ALBERT

Description: (1). During 2003 a total of 3,852 Metric Tonnes (MT) of fish was landed on Mahe, Praslin and La Digue by 405 fishing boats. 80.5% of the total catch was landed on Mahe alone. The total artisanal catch decreased by 1063 (MT) compared to 2002, whilst the number of boats operating increased by 31 over the same period (excluding sport fishing vessels). (2). The most important species groups landed (greater than 5% of the total catch) were carangues (33.6%), job (15.8%), bourgeois (9.1%), cordonier (6.6%), capitaine (6.1%), becune (6.0%), and maquereau doux (5.4%). Compared to 2002, there were notable increases in the relative importance of cordonier and bourgeois to the overall catch. (3). Peak landings occurred in November (463.7 MT) and the lowest catch was recorded in September (137.3 MT). The average monthly catch in 2003 was 321 (MT). (4). Slight seasonal variation in total catch was observed in 2003. The mean monthly catch during the months of May — October, inclusive; was 290.5 MT, compared to a mean montly catch of 318.1 MT during the months of December — March, inclusive. In contrast to the patterns observed in 2001 and 2002, the highest catches for carangues occurred in November rather than April. Catches of cordonnier continued to increase (254.7 MT) over the previous two years, with peak monthly catches coinciding with the peak spawning months for those species, namely October to December. (5). The percentage of the total artisanal catch taken by the small boat fishery (pirogues and outboards) was 28.3%, similar to the estimate obtained in 2002. Fishermen on foot landed 0.6% of the total artisanal catch, with octopus catches from this fishery totaling 21.3 MT in 2003. 5.4 MT of maquereau were landed by pirogues using beach seines. Carangues (22.6%) replaced maquereau doux (19.2%) as the most important species landed by vessels with outboards in 2003, other important groups in this fishery including cordonier (22.3%) and other trap fish (11.9%). In 2003, landings by the small boats and foot fishermen were divided equally between pelagic and semi-pelagic species (48.2%) and demersal/ reef species (51.8%). (6). Typical of previous years, the whaler handline fishery dominated artisanal fisheries catches, accounting for 63.4% of total landings in 2003. An average of 96 whalers operated each month during 2003, an increase of 5 vessels compared to 2002. Carangues made up 42.1% of the total whaler handline catch. Other important species in the catch were, in order of importance, job gris (22.1%), becune (8.3%) bourgeois (8.3%) and bonite (3.7%). For the second consecutive year, catches of bourgeois by the whaler handline fishery increased, by 22.2% over 2002. (7). A maximum of 16 schooners were in operation during 2002 and these vessels accounted for 6.8% of total landings. Bourgeois was again the most important species caught (36.9%), followed by the 'others' category (18.6%) and job gris (8.5%). The spanner crab Ranina ranina accounted for 5.8% of schooner landings. (8). Fish purchases from the artisanal fisheries by Oceana Fisheries Co. Ltd. were equivalent to 10.4% total landings (400.7 MT). Major species groups purchased were red snappers and bourgeois (219 MT), job (57.4 MT), groupers (30,6 MT), capitaine (23.2 MT), octopus (21.9 MT) and carangue (17 MT). (9). Fish purchases from foreign longline and purse seine vessels by Oceana Fisheries Co. Ltd. were 245.9 MT during 2002. Species purchased were all pelagic, of which bonito bait was the most common (112.8 MT), followed by yellowfin (40.3 MT), dorade (37.3 MT) and skipjack (14.1 MT). (10). Fish exports by Oceana Fisheries Co. Ltd. amounted to 201.1 MT, a decrease of around 25 MT compared to 2002. These exports were valued at SR 5.6 million (C.I.F). Compared to the previous year, the markets shifted in order of importance in 2003, with Mauritius constituting the major importer of Seychelles fish products (69.9 MT), followed by Reunion (55.6 MT), England (50.1 MT) and France (14.6 MT). Pelagic fishes (33.8%), bourgeois (29.5%) and job (15.8%) were the most important fish groups exported. (11). A comparison of data collected between 1991 and 2003 follows, The proportion of catch by boat type and number of boats operating shown in the following table does not include the research vessel (RJV L'Amitie) of the Seychelles Fishing Authority, which landed 3.1 MT of fish in 2003, contributing 0.1% to the total artisanal catch.

Description: Published

Description: (1). During 2002 an estimated total of 4915 tonnes of fish was landed on Mahe, Praslin and La Digue by 374 fishing boats. 83.1% of the total catch was landed on Mahe alone. The total catch increased by 625 tonnes compared to 2001, and the number of boats operating decreased by 3 over the same period. (2). The most important species groups landed (greater than 5% of the total catch) were carangues (41.5%), job (12.4%), capitaine (6.8%), becune (6.1%), maquereau doux (5.7%) and bourgeois (5.7%). (3). Peak landings occurred in October (576.5 MT) and the lowest catch was recorded in January (222.51 MT). The average catch per month was 409.6 tonnes. (4). Seasonal variation in catches of demersal species was less marked compared to previous years. The mean monthly catch during the SE Trades (May — October, inclusive) was 420.5 MT, compared to a mean monthly catch of 359.4 MT during the NW monsoon (December — March, inclusive). High catches were probably maintained during the period of May to October in 2002 due to the comparatively weak strength of the SE Trades in that year, as determined by lower than average wind speeds for most months in that period (Meteorological Office, pers. comm.). Identical to the pattern observed in 2001, the highest catches for carangues occurred in April. Catches of cordonnier in 2002 (203.0 MT) were more than double those recorded in 2001 (90.5), and were lowest during the period of March to June, inclusive. (5). In total, the small boat fishery accounted for 26.4% of fish landings during 2002. Compared to the total artisanal catch, the percentage catch by boat type for the small boat fishery was as follows: fishermen on foot — 0.6%; pirogues — 0.6%; outboards -25.2% and whalers with traps — 2.2%. Fishermen on foot mostly landed octopus (87.0%), although cordonnier catches by this category were also recorded in 2002 (12.6%). Due to changes in fisheries fieldworker coverage in 2002, landings of maquereau by pirogue were not recorded, with cordonnier (57.6%) and other trap fish (23.2%) dominating landings instead. The predominant species groups landed by outboards were, in order of importance, maquereau doux (22.6%), carangues (21.7%), other trap fish (13.9%) and cordonnier (13.6%). Whalers with traps landed mainly capitaine (61.3%), other trap fish (20.1%) and cordonnier (12.3%). In 2002, landings by the small boat fleet were once again approximately divided equally between pelagic (51.3%) and demersal/ reef species (47.4%). (6). The whaler handline fishery accounted for 67.9% of total landings. An average of 91 whalers operated each month during 2002, indicating an increase of 1 vessel operating when compared to 2001. Carangues made up 52.5% of the total whaler handline catch. Other important species in the catch were, in order of importance, job gris (16.4%), becune (8.4%) bourgeois (5.0%), bordemar (2.6%) and vara vara (2.2%). Catches of Bourgeois decreased by 28.8% in 2002 compared to the catch of 2001. (7). Purchases from the artisanal fisheries by Oceana Fisheries were equivalent to 10.3% of total landings (504.2 MT). Oceana Fisheries purchased all fish from the Port Victoria site. Major species groups purchased were red snappers and bourgeois (57.5%), job (12.7%), groupers (5.2%) and capitaine (5.9 %). (8). Fish purchases from foreign longline vessels were in the order of 152.3 MT of frozen fish (gutted and ungutted) during 2002. Species purchased were all pelagic, of which bonito bait was the most common (98.0 MT), followed by yellowfin (18.9 MT), dorade (12.6 MT) and skipjack (12.6 MT). (9). Fish exports by Oceana Fisheries amounted to 226.6 MT, 85.9% of which was fresh and 14.1% frozen. These exports were valued at SR 7.1 million (CIF). Major destinations for the fish were England (34.5%), Reunion (30.3%) and Mauritius (17.0%). Pelagic fish (41.5%), bourgeois (23.4%), and Job (19.2%). formed the most important fish groups exported. (10). A comparison of data collected between 1990 and 2002 follows. The proportion of catch by boat type and number of boats operating shown in the following table do not include the research vessels of the Seychelles Fishing Authority which landed 11.7 tonnes of fish in 2002, contributing 0.2% of the total catch.

Description: Published

Description: We study the flow of a thin liquid film along a flexible substrate. The flow is modelled using lubrication theory, assuming that gravity is the dominant driving force. The substrate is modelled as an elastic beam that deforms in two dimensions. Steady solutions are found using numerical and perturbation methods, and several different asymptotic regimes are identified. We obtain a complete characterization of how the length and stiffness of the beam and the imposed liquid flux determine the profile of the liquid film and the resulting beam deformation. © 2013 Cambridge University Press.

Description: The Mackenzie River is the seventh longest river in the world and with its tributaries drains a million sq. miles of northern Canada. Its drainage basin includes almost all of that portion of the District of Mackenzie lying south of the so-called “tree line”, two large sections of Yukon Territory and portions of the provinces of Saskatchewan, Alberta, and British Columbia. When flying from Fort Smith, lat. 60° N., to Inuvik near the Arctic Ocean it seems to be an endless expanse of swamp and tundra with almost no possibilities for logging, either now or in the future. Closer inspection, however, shows that there are forested areas capable of supplying timbers suitable for lumber and heavy construction, as well as poles for piling and mining timbers. It is with these forests that this article is primarily concerned.

Description: A boundary-layer model, based on computational results, describes a number of features of two-dimensional convection in a porous medium: the heat flux, velocity, length and temperature scales and the pattern of flow. The cell structure is different from that for convection in a viscous fluid. The model is valid for a limited range of the Rayleigh number. © 1976, Cambridge University Press. All rights reserved.

Description: The problem of the stability of a fluid with time-dependent heating has been investigated by Morton (1957), Lick (1965) and Foster (1965). Morton and Lick assumed that the rate of change of the temperature profile is small compared with the growth rate of the disturbances (quasi-static assumption). This assumption is invalid near the onset of instability (as defined by ∂/∂t = 0), and Foster has therefore used an initial-value approach.In this paper the range of validity of the quasi-static assumption is discussed, and results of a time-scaled analysis and calculations based on this are compared with the work of Foster; the agreement is found to be good. We restrict our attention to a semi-infinite fluid initially at a constant temperature; at time t = 0 a temperature difference ΔT is applied at the (lower) horizontal boundary (case (A) of Foster).

Description: In this paper we consider two-dimensional steady cellular motion in a fluid heated from below at large Rayleigh number and Prandtl number of order unity. This is a boundary-layer problem and has been considered by Weinbaum (1964) for the case of rigid boundaries and circular cross-section. Here we consider cells of rectangular cross-section with three sets of velocity boundary conditions: all boundaries free, rigid horizontal boundaries and free vertical boundaries (referred to here as periodic rigid boundary conditions), and all boundaries rigid; the vertical boundaries of the cells are insulated. It is shown that the geometry of the cell cross-section is important, such steady motion being not possible in the case of free boundaries and circular cross-section; also that the dependence of the variables of the problem on the Rayleigh number is determined by the balances in the vertical boundary layers.We assume only those boundary layers necessary to satisfy the boundary conditions and obtain a Nusselt number dependence $N sim R^{frac{1}{3}}$ for free vertical boundaries. For the periodic rigid case, Pillow (1952) has assumed that the buoyancy torque is balanced by the shear stress on the horizontal boundaries; this is equivalent to assuming velocity boundary layers beside the vertical boundaries (rather than the vorticity boundary layers demanded by the boundary conditions) and leads to a Nusselt number dependence N ∼ R¼. If it is assumed that the flow will adjust itself to give the maximum heat flux possible the two models are found to be appropriate for different ranges of the Rayleigh number and there is good agreement with experiment.An error in the application of Rayleigh's method in this paper is noted and the correct method for carrying the boundary-layer solutions round the corners is given. Estimates of the Nusselt numbers for the various boundary conditions are obtained, and these are compared with the computed results of Fromm (1965). The relevance of the present work to the theory of turbulent convection is discussed and it is suggested that neglect of the momentum convection term, as in the mean field equations, leads to a decrease in the heat flux at very high Rayleigh numbers. A physical argument is given to derive Gill's model for convection in a vertical slot from the Batchelor model, which is appropriate in the present work.

Description: In this paper we assume the existence of a nonlinear boundary layer centred on the critical point, and explore its effect on the development of unstable parallel shear flows. A velocity matching condition derived in a qualitative discussion suggests a growth of harmonics which differs from that predicted by previous theories; however, the prediction is in excellent agreement with experimental data. A hyperbolic-tangent velocity profile, subjected to perturbations with wavenumbers and frequencies close to marginal values, is then chosen as a mathematical model of the nonlinear development, both temporal and spatial instability growth being considered. A singularity in the analysis which has been treated in previous theories by the introduction of viscosity is dealt with in the present work by the introduction of a growth boundary layer. The asymptotics are non-uniform and the time-dependent solution does not resemble the steady viscous solutions, even as the growth rate tends to zero. The theory suggests that the instability will develop as a series of temporally growing spiral vortices, a description differing from that of a cat's-eye pattern predicted by existing theories, but in accord with experimental and field observations. © 1974, Cambridge University Press. All rights reserved.

Description: 1. Laboratory incubation studies with topsoil samples of the Kikuyu red loam coffee soil have shown that active nitrification of the natural soil nitrogen stops at a soil moisture level just below the permanent wilting percentage. Ammonification of natural nitrogen in this soil does not cease at this moisture level and ammonia nitrogen accumulates substantially, although the values found at the end of the 32-day incubation period, and the rate of ammonification are significantly lower as the moisture level is decreased from ⅚ to of the permanent wilting percentage.

Description: SUMMARYEwo milk yield data obtained by the lamb suckling technique from nutritional experiments were analysed statistically to obtain estimates of the several components of variation. Diurnal variation was studied. The fitting of a sinusoidal curve removed a significant amount of variation.There was a highly significant correlation between successive milk yields obtained at 4 h intervals. Number of lambs suckled and body weight of ewe at parturition had a significant effect on total daily milk yield.The variation within ewes after the removal of diurnal variation and between ewes after the removal of the effects of number of lambs suckled and body weight at parturition were computed. These sources of variation were combined in a general equation which enabled the prediction of the standard errors associated with daily milk production for a given sampling technique. The practical application of the predicted standard errors is discussed.