摘要:

The period of activity of mullet spermatozoa suspended in seawater was similar to that of sperm suspended in osmolar equivalent dextrose solution or artificially prepared seawater. Sperm activity was longest in solutions of pH and osmolarity closely approaching that of normal seawater. Temperatures lower than those at which spawning normally occurs greatly increased the period of activity. Undiluted milt stored at 10° C couid be activated by the addition of seawater for a period of 36 h

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb03654.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

A series of nettings for roach in Chew Valley Lake carried out by members of the Zoology Department, Bristol University, has revealed a marked decline in the population between 1965 and 1968. Fish from the main Lake were found to be heavily parasitized withLigula intestinalis(L.) while those from the inflow pool (Herriott's Pool) were practically free from infection. It is considered that the decline of the roach can be linked to the incidence ofLigula, but that clean fish from the inflow pool may provide breeding stock and maintain the production of fry, which serve as food for the trout.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb03655.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Intracranial inoculation of infectious pancreatic necrosis virus (IPNV), a pathogen of several species of trout, produced pancreatic necrosis in suckling Swiss albino mice. Peri‐nuclear halos, cytoplasmic vacuoles, and necrosis were found in histologic sections of pancreas taken from mice killed 21 days post‐inoculation. Virus was recovered from the pancreas of mice killed as early as 10 days post‐inoculation. Rivers' postulates were fulfilled. Virus recovered from the infected mouse pancreas was neutralized by IPNV specific antiserum. The significance of the mouse as an experimental host is disc

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb03656.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Records of the distribution of the genusArgulusin Scotland are given. The occurrence of A.coregoniThorell in the River Clyde is confirmed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb03657.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Turbot (11–70 cm long) and brill (21–70 cm long) were collected in the summer of 1968 north of the Brown Bank, Texel Hole and were infected byBothriocephalus scorpii.Infections occurred even in the first year of life of the fish. In turbot, with increasing length, the average weight of tapeworm rose from 0–6 to 14‐9 g/flsh. Brill were less commonly infected and then only slightly. The intermediate host of the tapeworm seems to beGobiusspecies, upon which juvenile turbot and brill pr

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb03658.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The food ofTilapia mariae(Boulenger),Tilapia guineensis* (Bleeker) andTilapia melano‐theron melanotheron*(Rupell) were investigated. It is shown that T.guineensisandT. m. melanotheronwhich were the more abundant species had similar food habits. The intensity of feeding of both species and the possible competition for food between them are discusse

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb03659.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The production of the young stages of four species of cyprinid fish in the River Thames was estimated. From the time when underyearling fish became fully vulnerable to the special fine mesh net used, to the end of their first year, production is 39 g/ma/year compared with 83‐3 g/m2/year for fish over 1‐year old. The contribution of fecundity to population production varied widely, from 6.1 to 0.4 g/m2/year, but was only a small part of total production. The most productive part of the population was that found between spawning and prior to full vulnerability to the net. Production of this part of the population could be estimated only indirectly and was found to be 58‐6 g/m2/year. In the four populations studied production during the first year of life was 66 to 73 % of total cohort production in 1967 and only 39 to 64% in 1968. Total fish production in the Thames was estimated at 197 k cal/m2/year; this high result is a consequence of the very high densities found: up to 96‐9 fish/m2 were present in August 1967. Ten km of the Thames would contain about 54 000 000 fish in August, falling to around 8 000 000 in winter. The production: biomass ratios for the four species varied from 1–1 to 1′9 in 1967 and from 0–7 to 2‐0 in 1968.Very heavy, possibly density dependent, mortality occurs in the first year of life; the annual instantaneous mortality rates are very high, ranging from 6–4 to 8–7. Mortality is heaviest during the first 2 to 3 months after spawning; the instantaneous mortality rates during this period v

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb03660.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

In the cichlid teleostTilapia mossambicasecondary chill coma following exposure to 11° C in freshwater is associated with decreases in plasma osmolarity, sodium and chloride ion concentrations. Fish exposed in seawater diluted to give a NaCl concentration of 5%0 show no signs of coma nor are there decreases in osmolarity or sodium and chloride ion concentrations.It is suggested that the restrictions of T. mossambica to estuaries at the southern end of its distribution in southern Africa relates to the maintenance of near normal sodium and chloride ion concentrations at low temperatures during winter

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb03661.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The examination of the stomach contents of 253 grayling from the River Lugg has provided some evidence of a possible depression of feeding activity during the summer months. The diet was varied but bottom food predominated, especially insect larvae, Crustacea and molluscs. Some surface foods were taken but plant material was rarely eaten. Substrate material, detritus and debris and even large pebbles were eaten, mainly in summer. Most seasonal variations in the diet could be related to variations in availability. Fish were not eaten but cyprinid and salmonid eggs were eaten at the appropriate season. In general, increasing amounts of larger food items were eaten by the older grayling.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb03662.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The total protein level is reduced and the electrophoretic pattern of the serum is changed in troutSalmo trutta L.infected with UDN, as in the Atlantic salmon. However, the changes in the trout are not as characteristic as those in salmon and thus are of very limited use in diagnosis of outbreaks of this disease among trout.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb03663.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY