摘要:

Abstract.Fish farming activities based on salmonid smolt production in cages were monitored in a coastal freshwater lake in western Norway. Yearly ongrowth in the fish farm increased from 350kg in 1979 to 15150kg in 1985, while maximum biomass of standing stock increased to nearly 14000kg in the same period. Maximum daily mortality observed was 0·37% of total stock in August 1983 due to anIchthyobodo necatorinfection.Except for 1983, between 61 and 73% of annual amount of feed was used in the second half of the year. Total feed amount used in 1979–85 was 77750kg. The phosphorous effluents decreased from 88 to 90% of the feed content to 80·4% in 1984–85.A set of easily calculated parameters for judging management possibilities and success in cage farming is proposed: annual heat sum; mortality rate; growth rate; feed conversion; and phosphorous retention in

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00426.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Full‐sib families ofPenaeus stylirostrisStimpson andPenaeus vannameiBoone were grown under controlled conditions in five experiments. Total length of shrimp larvae was measured at the following substages: protozoea one, mysis one and postlarva one. Analysis of variance showed that families differed significantly in size in all experiments at all substages tested. The average size possessed by a group of larvae early in development was significantly correlated with the size obtained in the later stages inP. siylirosiris, but not inP. vannamei. The component of variance in size due to family differences was determined and used to estimate heritabilities of size at the three larval substages in both species. Estimated heritabilities were higher forP. stylirostristhanP. vannamei. InP. vannamei. the hcritability of size is greater for the protozoea and postlarval stages than the mysis stag

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00427.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Seedlings ofLaminaria groenlandicaRosenvinge.L. saccharina(L.) Lamour. andCymathere triplicata(Post.&Rupr.) J. Ag. were produced directly from mixed gametophytes and indirectly from cloned gametophytes. When cultivated in the sea, these seedlings produced up to 8 wet kg.m−1of cultivation rope forL.saccharina, 20 wet kg.m−1forL. groenlandicaand 2·7 wet kg.m−1forC. triplicata. These values are similar to those reported from other parts of the world. Plant sizes for cultivatedL. groenlandicaandC. triplicatawere greater than observed in wild stands Production byL. groenlandicawas positively correlated with nutrient concentrations and negatively correlated with temperature. The time required to achieve harvestable size may he reduced from 16 to 9 months by employing seedlings produced indirectly from cloned gameto

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00428.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.In a closed recirculating fish culture system with a rotating disc filter serving as ‘biofilter”, waterquality was maintained by the addition of hydrolysed corn starch in the settable solids tank. According to the feed uptake by rainbow trout. Salmo gairdneriRichardson, starch was introduced to adjust a nutrient relation of organic C:N of 1·6:1 for the bacterial biomass. Trout grew from 42 g to 254 g in body weight in 118 days. No differences in feed uptake and feed conversion rate were observed in a control group held in a flow‐through system with tap water as culture

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00429.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.The transportation of live fish in sealed plastic bags was examined. Water parameters and loading densities were analysed. Based on several assumptions an estimation of oxygen consumption during transport was performed indicating that metabolism during transport was about three times higher than routine metabolism. There was some evidence that small fish were more affected by transportation stress, and that large fish need a longer starvation time before transport to reduce ammonia excretion sufficiently.

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00430.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.The effects of different types of feed, given singly or in combination, on the growth and survival of bighead carp,Arislichlhys nobilisRichardson, larvae reared for a period of 12 weeks were determined. Growth was highest for fish fed with the combination ofMoinaand artificial feed followed by fish fed with artificial feed alone. Significantly lower (P0.01) from those givenMoina+ artificial feed. Consequently, normalized biomass index was significantly high (P<0.05) in fish fed with the combination of green water,Moinaand artificial f

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00431.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Four populations of 42 specimens (mean initial b.wt 64·02–65·29g) of Tilapia aureus (Steindachner), were reared for 15 weeks in 600‐1‐capacily cylindrical plastic tunks, from a closed circulated system, al four feeding levels (1,2,3 and 4% of b.wt daily). A feeding level of 2% of b.wt daily seems to be the best, taking into consideration biological (specific growth rale, food conversion rate, protein efficiency ratio, values of total plasma lipids, cholesterol and triglyceridcs. haematocrit, proximate carcass analyses, body weight‐length relationships) and economical (feed cost) criteria. Also, it is concluded that for T. aureus the use of closed or semiclosed circulated systems could he us satisfactory as other forms of intensive productio

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00432.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Analyses of the Sr‐contenl in scales of Atlantic salmon,Salmo saiar L., smolts from two hatcheries revealed significant (P<0·001) differences. These differences were reflected in the Sr‐conients of their respective diets. Sr‐values in scale samples taken from wild salmon smolts from 10 Norwegian rivers showed a considerable variation. Analysis of variance showed that sampling site was the major source of variation. In general the Sr‐content in scales cannot be used to distinguish between hatchery‐reared and wild salmon smolls, although the present results nevertheless suggest that such a distinction is possible in some localities.The Sr‐contenl of the vertebrae was somewhat lower than that of the scales in both hatchery‐reared and wild smolls. The Sr‐conient of the scales of sea trout,Salmo truttaL., smolts from one of the sampling sites was significantly (P<0·001) higher than that of scales of Atlantic salmon smolts from the same site. The Sr‐content of the scales of all the salmon smolts sampled from a lake was higher than the values recorded for sea trout and salmon after their stay in the sea. Use of the Sr‐contenl of the scales todistinguish between migratory and resident individuals should theref

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00433.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Nine thousand fingerling (0+) brown trout,Salmo truttaL., (size 50–90 mm) were fin‐clipped in six different ways and released in small streams in September 1984 and 1985. A total of 2625 fish were recaptured by electrofishing the year after stocking. Differences in survival between fin‐clip groups were found in one out of eight stockings. No growth differences were found among the several groups. Pectoral and anal fins regenerated most, while adipose fins regenerated least. Single fin‐clipping is a recommended marking method for fingerling brown trout during short‐term studies. Multiple fin‐clips may result in lower survival. Regeneration of fins, especially pectoral and anal fins, make the clipping of these fins less adapted to long‐term i

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00434.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Tilapia, probably Africa's best candidate for aquaculture, is faced by the problems of small size due to overpopulation in culture systems.This paper reports the effect of high salinity on the reproduction ofOreochromis niloticus(L.) while testing the effect of a 20% protein supplemental feed on the growth and survival of this species in brackishwater ponds. The trial was run for 120 days in six 100‐m2ponds with fingerlings having an initial average weight of 2·80g. Salinity in the ponds rose from 25 ppt. to 50 ppt. during the culture period. Sampling for reproduction check was conducted every 2 weeks and 20% of the fish population were weighed to monitor growth changes and adjust quantity of feed fed. A 20% protein feed was fed at the rate of 5% and 3% of the total fish biomass during the first and second, and third and fourth months of the trial respectively. After 120 days the fish in each replicate were counted and weighed in bulk to obtain total weight while 50 females from each replicate were dissected and gonads examined. Results showed that growth was significantly different (P0·05). 95% of the females were gravid but did not spawn. This suggests that gonadal development and onset of reproduction can be delayed by high salinities, which may be another practical method of population control in the culture ofO. nilot

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00435.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY