摘要:

The nutritional dynamics ofGymnotus carapowere studied in 3253 male and female specimens collected in the Lobo Reservoir over a period of 18 consecutive months (September 1978 to February 1980). Analysis of the repletion stages, of mean repletion grade and index showed that the fishes exhibited better feeding conditions after the reproductive season. The condition factor was determined and shown to be influenced by the ovarian weight at the time of reproduction, but was little influenced by testis weight. The effect of stomach weight is negligible for both males and females.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04807.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The occurrence of stones, sediment and fish scales was determined among the stomach contents of some 5000 fish. These fish comprised representatives of more than 70 different demersal species, sampled at 250 m bathymetric intervals, from the Rockall Trough, northeastern Atlantic Ocean, at depths ranging from 500 to 2900 m. Stones only occurred in stomachs of fish caught at 500–1000 m depth, their incidence in stomachs with food present being 4.6% at 500m, 1.1% at 750 m and 1.3% at 1000m depth. Sediment occurred in 9%, fish scales in 7%, of stomachs with contents. Sediment and scales co‐occurred in the stomachs of primarily benthopelagic feeding fish. The sediment, however, was associated with the less dominant epibenthic components of the diets while the scales occurred with the more common benthopelagic components. The co‐occurrence of sediment, scales and benthopelagic prey may arise through the former items having longer residence times in the stomachs than, for example, epibenthic prey. There is no evidence of increased occurrence of sediment (and its associated meiofauna) in the diets of fish on the lower slope at depths of 1500–2900 m in the Rockall

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04808.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

A survey of the parasites of 243 fish belonging to 13 species, from the Corrib catchment area, western Ireland, was undertaken. At least 32 species of metazoan parasites were shown to be present.Diplostomum gasterostei, Tylodelphys clavata, Eubothrium salvelini, Cucullanus truttae, Raphidascaris acus, Ergasilus gibbusandSalmincola gordoniappear to be first records for Ireland andPhyllodistomum conostomumhas not previously been reported from the British Isles. New host records involvingLamptera planeri, Salvelinus alpinus, Abramis brama, Noemacheilus barbatulus, Anguilla anguillaandPungitius pungitiusfor the British Isles are given.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04809.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

External features of the development of fry of the brown acara,Aequidens portalegrensis, are described. There is evidence that thyroxine is a melanophore‐concentrating hormone early in larval life. There is also evidence that adrenal corticosteroids are of importance in the growth and development of fry. The development of the retina is described. All structural components of the adult retina are present by 7 days after fertilization, when rods and the capacity for visual accommodation appear. Double cones first appear a day previously; circumstantial evidence suggests that they originate from the incomplete fission of single cones. The development of the optic tectum is similar to amphibians. The pace of tectal differentiation is slower than that of the retina. When the fry become free‐swimming (+ 6 days), the wall of the tectum comprises a thickstratum periventricularewith, external to this, a thinstratum corticalis.Thestratum corticalissubsequently increases in thickness, concomitant with the migration of individual neurones from thestratum periventriculare.The distinct stratification of the adult optic tectum is not apparent until shortly after the transition to the juvenile phase (+24 da

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04810.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Marking experiments on perch,Perca fluviatilisL., pike,Esox luciusL., and charr,Salvelinus alpinusL., have been carried out in Windermere. Numbered tags were used for individual identification, except in some short term experiments on charr. A total of 13 182 perch and 4696 pike were tagged; 2066 charr were tagged subcutaneously and marked with a fin clip. In the short‐term experiments 2015 charr were marked with a fin clip or punched hole. Perch were recaptured up to 8 years after tagging, pike 12 years and charr 5 years. Estimates of numbers and mortality were not satisfactory, except for limited sections of the populations of pike and charr. The main reasons for the unsatisfactory results were: for perch, unknown mortality at time of tagging; for pike, selectivity of the gillnets and in some years low numbers tagged; for charr, restriction to few spawning sites and in some places low numbers recaptured. The experiments provided useful information on movements and growth, which could not have been obtained in any other wa

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04811.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Movements of native brown trout,Salmo trutta, 1 + and older, were limited with up to 93% of recaptured marked fish occupying sites where previously caught. Movements>50 m were rare with the majority<15 m. Between sampling occasions, the population could be separated into a static component and a smaller mobile component but there was no evidence of a permanently mobile group. The proportion of mobile native fish increased after stocking with hatchery‐reared trout. Displaced native trout (1 + and older) showed the ability to home from 75 m upstream to 111 m downstream of a release sit

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04812.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The variation in egg size present in the eggs of Arctic charr,Salvelinus alpinus, was significant for the survival and growth of newly hatched alevins. Alevins from large eggs were larger, grew more quickly, and suffered less initial mortality than alevins from small eggs. The yolk sac was proportionately larger in alevins from large eggs. The largest eggs produced a relatively high proportion of abnormal alevins.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04813.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The aim of this study was to investigate ageing of ovulated eggs retained in the ovarian lumen of captive turbot,Scophthalmus maximusL., prior to handstripping. The ovulation times of egg‐batches were determined by catheterization, handstripping and plotting the percentage fertilizations and hatches of resulting eggs against time. The catheterization experiments showed that eggs age and change appearance rapidly after ovulation. The stripping method demonstrated that freshly‐ovulated eggs showed greater than 90% fertilization and up to 97% hatch, but ovulated eggs retained in the ovary lumen for 1 day before stripping gave 0% hatch. The turbot showed precise ovulatory rhythms. The time between ovulations varied between individuals but was constant for any one female, making it possible to predict future ovulation times. Three of the females studied had ovulatory periods of alternating len

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04814.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Experiments were conducted to determine the adaptability of the guppy to various salt concentrations. The guppy,Poecilia reticulata, (total length 11–40 mm) were subjected to abrupt and gradual changes from fresh water (salinity=0.1%) to various salinities (%). No mortality occurred when the fish were transferred from fresh water to 50% sea water (19.5%). Through gradual adaptation from 50% sea water to 80% of the fish were able to tolerate 100% (39%) sea water for 7 days. After a 7 day stay in sea water, fish were readapted to fresh water during a 3 h period. Through gradual adaptation fish were also able to tolerate salinities ranging from 39.0% (100% sea water) to 58.5%. After a 30 day stay in 150% sea water (58.5%), fish were readapted to fresh water over a 5 h period. The results indicate that they were well able to tolerate the abrupt change from 100 or 150% sea water to fresh water. Females that stayed in 150% sea water (58.5%) for 30 days had embryos in their gonad

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04815.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The histochemical nature of the protein within the large granules of the intestinal granule cells was examined in rainbow trout,Salmo gairdneri, from the time of earliest appearance of the cells in the lamina propria until a layer of granule cells was established in 12‐month‐old juveniles. At all times the granule cell granules contained large quantities of protein. This material appeared to be predominantly cationic in nature as judged from results obtained with alkaline fast green FCF together with deamination controls. In addition, there was no major acidic protein within the intestinal granule cell granu

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04816.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY