Rice field fisheries: a resource for Cambodia

Small-scale fisheries in and around rice fields in the lowland areas of Cambodia are greatly underestimated and undervalued. Their contribution to the protein requirements of the poor rural households is significant. In Svay Rieng province, they could provide 65-75% of the animal protein requirements of these households. The value could well be around 40% of the value of rice production. It is, therefore, important that these natural stocks and the fisheries are managed well and that developmental activities explicitly consider their impact on these fisheries.

Multiple environmental states affecting penaeid shrimp production in Peru

A modification of the Schaefer surplus-production model was used to account for environmental induced variations of shrimp (Penaeus vannamei) catch in northern Peru. Based on time series of catch, effort, river discharge and sea surface temperature, fluctuations in catch of shrimps are explained and discussed with respect to multiple level of carrying capacity and hence different maximum sustainable yields.

Fish demand and supply projections

It has been predicted that the global demand for fish for human consumption will increase by more than 50% over the next 15 years. The FAO has projected that the increase in supply will originate primarily from marine fisheries, aquaculture and to a lesser extent from inland fisheries, but with a commensurate price increase. However, there are constraints to increased production in both marine and inland fisheries, such as overfishing, overexploitation limited potential increase and environmental degradation due to industrialization. The author sees aquaculture as having the greatest potential for future expansion. Aquaculture practices vary depending on culture, environment, society amd sources of fish. Inputs are generally low-cost, ecologically efficient and the majority of aquaculture ventures are small-scale and family operated. In the future, advances in technology, genetic improvement of cultured species, improvement in nutrition, disease management, reproduction control and environmental management are expected along with opportunities for complimentary activities with agriculture, industrial and wastewater linkages. The main constraints to aquaculture are from reduced access to suitable land and good quality water due to pollution and habitat degradation. Aquaculture itself carries minimal potential for aquatic pollution. State participation in fisheries production has not proven to be the best way to promote the fisheries sector. The role of governments is increasingly seen as creating an environment for economic sectors to make an optimum contribution, through support in areas such as infrastructure, research, training and extension and a legal framework. The author feels that a holistic approach integrating the natural and social sciences is called for when fisheries policy is being examined.

Contribuição ao estudo do efeito tridimensional de instalação e de grupo em estacas cravadas em areia.

O efeito de instalação de estacas cravadas em areia, que promove um aumento da compacidade do solo e de seus parâmetros de resistência e deformabilidade, é analisado nesta dissertação em conjunto com o efeito de grupo. O procedimento estabelecido objetiva quantificar a melhoria após a instalação de um grupo de estacas e foi desenvolvido nesta pesquisa a partir da contribuição de Alves (1998). Para a utilização deste procedimento, foram propostas correlações do módulo de Young do solo em função da resistência à penetração NSPT (ou da resistência à penetração normalizada N60), a partir de um banco de dados obtido da literatura, visando não apenas as aplicações implementadas neste estudo, como também nortear futuras aplicações práticas. Na análise de casos documentados da literatura, foi utilizado o programa Plaxis 3D Foundation. Inicialmente foi procedida a calibração do programa através da reprodução de um caso de instrumentação de um grupo de estacas na argila rija de Londres, muito bem documentado por Cooke et al. (1980). Os resultados das simulações, com parâmetros do solo obtidos da literatura, se ajustaram muito bem aos resultados experimentais, seja nos valores de recalque, seja nos diagramas de transferência de carga. Posteriormente, a melhoria do solo por efeito da instalação foi estimada, através do procedimento estabelecido nesta dissertação, baseado em Alves (1998), a partir das características iniciais do solo antes da instalação de um grupo de estacas em modelo reduzido em solo arenoso. Obtidos os parâmetros melhorados previstos para o solo após a instalação, estes foram aplicados a um grupo de 9 estacas, para diferentes espaçamentos relativos, como dados de entrada no programa Plaxis. A comparação dos resultados experimentais com aqueles simulados numericamente sinaliza para o potencial tanto do programa Plaxis, na reprodução do comportamento do conjunto, como do modelo de Alves (1998), que norteou o procedimento proposto nesta pesquisa. O fator de escala, ressaltado na dissertação, bem como outros aspectos relevantes observados nas análises realizadas, são propostos como temas futuros a serem investigados na continuidade desta linha de pesquisa.

The Bay Scallop, Argopecten irradians, Massachusetts Through North Carolina: Its Biology and the History of Its Habitats and Fisheries

This article covers the biology and the history of the bay scallop habitats and fishery from Massachusetts to North Carolina. The scallop species that ranges from Massachusetts to New York is Argopecten irradians irradians. In New Jersey, this species grades into A. i. concentricus, which then ranges from Maryland though North Carolina. Bay scallops inhabit broad, shallow bays usually containing eelgrass meadows, an important component in their habitat. Eelgrass appears to be a factor in the production of scallop larvae and also the protection of juveniles, especially, from predation. Bay scallops spawn during the warm months and live for 18–30 months. Only two generations of scallops are present at any time. The abundances of each vary widely among bays and years. Scallops were harvested along with other mollusks on a small scale by Native Americans. During most of the 1800’s, people of European descent gathered them at wading depths or from beaches where storms had washed them ashore. Scallop shells were also and continue to be commonly used in ornaments. Some fishing for bay scallops began in the 1850’s and 1860’s, when the A-frame dredge became available and markets were being developed for the large, white, tasty scallop adductor muscles, and by the 1870’s commercial-scale fishing was underway. This has always been a cold-season fishery: scallops achieve full size by late fall, and the eyes or hearts (adductor muscles) remain preserved in the cold weather while enroute by trains and trucks to city markets. The first boats used were sailing catboats and sloops in New England and New York. To a lesser extent, scallops probably were also harvested by using push nets, picking them up with scoop nets, and anchor-roading. In the 1910’s and 1920’s, the sails on catboats were replaced with gasoline engines. By the mid 1940’s, outboard motors became more available and with them the numbers of fishermen increased. The increases consisted of parttimers who took leaves of 2–4 weeks from their regular jobs to earn extra money. In the years when scallops were abundant on local beds, the fishery employed as many as 10–50% of the towns’ workforces for a month or two. As scallops are a higher-priced commodity, the fishery could bring a substantial amount of money into the local economies. Massachusetts was the leading state in scallop landings. In the early 1980’s, its annual landings averaged about 190,000 bu/yr, while New York and North Carolina each landed about 45,000 bu/yr. Landings in the other states in earlier years were much smaller than in these three states. Bay scallop landings from Massachusetts to New York have fallen sharply since 1985, when a picoplankton, termed “brown tide,” bloomed densely and killed most scallops as well as extensive meadows of eelgrass. The landings have remained low, large meadows of eelgrass have declined in size, apparently the species of phytoplankton the scallops use as food has changed in composition and in seasonal abundance, and the abundances of predators have increased. The North Carolina landings have fallen since cownose rays, Rhinoptera bonsais, became abundant and consumed most scallops every year before the fishermen could harvest them. The only areas where the scallop fishery remains consistently viable, though smaller by 60–70%, are Martha’s Vineyard, Nantucket, Mass., and inside the coastal inlets in southwestern Long Island, N.Y.

The History of Oyster Farming in Australia

Aboriginal Australians consumed oysters before settlement by Europeans as shown by the large number of kitchen middens along Australia's coast. Flat oysters, Ostrea angasi, were consumed in southeastern Australia, whereas both flat and Sydney rock oysters, Saccostrea glomerata, are found in kitchen middens in southern New South Wales (NSW), but only Sydney rock oysters are found in northern NSW and southern Queensland. Oyster fisheries began with the exploitation of dredge beds, for the use of oyster shell for lime production and oyster meat for consumption. These natural oyster beds were nealy all exhausted by the late 1800's, and they have not recovered. Oyster farming, one of the oldest aquaculture industries in Australia, began as the oyster fisheries declined in the late 1800's. Early attempts at farming flat oysters in Tasmania, Victoria, and South Australia, which started in the 1880's, were abandoned in the 1890's. However, a thriving Sydney rock oyster industry developed from primitive beginnings in NSW in the 1870's. Sydney rock oysters are farmed in NSW, southern Queensland, and at Albany, Western Australia (WA). Pacific oysters, Crassostrea gigas, are produced in Tasmania, South Australia, and Port Stephens, NSW. FLant oysters currently are farmed only in NSW, and there is also some small-scale harvesting of tropical species, the coarl rock or milky oyster, S. cucullata, and th black-lip oyster, Striostrea mytiloides, in northern Queensland. Despite intra- and interstate rivalries, oyster farmers are gradually realizing that they are all part of one industry, and this is reflected by the establishment of the national Australian Shellfish Quality Assuarance Program and the transfer of farming technology between states. Australia's oyster harvests have remained relatively stable since Sydney rock oyster production peaked in the mid 1970's at 13 million dozen. By the end of the 1990's this had stabilized at around 8 million dozen, and Pacific oyster production reached a total of 6.5 million dozen from Tasmania, South Australia, and Port Stephens, a total of 14.5 million dozen oysters for the whole country. This small increase in production during a time of substantial human population growth shows a smaller per capita consumption and a declining use of oysters as a "side-dish."

Uganda aquaculture value chains: strategic planning mission: summary report

This report presents the findings and recommendations of a strategic planning mission to reevaluate the feasibility of WorldFish implementing a fish value chain research program in Uganda under the CGIAR Research Program on Livestock and Fish (L&F). The over-arching goal of L&F is to increase productivity of small-scale livestock and fish systems so as to increase availability and affordability of meat, milk and fish for poor consumers and, in doing so, to reduce poverty through greater participation by the poor along animal source food value chains. This will be achieved by making a small number of carefully selected animal source food value chains function better, for example by identifying and addressing key constraints and opportunities (from production to consumption), improving institutional arrangements and capacities, and supporting the establishment of enabling pro-poor policy and institutional environments.

Uganda aquaculture value chains: strategic planning mission report

This report presents the findings and recommendations of a strategic planning mission to reevaluate the feasibility of WorldFish implementing a fish value chain research program in Uganda under the CGIAR Research Program on Livestock and Fish (L&F). The over-arching goal of L&F is to increase productivity of small-scale livestock and fish systems so as to increase availability and affordability of meat, milk and fish for poor consumers and, in doing so, to reduce poverty through greater participation by the poor along animal source food value chains. This will be achieved by making a small number of carefully selected animal source food value chains function better, for example by identifying and addressing key constraints and opportunities (from production to consumption), improving institutional arrangements and capacities, and supporting the establishment of enabling pro-poor policy and institutional environments.

Time-resolved volumetric measurement of fine-scale coherent structures in turbulence.

We present full volumetric (three-dimensional) time-resolved (+one-dimensional) measurements of the velocity field in a large water mixing tank, allowing us to assess spatial and temporal rotational energy (enstrophy) and turbulent energy dissipation intermittency. In agreement with previous studies, highly intermittent behavior is observed, with intense coherent flow structures clustering in the periphery of larger vortices. However, further to previous work the full volumetric measurements allow us to separate out the effects of advection from other effects, elucidating not only their topology but also the evolution of these intense events, through the local balance of stretching and diffusion. These findings contribute toward a better understanding of the intermittency phenomenon, which should pave the way for more accurate models of the small-scale motions based on an understanding of the underlying flow physics.

Gear modifications for fishing octopus, Octopus vulgaris, on live-bottom and adjacent flat bottom habitats in coastal waters off North Carolina

The Common Octopus, Octopus vulgaris, is an r-selected mollusk found off the coast of North Carolina that interests commercial fishermen because of its market value and the cost-effectiveness of unbaited pots that can catch it. This study sought to: 1) determine those gear and environmental factors that influenced catch rates of octopi, and 2) evaluate the feasibility of small-scale commercial operations for this species. Pots were fished from August 2010 through September 2011 set in strings over hard and sandy bottom in waters from 18 to 30 m deep in Onslow Bay, N.C. Three pot types were fished in each string; octopus pots with- and without lids, and conch pots. Proportional catch was modeled as a function of gear design and environmental factors (location, soak time, bottom type, and sea surface water temperature) using binomially distributed generalized linear models (GLM’s); parsimony of each GLM was assessed with Akaike Information Criteria (AIC). A total of 229 octopi were caught throughout the study. Pots with lids, pots without lids, and conch pots caught an average of 0.15, 0.17, and 0.11 octopi, respectively, with high variability in catch rates for each pot type. The GLM that best fit the data described proportional catch as a function of sea surface temperature, soak time, and station; greatest proportional catches occurred over short soak times, warmest temperatures, and less well known reef areas. Due to operating expenses (fuel, crew time, and maintenance), low catch rates of octopi, and high gear loss, a directed fishery for this species is not economically feasible at the catch rates found in this study. The model fitting to determine factors most influential on catch rates should help fishermen determine seasons and gear soak times that are likely to maximize catch rates. Potting for octopi may be commercially practical as a supplemental activity when targeting demersal fish species that are found in similar habitats and depth ranges in coastal waters off North Carolina.

Toward a rule-based biome model

EXTRACT (SEE PDF FOR FULL ABSTRACT): Current projections of the response of the biosphere to global climatic change indicate as much as 50 to 90% spatial displacement of extratropical biomes. The mechanism of spatial shift could be dominated either by competitive displacement of northern biomes by southern biomes or by drought-induced dieback of areas susceptible to change. The current suite of global biosphere models cannot distinguish between these two processes, hence the need for a mechanistically based biome model. The first steps have been taken toward development of a rule-based, mechanistic model of regional biomes at a continental scale. ... The model is in an early stage of development and will require several enhancements, including: explicit simulation of potential evapotranspiration, extension to boreal and tropical biomes, a shift from steady-state to transient dynamics, and validation on other continents.

On the production and nutritive value of fish meal from Silver belly (Leiognathus spp.) landings at Rameswaram

Silver belly (Leiognathus Spp.) forms a major fishery in recent years in the Rameswaram island but fetches for the fishermen very low prices ranging from Rs. 0.03 to 0.12/Kg only, there being practically no demand for the fish. The possibilities of utilizing this cheap fish are discussed and the processing method described. During the glut season the cost of production of Silver belly fish meal works out to competitive prices of Rs. 500 to 700/ton. The silver belly fish meal is of high quality with good protein content averaging 57.71% in commercial samples and 61.90% in laboratory samples and with a high pepsin digestibility of 90.0% to 92.5%. The essential amino acid composition of the Silver belly fish meal compares very favorably with other round fish meals, with high contents of lysine, leucine, arginine, isoleucine, methionine, phenyl alanine, threonine and valine. Since there is good demand for fish meal as poultry and cattle food both in the internal and external markets, there is good scope for large scale production and sale of fish meal.

Dynamics of in-plane arch rocking: An energy approach

This study employs an analytical model to describe the rocking response of a masonry arch to in-plane seismic loading. Through evaluation of the rate of energy input to the system, the model reveals the ground motions that cause maximum rocking amplification. An experimental investigation of small-scale masonry arches subjected to past earthquake time histories is used to evaluate the analytical model and to explore arch rocking behaviour. The results demonstrate that rocking amplification can occur, but is highly sensitive to slight variations in the ground motion. Thus, the accuracy to which the arch response can be predicted is brought into perspective. The concept that the primary impulse of an expected ground motion is fundamentally important in predicting arch collapse is evaluated in light of the developed energy approach. Finally, a statistical method is proposed for predicting the probability of arch collapse during seismic loading.

Culture practices of freshwater giant prawn in some selected areas of Mymensingh

A study was conducted to examine the culture practices of freshwater giant prawn, Macrobrachium rosenbergii in some selected areas of Mymensingh. Based on a sample of 100 farmers from three different upazila, namely Phulpur, Gouripur and Ishwargonj in Mymensingh district, 94% of farmers cultured prawn with fish in their pond. Only 6% of farmers cultured prawn, fish and dike crops for higher economic return. The culture period is typically nine months; hatchery produced post-larvae were stocked from May to June and harvested from November to January. Per hectare production of prawn, 375 kg/yr was very low because the farmers followed simple culture method. Most of the farmers made a profit of Tk. 68,403/ha/yr and the major costs incurred were for purchasing prawn seed and feed. The culture of prawn in pond system is technically possible under different conditions though expansion of small-scale prawn farming mainly depends on reduction of production costs. Future targets could be integration of pond prawn culture with other agricultural activities especially dike cropping and rice production in the monsoon.

Application of scalar dissipation rate modelling to industrial burners in partially premixed regimes

The objective of this paper is to test various available turbulent burning velocity models on an experimental version of Siemens small scale combustor using the commercial CFD code. Failure of burning velocity model with different expressions for turbulent burning velocity is observed with an unphysical flame flashback into the swirler. Eddy Dissipation Model/Finite Rate Chemistry is found to over-predict mean temperature and species concentrations. Solving for reaction progress equation with its variance using scalar dissipation rate modelling produced reasonably good agreement with the available experimental data. Two different turbulence models Shear Stress Transport (SST) and Scale Adaptive Simulation (SAS) SST are tested and results from transient SST simulations are observed to be predicting well. SAS-SST is found to under-predict with temperature and species distribution.