摘要:

Yolk‐sac fry of brown trout were exposed to three levels of single trace metals (Cu, 20,40,80 nmol 1‐1; Pb, 12·5,25,50 nmol 1‐1; Zn, 75,150,300 nmol 1‐1) typical of concentrations reported for acid soft waters, in flowing, artificial, soft water media maintained at pH 4·5 and [Ca] of 20 or 200 μmol 1‐1for 30 days.Mortalities were high in fry subjected to all levels of the three trace metals at [Ca] 20 μmol 1‐1, with 80% of the total deaths occurring between days 11 and 15 of the experiment. 25% mortality occurred at low [Ca] and pH 4·5 in the absence of trace metals, with only one death recorded at [Ca]200 μmol1‐1’(Cu, 80 nmol 1‐1). At high [Ca] all three levels of Cu and Pb impaired net Na and K uptake; Cu was the only metal to reduce the uptake of Ca. The Zn treatments had no significant effect on mineral uptake. Calcification of centra was reduced by all three Cu treatments at [Ca]200 μmol 1‐1. The lowest Zn concentration (75 nmol 1‐1) was the only other treatment to impair skeletal development. In the absence of trace metals, low [Ca] significantly reduced Ca, Na and K uptake, skeletal calcification and dry mass at pH 4·5.The deleterious effects of low Cu, Pb and Zn concentrations at low pH and low [Ca], and the ameliorative effect of higher ambient [Ca], are discussed in relation to fisher

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb02985.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The killing ability of rainbrow trout macrophages for the infective larval stages ofDiploslomum spathaceum, cercariae and diplostomules, was investigated. Isolated macrophages kill significant numbers of diplostomules at effector: target ratios of 150: 1 or greater.In vitrokilling was not increased using antiserum‐coated larvae orin vivo‐activated macrophages individually, but when they were combined increased killed occurred. Diplostomules were capable of eliciting respiratory burst activity from macrophagesin vitro, suggesting that reactive oxygen species may have a role to play in the killing mechanism. The importance of macrophage activation in the protection afforded by immunization against this parasite is discus

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb02986.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Oxygen consumption rates during embryonic and the first 38 days of larval development of the striped mullet were measured at 24° C by differential respirometry. Measurements were obtained at the blastula, gastrula and four embryonic stages, and at the yolk‐sac, preflexion, flexion and post‐flexion larval stages.Oxygen uptake rates of eggs increased linearly from 0.024 μl O2per egg h‐1(0·323 μl O2mg‐1dry wt h‐1) by blastulae to 0·177 μlO2per egg h‐1(2·516 μlO2mg1dry wth‐1) by embryos prior to hatching. Respiration rates did not vary significantly among four salinities (20,25, 30, 35%0).Larval oxygen consumption increased in a curvilinear manner from 0·243 μl O2per larva h‐1shortly after hatching to 18·880 μl O2per larva h‐1on day 38. Oxygen consumption varied in direct proportion to dry weight. Mass‐specific oxygen consumption rates of preflexion, flexion, and postflexion larvae did not change with age (10·838 μl O2mg1dry wt h‐1).Larval oxygen consumption rates did not vary significantly among salinities 10–35%. Acute temperature increases elicited significant increases in oxygen consumption, these being relatively greater in yolk‐sac larvae (Q10= 2·75

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb02987.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

A histological study was made of the intestine and pyloric caeca of green sunfish,Lepomis cyanellus(Centrarchidae). The intestinal and caecal walls are histologically very similar, consisting of a mucosa (epithelial layer), submucosa (lamina propria and stratum compactum), muscularis (circular and longitudinal layers) and the serosa. Cellular constituents of the mucosal layer include absorptive, columnar epithelial cells, mucous‐secreting goblet cells, and various leucocytes, the majority of which are lymphocytes. Other than relative size and the entrance of the bile duct at the base of the first caecum, no difference was found among caeca.When fish were nutritionally stressed, a greater variety and number of leucocytes and shifts in the numbers of lymphocytes and goblet cells of the mucosal layer were the only observable effect

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb02988.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Most studies on feeding‐related activities of fish in cold water (0° C) have not used eurythermal species or examined a broad suite of activities. In this study we report on the feeding, growth, behaviour and conversion‐efficiency of 0 + Atlantic cod in response to water temperature and food availability. In one experiment, activity, opercular beat and growth decreased with decreasing temperature over the range 8·3–0·6° C. However, the conversion efficiency increased with decreasing temperature, a result partly explained by the relative change in activity and opercular rate. In another experiment, temperature had a linear effect on growth in cod fed different food rations. Both food availability and temperature were found to influence growth in group 0 + cod. The specific growth rate of cod in this experiment exceeded 2% day‐1. Growth data collected from cod sampled in the field during the cold‐water period showed a progressive increase of mean length over the season. Overall, these results demonstrate that 0 + cod have adapted to life in cold‐water environments, in contrast to adult cod which mostly inhabit warm

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb02989.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Winter flounder from Passamaquoddy Bay, N.B. undergo an annual fast from November to May which results in a decrease in the slope of the length‐weight relationship (3·17 to 2·54), in the condition factor (9 to 12%), in the liver (75%) and white muscle (24%) lipid contents, and an increase in muscle water content (2·4%). Winter flounder appear to have sufficient lipid reserves to support the winter fast, as muscle water content declined only at the onset of feeding.The intestine could be divided into pyloric caeca (4), foregut, midgut and hindgut. Mucosal folding was reduced in all sections of the intestine during the fast. Goblet cell number declined, but little change in enterocyte ultrastructure was observed. Intestinal length remained the same, although the caeca shortened. Overall, mucosal mass declined by 57% from May to January, while surface area declined by 50%. This value is less than that in literature reports for a fast of shorter duration in freshwater rainbow trout. We propose that the continued need for salt and water transport for osmoregulation maintains the proximodistal gradient of mass and surface area and ameliorates the effect of starvation on mucosal mass and

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb02990.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The role of photoperiod as an environmental factor controlling reproduction, particularly the duration and ending of the breeding season, in the barbel was investigated by tank experiments. The experiments used a population of barbel matured in captivity which were stripped of eggs at frequent intervals: 10–15 'spawnings’for each female were obtained at 15‐day intervals.A decreasing photoperiod (16·5 light: 7·5 dark→8L: 16D), for an annual cycle contracted to 6 months duration, inhibited the spawning of both female and male fish. This allowed two periods of reproduction (February‐May and September‐November) within one year. Under natural or constant (10L: 14D) photoperiod conditions, spawning came to an end spontaneously. The rate (accelerated, slow or natural) of daylength increase did not affect the onse

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb02991.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The chemical composition and energy content of North Sea plaice during the spawning period were examined in mature males and females and in immature fish, to study differences in the allocation of energy over reproduction and somatic growth between the sexes.At the beginning of the spawning period mature males and females had equal dry weights of lipid that were 70% higher than in immatures. Protein content in mature males was equal to that in immatures but was 23 % higher in mature females. Immature males and females did not differ in chemical composition. At the end of the spawning period, spent and immature fish had equal lipid contents, but protein content in spent females was 10% lower than in spent males, and 17% lower than in immatures. Gross energy content of the body decreased by 44% (65·2 to 36·3 J cm‐3) in mature females, 27% (55·0 to 40·OJ cm‐3) in mature males, and 9% (48·7 to 44·2J cm‐3) in immatures. Energy content of plaice eggs was estimated at 6·60 kJ per 1000 eggs.Reproductive investment was estimated from the energy loss during the spawning period and included the energy of sex products and spawning metabolism. Somatic growth comprised the annual increase in energy content of fish. The pattern of energy allocation over reproduction and somatic growth differed between males and females. Males started their reproduction at a smaller length and a younger age and allocated a higher proportion of the available energy into reproduction than females. Available energy resources for somatic growth and reproduction (surplus production) were equal between the sexes up to a length of about 30 cm. Beyond this length male surplus production levelled off whereas female surplus production continued to increase. The differences in surplus production and the allocation patterns are discussed.For female plaice the energy allocated into egg production was estimated as between 48 and 64% of the total amount of energy lost during spawning. The remaining energy is used for metabolism during the spawning period, yielding an estimate of the metabolic rate of mature females of between 6·4 and 9·1 kJ day‐1. A maximum estimate of the metabolic rate of mature males

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb02992.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Genetic distances based on electrophoretic variation and multivariate analysis of several morpho‐metric and meristic characters suggest that populations of sardine and anchovy from the Aegean and Ionian seas do not form one panmictic population. The distinction between these two classes of populations emerges only as a statistical property, and for some characters the within‐sea variation is larger than the between‐sea variation. Thus, the reproductive isolation between populations inhabiting the two seas appears to be only partial. Our findings do not support the‘ pure‘ or‘ discrete‘ stock concept. Instead, they provide evidence for the dynamic population structure model according to which physical (e.g., hydrographic) or biological (e.g., predation or behaviour) factors impose a population structure maintained in a semi‐equilibrium state under the opposing influences of migration and selection. Such a dynamic state may not be stable in the long run, and it may not allow for the accumulation of genetic divergence necessary for the emergence of higher taxa. It must, nevertheless, be taken into account in the management of exploited natu

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb02993.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

An optimal foraging model was used to predict prey selection based on both energy maximization and number maximization strategies. The influence of chemical cues and relative abundance on rainbow trout diet selection was examined under laboratory conditions.In most fish, diet composition was strongly influenced by chemical cues. No fish followed an energy maximization strategy, and selection of prey based on taste persisted despite large caloric penalties associated with these choices. In the absence of chemical cues, diet composition was based on relative abundance of prey (a number maximization strategy). Within the feasible constraints of the optimal foraging model lie a large number of possible diet combinations which would provide sufficient energy for growth and reproduction. This provides a wide scope for feeding flexibility. Response to prey chemical cues may be the basis for observations of individual diet variability in trout.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb02994.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY