Vertical structure of tidal current in a typically coastal raft-culture area

In this paper vertical structure of tidal current in a typically coastal raft-culture area is discussed by field measurement and a numerical model. The observations show that the vertical structure changed dramatically. A tidal surface boundary layer (SBL) is well formed due to the frictional effects induced by extensive, high-density suspended culture as surface obstruction. Both the aquaculture drag and the bottom friction are much higher than those in non-raft-culture areas, and show an obvious variation with tidal flow. The significant earlier ebbing and earlier flooding appear in the upper water column instead of the seabed. And the maximal phase lag is about 1 h within one tide cycle. A 1D hydrodynamic model was modified to include the SBL and parameterized with the field data. It replicated the observed velocity profile and was then used to investigate the impacts of varying culture density and bottom friction on the vertical tidal-current structure. Modeling results indicate that the surface current velocity was largely damped because culture activities enhanced the frictional effects on flow intensively. The magnitude and vertical structure of tidal current are determined together with aquaculture drag and bottom friction. In addition, the vertical velocity structure has a nonlinear trend along with culture density and bottom friction. This study is a theoretical foundation for optimizing aquaculture configuration through regulating culture density and species distribution.     

Effective communication tools to engage Torres Strait Islanders in scientific research

Often, research activities in Torres Strait have not delivered full benefit to Torres Strait Islanders due to a lack of consultation, ineffectual communication of research information and lack of empathy for the needs of Islander communities. As for other stakeholder groups, integration of Islanders into the research process through practical involvement in research may overcome these problems. Three case studies from research projects conducted in Torres Strait are discussed to highlight a variety of communication and engagement activities carried out by non-Indigenous researchers. How these communication and extension activities facilitate collaboration between Torres Strait Islander and non-Indigenous researchers provides insight in the importance of these activities to the relative success of research projects.     

Benthic input rates predict seagrass (Posidonia oceanica) fish farm-induced decline

Fish farms represent a growing source of anthropogenic disturbance to benthic communities, and efficient predictors of such impacts are urgently needed. We explored the effects of fish farm benthic organic and nutrient inputs on the population dynamics of a key seagrass species (Posidonia oceanica) in four Mediterranean deep meadows adjacent to sea bream and sea bass farms. We performed two annual plant censuses on permanent plots at increasing distance from farms and measured benthic sedimentation rates around plots. High shoot mortality rates were recorded near the cages, up to 20 times greater than at control sites. Recruitment rates increased in variability but could not compensate mortality, leading to rapid seagrass decline within the first 100 m from cages. Seagrass mortality increased with total sedimentation rates (K=0.55, p<0.0002), and with organic matter (K=0.50, p=0.001), total nitrogen (K=0.46, p=0.002) and total phosphorus (K=0.56, p<3.10(-5)) inputs. P. oceanica decline accelerated above a phosphorus loading threshold of 50mg m(-2)day(-1). Phosphorus benthic sedimentation rate seems a powerful predictor of seagrass mortality from fish farming. Coupling direct measurements of benthic sedimentation rates with dynamics of key benthic species is proposed as an efficient strategy to predict fish farm impacts to benthic communities.     

Empirical models to identify mechanisms driving reductions in tissue mercury concentration during culture of farmed southern bluefin tuna Thunnus maccoyii

Two empirical models are presented to elucidate the mechanisms driving reductions in the mercury concentration of southern bluefin tuna (SBT) during culture. Model 1 predicts temporal fluctuations in mercury concentration in response to growth dilution. Model 2 predicts the combined effects of growth dilution and linear mercury accumulation. Model 2 was found to be the more accurate model. Over a typical farming period of 136 days, growth dilution resulted in a reduction in mean mercury concentration of SBT edible tissues from 0.51 mg/kg down to 0.33 mg/kg. Extended culture beyond 136 days resulted in an increase in mercury concentration due to the combined effects of mercury accumulation and seasonal lipid depletion. Results indicate that under current industry practice, cultured SBT can be consumed twice as frequently as that of wild caught SBT while maintaining total dietary mercury intake below national recommendations.     

The influence of pearl oyster farming on reef fish abundance and diversity in Ahe,French Polynesia

Many cultured pearl farms are located in areas of the Pacific that have thriving, highly diverse fish communities but the impacts of farming on these communities are poorly understood. We studied the effects of pearl oyster farming on shore fish abundance and diversity in the lagoon of Ahe, French Polynesia by adapting roving diver census methods to the coral reef bommies of the lagoon and compared 16 sites with high pearl farming impact to others with no direct impact. Pearl farming has a slightly positive effect on reef fish abundance (N) and no significant impact on fish diversity (H) or community composition. This is important when considering the ecological sustainability of pearl farming in French Polynesia and suggests that a potential synergy between pearl farms and marine conservation should be further explored.     

长江流域外来鲟入侵风险评估、适生区预测及影响因素分析

长江流域外来鲟的养殖规模庞大,养殖逃逸成为外来鲟进入长江流域的主要途径,影响本地鲟种群生存。根据世界鱼类数据库(FishBase),10种主要养殖的外来鲟中,西伯利亚鲟已被列为德国和奥地利的入侵物种,匙吻鲟已被列为白俄罗斯的入侵物种。为了评估长江流域外来鲟的入侵风险,量化流域内入侵风险最高的外来鲟的适生区,本文使用水生物种入侵性筛查工具(AS-ISK)评估10种主要养殖的外来鲟和5种相关鱼类(虹鳟、尼罗罗非鱼、斑点叉尾鮰、鲮和丁鱥)的入侵风险;使用最大熵算法,基于当前和未来时期(2021—2040年)气候模式下的生物气候变量以及海拔,对于入侵评分最高的外来鲟在流域内的适生区进行预测与分析。结果表明,匙吻鲟在外来鲟中入侵评分最高,表明其在长江流域入侵风险最高。适生区预测时,最热季降水量、年降水量、最热月份最高温度、最冷月份最低温度、昼夜温差的月平均值和降水季节性变异系数是影响匙吻鲟在长江流域分布的主要变量。当前时期,匙吻鲟在长江流域中下游地区具有较大范围的适生区,主要包含湖南、湖北、安徽和江西等省份的部分地区,其中Ⅲ级适生区(高适生区)面积约为2996.8 km²;...     

虾池环境生物修复作用菌的生产发酵与菌体收集工艺优化

为了实现所筛选的对虾养殖环境生物修复作用菌的产业化生产,本文选择三株具有高效降解有机污染物能力的菌株为代表,对作用菌的发酵生产和菌体收集工艺进行了优化。结果表明,作用菌的最适发酵培养基配方(g/L)为蛋白胨 25,酵母粉 5,磷酸铁 0.2,灭菌前培养基的 pH 可先调为 8.0,搅拌方式为搅拌1h 间隔 1h, 出罐时间以 20h 为宜。菌体收集以等电点沉降法效率最高、成本最低,其中菌株 Lt7222 的最适沉降 pH 为 3.67、Gy7018 为 4.02、Lt7511 为 3.40。菌体回收率可达 90 %,回收后菌体的存活能力几乎不受影响。     

Assessing prospects for shrimp culture in the Indian Sundarbans: A combined simulation modelling and choice experiment approach

India's Sundarbans region lies within the state of West Bengal and is part of the world's largest mangrove ecosystem. Low-intensity shrimp aquaculture is present, but the potential exists for more intensive development. We argue for avoiding environmental damage and social conflict by adopting appropriate policies now. In this study, we combine ecological simulations and a choice experiment to evaluate several policy scenarios. Such comparative evaluations combining different disciplinary tools are rare. While our ecological modelling supports severe restrictions on shrimp farming activities, local stakeholders prefer a more diverse strategy. Both models indicate that large-scale commercial shrimp aquaculture is least desirable.     

对虾养殖池水域环境细菌的动态变化

于1990年6月下旬-10月初期间，每隔7－10d在大连市金州区董家沟镇养虾场突池定点采样一次，3h内带回实验室进行细菌培养计数，研究对虾养殖池水域环境中细菌的动态变化。结果表明，对虾养殖池水中异养菌和弧菌的数量变化与水温的变化趋势相同；6—7月末，细菌增长比较缓慢；8月初开始，细菌数量增长较快，8月中旬达到全年的最高值，异养菌为3．4×105cell／ml，弧菌为1．9×105cell／ml；而后随着水温的下降，水中细菌逐渐减少。底记泥浆中，细菌数量一直呈上升趋势，不受水温的影响；异养菌最高达6×107cell／ml，弧菌达1．5×106cell／ml。     

New Zealand seafood firm competitiveness in export markets: The role of the quota management system and aquaculture legislation

New Zealand's quota management system (QMS) was implemented in 1986 to address problems caused by a regulated open entry management system in place for the previous two decades. Excess capacity in the inshore fisheries caused several stocks to become depleted and conflicts to intensify between fishing sectors. The allocation of individual transferable quota (ITQ) was viewed as the best way to improve efficiency within the over-capitalised inshore fisheries and provide incentives for developing the deepwater fisheries. The expected benefits of the QMS fit with the political climate at that time, as the government was using market forces to address the deteriorating economy. This article outlines the results of a research project that involved four medium to large-sized, highly vertically integrated New Zealand seafood firms. The purpose of the project was to identify these firms’ sources of competitiveness in export markets and the process the firms used to develop sources of competitiveness, while adapting to rapid and radical changes to the political and business environment and transformation of the fisheries management system. The project's results show that the basis to seafood firm competitiveness is the security of supply to the fisheries resource provided by the QMS and aquaculture legislation. The project also outlines the role that government policies have in sustaining firm- and industry-level competitiveness. This article contributes to the broader discussion on the application of ITQ and other types of long-term access rights to the management of fisheries and does not express the views of the Ministry of Fisheries.