the buccal and pharyngeal jaws are present, the suspensoria and hyoid bars are partially developed, and the parasphenoid partially closes the hypophyseal fenestra. These structures delimit a buccal cavity that is probably functional, i.e. capable of participating in the intake of exogenous food. Next to continue its development is principally the splanchnocranium, completing the walls of the buccal cavity. Cartilage resorption parallels the appearance of endochondral ossifications (except for the trabecular bars). Braincase closure begins to accelerate once the buccal system is complete.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1997.tb01355.x
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