摘要:

AbstractRecently, we examined the specific resistance of two carp lines (W and R8) and their hybrid, to experimental bath challenges with atypicalAeromonas salmonicida. These experiments indicated a genetic difference in resistance, the W carp being most susceptible. In the present study, fish of the same spawnings were grown in pond culture, to examine the correlation between disease resistance observed in the laboratory and survival rate in the field, as well as to examine the production potential of the hybrid. Hybrid advantage resulted in higher average weights at the field samplings. Correlation of the field survival rates with specific resistance toA. salmonicidawas pronounced. Survival of the W carp after winter was much lower (47%) than survival of the R8 (93%) and hybrid carp (93%).

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00872.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe present study describes a uniform method for cryopreservation of semen of Salmonidae (Oncorhynchus mykiss(Walbaum),Salmo trutta f. farioL.,Salmo trutta f. lacustrisL.,Coregonussp.). It presents a new type of extender and experiments demonstrating that warming of frozen/thawed semen to 20°C prior to fertilization significantly increases the fertilization rate. Freezing is performed in straws in the vapour of liquid nitrogen and for insemination a diluent technique is used. The consistency of the method was tested by repeating the experiments with different batches of semen and eggs. The following fertilization rates (% of control) were obtained:Oncorhynchus mykiss: 89.6 ± 16.0% (mean ± standard deviation,n= 25,nof control = 20, sperm/egg ratio of 1.6 ± 0.2 × 106spermatozoa/ egg).Salmo trutta f. fario: 93.8 ± 6.4% (n= 12,9.9 ± 1.2 × 106spermatozoa/egg),Coregonussp.: 92.8 ± 2.4% (n= 6, 0.5 × 106spermatozoa/egg),Salmo trutta f. lacustris: 85.0 ± 8.4% (n= 12, 4.8 ± 1.4 × 106sper

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00873.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractSmolt characteristics were investigated in sympatric anadromous and resident Arctic charr.Salvelinus alpinus(L.), of a similar size (11‐20 cm), A group of first‐time migrant anadromous charr was caught while descending the Hals River and two groups of resident conspecifics were caught in Lake Storvatn. one before, and one after, the sea‐run of anadromous fish had terminated. When sampled immediately after capture in fresh water the anadromous group had a higher proportion of fish visually classified as smolts. and these charr had higher gill Na+‐K+ATPase activity, higher densities of developed chloride cells in the gills, a lower condition factor, and lower plasma osmolality, than resident fish. When exposed to sea water (33%o S), only minor differences in mortality and plasma electrolyte levels were observed between anadromous and resident fish, average values of plasma osmolality and chloride concentrations being 377 mOsm and 169 mM and 387 mOsm and 174 mM, respectively. The results suggest that the first‐time migrant Arctic charr had undergone some of the physiological changes that are considered typical for a parr‐smolt transformation before they left fresh water. Such changes did not appear to have occurred in sympatric, resident, fish of a similar size. The parr‐smolt transformation in the first‐time migrants may, however, have been incomplete, because the fish did not appear to have the ability to rapidly re‐establish osmo‐ and ionoregutatory homeostasis after direct tr

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00874.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractShrimp,Penaeus monodon(Fabricius) andPenaeus merguiensis(de Man), culture on East Java is described with special attention to the differences in production characteristics between areas and districts. Traditionally, tambak culture developed along the North coast of East Java where the majority of modern tambaks are still located. The practice never developed extensively on Madura's Island. With the exception of the latter, intensification, startingin 1984‐1987, touched all areas. In 1991, the combined production of PmonodonandP. merguiensisreached 35 000 Mt, representing a value of US$ 220 × 106. The following year, a decline in total production was noted, mainly caused by a diminished production of intensive farms. Possible causes for this production drop are explor

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00875.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA commercially available soybean molasses (alcohol extract from soybean meal) was included at levels of 0. 5,10,15 and 20% in a fish meal based diet for Atlantic salmon,Salmo salarL., weighing about 75 g. These inclusion levels supplied dietary alcohol soluble components corresponding to levels that would have been obtained if a standard soybean meal was included at levels up to about 70%. The fish were reared in fresh water at 9oC and with a minimum of 7 ppm O2at outlet, and fed the experimental diets for 14 days before the faeces were stripped. Digestibility coefficients were determined using chromic oxide as an indigestible indicator. The digestibility of fat, and particularly the long‐chained, saturated‐and monounsaturated fatty acids, were significantly reduced by increasing the inclusion level of soybean molasses, whereas digestibility of dry matter, protein (%N x 6.25) and polyunsaturated fatty acids were not affected significantly. The present results show that alcohol‐soluble components of soybeans may be responsible for a significant part of the negative effects of standard soybean meal in diets for Atlantic s

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00876.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractMicrotagging is an adequate method of ensuring correct recapture estimates in enhancement of natural lobster,Homarus gammarus(L.), stocks through releases of cultured juveniles. This paper compares three lobster size categories (8‐10, 12‐14 and 16‐18 mm), two tag lengths (0.5 and 1.0 mm), and two methods of holding the animal during marking with respect to tag retention and survival. A total of 1721 individuals were used in the experiment. The results did not reveal any obvious trends in tag retention related to either different tag lengths or different lobster sizes. Lobster held laterally during tagging showed higher tag retention (94‐99%) than lobsters held with the ventral side uppermost (74‐97%). Examination, using X‐ray, of 81 juveniles which had tested negative for the presence of tag by the magnetic sensing device, showed that four of these in fact had tags. This suggests that the true tag retention figure could be higher than shown in the results. The cumulative mortality ranged from 0 to 4.7% after 3 days, but only for the smallest animals marked with 1 ‐mm tags laterally: this was significantly higher than in the control group. After 20 days, the cumulative mortality ranged from 0 to 5.7%. but there were no significant differences between experimental and c

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00877.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe objectives of this study were the determination of mortality, growth, condition factor and meat yield, biochemical variables, and somatic secondary production ofPinna rugosa(Sowerby, 1835) in suspended and bottom conditions in Bahia de La Paz, Mexico. The use of each of these parameters was analysed as a decision element for managing the resource. The experimental design was based on the recruitment of wild spat on collectors and introducing bivalves of the same size into different areas. In each area, bivalve samples were used both in suspended trays, and lying on the bottom, approximating their natural occurrence, but surrounded by a plastic mesh fence. The stocking densities in both cultivation systems were 50, 100 and 150 m−2. The organisms were checked monthly for almost 2 years, recording various measurements. In one of the treatments that most closely represented the average, the growth values were 19.5 mm month−1and 14.5 g month−1in the first year, a length‐growth Von Bertalanffy K of 0.118 and an instantaneus growth rate in weight G of 4.77. During the first year, there was annual mortality of 22% on the bottom and 11% at the surface, with somatic secondary production, in dry weight, of 17.8 g per organism. The results of the estimation of each variable were submitted to a multifactorialanova. NO significant differences in K as a function of sites, cultivation systems or density could be found. The effect of site on instantaneous growth rate G was significant. The largest values were from the inner bay (site 1) where the highest mortality rate also occurred. Among condition factor, meat yield and biochemical components, only lipids showed a difference for systems and site factors. We concluded that secondary production gave statistical elements for the selection and culture decision‐making in all factors tested. The results showed good aquaculture prospects for

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00878.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractFour isocaloric isonitrogenous rations containing various levels (0,10, 15 and 20%) of chicken offal silage as a replacement for fish meal were fed to three replicate groups ofOreochromis niloticus(L.) fingerlings with a mean initial weight of 10.8g. Ten fish per tank were tested for 5 weeks in 40‐1 aquaria. The aquaria were put together in a flow‐through system utilizing underground water (24 ± 3°C). Weight gain, feed conversion, protein efficiency ratio and proximate body composition did not vary significantly between treatments. These results indicate that, on an isocaloric/ isonitrogenous basis, chicken offal silage can make up as much as 20% ofO. niloticuscommercial feed as a replacement for fish meal without any effect on growth or proximate body composition under the experimental condi

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00879.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1995.tb00880.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY