摘要:

AbstractMacadamia presscake, the by‐product from oil extraction process of low‐grade kernels of macadamia nuts, was evaluated as a dietary protein supplement for tilapia,Oreochromis niloticus(L.), reared in outdoor concrete cisterns. Five isoproteic diets (28% crude protein) were fed to tilapia for 100 days. The diets comprised a control, which contained full‐fat soybean as the protein source, and four test diets in which the full‐fat soybean meal was progressively substituted (10%, 20%, 50% or 100%) with macadamia presscake. Final weight, daily weight gain, specific growth rate and apparent protein digestibility were significantly different (P0.05). Body protein deposition was not affected by the inclusion level of mac‐adamia presscake in the diet. Results showed that macadamia presscake was suitable as a dietary protein supplement for tilapia when incorporated up to 50% replacement for soybean protein. The nutrient content of full‐fat soybean meal is apparently similar to that of macadamia presscake but the quantity of macadamia presscake in fish feeds may be limited due to the less‐than‐optimal amino acid balance in macadamia pr

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00926.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe viability of batches of larvae reared to produce lobsters,Homarus gammarus(L.), for stock‐supplementation experiments varied widely and rendered the timing and numbers of juveniles available for release unpredictable. Egg lipid reserves, time of hatching, exposure to low salinity during incubation and the influence of feeding regimes on water quality during larval culture were among the factors judged most likely to have affected viability.There was considerable variation in the lipid content of eggs from different females captured in 1989 and 1990. The proportion of lipid in eggs from females caught in 1990 was higher (10‐20%) than that in eggs from females caught in 1989 (6‐11%). The fatty acid content of eggs declined 72‐80% during development although the overall proportions of fatty acids remained similar. Analysis of eggs and larvae from a single brood showed that rapidly developing eggs and the larvae that hatched from them contained greater triacylglyceride lipid reserves (by 49% and 15% respectively) than those which developed more slowly and hatched later.Exposure to reduced salinity (below 29 psu) prolonged development (by 30%), increased losses (to>50%) and reduced the ratio of n‐3:n‐6 fatty acids (from 35‐48 to 18‐29) of eggs being incubated by captive, wild‐caught, female lobsters. Larvae hatching from eggs held in reduced salinity (23 psu) survived less well (3% compared with 15%) than those incubated in sea water of 29 psu.The rate and degree to which fouling organisms became attached to larvae was related to feeding regime but not to development rate. A diet of mysids supplemented with mussel produced most fouling, generally poorer growth and a higher incidence of moulting abnormalities than a diet of mysids supplemented withArtemianauplii. Among larvae fedArtemia, those developing early were significantly larger at instar 4 than late developers (56.4 mg cf. 49.8 mg,P<0.05), but such differences in weight were not maintained by juveniles during the following 31 days of culture.The ecological and aquacultural implications of the resu

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00927.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis study examined whether rapid recovery from stress‐induced impairment in predator evasion, observed in previous studies on coho salmon,Oncorhynchus kisutch(Walbaum), was a general characteristic of different stocks of the same species and different species of Pacific salmon. We monitored stress‐induced non‐predator mortality, predator evasion and Cortisol concentrations of smolts of coho and spring Chinook,O. tshawytscha(Walbaum), after administration of standardized single and multiple handling stresses. Marked differences in the response to handling stress among stocks of coho and spring chinook smolts were evident, with recovery from impaired predator evasion occurring within 24 h of a 30‐s handling stress for coho smolts and 24 h of a 1‐min handling stress for spring chinook smolts. Differences in stress‐induced non‐predator mortality among stocks were also observed. The results point to the importance of screening hatchery salmonid stocks to assess differing capabilities of dealin

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00928.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractDiets with increasing levels of potato and maize starch were fed to duplicate groups of maturing cod,Gadus morhuaL., from June 1991 to January 1992.The level of starch in the diet did not influence feed conversion factors, broodfish growth or gonadal development. Low levels of fillet glycogen were measured at all samplings, without variations according to dietary starch, or to developmental stage of the brood fish. During the reproductive phase no decreases were measured in relative liver size or liver protein, lipid or glycogen, indicating no net use of stored energy from the liver to build up gonads as long as the fish was offered feed. The variations in dietary starch vs. protein did not alter the composition of gonad dry matter, protein, lipid or glycogen levels. However, dry matter and protein levels increased during maturation in all groups.Plasma glucose levels were within normal ranges in all dietary groups at all sampling times, indicating no negative effects of high levels of dietary starch in brood fish, as also confirmed by stable and normal haematocrit, red blood cell count, and mean cell volume in blood. Haemoglobin, mean cell haematocrit and mean cell haemoglobin concentration decreased during the reproductive phase. Serum haemolytic complement activity did not vary between dietary treatments. Glycogen, dry matter, protein and lipid levels in eggs did not vary between dietary treatments of brood fish. Very low levels of glycogen were measured, suggesting that this energy reserve was of minor importance. Dry matter and lipid levels were quite stable in relation to egg developmental stage: protein levels decreased from day 0 until hatching.

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00929.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractSexual dimorphism in yellow eels,Anguilla anguilla(L.). was studied to clarify the differences between sexes. The focus was on the relationship between length/weight and sex. Three samples of eels, grown in captivity in different places in Israel, were studied. Females were significantly lighter than undifferentiated eels in the length range 33‐47 cm. The regression coefficient did not differ significantly between females and undifferentiated eels. Sex induction, by a single injection of human chorionic gonadotropin, resulted in a higher loss of body weight during differentiation into the female than into the mal

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00930.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA dynamic model to simulate growth of the African catfish.Clarias gariepinus(Burchell), was parameterized and calibrated for Nile tilapia.Oreochromis niloticus(L.), and rainbow trout,Oncorhynchus mykiss(Walbaum). The model predicts fish weight and fat percentage from the amount and composition of the feed and water temperature. The major factor determining the efficiency of feed conversion is the proportion of energy provided by protein oxidation, which is positively related to the protein feeding level and the protein/energy ratio of the feed.The model predicted fresh weight of the herbivorousOreochromis niloticusin independent experimental data with a mean deviation of ‐2.1% (range ‐23% to +37%) of observed values (fish weights 10‐40 g), For the carnivorousOncorhynchus mykiss, this value was 4.8% (range ‐21% to +24%, 50‐800 g), Options for further improvement of the model are discussed. We conclude that the structure of the model applies to a broad range of fish species and feeding schedules, provided that both feed and fish are characterized by a set of specific p

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00931.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractFish need oxygen for aerobic generation of energy for body maintenance, locomotion, feeding and biosynthesis. The rate of oxygen uptake of most fish is limited by diffusion through the gills, and gill surface area grows at a slower rate than body mass. We hypothesize, therefore: (1) that the maximum rate of feed intake is related to the capacity to take in oxygen for processing of this feed; and (2) that the maximum rate of feed intake relative to body size decreases with increasing body size to a point where growth is zero. An oxygen limitation module based on this theory was incorporated into an existing dynamic simulation model for the Nile tilapia,Oreochromis niloticus(L.).The module calculates the maximum potential oxygen supply to the fish on the basis of Fick's law of diffusion and the allometric relationship between body weight and gill surface area. Total oxygen demand of the fish is computed as the sum of routine metabolism, feeding metabolism and energy needed for biosynthesis. In the module, the feeding rate is limited to a level where total oxygen demand does not exceed the potential supply.The model is used to simulate feeding and growth ofO. niloticus. Simulation results provide strong support for the oxygen limitation theory. Hence, the model can be used for the analysis of fish growth as affected by feed amount, feed composition, as well as environmental conditions (temperature, dissolved oxygen concentration). It also explains differences in final size between fish species, and within species under different conditions.

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00932.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractAcute toxicity tests were carried out for four compounds commonly used against various fish pathogens to determine their 24‐h LC50values to fry of the African catfish,Clarias gariepinus(Burchell). Compounds tested and their calculated 24‐h LC50values (mg l−1) were as follows: praziquantel (13.4); malachite green oxalate (0.14); acriflavin neutral (10.0); and mebendazole (315). The results show that dosage levels of malachite green oxalate, praziquantel and acriflavin neutral recommended in the literature for the control of most fish ectoparasitoses caused substantial mortalities and cannot be applied toClarias gariepin

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00933.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractCritical thermal maxima (CTMax) and minima (CTMin) were determined forProchilodus scrofaSteindachner of two sizes (19.5 ±7.2g and 249 ± 42.4 g). acclimated at 15. 20, 25, 30 and 35 ± 1°C. The CTMax and the CTMin for the smaller fish were 33.9. 36.7. 38.7, 40.3. 42.0°C and 5.0, 7.2. 9.2. 10.3. 13.4oC and for the larger (Ish 33.3, 35.7, 38.2. 40.6. 42.6°C and 6.5, 8.2. 10.8. 12.4, 14.6°C. respectively, at each acclimation temperature. The CTMin from smaller fish were significantly lower than those from larger ones but the CTMax did not show any such difference. These results indicate thatP. scrofais suitable for culture in south‐eastern and even in southern Brazil where winter temperatures may drop to very low levels, mainly at night. The zone of thermal tolerance calculated by CTMax and CTMin was equivalent to 1046°C2and 964.2°C2, respectively, for smaller and larger fish, showing a high degree of eury

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00934.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY