摘要:

Twelve sea ravens,Hemitripterus americanus, were tested individually for three day periods in electronic shuttleboxes to measure their preferred and avoided temperatures, diel activity pattern and relationship of activity to temperature. The fish avoided temperatures below 9°C or above 25°C, preferring temperatures with a central tendency of 15–17°C. The fish were primarily nocturnal, being more active at night than by day. Locomotor activity increased eightfold between 10 and 20°C, but exhibited an anomalous decrease between 14 and 18°C, corresponding to the preferred‐temperature zone, characteristic of maximal summer temperatures in the natural

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03888.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Hatchery‐raised coho salmon were marked with stable strontium prior to their release to sea. Returning marked spawners were correctly identified after 18 months at sea by measuring the Strontium (Sr) concentration of the central region of their scales and vertebra

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03889.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Snakeheads were adapted to fresh water (1 mOsm kg−1), 25% sea water (230 mOsm kg−1), 33% sea water (320 mOsm kg−1) and 40% sea water (380 mOsm kg−1) for 20 days. Exposure to salt water resulted in tissue dehydration, elevations of plasma osmolality, Na+, Mg2+, Cl−and protein concentrations and stimulation of branchial Na+‐K+‐ATPase activity. These changes were accompanied by concomitant decline of the hepatosomatic index and liver glycogen concentration. The routine rate of oxygen consumption was increased in snake‐heads adapted to 33% sea water. These data were taken to indicate a stressful effect of salinity to the snakehead despite documentation of its ability to penetrate into

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03890.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

A number of parameters were measured in a population of perch whose numbers had declined steeply in a habitat subjected to increasing eutrophication, and these measurements were compared with those taken before the population decline. Contrary to expectation, no adaptive responses were identified. The growth rate of perch up to the age of III had only declined slightly, and there was a marked preponderance of young fish. Relative growth rate was consistent despite the population decline. No dominant year class was apparent. Mean instantaneous mortality rate and annual survival rate were calculated, and the length‐weight relationship was analysed. Feeding strategy had not altered since an earlier study. A decline was seen in the percentage of perch maturing at early age. Ripeness coefficients and fecundity estimates were calculated. A previously documented spawning migration was confirmed. The absence of the expected adaptive changes is discusse

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03891.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

In the absence of a suitable key for the identification of adult British grey mullets, a simple key has been compounded from the relevant literature; the 1957 key of Perlmutter, Bograd and Pruginin was used for the identification of juvenile specimens. The correspondence between identifications of young and old fishes was checked by rearing fishes in the laboratory and by gel‐electrophoresi

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03892.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Plasma cortisol levels of fingerling rainbow trout were measured as an index of the stress resulting from various procedures used for transport of the fish for stocking. When transported under ‘normal’ conditions, which included water at the hatchery acclimation temperature (10–11°C), O2saturation or supersaturation, and neutral pH, there was a marked increase in plasma cortisol levels within 0.5 h, which was maintained over the next 4 h of transport; there was a significant decrease in plasma cortisol by 8 h of transport. It was found that the plasma cortisol levels at 4 and 8 h were not appreciably altered by transport under partial O2desaturation, O2saturation, O2supersaturation, or 0.5% NaCl, or by anaesthesia with tricaine methanesulfonate (MS 222) prior to capture and transport in MS 222‐free water or 0.5% NaCl. A 15 min exposure to an immobilizing dose of buffered or unbuffered MS 222, or 2‐phenoxyethanol, caused an increase in plasma cortisol of about 2 h duration, indicating that anaesthetics are themselves stressful. Exposure to chilled water (1° C) caused a large increase in plasma cortisol levels by 4 h after initiation of exposure; plasma cortisol had decreased at 1 day, and by 2 days a constant level was reached which was above the level in fingerling trout under ‘normal’ hatchery conditions. Trout acclimated to chilled water for 24 h and transported in chilled water had an increase in plasma cortisol during transport. Anaesthesia prior to transport or addition of salt did not reduce the stress of transport as judged by plasma cortisol levels. The results indicate that stress from capture and transport during stocking cannot be avoided using

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03893.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The distribution, external surface morphology and ultrastructure of taste buds in the oropharyngeal cavity of the rainbow trout,Salmo gairdneriRichardson, were studied using scanning and transmission electron microscopes (SEM and TEM). The SEM revealed three taste bud types, varying only in their degree of elevation from the general level of the epithelium. Types I and II were located on elevated papillae associated with teeth on the dentary, maxilla, palate, tongue and pharyngeal pads while the unelevated Type III were mainly found in the anterior (branchial) pharynx.Each taste bud was composed of four cell types: basal, dark, intermediate and light cells, the apical processes of the last three filling the taste pores. The intermediate and light cells appeared similar in ultrastructure, varying only in the amount and organization of smooth endoplasmic reticulum (SER) in their cytoplasm. In addition to its contacts with the processes of intragemmal nerves distally, the basal cells established independent contacts with processes of extragemmal nerves basally. It is suggested that the distribution of the taste buds and their close association with teeth are adaptations to the predatory feeding habit of the rainbow trout. Age differences may account for the existence of two types of gustatory cells and the manner of innervation of the taste bud suggests the existence of two pathways for the transmission of gustatory sensation to the central nervous system (CNS).

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03894.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The effect of feeding an isocaloric and isonitrogenous trout diet that contained different levels of digestible carbohydrate (cerelose) to rainbow trout at either 10 or 15° C on liver glycogen and liver weight was determined in two fasting studies of 12 and 41 days duration. Trout fed diets with increased levels of digestible carbohydrate (HC) had significantly higher liver‐body weight ratios (LW) and liver glycogen (LG) than trout reared on low digestible carbohydrate diets (HF). Both LW and LG declined in fasting trout previously fed HC diets but declined little in fasting trout previously fed HF diets. Trout reared at 10° C had higher LW and LG than trout reared at 15° C on either the HC or HF diets. During fasting, the trout reared on HC diets at 10° C required a longer period of time for the LG and LW to decline to the levels of trout reared on the low carbohydrate diets, than did trout reared on the HC diets at 15° C. The results indicate that both pre‐fasting diet and water temperature can affect liver glycogen utilization and liver weight in fasting trout. Prolonged elevation of LW and LG in fasting trout could jeopardize the survival rate of stocked trout, particularly at low water temp

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03895.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The osmoregulatory capabilities of juvenile striped mullet,Mugil cephalus L., of three size‐groups (20–29, 30–39 and 40–9 mm s.l.) were compared in a series of six salinities ranging from fresh water to full sea water. The two smaller size‐groups were able to tolerate instantaneous transfer from the brackish water in which captured, to all salinities but fresh water, while the 40–69 mm group were tolerant of instantaneous transfer to all experimental salinities. At high environmental salinities, the osmotic regulatory capabilities improved with growth in size to an apparently definitive condition in fish of 40–69 mm s.l. The smallest of these individuals were estimated to be about 7.5 months old. The osmotic regulatory capability in waters of low salinity had reached a definitive state with the development of tolerance to such salinities. The ontogenetic pattern forMugil cephalusis virtually identical to that of the Atlantic salmo

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03896.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Rainbow trout were exposed to sublethal concentrations of Permethrin in water (0.09, 0.18 and 0.35 μg l−1) and in food (85, 180 and 350 μg kg−1dry diet) in 20–0 day experiments. Histological changes in the gills included epithelial separation or necrosis, mucus cell hyperplasia, clubbing of epithelial cells or hyperplasia and fusion of adjacent secondary lamellae. These changes were noted in all fish, suggesting that the pesticide or its metabolites reached the gills not only directly through the water, but also indirectly via the circ

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03897.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY