Reproduction, age and growth of the Indian mackerel, Rastrelliger kanagurta (Cuvier, 1816) from Sofala Bank, Mozambique

A compilation of all the available information on the main small pelagic fish resources of Mozambican waters is presented. Resource data on distribution areas, reproduction, age, growth and stock size are described. Actual catch and catch per unit of effort of the commercially exploited stocks are also given. Results of the preliminary assessment of the stocks of scad and mackerel and the problems involving the assessment of Kelee shad stock at Maputo Bay are discussed.

Biological observations in Indian mackerel, Rastrelliger kanagurta (Cuvier) 1816, (Pisces: Scombridae) from East African waters

The present study was under taken to provide further and more detailed information on the apparent seasonal and relative abundance of the species, food and feeding habits. Spawning season and size composition. The incidence of parasites, in relation to the month of the year and the fish length, was also examined.

Using Remote Sensing and Spatial Information Technologies to Detect and Map Two Aquatic Macrophytes

This paper describes the light reflectance characteristics ofwaterhyacinth [Eichhornia crassipes (Mort.) Solms] and hydrilla [Hydrilla verticillata (L.F.) Royle] and the application of airborned videography with global positioning system (GPS) and geographic information system (GIS) technologies for distinguishing and mapping the distribution of these two aquatic weeds in waterways of southern Texas. Field reflectance measurements made at several locations showed that waterhyacinth generally had higher near-infrared (NIR) reflectance than associated plant species and water. Hydrilla had lower NIR reflectance than associated plant species and higher NIR reflectance than water. Reflectance measurements made on hydrilla plants submerged below the water surface had similar spectral characteristics to water. Waterhyacinth and hydrilla could be distinguished in color-infrared (CIR) video imagery where they had bright orange-red and reddish-brown image responses, respectively. Computer analysis of the imagery showed that waterhyacinth and hydrilla infestaions could be quantified. An accuracy assessment performed on the classified image showed an overall accuracy of 87.7%. Integration of the GPS with the video imagery permitted latitude/longitude coordinates of waterhyacinth and hydrilla infestation to be recorded on each image. A portion of the Rio Grande River in extreme southern Texas was flown with the video system to detect waterhyacinth and hydrilla infestaions. The GPS coordinates on the CIR video scenes depicting waterhyacinth and hydrilla infestations were entered into a GIS to map the distribution of these two noxious weeds in the Rio Grande River.

Porotergus ellisi. Una nueva subespecie de gimnótido de la Argentina (Pisces: Gymnotoidei).

Debido a una revisión de la colección del Museo de La Plata he encontrado cuatro gimnótidos que a mi juicio corresponden a una nueva especie del género Porotergus Ellis. (PDF tiene 10 paginas.)

Ecological limits of high-density milkfish farming

In the Philippines at present, milkfish farming in ponds includes a wide range of intensities, systems and practices. To make aquaculture possible, ecosystems are used as sources of energy and resources and as sinks for wastes. The growth of aquaculture is limited by the life-support functions of the ecosystem, and sustainability depends on matching the farming techniques with the processes and functions of the ecosystems, for example, by recycling some degraded resources. The fish farm has many interactions with the external environment. Serious environmental problems may be avoided if high-intensity farms are properly planned in the first place, at the farm level and at the level of the coastal zone where it can be integrated with other uses by other sectors. It is believed that the key to immediate success in the mass production of milkfish for local consumption and for export of value-added forms may be in semi-intensive farming at target yields of 3 tons per ha per year, double the current national average. Intensive milkfish farming will be limited by environmental, resource and market constraints. Integrated intensive farming systems are the appropriate long-term response to the triple needs of the next century: more food, more income, and more jobs for more people, all from less land, less resources, and less non-renewable energy.