Validation of the performance of the Aquantic 2100A fish counter

This report looks at the validation of the performance of the Logie 2100A fish counter which was carried out at Forge Weir (River Lune) and Gunnislake Fish Pass (River Tamar), using a video recording system.

Spawning and hatching performance of the silvery black porgy Sparidentex hasta under hypersaline conditions

Abu Al Abyad island is characterized by harsh environmental conditions. A preliminary trial conducted at the island to investigate the spawning and hatching performance of the blue finned sea bream Sparidentex hasta indicated that the fish can be successfully bred at high salinity levels exceeding 50 ppt.

An assessment of the stock of scad and mackerel at Sofala Bank and Boa Paz, Mozambique

The fishery for scad and mackerel along the coast of Mozambique began as a licensed fishery in 1977. In 1980, Mosopesca, a joint venture between Mozambique and the Soviet Union was formed and the licensed fishery ceased. Mosopesca started fishing with four vessels, but since 1984 the number of vessels has gradually been increased and at the end of 1985 a total of seven vessels was in operation. This report contains an updated assessment based mainly on information collected from July 1984 to May 1986.

A PCSR model to improve performance of the fish commodity system

There is now, more than ever before, a growing demand in this country for research to be directed towards the development programmes of the country. Researchers have come under increasing pressure to relate their work to specific development problems and design their investigations to produce results which will be applicable in addressing these problems. The Fish Commodity Systems Economics (U) Project is an attempt to strengthen the focus of studies at UFFRO and elsewhere within the fish system towards the problems of the fish commodity sub-sector in Uganda in order to formulate measures which will improve the performance of the sub-sector in alleviating some of the nation's socio-economic problems

Daily timing of emersion and elevated atmospheric CO2 concentration affect photosynthetic performance of the intertidal macroalga Ulva lactuca (Chlorophyta) in sunlight

The lunar day differs in length from the solar day so that times of low tide vary from day to day. Thus, aerial exposure of intertidal seaweeds may be during the day or during the night. We measured photosynthetic CO, assimilation rates of the intertidal green macroalga Ulva lactuca during exposures of varied daily timings during sunny days of summer to establish how photosynthetic performance responds to emersion timing under varied CO2 levels [at ambient (360 ppmv) and 2x ambient (720 ppmv) atmospheric CO2 concentrations]. There was an increase in net photosynthetic rates following some duration of exposure when the initial timing of exposure occurred during early morning (06.30 h) and late afternoon (17.15 h). In contrast, net rates exhibited a sharp decline with exposure duration when the initial timing of exposure occurred at 09.30 h, 15.30 h and especially at noon (12.30 h), implying the occurrence of a severe photoinhibition resulting from mid-day insolation. Doubled atmospheric CO2 concentration significantly enhanced the emersed photosynthetic rates, indicating that the emersed photosynthesis is CO2-limited at ambient CO2 levels. However, increasing CO2 barely stimulates the emersed photosynthetic rates during mid-day insolation.

Influence of thermal isolating grooves on the performance of the Mach-Zehnder interferometer-type thermo-optic variable optical attenuator

Two types of silicon-on-insulator thermo-optic variable optical attenuators (VOAs) based on a Mach-Zehnder interferometer and a multimode-interference coupler are fabricated, one with thermal isolating grooves to improve heating efficiency and the other without Comparison of optical and electrical properties, such as insertion losses, the maximum attenuation levels and the corresponding power consumptions, and the response times, is carried out between the two types of VOAs. The comparison results Indicate that use of thermal isolating grooves leads to better values for most characteristics and is an effective way to improve the performance of Mach-Zehnder interferometer-type thermo-optic devices. (c) 2005 Society of Photo-Optical Instrumentation Engineers.