ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05493.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Assimilation efficiencies were measured by comparing the amount of nutrient in the food and faeces of fish from the natural environment. The comparison of nutrients was made in relation to reference markers: ash, hydrolysis‐resistant ash (HRA) and hydrolysis‐resistant organic matter (HROM). Assimilation efficiencies of nutrients computed using ash and HRA as reference markers were significantly (P<0.05) lower than those measured with HROM; digestibility estimates of protein were the least influenced by the type of marker used. Generally, HROM appears to be the most suitable reference marker for a digestibility study in an herbivorous fish such asOreochromis niloticus.Nutrient composition gradient examined by analysis of stomach, intestinal and rectal contents showed that digestion of all nutrients was completed when the food passed two‐thirds of the way through the length of the intestine. Most of the nutrients were significantly (P<0.05) affected by the processes of digestion and assimilation in different sections of the gut, and a decline in the quantity of nutrients was obvious towards the r

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05494.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Whole herring,Clupea harengus, were digested and emptied from cod stomachs much more slowly than meals of minced herring, showing that prey integrity is an important factor controlling emptying. Increasing the energy content of the minced herring by addition of fish meal and oil led to a reduction in the percentage of the meal emptied in the 24 h subsequent to feeding, but rates of energy throughput on the enriched herring diet were high. The physical form of the diet appears to be more important than energy content in the control of gastric emptying in cod. The results are discussed with respect to possible effects of dietary type on absorptive and metabolic processes.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05495.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Vertebral defects in adult fourhorn sculpin were used to trace heavy metal pollution in the Gulf of Bothnia (Baltic Sea). From 1978 to 1984 a total of 9789 specimens from 22 localities were X‐rayed and analysed for vertebral deformities, e.g., scoliosis, deformation and/or dislocation of individual vertebrae, etc. The frequency of fish with vertebral defects ranged between 4.3 and 39.7%, the highest frequencies being found in the vicinity of a metal ore smeltery (Rönnskärsverken) emitting heavy metals and arsenic. The possible influence of genetic factors, migration, sex, size, age and parasitic infections on the results are discussed and evalua

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05496.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The feeding habits of the Lessepsian migrantSiganus luridusin the eastern Mediterranean (Kastellorhizo Isle, Dodecanese, Greece) are examined. The stomach contents of 209 specimens, 131–250 mm total length, collected by bottom trammel nets, April 1985 July 1986, were analysed. Feeding intensity was high, although it significantly declined during the spawning period in summer.Siganus luridusfeeds on a diverse assemblage of benthonic algae including 24 genera (seven green, eight brown and nine red algae) contributing 84.4% by weight (green algae 3%, brown 70.3%, red 11 %).Posidonia oceanica, diatoms, hydrozoa and sand were also found in the stomachs examined. On an annual basis,Dictyotasp.,Cysloseirasp.,Sphacelariasp.,Gelidiumsp.,Dictyopteris membranacea, Kuckuckia spinosaandPadina pavonicapredominated in the diet. Diet overlap, on a weight basis, indicated a similar food spectrum during spring and summer which was different from that in autumn.The high feeding intensity ofS. luridusduring the year (except for the spawning period), its nonselective euryphagous nature, its high competitive potential, and its position in the food web of the eastern Mediterranean ecosystem are important characteristics that, along with suitable oceanographic and ecological conditions for the development and survival of young stages, have enabled the successful establishment and build‐up of the population of this Lessepsian migrant in its new environment. Possible competitive implications in the eastern Mediterranean ecosystem are also discus

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05497.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Over its exceptionally wide geographical range the minnow displays a remarkable variability in its life history. In southern England many fish mature after one year and few fish survive to their third birthday. Very few fish spawned for more than one season but a 65‐mm female is estimated to spawn up to 3172 eggs over the extended spawning season. In the River Utsjoki in Finnish Lapland maturity was strongly size‐dependent and delayed until the fish reached 5, 6 or even 7 years of age, with a maximum age of 13 years at a length of only 75 mm. Unlike some other small‐sized species in unproductive environments, individual females continued to spawn successive clutches of eggs though over a much shorter spawning season. The maximum estimated egg production was 824 for a 65‐mm fish. Temperature had a strong direct or indirect effect on growth, with significantly lower growth increments in cold summers. At a second Arctic site in eastern Lapland growth rates were higher and maturity earlier, yet clutch size was greatly reduced with a seasonal fecundity estimate of only 314. There were only small differences in size of eggs or larvae between the populations. Evidence from other species indicates that most of the observed changes over the range of the minnow are phenotypic responses to the contrasting environments. However, the different strategies displayed at the two Arctic sites could represent the results of selection for differences in pre‐ and post‐reproducti

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05498.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Turbot were fed either a basal diet containing approximately 100 mg zinc kg−1or a similar diet supplemented with 1000 mg kg−1; the fish were sampled over a period of 220 days. At final sampling there was no significant difference between control and test animals in hepatic and renal metallothionein levels, hepatic and renal zinc levels and white muscle, skin and bone zinc concentrati

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05499.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Windowpane flounder,Scophthalmus aquosusMitchill, were exposed for 60 days to 5 or 10 μg 1−1mercury and gill samples were examined by scanning electron microscopy. The response of the gill epithelium was different at the two levels of mercury exposure. The number of chloride cell apical pits and gill filaments bearing ‘cratered’ epithelial cells increased at the 5‐μg 1−1level and decreased at the higher exposure level.Focal swellings demonstrated a dose‐dependent relationship, their numbers being greatest at the higher exposure level. Marked fragmentation of pavement cell microridge patterns and swelling of the respiratory epithelial cells was evident at the 10‐μg 1

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05500.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The karyotypes of two samples ofSalmo salarfry used to repopulate the rivers of Asturias (northern Spain) during 1986 were analysed: chromosomal polymorphism differed significantly between them. The need to repopulate with non‐heterogeneous stocks is suggeste

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05501.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Emergence pattern and developmental status at emergence of Baltic salmon fry from the Umeälven hatchery stock (63°50′N, 20°25′E) were studied at 6, 10 and 12°C in the laboratory. The number of days and degree days from hatching to 50% emergence decreased exponentially with increasing temperature. Synchronization of emergence increased with temperature. Optimal temperature for incubation of yolk‐sac alevins was 10°C, which resulted in the largest fry at emergence and the lowest death rate. Fry kept at 6°C had the lowest mean weight and at 12°C the highest death rate. The fry emerged at an earlier developmental state with more yolk at 12°C than at 6°C. The Baltic salmon had a faster developmental rate during the gravel‐phase, as compared to more southern Atlantic sa

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1988.tb05502.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY