摘要:

SummaryMullet fingerlings (Liza ramada) were fed three different commercial feeds (two types of pellet trout feed and one eel paste); growth performance was monitored for 14 weeks in an open as well as a closed intensive aquaculture system. The1 mullet fingerlings exhibited different growth and survival rates according to the various feed types. Weight increase and survival were poorer and the differences between the feeding treatments were more pronounced in the flow through system. These findings are discussed in relationship to differences in the stability of the feed and to the physical and chemical criteria in each rearing system.

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1989.tb00488.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryCryo‐preservation of carp, Cyprinus carpio,spermDeep‐freezing trials of carp sperm were carried out by varying several factors such as the basic saline solution, the cryoprotectors added (glycerol, propanediol, ethylene glycol and DMSO), the media (Menezo‐INRA B2, egg yolk, urea) and the deep‐freezing and dilution rates. The success of deepfreezing was judged by the percentage of motile spermatozoa, intensity of motility, fertilizing ability and morphological integrity of the spermatozoa studied under the scanning electron microscope. DMSO was the best cryoprotector and the mineral composition of the dilution medium the least important factor, but there was noticeable improvement after organic compounds were added. The following mixture has been proposed: NaCl 100 mM + KC1100 mM, Tris 20 mM, pH 8: 37%, Menezo medium B2INRA: 15%, urea 5%, DMSO: 10%, fresh sperm: 33%. Optimal deep‐freezing rate was: 5°C/min from 2 to‐7°C and 25°C/min from‐7 to‐70°C. In these conditions, about 70 to 80% of the spermatozoa were motile after thawing compared to fresh control sperm, but fertilizing ability was not more than 30 to 40% of that with fresh sperm. The percentage of spermatozoa considered intact was 66% after thawing as against 83% for fresh control sperm. The motility and fertilizing ability of deep‐frozen sperm were significantly improved when the dilution rate at insemination was re

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1989.tb00489.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThe effect of various doses of luteinizing hormone‐releasing hormone analogue (LHRHa) ranging from 1 to 100 μg/kg body weight on the spawning response of mature female sea bass,Lates calcarifer(Bloch) was tested. A single intramuscular injection of LHRHa resulted in a dose‐related increase in the spawning rate (number of spawnings of each fish over four consecutive days) of mature fish. An LHRHa dose of 5 μg/kg and less induced low spawning rates of 16.7% to 37.5% or at least one spawning every four days. However, mature sea bass spawned more than once (43.8–58.3%) in four days at dose levels of 10 μg/kg and above. Hormone treatment within the dose range tested did not influence the number, fertilization and hatching rates of spawned eggs.The influence of initial oocyte size on the LHRHa‐induced spawning response of mature sea bass was also examined. Sea bass with an initial oocyte diameter of 0.30–0.39 mm did not respond to the single injection of 100 μg LHRHa/kg. In contrast, LHRHa induced spawning among sea bass with an initial egg size of 0.40–0.49 mm, although two of four sea bass of the same stage of ovarian maturity spawned spontaneously. Fish having an initial oocyte size of 0.50–0.55 mm spawned with and without LHRHa treatment. Spontaneous spawning among saline‐injected sea bass occurred at a later time (24–58 h post‐injection) compared to fish induced to spawn by a single injection of LHRHa (8–36 h post‐injection). The initial spawning response time interval for fish with an initial egg size of 0.50 mm or greater was further reduced to 8–9 h by LHRHa. These results indicate that LHRHa can successfully induce spawning in mature female sea bass which have attained a critical oocyte diameter and that the spawning response interval is reduced with a further increase in egg size beyond the c

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1989.tb00490.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryBased on length frequency data, the following growth and mortality parameters were derived for the stock of Indian oil sardine,Sardinella longiceps, off the southwest coast of India:L∞= 21 cm, K = 1.4 year‐1, Z = 4.2 year‐1, M = 2.0 year‐1, F = 2.2 year‐1The fishing mortality (F) required to maintain the spawning stock at the optimum level was estimated to be 1.8 year‐1. At this level of fishing mortality, the maximum sustainable yield per annum was estimated around 45 × 109in numbers and 300,000 tonn

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1989.tb00491.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryGrowth and survival of replicate batches of African sharptooth catfish (Clarias gariepinus) larvae were monitored in 0, 2.5, 5.0, 7.5 and 10 ppt salinity. No significant differences in mortality or growth rate were evident between 0 and 5 ppt salinity. At 7.5 ppt mortality rate was higher and larval growth rate declined in comparison to the lower salinities. At 10 ppt all larvae died within 48 hours. The condition factor of the larvae similar between 0–2.5 ppt and displayed a declining trend between 2.5–7.5 ppt. Osmoconcentratkm of blood plasma of C.gariepinusin fresh water was 280 ± 20 mOsm/kg which is equivalent to 9.5 ppt salinity. It was concluded that 0–2.5 ppt is the optimal sclinity range for larval rearing and that short‐term exposure to higher salinities (2.5–7.5 ppt) could be effective in the treatment of ectoparasiti

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1989.tb00492.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryTilapiine fish are known to become stunted under different environmental conditions. Of the tilapia,Oreochromis mossambicus(Peters), once considered to be the aquatic chicken, is now treated as a nuisance species in some countries because of its tendency to stunt easily. O.mossambicusis the mainstay of the commercial gillnet fishery in existence in the multitude of reservoirs in Sri Lanka for over 35 years. Published and new evidence on O.mossambicuspopulation traits are presented with a view to evaluating whether the populations in Sri Lankan reservoirs are stunted or not. The main lines of evidence considered are the mean size at maturity (Lm), the proportion of individuals below 20 cm total length in the commercial landings, and growth performance of the individual reservoir populations. Statistically valid inter‐relationships exist between the mean length at maturity and the proportion of undersized individuals (below 20 cm) in the landings, and the ratio of the reservoir catchment or watershed area to surface area. Evidence on Lm indicate that there is a tendency forO. mossambicuspopulations to stunt, however, evidence on growth and mean landing size do not indicate stuntin

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1989.tb00493.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SummaryThe population of the Scottish Highlands and Islands had been in a steady decline because of a lack in employment opportunities. Under strong encouragement by the Highlands and Islands Development Board, salmon farming has been a significant factor in reversing this decline. In 1988, aquaculture development in Scotland exceeded 20,000 tonnes of salmon, and provided about 1,600 jobs in fish farming, 120 jobs in feed production, and another 1,800 jobs in processing; it is estimated that over 5,000 people are employed in activities serving aquaculture. The spin‐off effects of this development are analyzed in detail. Aquaculture production is compared to the “hands on” value of other industries in the Highlands and Islands of Scotland; worth over £ 80,000,000 at the farm gate, salmon farming ranks alongside beef production and white fish in economic value. A salmon production of 60,000 tonnes is predicted for 1990. Taking the expansion of the salmon industry and other aquaculture activities into account, the calculated impact zone covers about 480 ha only and will occupy only about 0.01 % of national scenic areas. Future prospects in the industry as well as user‐conflicts are d

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1989.tb00494.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Schumann, Eckart H. (ed.): Coastal Ocean Studies off Natal, South Africa. Berlin‐Heidelberg‐New York‐London‐Paris‐Tokyo‐Hong‐KongRoyce, W. F.:Fishery Development.Orlando/San Diego/New York: Academic Press 1987Ellis, A.E. (Ed.):Fish Vaccination.London, San Diego: Academic Press 1988.Potts, G.W., Wooton, R.J. (Eds.):Fish Reproduction: Strategies and Tactics.London/San Diego/New YorkShepherd, C., Bromage, N.:Intensive Fish Farming.BSP Professional Books div. of Blackwell Scientific Publications Ltd. 1988.Blüm, V., Casado, J., Lehmann, J., Mehring, E.:Farbatlas der Histologie der Regenbogenforelle.Hrsg. von d. Landesanstalt für Fischerei Nordrhein‐Westfalen. Berlin, Heidelberg, New

ISSN:0175-8659    

DOI:10.1111/j.1439-0426.1989.tb00495.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY