一种新型对虾多池循环水综合养殖模式

１１对对虾虾养养殖殖模模式式现现状状的的简简介介我我国国对对虾虾养养殖殖业业已已经经有有几几百百年年的的历历史史 ,,其其发发展展过过程程伴伴随随着着养养殖殖模模式式的的演演变变。。最最初初在在港港湾湾进进行行粗粗放放的的鱼鱼养养殖殖和和港港养养。。大大规规模模修修建建池池塘塘进进行行对对虾虾养养殖殖 ,,只只是是近近３３００ａａ在在各各种种适适合合的的养养殖殖种种类类的的人人工工育育苗苗获获得得突突破破之之后后才才发发展展起起来来 ,,并并在在９９００年年代代初初达达到到高高峰峰。。９９００年年代…     

Soil salinity and sodicity in a shrimp farming coastal area of the Mekong Delta,Vietnam

Soil salinity and sodicity are environmental problems in the shrimp farming areas of the Cai Nuoc district, Ca Mau province, Vietnam. In 2000, farmers in the district switched en masse from rice cropping to shrimp culture. Due to recent failure in shrimp farming, many farmers wish to revert to a rotational system with rice in the wet season and shrimps in the dry season. So far, all their attempts to grow rice have failed. To assess soil salinity and sodicity, 25 boreholes in shrimp ponds were analysed in four consecutive seasons from 2002 to 2004. The results showed that soil salinity was quite serious (mean EC_e 29.25 dS m⁻¹), particularly in the dry season (mean EC_e 33.44 dS m⁻¹). In the wet season, significant amounts of salts still remained in the soil (mean EC_e 24.65 dS m⁻¹) and the highest soil salinity levels were found near the sea. Soil sodicity is also a problem in the district (exchangeable sodium percentage range 9.63–72.07%). Sodicity is mainly a phenomenon of topsoils and of soils near the sea. Both soil salinity and sodicity are regulated by seasonal rainfall patterns. They could together result in disastrous soil degradation in the Cai Nuoc district.     

Plankton community as an indicator of water quality in tropical shrimp culture ponds

The plankton was examined as an indicator of water quality in 14 shrimp Litopenaeus vannamei farms in Brazil in 2003. The ponds were categorized by high stocking density (>30 PL m⁻²) of phytoplankton, consisting of 51 species with concentrations ranging from 365,218 ± 416,615 cells mL⁻¹ to 1,961,675 ± 3,160,172 cells mL⁻¹. Diatoms contributed to almost 70% of the species number and high densities resulted from Cyanophyta blooms, mainly Pseudanabaena cf limnetica. Forty zooplankton taxa were registered and were essentially composed of typical marine euryhaline species and suspension-feeders. Copepoda dominated (45%) the make-up, followed by Protozoa (18%), Rotifera (12%), and Mollusca (12%) larvae. Zooplankton varied from 972 ± 209 ind m⁻³ to 4235 ± 2877 ind m⁻³. Enhanced nutrient input affected plankton density and composition. Diatom and Copepoda dominance was replaced by cyanobacteria, protozoan, and rotifers as nutrient concentrations increased with the cultured period, indicating that plankton structure is affected by eutrophic conditions.     

湛江地区沿海游泳虾类调查报告

本文整理了真虾类标本共21种,隶属6科9属,其中有的种类是虾捕捞业中常见的种类,有一定的产量;有的种类是虾养殖中的敌害。     

Sediment transport near the Tauranga entrance to Tauranga Harbour

Abstract

Sediment transport at the Tauranga Entrance was studied in relation to tidal currents and waves. Bedforms resulting from tidal flow were investigated with scuba divers and echo‐soundings. The alignment and scale of bedforms indicated the direction and approximate rate of sediment transport. Sediment transport was measured directly using sediment traps, and results were compared with rates calculated by another method. Maximum sediment transport rates of 20 000–30 000 g.m^?1 per half tidal cycle occur near the inlet gorge, but rates vary considerably in time and space, depending mainly upon power of tidal currents. A model of sediment transport for this inlet has been evolved based on tidal flow streamlines, bedform features, and the measured and calculated rates of sediment transport.