摘要:

This study describes peculiarities of sperm production by anadromous and precocious parr Atlantic salmon. It was possible to obtain 15 sperm samples with total volume of 130 cm3from anadromous males at the peak of the spawning run. Changes in the sperm characteristics with the increase of the sea‐life age and weight of anadromous males are shown. Such changes are also shown throughout the spawning period. The properties of parr spermatazoa were investigated and it is suggested that these spermatozoa are suitable for inseminatio

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03753.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Brown trout were subjected to the hyperosmotic infiltration method of bacterial immunization. The route of entry ofE. coliinto fish was observed by the immunoperoxidase technique on instantly frozen tissue to be through the gills. The passage of bacteria directly into the lateral line system of the fish was not observed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03754.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The distribution of 0+ perch,Perca fluviatilisL., in a lacustrine environment is described. Since the perch occupied many different habitats within the ecosystem throughout their first year of life a number of sampling techniques were required to sample the population. The early larvae and post larvae were planktonic and their distribution could be related to the effect of the winds. As soon as the young perch developed fins an inshore migration began. Virtually all the fish had completed this migration by the time they reached a total length of 19 mm but the majority of the population reached the shoreline before attaining this size. During June and August the 0+ perch formed large shoals around the shoreline especially in sheltered areas in water less than 3 m deep. At the end of August probably in response to falling lake temperatures the perch fry migrated into deeper water.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03755.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The survival times of hatchery reared year‐old brown trout (Salmo trutta) were tested in solutions containing various ions at pHs between 3.5 and 4.0. The effect of calcium in prolonging the survival time compared with that in deionized water at all pHs tested, was more marked than that of sodium which was only effective at pH 4.0. Potassium and magnesium had no effect individually, but aluminium prolonged the survival time in sodium solutions. Fish from a naturally acid river (Tovdal‐Norway) survived significantly longer than hatchery reared fish, indicating the importance of the previous history of the fish to their sensitivity to low

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03756.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

In clinically normal, cachectic and diseased teleost fish, haemosiderin is observed mostly in the melano‐macrophage centres of the spleen and to a much lesser extent in the centres of the kidney and liver. When rainbow trout that had been splenectomised were starved, accumulation of haemosiderin was diverted to the kidney melano‐macropha

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03757.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Growth data for grass carp,Ctenopharyngodon idella, in managed small impoundments were examined for density related effects. Ponds ranged in area from 0.02 to 5.0 ha; various species stocking combinations were used. Growth during the first year of life was strongly affected by density. Total standing stock increased and average size decreased with increasing density. This growth–density relationship was more variable among fish in the second year of life, primarily because of differences in availability of preferred food in different ponds. Survival tended to vary during the first year of life depending on the size at stocking but was uniformly high in the second yea

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03758.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

A metamorphosing notacanth leptocephalus is reported from the Porcupine Sea‐Bight, southwest of Ireland. It is described and compared with juvenileNotacanthus chemnitziandN. bonaparteifrom the same area. The adult diagnostic features evident are shown to conform withN. chmnitzi.The posterior location of the anus in the leptocephalus relative to the post‐metamorphic condition is noted. The ecological significance of the benthopelagic occurrence of this exceptional larva in slope waters is conside

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03759.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Early sexual maturity occurred in the majority of male Atlantic salmon parr. Levels of the plasma androgens testosterone and 11‐ketotestosterone rose steadily as the male parr matured, and decreased as the testes regressed. No such progressive changes were observed in the plasma gonadotrophin (GTH) levels, although the pituitary GTH levels were much higher in mature than in immature male parr; reasons for this, incluiding the possibility that the GTH radioimmunoassay employed is inadequate, are discussed. All female parr remained immature throughout the year, although the gonadosomatic index did show an annual cycle. Adult salmon had higher GTH and sex steroid levels than parr at the same stage of sexual maturity, the levels corresponding to the degree of sexual development of the adult fis

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03760.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Fry were reared in Windermere lakewater at pH 7.0 or acidified to pH 4.5–5.0. Oxygen uptake by 0.1–5.0 g fry was compared at pH 7.0 and 4.0, using artificial lakewater in the respirometer. No significant differences in oxygen uptake were found at these two pH levels. Measurements of oxygen uptake by sea trout fry (Salmo truttaL.) at pH 7.0 are inclu

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03761.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The atrial myocardial cell in three teleostean speciesGadiculus thoriJ. Smith,Melanogrammus aeglefinus(L.) andOnos cimbriusL. is described. The contractile material is located in the periphery of the cell, whereas the nucleus and mitochondria occupy the central part. The tubules of the sarcoplasmic reticulum are of larger diameter at the Z‐band levels than elsewhere in the sarcomere. The transverse part of the intercalated disc is composed of alternating desmosomes and intermediate junctions. In the longitudinal part of the disc desmosomes occur, situated in close proximity to Z‐bands. Short nexuses were found in the longitudinal part of the disc, usually near the transverse part. InG. thorinumerous atrial specific granules were seen. A high number of mitochondrial granules and glycogen granules seems to occur inO. cimbrius.In the atrial myocardial cell of two or six day‐old larvae ofM. aeglefinus.the contractile material is organized into thin myofibrils, and numerous ribosomes are located in the sarcoplasm.The results of the present work are compared to those previously described in the teleostean atrium and ventricle. The differences in the heart structure within the gadoid family are discussed from a functional and an evolutionary point of

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03762.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY