Field investigations and multi‐indicators for shallow water lagoon management: perspective for societal benefit

相似文献   

A comparative analysis of habitat quality between artificial and natural creeks in the Mediterranean killifish Aphanius fasciatus: Implications for conservation

1. In transitional water ecosystems, habitat loss is one of the major threats to fish biodiversity. This is particularly true in the case of temperate salt marshes. Good quality artificial novel habitats may compensate for the loss of natural habitats, acting as a refuge for fish populations.
2. The aim of this study was to use coloured ornamental traits exhibited by the males of a small lagoon-resident fish, the Mediterranean killifish Aphanius fasciatus (Valenciennes, 1821), to assess habitat quality in both the natural and artificial creeks of the Venice lagoon.
3. The conspicuousness of two secondary sexual traits, the yellow/orange caudal fin pigmentation and the contrast between white and dark vertical bars on body sides, proved to be greater in artificial habitats compared to natural salt marshes, highlighting the refuge function of artificial creeks.
4. The use of secondary sexual traits could be extended to other fish species and to other aquatic habitats as a non-invasive approach. This would allow the identification of good quality habitats in the context of fish population management and conservation.

     

Passive monitoring of phenological acoustic patterns reveals the sound of the camouflage grouper,Epinephelus polyphekadion

1. Passive acoustic monitoring (PAM) is a non‐invasive technique that uses hydrophones to monitor populations and ecosystem dynamics. Although many applications of PAM have been developed in recent years, it has never been used to identify a calling marine species.
2. The south pass of Fakarava Atoll, French Polynesia, hosts spawning events of many reef fish species, including the camouflage grouper Epinephelus polyphekadion, with a spawning aggregation abundance exceeding 17 000 individuals during the full moons of June and July.
3. The current study aimed to use PAM to distinguish camouflage grouper sounds among the vocal activities of all fish recorded during the aggregation periods. Audio recordings analysis resulted in the identification of 29 sound types, some of which showed diel and lunar patterns.
4. Temporal analysis of these sounds in relation to spawning activities allowed the identification of camouflage grouper calls. These calls can be described as a single pulse or a series of ‘boom(s)’ with a pulse duration of ~44 ms and a low dominant frequency of 103 ± 31 Hz. Video recordings show that the camouflage grouper produces the ‘booms’ to initialize spawner ascent and to promote synchronous gamete release into the water column.
5. The study highlights for the first time that PAM can be used to identify the previously unknown sound of a fish species. Moreover, we can use it to understand the phenology of some biological activities for improving the resolution of fish biodiversity assessments.

     

Conservation of aquatic invertebrates: concerns,challenges and conundrums

相似文献   

氧化塘处理造纸污水

采用多级串联生物稳定塘法处理草浆造纸废水获得了可喜成果;本文介绍了氧化塘处理造纸污水的工程概况、治污条件及废水处理工艺流程。     

Preliminary study on broodstock rearing,induced breeding and grow‐out culture of the sea cucumber Holothuria scabra in Sri Lanka

Experiments were conducted to identify suitable methods for broodstock rearing, induced breeding and grow‐out culture of Holothuria scabra in Sri Lanka. Two hundred and seventy‐two brooders (500–600 g) collected from off Mannar were individually packed in oxygen‐filled polythene bags with and without sea water and transported to a sea cucumber hatchery at Kalpitiya. Lagoon pens, sand‐filled fibreglass tanks and bare tanks were used in triplicates to maintain brooders. Spawning was initiated using air dry, water jet and thermal‐stimulation methods. Hatchery produced juveniles with an average weight of 11 ± 5 g were reared (2 individuals m^?2) in lagoon pens, mud ponds and fibreglass tanks in triplicates. The significantly high evisceration rate was observed when brooders were transported without sea water (t‐test, P < 0.05). Brooders maintained in bare tanks showed a significant weight reduction than the brooders in sand‐filled tanks and lagoon pens (anova , P < 0.05, d.f. = 2). Thermal stimulation (ambient temperature ± 3–5°C) was found to be the most successful method of spawning initiation of H. scabra. The mean (±SD) percentage males and females participated for spawning per trial was 9.2 (±10) and 4.6 (±5.6) respectively. On an average, 1.16 millions of eggs (±1.03 SD, n = 5) were obtained per spawning trial. H. scabra juveniles reared in tanks showed significantly lower growth rate than the juveniles in pens and ponds (anova , P < 0.05). Lagoon pens and sand‐filled tanks are suitable to maintain brooders and lagoon pens can be successfully used for mass rearing of juveniles.     

Spatiotemporal variability in soil salinity and its effects on rice (Oryza sativa L.) production in the north central coastal region of Vietnam

Abstract

To better understand the adverse impacts of soil salinization and promote rice (Oryza sativa L.) production in crops from the north central coastal region of Vietnam, the spatiotemporal variability of soil salinity and its effects on rice production were investigated. Experiments were conducted at 19 plots widely distributed in the Quang Phuoc commune, in the Quang Dien district of the province of Thua Thien Hue in the north central coastal region of Vietnam. We determined the elevation of the 19 plots to evaluate the influence of elevation on salt accumulation. Soil samples from the 19 plots were collected in January, May and September 2012 and 2013 to study the spatiotemporal variability of salinity. A soil saturation paste was prepared and used to measure electrical conductivity (ECe). The elevation measurements obtained suggest that the research site could be divided into low- and high-elevation plots, with elevation of the low-elevation plots ranging from –0.52 to 0.07 m and the high-elevation plots from 0.26 to 0.86 m (one of the sampling plot was designated with an elevation of 0 m and the elevations of the remaining 18 plots were measured relative to that). ECe was high at low elevations. In conclusion, although the differences in elevation between the 19 plots were very small (centimeters to decimeters), they still led to large differences in soil salinity levels. In the high-elevation plots, soils were irrigated with freshwater, thus maintaining low ECe levels throughout the year (< 1.0 dS m^?1). In contrast, in the low-elevation plots, soils were subject to seawater intrusion, resulting in high ECe levels in all seasons (> 1.9 dS m^?1). We recommend several solutions to limit the unfavorable effects of salinity and promote rice production. First, a comprehensive dike system should be constructed along the lagoon to prevent seawater intrusion onto land. Second, it will be necessary to construct adequate drainage facilities in the depressed areas to promote rapid water drainage into canals during and after flooding and irrigation. Third, because ECe was high from May to September, adequate fresh irrigation water should be frequently supplied to lower the ECe during this period.     

Movement of sonically tagged bluespine unicornfish,Naso unicornis,in relation to marine reserve boundaries in Rodrigues,western Indian Ocean

• 1. The lagoon fishery of Rodrigues has considerable socio‐economic importance; however, catches have declined by 50% in recent years. The bluespine unicornfish, Naso unicornis (Forsskål 1775) is an important component of the fishery.
• 2. To begin to assess whether marine reserves might benefit this species, sonic telemetry was used to track individual fish in one of Rodrigues' four marine reserves. Seven unicornfish were caught in the Grand Bassin reserve and tagged with abdominally implanted acoustic tags.
• 3. Over a period of 57 days their locations were determined up to 21 times using a hand held hydrophone and receiver. Individual minimum convex polygon (MCP) home ranges varied from ～10 000 m² to ～274 000 m² and were not correlated with fish size. Kernel estimates of core areas (50% utilization distribution) varied from ～5000 m² to ～175 000 m². All seven fish stayed within the marine reserve and the largest home range occupied less than ～2% of the area of the marine reserve.
• 4. Fish remained on the outside edge of the lagoon on the shallow reef slope and among coral patches. These findings suggest that bluespined unicornfish biomass and numbers should increase if the Grand Bassin marine reserve is closed to fishing. Long‐term monitoring will, however, be required to demonstrate this outcome. Copyright © 2010 John Wiley & Sons, Ltd.

     

杭州湾人工潟湖夏季浮游植物群落演替与环境因子的关系

金山城市沙滩是东海杭州湾的一处人工潟湖,是上海首个滨海4A级景区,由于潟湖本身复杂的物理海洋学性质,为了确保金山城市沙滩水质优良,近年来一直在对其进行生态修复。本研究从2016至2018年,连续3年夏季对该潟湖浮游植物群落结构及其变化与环境因子之间的关系进行了调查,结果显示:2016—2018年夏季浮游植物种类不断增多,共发现浮游植物7门109种,其中硅藻门(Bacillariophyta)、蓝藻门(Cyanophyta)和绿藻门(Chlorophyta)种类较多。优势属共发现13个,优势度较大的是微囊藻属(Microcystis)、囊裸藻属(Trachelomonas)、直链藻属(Melosira)和小环藻属(Cyclotella),其中微囊藻属是夏季第一优势属,其他优势属重合度小。2016—2018年浮游植物丰度变化很大,分别为50.78×10~4～5 957.52×10~4个/L、5.35×10~4～25.67×10~4个/L和474.87×10~4～1 026.94×10~4个/L,其中微囊藻丰度最大,分别占97.88%、68.18%和77.23%。调查期间,浮游植物的多样性指数(H′)和均匀度指数(J′)先增大后减小,但总体呈上升趋势,而第一优势属优势度总体下降,说明经过生态修复,水体浮游植物群落发生正向演替,生态风险有减小趋势。RDA分析表明,总氮、总磷、铵盐、亚硝酸盐、无机磷和硅酸盐是影响浮游植物群落的重要环境因子。其中硅酸盐、亚硝酸盐、铵盐和无机磷与该潟湖的浮游植物群落相关性较大。