摘要:

AbstractOptimum conditions for hydrostatic pressure treatment for duplication of chromosome set in gynogenetically activated fighting fish,Betta splendens(Regan), eggs were identified. Maximum survival of heterozygous gynogens was 50%, when 2·5‐min‐old eggs, after insemination with UV irradiated tilapia sperm, were pressure shocked at 7000psi for 6 min. The frequency (21%) of homozygous gynogenetic fry was high, when the 34min (post‐insemination) old eggs, which were inseminated with tilapia sperm, were pressure shocked for 5 min. Sex ratio of gynogenetic progeny suggested that the mechanism of sex determination in this fish is homogametic female and heterogameti

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00569.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractLarval and juvenile barramundi,Lates calcarifer(Bloch), were reared intensively on test diets comprising nutritionally supplemented and unsupplemented rotifers,Brachionus plicatilisMuller, and brine shrimp,Artemia salinaL. Both growth and survival of barramundi larvae fed on nutritionally supplemented brine shrimp were superior to those of larvae fed on untreated brine shrimp. Barramundi larvae fed diets incorporating untreated brine shrimp exhibited a mortality syndrome which commenced from 20 to 30 days after hatching and resulted in almost total mortality within the next 10 days. Analyses of the proximate, fatty acid and amino acid composition of the live food organisms used in the test diets, and reference samples comprising barramundi egg yolk and extensively reared juvenile barramundi, suggest that this mortality syndrome was primarily associated with the fatty acid composition of the food organisms, particularly the relative amount of 20:5n‐3 in the brine shrimp fed to the larvae. These results, and the work of other authors, indicate that there are two mortality syndromes which affect intensively culturedL. calcariferlarva

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00570.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effectiveness of live‐algae replacement diets for the conditioning and spawning success of adult Manila clam,Tapes philippinarum(Adams and Reeve), was assessed. Two dried diets were tested: a diet of driedTetrasetmis suecica(Kylin) Butch, and a mixed diet of driedT. suecica(70%) and driedCyclotella crypticaReimannet al.(30%). These diets were compared with three live diets:Skeletonema costatum(Grev.) Cleve,Dunaliella tertiolecta(Butcher) andT. suecica.An unfed group was used as a control. The same ration (dry weight) of food was supplied for all groups at 6% of the dry meat weight per day. The broodstock were conditioned for 7 weeks. After 4 weeks none of the animals was ready to spawn. After 6 weeks all the diets promoted spawning and after 7 weeks the unfed group also spawned. It seems that dried algal diets are effective for conditioning and spawning of Manila clams, as the dry meat weight, condition index and fecundity of broodstock fed these diets were significantly greater than for unfed animals. However, the fecundity and proportion of parental lipid released in the eggs of clams conditioned with dried diets was lower than for the clams conditioned with live alga

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00571.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractApparent digestibility coefficients were determined for six feedstuffs, subsequent to their processing into pelleted feed for tropical freshwater catfish,Mystus nemurus(Cuvier&Valenciennes), using a reference diet and test diets composed of 70% reference diet and 30% test ingredient. It was found that most ingredients were fairly well digested except maize and chicken viscera. Digestibility coefficient for protein (P), dry matter (DM) and energy (E) were: (1) fish meal: 97·8% P,97% DM. 77·88% E: (2) soybean meal: 86% P,95·55% DM, 67·89% E: (3) rice bran: 81% P,85·81% DM, 67·93% E: (4) copra meal: 79·90% P, 86% DM, 71·89% E: (5) maize: 51·93% P, 49·0% DM, 63·40% E and (6) chicken viscera: 37% P,29% DM, 52% E.Digestibility coefficients for feedstuffs indicated that animal protein product, such as fish meal and grain by‐product, such as rice bran were more digestible than starchy and fibrous feed, e.g. maize. Chicken viscera was poorly digested largely due to inefficient processing. As most feedstuffs were well digested, ingredient selection should, therefore, be based primarily on their protein content, amino acid composition and

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00572.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractCompared to the extensive number of studies in nutritional immunology in humans as well as in livestock, the evaluation of nutritional impact on fish health is in its infancy. The mechanisms by which single nutrient modulate immunity are frequently not understood, even if experiments give some indication of the mode of action. With current knowledge in fish nutrition, the methods and criteria for optimal nutrient recommendations should be reevaluated to include health factors such as immunolgy and disease resistance. By increasing knowledge of the role of different nutrients in the general metabolism and in immunity, and by improving rearing conditions, it may be possible to reduce losses due to diseases by retarding the progress of diseases, improving recovery and improving protection through vaccines.This review covers research on dietary level of carbohydrate, n‐3 polyunsaturated fatty acids, vitamin E and vitamin C in salmonids, of which the vitamins have been by far the most studie

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00573.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Hypoosmoregulatory capacity was examined in anadromous Arctic char,Salvelinus alpinus(L.), caught whilst migrating towards the sea in the river Å‐elva, northern Norway (69°04′N and 17°00′E). Metacercariae of the marine digeneanCryptocotyle lingua(Creplin) were found on 47% of the fish investigated, demonstrating that they had been in brackish or sea water on at least one previous occasion. The fish were randomly divided into three groups, and exposed to sea water (35 ppt salinity at 5–6°C) for 7 days‐ one group immediately after capture, and the other two groups after 16 days of acclimation in fresh water and brackish water (15–17ppt), respectively. Blood plasma osmolality, Na+and Mg2+levels showed only a small and transient rise during seawater exposure, and there were only minor changes in muscle water content, irrespective of prior treatment. A slight, but insignificant, reduction in hypoosmoregulatory capacity appeared to occur in the groups retained in fresh water or brackish water for 16 days prior to seawater exposure. The results did not indicate that the fish show any improvement of hypoosmoregulatory capacity following a period of acclimation in brackish water. The hypoosmoregulatory capacity of seaward‐migrating Arctic char is well developed before they enter the sea, and may be comparable to that seen in salmonids which undergo a parr‐smolt transformation. There was a negative correlation between blood plasma electrolyte levels and both body length and weight, indicating that hypoosmoregulatory capacity was affected by the size of the fish. The effects of body size upon the development of hypoosmoregulatory capacity are discussed with respect to estuarine residence and the constraints placed upon the survival of small fish in full

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00574.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractIn one experiment, temperature and feed ration were varied for rainbow trout,Oncorhynchus mykiss(Walbaum), with an initial size of about 1200g. In two experiments the feed ration was varied between parallel tanks, with naturally fluctuating ambient temperatures, and containing rainbow trout with an initial size of about 1000g and 400–550g, respectively. Growth and feed efficiency were measured in all experiments. Anad libitumfeed ration without wastage produced the most effective energy utilization in most experimental groups. At best an average of 50% of the gross energy was utilized for growth. The relation between growth rate and feed ration was linear, and there was no optimum point for feeding below this level. The observed intake of energy is compared with growth, measurements of digestibility, feeding and starving metabolism. It is also linked to earlier observations of intake by rainbow trout fingerlings to give equations expressing the energy needs of rainbow trout of different sizes (30–1500g). These are intended to be used for efficient rearing at different temperatures (10–

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00575.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY