摘要:

SummaryThe capability of planktonic yolk‐sac larvae of red sea breamPagrus majorin detecting food was examined in the laboratory to ascertain basic knowledge on the early life history of this marine fish. After infrequent vertical burst swimming followed by slight rising or sinking, the larvae remained motionless within thin layers of concentrated food extract (rotifer,Brachionus plicatilis). At the moment of hatching, the larvae already have receptor cells with several cilia arranged radially in their open nostrils. Thus it is likely that by means of their vertical movement they are capable of sensing the thin food patch layer. We suggest that planktonic larvae ofPagrus majorare capable of detecting and remaining within food patches even before the onset of feeding. The onset of food detection in the earlier stages may be, to some extent, the more efficient strategy for larval survival and growth because this ability could contribute to a reduction in energy consumptio

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1991.tb00519.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryThe goal of the experiment was to refine a simple and practical method for inducing gynogenesis in rainbow trout. To eliminate the male genome, UV‐irradiation was used in combination with seminal fluid dilution and continuous stirring. Sperm motility was controlled. A visible recessive marker (yellow colour) as well as the Hertwig Effect were applied to assess the outcome of induced gynogenesis. Sperm irradiation by UV (energy output 2075 μW/cm2) for more than 5 minutes and 10 minutes in dilutions of seminal fluid of 1:40 and 1:20, respectively, resulted in yellow coloured feeding fry in the diploidized groups, whereas non‐viable larvae were produced in the haploid groups. The highest survival rate for gynogenomes (from insemination until first‐feeding fry) wa

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1991.tb00520.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryThe effect diel variation in availability and vulnerability has on the fish capture process of a groundfish survey trawl was examined from data collected during an experiment measuring fish escapement underneath the footgear. The survey trawl was significantly more efficient at night in capturing American plaice,Hippoglossoides platessoides, and yellowtail flounder,Limanda ferruginea, but no difference was found in catches of Atlantic cod,Gadus morhua.This increase in capture efficiency at night is related to an increase in availability and vulnerability associated with diel variation in light intensity. No evidence of diel vertical migration was found and changes in availability were linked to visual dependent gear avoidance by the fish.Regardless of light conditions, the survey trawl had a very low capture efficiency for juveniles of the three species studied. Escapement of this size group was extremely high during both day and night periods due to a fast towing speed, use of large bobbin gear, and possible mesh selection.

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1991.tb00521.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryThe susceptibility of turbot, coho salmon, and rainbow trout to strains ofVibrio anguillarumof serotypes 01 and 02 and their extracellular products (ECP) was investigated in order to clarify the role of exotoxins in the mechanism of virulence of both serotypes. AllV. anguillarumisolates were virulent for trout, salmon, and turbot. Despite the origin of the strains tested, rainbow trout was the most susceptible fish species to experimentally induced vibriosis. Coho salmon and turbot did not differ significantly in their susceptibility toV. anguillarumlive cells. In contrast, the ECP fromVibriostrains of serotypes 01 and 02 exhibited similar lethal dose for turbot, salmon, and trout (ranging from 4.52 to 7.32 μg protein/g fish). Therefore, differences in susceptibility to vibriosis are not completely due to a differential sensitivity of fish to the extracellular products ofVibriostrains. The ECP from 7 of 10V. anguillarumstrains possessed vascular permeability factors, and all the extracts displayed proteolytic, hemolytic and cytotoxic activities. All the biological activities of ECP were lost after heat treatment at 80° C/10 mi

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1991.tb00522.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryThe effects of natural blooms ofHeterosigma akashiwoon freshwater‐and saltwater‐acclimated juvenile chinook salmon were assessed. Rates of fish mortality in the blooms were independent of acclimation of fish to seawater and the ambient oxygen levels, but were dependent on concentration of algae and ambient water temperatures. No pathological abnormality to gills or other internal organs in the fish were evident. Aeration or oxygenation of fish cages did not enhance or inhibit fish survival in aH. akashiwobloom. Cause of death was considered to be due to a labile ichthyotoxic ag

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1991.tb00523.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryFor three selected weeks in July, August, and October 1985, catches from anchor net vessels at ten stations along the tidal Elbe River (northern Germany) were analyzed and related to oxygen conditions in the river. The oxygen concentrations decreased from an average of 6.6 ml/L in the estuary to an average of 1.4 mg/L upstream. Fish were found to be concentrated downstream from the low‐oxygen zone and at the entrance to a shallow side arm of the main stream. Highest catches of eel were made where oxygen levels were in the range of 1.2–3 mg/L, highest catches of flounder at 3–4 mg/L, and highest catches of juvenile and adult smelt in areas with more than 5 mgO2/L. Such a situation enables fishermen to make extraordinarily high catches. It is concluded that despite high levels of toxicants, the tidal Elbe still offers living conditions adequate for the mass of fish species as long as there is a sufficient supply of o

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1991.tb00524.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryAn ELISA for rapid detection of viral haemorrhagic septicaemia virus (VHSV, Egtved virus) in fish tissue was developed and tested with regard to sensitivity. The test is a valuable addition to traditional isolation of VHSV in cell culture when a rapid diagnosis is needed.

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1991.tb00525.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryMass mortality caused by Prymnesium saltans Massart in the Kleiner Jasmunder Bodden (Rügen), April 1990A report on the reasons, spread and extent of a mass mortality in a Bodden water near the Isle of Rügen (Germany). The cause of mass fish mortality was an abundance of the toxic algaePrymnesium saltansMassart, with approx. 300000000 cells per lite

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1991.tb00526.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY