ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03040.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Published estimates of ration and/or food conversion efficiency of various size groups of fishes from 75 different stocks belonging to 56 tropical and temperate species were standardized and re‐expressed as annual fish food consumption (Q) per unit biomass of the age‐structured population (B). Although derived from extremely heterogeneous sources, these estimates ofQ/Bshow surprisingly regular patterns. These allow confirmation of some earlier hypotheses, e.g. thatQ/Bincreases with water temperature and decreases with asymptotic weight. More interestingly, it is shown that the aspect ratio of the caudal fin of fishes that use the carangiform and related swimming modes (i.e. subcarangiform and thunniform) correlates closely withQ/B, when other factors are accounted for. A brief discussion of some implications of these and related results is provi

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03041.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Uptake and transport of soluble (ferritin) and particulate (Vibrio anguillarum) antigen from intestinal lumen to mucosal macrophages was studied using immunocytochemical and electron‐microscopical techniques. Both antigens were taken up by epithelial cells of the second gut segment, reached the supranuclear vacuoles and were finally transported to large intraepithelial macrophages. In contrast with particulate antigen, antigenic determinants of ferritin were demonstrated in the basal part of the epithelium and appeared to be released at the mucosal site.After anal intubation many small macrophages penetrated the intestinal epithelium, took up antigen and after 24 h disappeared again from the intestinal mucosa. This feature was antigen independent and also occurred after anal PBS‐intubation. The larger, less mobile macrophages stayed in the intestinal epithelium and finally exposed antigenic determinants (of both antigens) at their outer surface, suggesting an antigen‐presenting function. Whether these large macrophages can induce a local or mucosal immune response and whether the smaller mobile macrophages are involved in a systemic response is disc

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03388.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Fish in the Kanawha River were collected with a 0.5‐m plankton net in main‐channel borders and in open areas of backwaters and with a 1‐m2enclosed dropbox in shallow backwater habitats. Larval emerald shiners,Notropis atherinoides, were twice as dense, and gizzard shad,Dorosoma cepedianum, 2.5 times as dense in main‐channel borders as in backwaters; larvalLepomisspp. were 20 times as dense in backwaters as in main‐channel borders. SmallerLepomislarvae used open‐water backwater areas primarily; larger larvae migrated to vegetated backwater habitats later in the summer. Backwaters appear crucial for the maintenance of nest‐building fish species in temperate rivers, just as floodplains are necessary for the maintenance of high species diversity in tr

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03042.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The effects of hypoxia and paraquat (PQ) were investigated on the superoxide dismutase (SOD) activity in carp gill, liver and brain. Increases in SOD activity occurred in these organs following exposure to both PQ and hypoxia. PQ administration under hypoxic conditions significantly increased the SOD activity in the gill as compared to the level in animals in an hypoxic state without PQ treatment. No such change was observed in the liver or brain.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03389.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Exposure of brown trout,Salmo trutta, to zinc under continuous flow conditions over 96 h showed that both water hardness and pH exert major influences on the toxicity of the metal. 96‐h LC50 values for total zinc ranged from<0.14mg 1−1in alkaline soft water (pH 8; lOmg 1−1as CaCO3) to 3.20 mg 1−1in acidic hard water (pH 5; 204 mg 1−1as CaCO3). A variable reduction in zinc toxicity in hard water compared with soft water over the pH range 4–9 was attributed to high external calcium. Zinc toxicity was positively correlated with decreasing acidity over the pH range 5–7, the metal being most toxic at pH 8–9 where metal complexes predominate. Below pH 5 metal toxicity also increased, irrespective of hardness. Water hardness and pH interacted with zinc toxicity in a complex manner, apparently dependent on physical and chemical transformations of the metal, and as changes in uptake. detoxification and excret

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03390.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Fluctuations in the abundance of fishes may be caused by episodic mortalities or by more subtle variability in the daily growth and mortality rates of eggs and larvae. Survival response surfaces are used to illustrate the relative effects of episodic and subtle mortality during early life. It is the subtle variability associated with small changes in growth or mortality rates that may exert the greater effect on recruitment. Massive advective losses of eggs or larvae, failed egg production, and acute contaminant mortalities are examples of episodic events that may impact recruitment significantly but which need not be catastrophic. Stabilization of recruitments through density‐dependent growth rate variability in early life is demonstrated to be potentially important. Whether this mechanism actually is important in the sea remains to be determine

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03043.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The usefulness of both surface‐dependent and non‐surface‐dependent models for describing the gastric emptying process inScyliorhinus canicula(L.) was examined. In most cases the surface‐dependent models produced better fits than did the non‐surface‐dependent models. The exponential model (non‐surface‐dependent) only adequately described gastric evacuation in the case of small prey items with thin exoskeletons. On the other hand, the exponential model was clearly better than the linear model in all cases. Prey size had little effect on digestion rate. However, the number of prey items ingested was an important factor influe

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03391.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The relationship between vertical migration, estuarine retention and species‐specific patterns of longitudinal distribution of the pelagic larvae of rainbow smelt,Osmerus mordax, and tomcod,Microgadus tomcod, was investigated in the upper section of the St Lawrence Middle Estuary. We hypothesized that the species‐specific use of the vertical pattern of current exhibited by the two species results in the partitioning of the estuarine habitat in the longitudinal plane while assuring retention. Important differences in the longitudinal distribution of tomcod and smelt larvae were related to the ontogeny of their vertical distribution in the water column. In June, small tomcod and smelt larvae are generally associated with waters of salinities less than 5%o. As the larvae grow, their vertical distribution patterns change, leading to a horizontal separation of the two species. Tomcod juveniles migrate downstream into colder, more saline waters, whereas larger smelt larvae migrate upstream into warmer, tidal fresh waters. Ontogenetic changes in vertical distribution serve to concentrate larvae in specific conditions that may optimize physiological conditions and also permit population persiste

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03044.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Variation in the survival of herring between the egg stage and the age of recruitment to the spawning population has been examined for seven Atlantic herring populations in northern European waters. The sources of the variation have been partitioned between density‐dependent and density‐independent factors. The magnitude of the density‐independent component was found to be related to the scale of the processes controlling the dispersion and distribution of larvae from the various populations. We conclude that the spawning strategies of some populations are adapted to oceanographic conditions to maximize the probability of a particular larval transport pattern, although no single model could account for all spawning strat

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03045.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY