摘要:

The upstream spawning migrations of brown trout and sea trout were studied using stationary traps placed in Kirk Burn, a tributary of the upper Tweed. The sea trout spawning period extended from early November to the first week of December, while that of brown trout occurred from the middle of October to the third week of December. Sea trout were predominantly maiden spawners of ages 2.1+ and 3.1+ while brown trout were mostly age 2+ and 3+. Male‐female sex ratios approximated 1:1.4 in sea trout but 6 : 1 in brown trout. Brown trout males participated in the spawning activities of sea trout. Low water conditions in Kirk Burn hindered the upstream movement of spawning sea trout, while sudden increases in water level appeared to stimulate the upstream migration of both brown trout and sea trout. The suggestion is advanced that the freshwater resident brown trout of the Tweed which migrate upstream into the smaller tributaries to spawn is wholly, or at least partially, the progeny of anadromous parent

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04115.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

A total of 654 char,Salvelinus alpinus(L.) and 33 brown trout,Salmo truttaL., were examined for the plerocercoids ofDiphyllobothrium dendriticum(Nitzsch, 1824) andD. ditremum(Creplin, 1825). Only char were found to be infected. Both parasitic species were abundant. The incidence and mean intensity of infection forD. dendriticumwere 83.2% and 8.8, respectively; forD. ditremum93.7% and 45.0. There was no variation in the intensity of infection between different parts of the lake. The incidence and intensity of infection increased with the age of the fish to age 8+ for both species. From this age the intensity of infection leveled off or decreased. No differences in intensity of infection between the sexes were found. The frequency distribution of parasite counts were overdispersed and fitted the negative binomial distribution even within single age‐groups. The two parasite species showed a high positive correlation in intensity of infection,D. ditremumwas concentrated in the stomach and pyloric caeca.D. dendriticumwas more widely distributed within the host and was supposed to kill heavily infected fis

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04116.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The run of elvers ofAnguilla anguilla(L) up the Mex canal, Alexandria, Egypt, starts at the end of February and continues until June, with the main bulk of elvers arriving in April and May. Variations in the timing of this run may be attributable to variations in local ecological conditions. The run is affected by meteorological and hydrographic factors. The effects of the latter have been assessed, and a low oxygen content, a pH between 7.7 and 8.0, a chloride content between 2.1 and 2.3 Cl/1 and a temperature between 20 and 25°C have been found to encourage large numbers of elvers to migrate up the fresh water canal. In contrast to previous findings, the results of this study suggest that the mean length of elvers running increases towards the end of the season

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04117.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04118.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Fingerling grass carp (Ctenopharyngodon idella) were cultured in 380 1 circular fiberglass tanks at stocking densities of 0.53, 1.06, 1.59 and 2.11 fish/1. Fish were fed duckweed (Lemna minima) to satiation. Fish grew from 2.7 g to a maximum mean weight of 72.7 g in 88 days. Fish stocked at 0.53 fish/1 grow more rapidly than those stocked at higher densities. Mean daily consumption rates were strongly correlated with oxygen levels and when oxygen levels dropped below 4 mg/1 consumption was reduced approximately 40%. High biomass, growth, and survival rates obtained during this study indicate grass carp are well suited for intensive tank culture.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04119.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

A feeding trial was conducted in 55‐1 aquaria indoors with the grass carp (Ctenopharyngodon idellaVal.) using fresh duckweed (Lemnaspp.) as food. Faeces dry weight was closely correlated with dry weight of duckweed consumed based upon a linear regression. From this regression, the estimated true digestibility of dry matter was 65%. Samples of duckweed and fish faeces were analysed for crude protein and gross energy. Van Soest's Analysis was conducted on composite samples of duckweed and faeces. Apparent digestibilities were 80% for crude protein, 61% for gross energy, 72% for organic cell contents, and 30% for organic cell wall constituent

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04120.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Elvers ofAnguilla nebulosawere reared at 23°C in confined waters and their food intake, growth and conversion efficiency (K1:%) were studied. Elvers weighing 278.33±14.35 mg were fed on anad libitumdiet of the oligochaete wormTubifex tubifexfor 60 days. On an average, the test individuals consumed 99.55±19.81 mg food/elver/day amounting to 35.76% of the initial biomass; during the corresponding period the elvers exhibited a growth rate of 5.03±2.42 mg gain in weight/elver/day which is equivalent to 5.06% of the consumed food. Thus the ‘housekeeping’ of these elvers may be regarded as established. In 50 days, the food required amounts to 0.358±50 = 17.90 times the initially stocked biomass. That is, 1 kg of initially stocked elvers may need 17.90 kg ofT. tubifexto produce 0.912 kg of elver meat. A poor conversion ratio of 20 : 1 may be one reason for the slow growth of th

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04121.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Brown trout sera were examined by cellulose acetate (CAE) and polyacrylamide electrophoresis (PAE) and the protein concentrations measured by the Lowry method, before and after stimulation with haemocyanin, horse serum,Salmonella typhi‘H’ and human group ‘O’ erythrocytes. Uninjected fish contained 5.l1±0.71 g protein/100 ml. Protein concentration was unaffected by haemocyanin and horse serum but was significantly lowered byS. typhiand human group ‘O’ erythrocytes. Male and female fish gave similar responses. Uninjected and injected fish showed 8 components on CAE and 16 on PAE. Significant differences were found between injected and uninjected control fish and between antigen stimulated and uninjec

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04122.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The growth ofLiza malinoptera, which is analysed by its morphometric and length–weight relationships, is found to follow closely the so‐called cubic law for isometric growth. The relative condition factorKnis used to investigate the condition cycle and for maturity studies. Fecundity and ova size are estimated. The fish is a herbivorous iliophage utilising mainly mangrove plant detritus at the first trophic level. Fine particle selection is demonstrated during feeding. Studies on the morphology and histology of its alimentary tract indicate an adaptive correlation with its food and feeding hab

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04123.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY