ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1996.tb01266.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractTotal ammonia and total nitrogen efflux rates of the African catfish,Clarias gariepinus(Burchell), were measured under different temperature conditions (20, 25 and 30°C) and feeding regimes (50% protein, 40% protein and non‐fed for 10 days). Both ammonia and nitrogen efflux rates were directly related to temperature. At all experimental temperatures, the 50%‐protein‐fed groups excreted higher levels of ammonia nitrogen than both the 40% protein and non‐fed groups. No correlation of relative ammonia efflux (% ammonia/nitrogen) with either temperature or diet was observed under these experimental conditions. Such alterations caused by temperature and diet may have significant implications for an aquaculture system as low levels of dissolved ammonia are synonymous with optimum water

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1996.tb01267.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe culture of the carpet shell clams.Tapes decussatus(L.), a high‐priced clam is still a very recent activity. Three common methods of culture, culture park. polyculture ponds and trays inside a tank, were tested to assess which one gave better growth. Mean weights, length and width were recorded in order to determine non‐isometrical growth. The highest percentage mean weight gain and specific growth was observed for the carpet shells in the polyculture pond (89 x10‐3mm day‐1versus 2.2 x 10‐3and 3.3 x 10‐3mm day‐1in the park and the aquaria, respectively). Despite the lower temperatures, water fertility favoured faster growth of phytoplankton, and therefore, of clams in the pond cultured shells. It is concluded that growth in polyculture ponds with fish and shrimps produces the best results a

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1996.tb01268.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractGilthead seabream,Sparus aurataL., fed diets of equal vitamin C content were exposed to three different stressors–hyposalinity, shallow water and handling–and the effect of each on the internal homeostasis of the fish was evaluated. The individuals subjected to hyposaline stress exhibited no significant changes in plasma osmolality. Na+. Cl‐K+, glucose, protein and triglyceride concentrations. Hepatic glycogen content was significantly lower in the fish subjected to the lower salinity (12%o), while the red muscle glycogen was unaltered. Amongst the challenged individuals, tissue ascorbate content was not significantly altered. Shallow water stress significantly diminished the liver and red muscle glycogen content, and lowered the liver. kidney and spleen vitamin C concentrations in the stressed fish. No significant changes were recorded in the plasma glucose, protein and triglyceride concentrations. In response to handling stress, no significant differences were detected in any of the measured parameters, with the exception of plasma glucose levels and the splenic L‐ascorbic acid and ascorbate‐2‐sulphate (vitamin C2) contents. The lack of existing standardization of both experimental designs and analytical methods made comparisons of the present data with the work of other authors difficult, thus highlighting the necessity of coordinated research in

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1996.tb01269.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe development and testing of two fish growth models is described. The equations are based on the effects of fish weight and water temperature on the specific growth rate and ration of sea breamSparus aurataL. The models show a good fit and are proposed for prediction of harvesting time and food consumption. In particular, provided a fish‐stocking technique similar to that described in this study is followed, prediction can be made on the estimation of the optimum amount of food given to avoid food wastage and save storage space, the overall rearing period from the 2‐g fry stage up to the marketable size of 300‐350 g, and the optimal stocking period in order to produce marketable fish at the right time and at a satisfactory selling

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1996.tb01270.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractWolffish,Anarhichas lupusL. has internal fertilization. The eggs are released into water before the beginning of cleavage and stick together in clutches. To develop methods for separating eggs for subsequent incubation, changes during egg swelling and egg shell hardening were observed. Uninseminated eggs did not swell in ovarian fluid, but a perivitelline space formed in sea water because of a partial cortical reaction. In inseminated eggs kept in ovarian fluid, a cortical reaction took place and swelling was caused by elevation of the yolk membrane. Shrinkage of the yolk and absorption of water were observed after inseminated eggs were placed in sea water. Eggs swelled in ovarian fluid diluted by less than 30% sea water showed abnormal cleavage during subsequent development. An effective method for preventing egg stickiness after fertilization was to distribute them in trays with stagnant sea water for at least 5‐6 h. Milk was effective for loss of egg adhesiveness at 50% concentration, but some eggs cleaved abnormally and subsequent mortality was high. The influences of ovarian fluid and milk on initial egg development with respect to peculiarities of egg swelling are discusse

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1996.tb01271.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractArctic char,Salvelinus alpinusL., and Atlantic salmon,Salmo salarL., were fed a commercial diet with or without supplementation of 1.5% Na+‐lactate. Dietary Na+‐lactate enhanced growth of Arctic char, while that of salmon was unaffected. Dietary14C‐lactate was retained for significantly longer in the stomach of Arctic char than that of Atlantic salmon. Changes in intestinal cholytaurin hydrolase activity, a bacterially produced enzyme, may indicate that dietary lactate affects the intestinal microbiota of Arctic char but not that of Atlantic salmon. Analysis of bile acids of char showed that dietary Na+‐Iactate influenced neither intestinal nor gallbladder bile acid composition. Although Arctic char possesses the classical entero‐hepatic circulation pathway, no extra loss of bile acids from the fish was observed. It is concluded that the retention time of diet in the stomach of char is significantly longer than that of salmon. This may increase the antibacterial action of lactate in the former, favouring the colonization of lactic‐acid‐tolerant bacteria in the intestinal tract, some of which produce the enzyme cholytau

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1996.tb01272.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractDuring a longitudinal survey from June until October 1987 cytological blood parameters of smoltified marine cultured rainbow trout,Oncorhynchus mykiss(Walbaum), were monitored. In this period, the trout were exposed to environmental stress resulting in summer mortality. The statistical analyses showed that the observed summer mortality was preceeded by a shift in the relative abundance of different peripheral white blood cells (PWBCs), from lymphocytic to extremely granulocytic, which was mainly attributed to mature granulocytes. It was concluded that changes in relative abundance of PWBCs can predict health disturbances in marine‐cultured rainbow trou

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1996.tb01273.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractProduction characteristics and profitability of three carp‐tilapia stocking ratios (1:1, 1:2 and 1:5) were compared in a semi‐intensive polyculture system. The. experiment was carried out at the same total stocking density of 1 fish m2, in nine 1000‐m2earthen ponds. Common carp,Cyprinus carpioL., and a tilapia hybrid,Oreochromis niloticus(L.) x0. aureus(Steindachner), were stocked at a joint density of 900 fish per pond, while grass carp,Ctenopharyngodon idella(Cuvier&Valenciennes), and silver carp,Hypophthalmichthys molitrix(Valenciennes), were each stocked at 50 fish per pond in all treatments. Mean harvested weights of both common carp and the tilapia hybrid were markedly decreased upon the increase in density of their own species. Survival of all four species was over 80% in all three carp‐tilapia stocking ratios. The differences in relative profitability of the three carp‐tilapia stocking ratios did not exceed 10% on the basis of 1991 prices. However, based on 1994 prices, relative profitability of the 1:2, and particularly, the 1:5 carp‐tilapia stocking ratio were 35% and 41% higher than the 1:1 ratio, respectively. This was because of the increase in the price of large carp and tilapia of all sizes, and a decreases in the price of

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1996.tb01274.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe optimum growth, food intake, food conversion efficiency, final body composition and mortality of juvenileCichlasoma urophthalmus(Günther) was studied at different temperatures, ranging from 22.5 to 36.3°C. The results showed that food intake and specific growth rate increase rising to an apparent optimum at about 33.1°C. Multiple regression equations were derived which can be used to predict food intake and specific growth rate when temperature and initial body weight are kno

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1996.tb01275.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY