摘要:

Reproduction of rainbow trout Salmo gairdneri in acidic water was studied. Adults were exposed to waters of pH 4.5, 5.0, or 5.5 during the final 6 weeks of reproductive maturation; control acidities were pH 6.5–7.1. Progeny of acid-exposed females and control males had reduced survival through 7 d of development, hatching, and yolk-sac absorption, demonstrating that oo-genesis is sensitive to acidic conditions. Similar reductions in the survival of the progeny of acid-exposed males and control females indicate the sensitivity of spermatogenesis to low ambient pH. Among the progeny of unexposed adults, survival through 7 d of development and hatching was lower during rearing at pH 4.5, 5.0, or 5.5 than at pH 6.5–7.1. No eggs exposed to pH 4.5 survived to the eyed stage. Concentrations of plasma estradiol-17β, androgens, and 17α-hydroxy-20β-di-hydroprogesterone in acid-exposed adult rainbow trout revealed no gross physiological abnormalities. Plasma calcium concentrations in adult females were unaffected by low pH, but were decreased in adult males exposed to pH 4.5 for 42 d. Plasma sodium concentrations fell slightly in adult fish after 7 d of exposure to pH 4.5, 5.0, or 5.5 and continued to decline in fish exposed to pH 4.5. We conclude that reproduction of rainbow trout is likely to be affected by environmental acidification to pH values below 5.5, although responses may be modified by other biological and physical conditions.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<75:EOLPOR>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

At the Reeds Creek (West Virginia) state hatchery, mortality from enzootic furunculosis is most severe among brown trout Salmo trutta, intermediate in brook trout Salvelinus fontinalis, and virtually nonexistent in rainbow trout Salmo gairdneri. In each species, survivors of epizootics had developed similar levels of protective antibodies in their sera as demonstrated by microtiter agglutination and passive immunization experiments. We concluded that serum antibodies were not related to graded differences in resistance to furunculosis. These same fishes, however, produced a mucus precipitin that reacted with cell-free bacterial extracts in single-radial immunodiffusion assays. The mucus precipitin activity correlated with the resistance of the three species to furunculosis. Breeding studies with brown trout also showed that fish selected for a high level of mucus precipitin activity against Aeromonas salmonicida, the cause of fish furunculosis, produced progeny that were more resistant to furunculosis than other progeny produced from random matings. The nonspecificity of the mucus precipitin reaction was also confirmed by reactions with cell-free extracts from Vibrio anguillarum and Aeromonas hydrophila.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<83:SOSTF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Larvae (eleutheroembryos) of cisco Coregonus albula and whitefish C. larvaretus started to drift downstream in the Gudbrandsdalslågen River concurrently with the beginning of the spring freshets each year, 1981–1983. The duration of yearly outdrift lasted 2–5 weeks in late April and May. The yearly maximum out-drift was positively correlated with the rate of increase in water discharge, but not with water temperature during spring. Most larvae drifted downstream during night.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<89:DOCAWL>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The exchange rate of marked juvenile spots Leiostomus xanthurus between two adjacent tidal creeks was examined over 40 d in the Guinea Marshes of the York River estuary, Virginia. Spots were batch-sprayed with fluorescent pigments on 4–6 June 1984 and released into Little Monday Creek and a nearby smaller unnamed creek. Between 8 June and 17 July, 214 marked spots were recaptured. Of the 134 fish recaptured in the unnamed creek, 6.7% were from the adjacent Little Monday Creek, while 2.5% of the recaptures in Little Monday Creek were from the smaller unnamed creek. These results indicate that the exchange of juvenile spots between tidal creeks is relatively insignificant.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<93:EOMJSB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The sense organs of teleost larvae are incomplete at hatching but sensory cells progressively recruit during development. Cutaneous respiration becomes inadequate after a time but gills then develop. Soon after larvae hatch, the simple segmental myotome system becomes complex and the red muscle concentrates in the midflank position. Median and caudal fin development can be related to the hydrodynamic regime in which the larvae move. Spontaneous activity as well as activity due to feeding, vertical migration, and depth holding increase with age. The feeding behaviour of larvae can be related to the perception of food, feeding success, volume of water searched for food and food requirements. These variables are linked in feeding models to the species, size, and distribution of food available. More complex feeding models incorporate energetic values of larva growth and food, nonrandom food distribution and search patterns of the larvae, and stochastic changes of variables. Predation models are less advanced but larva responses to predators are being investigated.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<98:NLFCDO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Routine activities of early life history stages of fishes occur in an intermediate hydrodynamic environment (as identified by Reynolds numbers), between a zone where drag is linearly dependent on velocity and resistive forces make large contributions to thrust, and a zone where inertial forces dominate except in the boundary layer immediately adjacent to the body surface. Sprint performance carries larvae into this latter zone; thus, locomotor activities important for survival of both larvae and adults occur in the same hydrodynamic environment and similar selective pressures would be expected to influence locomotor morphology of larvae and adults. The simplest framework for evaluating and interpreting development of larvae recognizes the parental form as the developmental terminus and uses adult forms as references to identify similarities and discrepancies in larva structure. Three measures of locomotor structure are used to examine changes during development: (a) the ratio of caudal peduncle depth to maximum body depth, which is small in thunniform fish; (b) a body shape factor, which is small in chaetodontiform fishes; and (c) a transient swimming thrust factor, which is large in esociform fish. Similarities in form are found in yolk-bearing larvae and are attributed to oxygen demand. Similarities in the pattern of development of larvae directly towards the parental form are found for fusiform species, except for delayed development of the caudal fin in tunas that probably is due to the hydrodynamic regime of the tail. Convergence with parents does not occur during the larva stage of deep-bodied, compressed species. This is attributed to high drag of compressed forms at low Reynolds numbers and diet differences between larvae and parents. Although this framework is successful in identifying and interpreting problems, comparative studies of form, kinematics, and performance during biologically important activities are essential.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<115:FLMOEL>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Predation accounts for substantial mortality during the early development of many fishes. Numerous mechanisms have evolved to avoid predatory attacks. One of these is the C-type fast-start of adult fish responding to an abrupt and unexpected stimulus. This is a short-latency response in which the fish accelerates rapidly away from its position at the time of the attack. In the zebra danio Danio [Brachydanio] rerio, this is one of the earliest behavior patterns to appear during development. It can be readily elicited in embryos as early as 44 h after fertilization, 2 d before normal hatching begins. The behavior pattern is triggered by cells of the reticulospinal system located in the hindbrain. Attacks to the anterior region activate one of a pair of these cells, the Mauthner neurons, whereas attacks to the tail stimulate either a Mauthner neuron or other cells that trigger similar response patterns. In teleosts the early appearance of the reticulospinal escape system emphasizes the probable importance of predatory interactions even for the earliest stages of development.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<128:ROTTER>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Zebra danios Danio [Brachydanio] rerio were spawned and their eggs and larvae were reared in a simulated natural thermal regime, increasing from 21 to 30°C for 7 h and decreasing to 21°C for 17 h, daily. Burst-swimming performance was provoked by electrical stimulation of larvae (mean total length = 3.6 mm). Responses were filmed at 400 frames/s at temperature intervals of 3°C. Distance travelled in a specified time (St), maximum velocity, and maximum acceleration increased with temperature. Size-specific maximum velocity was considerably higher than previously reported for larvae. A predictive model relating Stto temperature was developed. In theory, the observed effects of temperature could have been due to changes in physiological rates or in water viscosity, but Reynolds numbers were too high for a substantial viscosity effect. The Q10for Stwas 1.6, that for maximum velocity was 1.4. Results suggest that, other factors being equal, larvae are potentially more vulnerable to predation at sunrise or at other times when water temperature is low.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<143:BPOLZD>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Although planktonic drift is presumed for larvae of most marine fish species, the extent of larva dispersal by intertidal species is largely unknown. Oblique tows with a net of 500-μm mesh were made at distances of 0, 4, 20, and 500 m from steep rocky shores, divers guiding the 0-m tows. Ichthyoplankton of the extreme nearshore area was more dense than that of offshore waters. Species composition shifted radically from inshore to offshore; intertidal species (cottids, stichaeids, pholids, gobiesocids) were dominant inshore. Larvae of rocky intertidal fishes occurred more frequently along rocky shores than on an adjacent sandy beach. The evidence suggests that larvae of rocky intertidal fishes resist offshore and possibly longshore dispersal. In contrast to information for sandy beaches, data for the rocky nearshore area reveal that all stages of larvae remain inshore, not just those within a narrow size range. Populations of rocky intertidal fishes may thus be relatively isolated genetically.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<149:LOPDOR>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The effects of delayed spawning by adult Pacific herring Clupea harengus pallasi on the viability of eggs and larvae were examined. Adults were captured 1–2 months prior to spawning and held in captivity. They completed maturation (ovulation), did not spawn, and maintained sexual readiness for 2–3 months beyond normal spawning time. During this period, eggs were fertilized artificially and incubated. At regular intervals fertilization rate, survival to hatching, hatching rate, and viable hatch were monitored. Spawning delays of less than 2 weeks after maturation had no detectable effect on fertilization, survival, or hatching rates. Longer delays resulted in progressive loss of egg and larva viability, although fertilization rates remained high, and time to hatching decreased as the holding period increased. When females were held at colder temperatures, deterioration in the rate of egg and larva survival was delayed. If mature females are held longer than 2–3 weeks prior to experimental work on eggs and larvae, abnormally low estimates of progeny survival could result.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<155:EODSOV>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor