摘要:

Utilization of storage lipids and storage proteins by non‐feeding north‐west Atlantic herring was assessed under conditions of: (1) concurrent gonad maturation and overwintering periods with differing rates of gonad development for males and females (spring‐spawncrs); (2) overwintering, reproductively dormant and spent males and females (autumn‐spawners); and (3) approximately equivalent rates of gonad development during late summer for males and females (autumn‐spawners). Storage lipids were depleted by all non‐feeding fish but storage proteins were depleted only by herring with measurable gonad development during the observation period independently of season (female spring‐spawners, maturing male and female autumn‐spawners). The analyses indicate that storage lipids sustain routine and active metabolism while storage proteins are utilized to develop gonad. Therefore, the relative investment into reproduction versus routine and active metabolism can be evaluated separately for non‐feeding herring using readily obtainable tissue proximate

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01157.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Samples of fed and unfed hatchery reared Atlantic salmon fry and parr were analysed for body water and whole body Na, K and Ca content. From these body parameters it is possible to estimate the relative proportions of the skeletal mass, and intra‐ and extracellular spaces. These data can be applied to estimating the nutritional status of parr sampled at random from hatchery, and possibly from wild populations. When fish with a dry weight of about 25 and 70 mg were deprived of artificial food for 27 and 21 days, respectively, the Na/K ratio rose to 0.59 and 0.80 compared with 0.37 in the controls. With fish of about 475 mg in weight, percentage water content was a better indicator of undernourishment. The use of the K+: Ca2+ratio to compare the amount of cellular material with the skeletal mass was a good indicator of nutritional depletion, especially in smaller fis

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01158.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Rates of predation on 0‐group plaice,Pleuronectes platessa. in aquaria were compared under four different combinations of conditions to test the hypothesis that the presence of sand in which they may bury affords a refuge from predators. The effect of light and darkness on predation rate was also examined, Two crustaceans, the shrimp,Crangon crangon, and the portunid crab,Liocarcinus holatus, and two fishes, cod,Gadus morhua, and pollack,Pollachius pollachius, were used as predators. Predaton rates were significantly higher in the dark for all predators except pollack. Predation rates in the absence of sand were signifcantly greater only for pollack. The results suggest that predation rates on plaice during their juvenile nursery stage on sandy beaches will be significantly greater during darkness than during the day. Burying in sand appears to provide only a partial refuge from predation, perhaps because natural predators have evolved effective methods of foraging for buried pre

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01159.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The growth, age composition, reproductive biology and diet ofGalaxiella nigrostriatain seasonal water bodies in south‐western Australia are described and compared withG. mundaand G.pusilla. Like the other twoGalaxiellaspecies, G.nigrostriatahas a 1 year life cycle. The mean length attained by femaleG. nigrostriataat sexual maturity is approximately 37 mm, compared with about 47 and 28 mm forG. mundaandG. pusilla, respectively. LikeG. munda, G. nigrostriatais a multiple spawner. Although all threeGalaxiellaspecies breed mainly in winter and early spring, spawning occurs earlier inG. nigrostriatathan in the other two species. An early production of offspring enables the young females and males of this species to reach approximately 78 and 88%, respectively, of their ultimate body length by early summer. Such a prolonged period of early and relatively rapid growth is advantageous toG. nigrostriata, since this species lives in water bodies that often dry up during the summer and early autumn and thus cannot grow during this period. The gonads start to undergo rapid development in autumn, when the pools begin to fill with water following the onset of the seasonal rains. All threeGalaxieltaspecies are carnivores.Galaxiella nigrostriatamainly takes prey from the water column and the water surface,G. pusillafocuses on prey in the water column and benthos, and G.mundafeeds widely on prey on the water surface, throughout the water column and from the benthos. The prevalence of small prey, such as cladocera and calanoid copepods, is greater in the diets of G.nigrostriataand G.pusillathan in that ofG. mund

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01160.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The yearly gonadal cycle of two Kinneret teleosts,Barbus longicepsandCapoeta damascinaand of their hybrid, was assessed by measuring the gonadosomatic index (GSI) in both sexes, as well as the spermatozoan index (SPI) in the males. SPI was established through a computerized analysis system, using light microscopy images of histological preparations of the testes.Barbus longicepsspecimens had highest GSI in March, 6.31 for males and 1.40 for females.Capoela damascinahad highest GS1 in January, 6.63 for males and 6.88 for females. In the male‐like hybrids, the highest GSI was 5.57 in February, and in female‐like hybrids 1.83 in March; no gametes were ever formed in hybrid gonads. The highest SPI appeared inB. longicepsin April, while inC. damascinathe highest SPI was found in March. In both species, the highest SPI was attained several weeks after the highest GSI was observed. It is suggested that the peak of the breeding season of both species is actually represented by the highest SPI. In males, the decreasing GSI, which corresponds to the highest SPI, represents the loss of gonad weight, which is due to the elimination of the spermatid residual bodies, prior to spermiation. In the females the decreasing GSI is the result of ovulation, and characterizes the peak of spawning activ

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01161.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The accumulation of 137‐caesium from water by alevins and fry of Atlantic salmon and brown trout was studied, At ‘normal’ pH (∼7.4), input rates (kWF) and equilibrium concentration factors (CFeq) of 137‐caesium were four to five times greater in both species of alevins than those in the fry. Input rates and equilibrium concentration factors were consistently greater in brown trout than in Atlantic salmon. The input rate of 137‐caesium was most rapid in kidney, gill and gut of fry. The majority of the radiocaesium was, however, deposited in muscle tissue which had consistently the longest biological half‐life of 50–90 days. 137‐Caesium input was significantly reduced at low pH (∼5.0) but output rates (kFW) were little affected. It is concluded that juvenile fish are more susceptible than adults to radiocaesium accumulation from freshwater but that food is the major source of 137‐caesium in freshwater fish. The behaviour of 137‐caesium is discussed wi

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01162.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Populations of brown troutSalmo truttawere monitored at a number of sites within a single stream, using an individual marking technique and recapturing uniquely marked fish repeatedly over a period of 12 months. Individual 1 + and 2 + resident brown trout in the Glenfinish River were found to consist of stationary and mobile component populations. The latter population consisted of a number of individuals observed moving mostly in an upstream direction, within a range of 0.03–2.24 km. On a large spatial scale, individuals in the stationary component population exhibited some degree of home site fidelity within the stream, over a period of 3–4 months, after which the fish tended to move from the site. Within sites, fidelity to either riffle or pool habitats, mostly the latter, was apparent in a proportion of the population. On a smaller scale, fidelity to the exact position with respect to boulders in the stream was also evident in a number of individuals. Home range size was calculated amongst these individuals, with ranges of up to 20 m recor

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01163.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The tilapiaOreochromis niloticusand the silver carpHypophthalmichthys molitrixwere exposed to toxic and non‐toxic strains of the cyanobacteriumMicrocystis aeruginosain order to determine if cells of the toxic strain were ingested and, if not, by what mechanism they were excluded. Enumeration of cyanobacterial particles before and after exposure to fish showed that there were no significant differences (P<0.05) at the end of the trial between the toxic treatment and the control consisting of toxicM. aeruginosawith no fish. Fish exposed to the non‐toxic strain increased opercular beat rate, elevating the volumes of water and food material passed over the gills whereas those that were held in the toxic strain did not. Of the cyanobacterial toxins (microcystins) presented to the fish, most were in the cyanobacterial cells, toxin levels in the water being below the level of detectability (<250 ng l−1), The ability of the fish to differentiate between toxic and non‐toxic cyanobacterial strains may thus be determined by very low levels of extracellular microcystins or/and other features which distinguish toxic from non‐toxicM. aeruginosastrains, such as cell surface c

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01164.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

We surveyed restriction site differences in mitochondrial DNA. (mtDNA) among five species of shad (Alosa) from North America and Europe. Allis shad,Alosa alosaand twaite shad,Alosa fallaxshared two divergent genotype groups, suggesting that the two forms are either a single species, or are distinct species that have hybridized. Phenetic and cladistic analyses of the relationships among the mitochondrial genotypes defined two groups of shad, corresponding to the subgenera,AlosaandPomolobus. The mean estimated sequence divergence between the mtDNAs of these two groups of shad was 6.5%. Taken in conjunction with fossil data, this divergence estimate suggests that the rate of mtDNA divergence between the two subgenera has been almost 10‐fold lower than the ‘conventional’ clock calibration for

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01165.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The influence of exposure to stressors on cortisol and the non‐specific immune traits lysozyme and serum haemolytic activity were examined in second generation rainbow trout (Oncorhynchus mykiss) selected for either high or low serum cortisol level following a confinement stress. Lysozyme and serum haemolytic activity were also assessed, together with levels of specific antibodies againstAeromonas salmonicidaA‐layer,Vibrio salmonicidaO‐antigen andVibrio anguillarumO‐antigen, following injection of vaccines against these pathogens.Significant differences in mean cortisol levels between the two selection lines were observed, but in only one of two stress experiments was the ‘high‐stress’ line found to have the higher cortisol level; in the other experiment the ‘high‐stress’ line had significantly lower cortisol levels than the ‘low‐stress’ line. Lysozyme levels were in four of four assessments higher in the high‐stress line than in the low‐stress line, whereas components of serum haemolytic activity tended to be lower in the high‐stress line than in the low‐stress line. Levels of specific antibodies against all three bacterial pathogens were elevated following the injection of the vaccines. Only antibody production againstA. salmonicidaA‐layer was significantly different between the two lines, the higher production of ant

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb01166.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY