Showing papers in "Aquaculture in 1984"

TL;DR: It is suggested that the multiple age structure of such a population is retained through counterbalancing advantages — potential for rapid growth among progeny from the small eggs of young spawners, and initial territorial dominance among progeni from the large eggs of older slower developing spawners.

TL;DR: It is concluded that low enzyme production as well as the absence of a stomach in the first few weeks after hatching are two important reasons for difficulties in rearing coregonids on an artificial diet.

TL;DR: Growth improved as the level of glucose, sucrose, dextrin and starch was increased from 0% to 40%, growth, food conversion efficiency (FCE), NPR, carcass fat and condition factor were reduced and the use of a-cellulose as an inert bulker in experimental diets for fish is discussed.

TL;DR: Retention of the second polar body in rainbow trout eggs was induced by 7000 psi early pressure shocks, which resulted in all-triploid progenies after fertilization with functional sperm, and in high yields of heterozygous diploid gynogenetic fry after insemination with gamma-irradiated sperm.

TL;DR: In both species ungutted and gutted body weight and body length were significantly influenced by sex and it was concluded that, when ranking families, correcting for sex might be important.

TL;DR: Visual and chemical determinations revealed that the individual optical isomers of astaxanthin were more efficacious than canthaxanth in pigmenting the flesh of rainbow trout.

TL;DR: The results indicated that maximum egg and fry survivals are achieved if the eggs are stripped 4–6 days post-ovulation, and determination of percentage fertilization is proposed as a management tool to predict subsequent egg and Fry performance.

TL;DR: Variations in salinity and in nutrient concentration had a greater effect on the final biomass than on the growth velocity, and the total protein of the culture and protein per cell increased when the salinity increased for a given nutrient concentration.

TL;DR: There is considerable opportunity to alter the age at sexual maturity in Atlantic salmon through selection and evidence was found that maturation of parr is a heritable trait and that it is independently inherited from maturation in the sea.

TL;DR: Serotonin induced spawning in six bivalve species using individual spawning techniques without any additional stimuli is shown to stimulate bivalves to spawn within 15 min.

TL;DR: The effects of α-tocopherol on the specific immunity and non-specific resistance of fish were studied and the possibility of immunopotentiation by vitamin E is also addressed.

TL;DR: In a series of fertility tests, the chemical constituency of the medium in which fertilization was attempted influenced the fertility of cryopreserved sperm.

TL;DR: From a practical point of view, weekly collection is feasible in second-season spawners, but a maximum of one stripping every 2 weeks appears appropriate for first- season spawners.

TL;DR: No effects of carotenoid levels were observed on the survival of eggs and alevins of Atlantic salmon (Salmo salar) in darkness, and diets supplemented with synthetic astaxanthin and cantaxanthins promoted growth rate during the early start-feeding period.

TL;DR: Seven elements are described for cultivation of the red abalone, Haliotis rufescens: broodstock management; spawning induction, fertilization, and early development; larval cultivation; forage culture; settlement and early-juvenile-stage cultivation; weaning; and grow-out.

TL;DR: Because heterozygosity was higher in oysters created during meiosis I than in other groups, the increased growth must be due toheterozygosity rather than to triploidy per se.

TL;DR: The infectivity study confirmed that IHHN disease is virus-caused and the gills and nerve cord/ganglia were shown to undergo significantly higher degrees of tissue damage in infected P. stylirostris compared withinfected P. vannamei.

TL;DR: There was no significant correlation between the percentage of the original number of eggs which hatched and any one aspect of egg composition, except for a weak positive correlation that differed significantly from those with zero hatching percentage in having higher egg weight, chorion weight, protein phosphorus and protein phosphorus.

TL;DR: Both age at metamorphic competence and concentration of natural inducer necessary to elicit metamorphosis in competent larvae of Phestilla are known to show wide variance among larvae, and it may be that a single model will not be appropriate for all marine molluscs.

TL;DR: The best temperature shock treatment with regard to percentage of triploids and percentage survival relative to controls was 26°C starting 1 min after fertilization, and Histological analysis of the gonads revealed sterility in triploid female fish.

TL;DR: Heat shocks or hydrostatic pressure shocks, when completed within 20 min of fertilization at 10°C, were found to induce 100% triploidy with 70–90% survival (relative to controls) in landlocked Atlantic salmon.

TL;DR: The level of protein in the diet had a greater effect on the enzyme total activities in the large shrimp (17–30 g) than in small shrimp ( a p ratio diets displayed lower activities than those fed the 2:1 ratio diet).

TL;DR: An investigation of body size variability among 13 strains of the rotifer Brachionus plicatilis demonstrated that strain is the most important factor determining lorica size.

TL;DR: Light regimes of constant length are alternatives to altered seasonal cycles for the modification of spawning time of rainbow trout, provided that spawning is not advanced more than 2–3 months, which indicates there is a period of photosensitivity in the first half of the annual cycle during which the trout can respond to long days.

TL;DR: Nitrogen excretion (total N, NH3 and urea-N) across the gills (ZN) and in the urine (UN) as well as in the feces (FN) was measured for individual rainbow trout in relation to dietary protein and lipid.

TL;DR: A weak negative correlation between fish weight and level of carotenoids in the flesh was found and the sex did not affect pigment deposition.

TL;DR: In two trials (I and II) carp kept in tanks were given six feed mixtures, with respectively a protein content at three different levels and an energy content at two levels, the protein content of the diet very strongly influenced the nutrient contents of the carp and the fat content showed the greatest differences.

TL;DR: The evidence indicates an endogenous origin of chitinolytic enzymes in the trout gastro-intestinal tract, and the presence of either antibiotic or bacteria in the diet had no effect on the digestibility of Chitin.

TL;DR: This paper shows how to evaluate these contributions in complex life cycles, in which individuals may be classified by size or developmental stage as well as age, and examines the possibility that natural selection in response to increased fishing pressure at sea is responsible for the recent increase in precocious maturation by male parr in the Atlantic salmon of the Matamek River, Quebec.

TL;DR: The relative effects of genotype and initial freshwater rearing on the incidence of sexual precocity in coho salmon males were examined and mean growth of progeny from the jack and normal male-sired groups was equivalent during the majority of the initial freshwaterRearing period.