摘要:

SummaryOverall microbial levels in the water system of a turbot farm were similar to those found in regular sea‐water. At the end of an incubation period, however, the numbers of colony‐forming units (CFU) inArtemiucultures and turbot eg incubation jars were up to four orders of magnitude higher than sea‐water level. Rinsing of the foot organisms (rotifers) prior to feeding them to turbot larvae, however, significantly reduced bacterial numbers, thus reducing the number of cross‐contaminations. Several species ofAeromonas, PseudomonasandVibrioamong others, were identified in the eggs and larvae, or in the water in which these were incubated. Scanning electron microscop shows that the surface of unfertilized turbot eggs is a breeding ground for bacteria; the removal of these eggs from incubation jars is therefore recommended. The epidermis of turbot larvae was virtually free ofmicroor

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1994.tb00138.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryGonadal maturation, rematuration, and spawning of nine‐ (1982 stock) and ten‐year‐old (1981 stock) milkfish reared in 150 and 200 m3concrete tanks were observed in 1990 and 1991. From 23 September to 9 November 1990, the 1981 stock spawned 15 times with an average daily collection of 61,000 ± 21,000 eggs. From 4 larval rearing trials, the mean overall survival rate (from eggs to 21 ‐day‐old fry) was 9.68 ± 4.3%. From 25 Aril to 31 October 1991, the stock spawned a totaf of 108 times. Mean daily egg collection increasef to 305,000 ± 32,000. Successful rearing trials conducted during the latter part of the spawning season had a mean overall survival rate of 17 ± 3% (n = 17) indicating that mass fry production techniques can be improved. Spawning of milkfish broodstock in concrete tanks provides an alternative to other existing methods of se

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1994.tb00139.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryVariability in length‐at‐age of marine species of fish was studied using age and growth data and population‐specific life history and environmental parameters for 168 species in 50 families (458 records). The shapes of distributions, the magnitude of variability, the patterns of variability with age and size, and the degree of overlapping of distributions were investigated using simple as well as multivariate statistical methods. Departure from normality was a widespread phenomenon. The most important pattern of variability was an increase to a maximum at an intermediate age or size followed by a decrease. The degree of overlapping was generally high, with only one or two distributions not significantly overlaped in most cases. The implications of these results for length frequency analysis and other areas of fisheries are disc

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1994.tb00140.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryThe relationshis among carcass weight, acid‐base‐balance of the blood as an indicator for metabolic load susceptibility, meat quality parameters, and body Composition were investigated in rainbow trout. Examinations were carried out in two replicates using a total of 300 trout from a Danish population. Within replicates, the trout were of aproximately the same age. In Replicate I trout, increasing carcass weight was accompanied by a more arkaline reaction of the blood. Carcass weight was significantly correlated with blood‐pH and bicarbonate concentration (.19 and 26). Regression coefficients, however, confirmed only an increase of bicarbonate concentration with increasing carcass weight (b = .013 mmol/L per g, sb= 0.005). In meat quality parameters, muscular pH24values decreased linearly in both replicates with increasing carcass weight, as shown by significant correlation estimates (‐20 and ‐.27) and regression coefficients (b = ‐.0006, sb=.0002, and b = ‐.001, sb= .0003). Relationshis of other meat quality parameters to inmeasing carcass weight were evaluated differently by correlation and regression coefficients. No relationship was found between carcass weight and body composition. In general, correlation estimates describing interrelations between acid‐base and meat quality parameters were on a very low level. Independent from carcass weight, there were clearly metabolically loaded and unloaded trout as well as trout with a mixed acid‐base‐status. Acid‐base parameters were significantly correlated with each other. Generally, estimates for correlations between meat quality parameters were on a very low level. Body composition arameters, dry weight and crude fat content were highly significantly correlated (0.47) in Replicate II; in Replicate I there

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1994.tb00141.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryHatche and wild sea bass (Dicentrarchus labrax) fry were transferred from sea water to low salinities and freshwater (FW) usiny three different operational protocols:1) direct exposure to ow salimues and FW (LC 50 test, ST 50 test); 2) quick acclimation to FW (48h); 3) slow acclimation to FW (17d). Direct exposure to freshwater led to e death of all fry. Comete survival was observed after direct transfer to salinities ≥ 9 ppt, both in wild and hatchery fry. Eatchery fry tolerate direct transfer to low salinities (LC 50=4.393 ppt) better than wild fry (LC 50 = 3.215 ppt). Slow acclimation rotocol leads to higher survival rates (nearly 90 %) than does the quick procedure. In 48h and 17d accimation trials wild fry tolerate FW better tlan hatchery fry. Hypotheses to explain observed differences in wild and hatchery tolerances to low salinities and FW are discusse

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1994.tb00142.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryScreening an Atlantic salmon (Salmo salarL.) salmon kidney cDNA library with total cDNA led to the isolation of a clone which hybridised strongly to both salmon kidney and spleen total cDNA probes. Analysis of the sequence identified the cDNA as the gene coding for subunit II of cytochrorne c oxidase (coxII). Northern blot studies revealed a transcript of approximately 700 bp in liver poly A+ mRNA. The DNA sequence of the Atlantic salmoncoxIIgene employs the mammalian mitochondrial genetic code and is strongly conserved when compared to other species.

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1994.tb00143.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SummaryObservations made over a three‐year period at the Fish Diseases Laboratory of the African Regional Aquaculture Centre (ARAC), Nigeria, revealed the gradual emergence of a new, highly infectious septicaemic condition in some widely cultivated freshwater fish species. The broad host range included:Heterobanchus bidorsalis, Clarias gariepinus, “Heteroclarias” (a hybrid of these two species, male and female respectively),Chrysichthys nigrodigitatus, andCyprinus carpio. Clinical signs and pathological lesions associated with the condition were tyical, irrespective of the fish species affected; natural outbreaks apeared to be associated with stress due to environmental factors. The bacterium isolated from moribund and freshly‐dead fishes was identified as aBacillussp., based on the observed cultural, morphological and biochemical characteristics. Fish reinfection trials confirmed that the isolate was the causative agent of the condition. Antibiotic sensitivity tests showed that the organism was sensitive to tetracycline hydroc

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1994.tb00144.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY