摘要:

AbstractThe application of computer modeling to the study of aquaculture ponds is reviewed. Two basic types of models are identified: empirical and mechanistic. In empirical models, the pond system is treated as a ‘black box’, and the relationship between inputs and outputs is determined by statistical analysis of data. In mechanistic models (‘internally descriptive’), processes taking place within the pond are identified and described mathematically. A framework for the development of a mechanistic model of an aquacullure pond is presented. Sample formulations for some critical variables are di

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00328.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractCanonical correlation analysis was used to study the influence of management factors on growth and yields in an experimental polyculture system. The major conclusions are: (1) yield of each species was affected mainly by its own stocking density, followed by interactions with other species; (2) the best yields and growth rates of tilapia were obtained with stocking weights of over 13 g and; (3) common carp,Cyprinus carpioL., was affected negatively by silver carp,Hypoihalmichihys molitrix(Valenciennes), density and positively by nutrient inputs. Its best performance was obtained at silver carp density below 1000/ha.Analyses of data from commercial production units are required to confirm these conclusions

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00329.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractSchilbe mystus(L.) andEutropius niloticus(Ruppel) (fm. Schilbeidae) from rivers of the Volta Basin were screened at 18 enzyme loci for electrophoretically detectable variation. The mean observed heterozygosity was 0.001 inS. mystusand 0.018 inE. niloticus. The possible causes of these rather low levels of genetic variation are considered in relation to natural and human influences in the Volta Basin river system. The results also suggest that the speciesS. mystusconsists of several distinct biological species and thatE. niloticusmay have evolved from within theSchilbegroup.

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00330.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Macrobrachium rosenbergii(de Man) post‐larvae were packed in plastic bags at packing densities of 100, 200 and 300 post‐larvae/bag and netting material was folded into the bag to study the effect of habitat materials. Packing density of 300/1 showed significantly better survival (P<0·05) than 100/1 after a 12‐h period. However, after 24h and 36h. packing density of 100/1 was significantly higher (P<0·05) than that of 300/1. Use of habitat material had some effects of reducing cannabalism and increasing survival of post‐larvae. The water quality parameters—temperature, dissolved oxygen, ammonia‐N, dissolved carbon dioxide and pH ‐were determined at 0h for control bags only and for all bags after 36

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00331.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Forces required to crack shells of a wild population of queen conchs,Strombus gigasL., from the Berry Islands. Bahamas and from three hatchery populations in Venezuela, the United States and Mexico were measured. Above about 55‐mm shell length, shell strength of wild conchs increased rapidly for small length increases. To reduce the effect of predation by crustaceans in seeding programmes we recommend release into nature at sizes larger than 55 mm. The regressions of shell length to cracking force of hatchery‐reared conchs from the wild population and the hatcheries differed significantly in slope or elevation, suggesting different shell lengths of conchs from different geographic locations, and between hatcher

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00332.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.The strong relationship found between the yield of bream,Abramis brama L., the average chlorophyll‐a concentration of the water and the shore‐line:water area ratio of the various parts of Lake Balaton can be described mathematically. Such a descriptive model seems to be suitable for the estimation and rough prediction of the bream yield. The regional differences between the bream yields within the lake are caused to a large extent by morphometric features, and to a lesser extent by the cholorophyll‐a concentration. A 10‐fold increase in the chlorophyll‐a content results only in a twofold increase in bream yield expressed in catch per unit of effort (CPUE); however, the shore‐line:water area ratio has a much stro

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00333.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.A modified flushing technique was used to sample the anterior gut contents of the stomachless cyprinids, the tench,Tinea tinea(L.), and grass carp,Ctenopharyngodon idellaVal., in the laboratory and the field. The method was developed to provide quantitative estimates by measuring optimum penelration of a catheter into the gut of tench from their fork length. Possible implications for the sampling of gut contents of other cyprinids are discussed.

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00334.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Brown trout.Salmo truttaL., estimates were obtained for the Owendoher, a tributary of the River Dodder. Data were collected at live stations on 21 occasions from May 1981 to May 1983. Total population densities ranged from 0·07 to 1·29 fish/m2Mean annual densities varied from 0·20 to 0·77 fish/m2. Trout in this stream are typically slow‐growing fish reaching a maximum length of 7·68, 13·05 and 17·54cm at the end of their first, second and third years respectively. Growth improved in a downstream direction with the highest rates recorded in stretches overlying limestone. There was some evidence of density‐dependent growth in the upper reaches Daily instantaneous growth rates were highest for all age groups during the months May to August but became depressed during the winter. There was considerable variation in the total monthly biomass figures with values ranging from 1·32 to 33·46 g/m2. Mean annual values ranged from 3·96 to 13·48 g/m2. Annual production (somatic) varied from 3·77 to 14·38 g/m2. in 1981–1982 and from 6·12 to 12·70 g/m2. in 1982–1983. The mean annual production figure for this stream was 11·24 g/m2. Production was contributed mainly by 1+ and 2+ trout at all stations. Egg production. accounting for 3–4% of the total estimate, was contributed mainly by resident 1+ and 2+ fish. It ranged from 0·33 to 0·45 g/m2in 1981–1982 and from 0·14 to 0·53 g/m2in the following year. Ratios of annual production to mean biomass (P/B̄) were highest for 0+ trout hut decreased with increasing age. The mean P/B̄ ratios for all age classes varied from 0·95 to 1·17. The mean value for the Owendoher stream was 1·1. The effects on production of changes in age structure, population density a

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00335.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00336.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1988.tb00337.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY