黑龙江省大水面河蟹综合养殖技术研究

河蟹为中国特产，因大螫上密生绒毛而称之为中华绒螯蟹(Eriocheir sinensis)。我国河蟹增殖和养殖技术在世界上处于领先地位。但目前的养殖方式主要是：池塘养蟹、湖泊网围养蟹、稻田养蟹、小型湖泊和小型水库养蟹，在大型水库尤其在高寒地区的大型水库从未有人进行过养殖。1999年我们通过对水库资源的调查，选择泥河水库和东湖水库(面积在40000亩以上)作为大水面河蟹养殖的试验场地。在对河蟹苗种品系进行慎重选择后．于1999至2001年进行大水面河蟹养殖，经过4个月的养殖，于当年8月中旬至10月上甸进行捕捞，回捕时平均规格达到100g／只，最大个体达200g／只，回捕率高达31％。结果证明，规格160-260只／kg的河蟹苗种是比较适合高寒地区．大水面养殖的。河蟹最佳投放期在春季，最佳生长期在7、8两个月，最佳回捕期在9月份。     

大水面种草养殖河蟹技术要点

河蟹原产于长江、珠江、辽河等内陆通海水系，我县2003年引进河蟹进行试养，并取得成功。通过几年的养殖探索，发现大水面种草养蟹技术简便易行，成本低，适合推广。此项技术是在大型湖泊、水库等养殖水体种植水草，进行生态养殖，其技术要点归纳如下：     

富春江水库河蟹增殖效果显著

富春江水库位于钱塘江中游，历史上曾盛产河蟹。自1958年动工兴建富春江电厂大坝后，河蟹资源逐年下降，1962年大坝竣工，河蟹也随之绝迹。为了恢复河蟹资源，建德县渔政站从1977年5月开始逐年向水库增殖放流蟹苗．几年来，共向水库投放蟹苗488公斤，蟹种900公斤。     

富春江水库人工放养蟹苗的探讨

富春江位于钱塘江中游，历史上曾盛产河蟹。自1958年9月动工兴建富春江电厂大坝以后，河蟹的资源量逐年下降，1968年12月大坝竣工，河蟹也随之在水库绝迹。为了恢复这一名特水产品，建德县渔政站从1977年5月开始，逐年向水库移植放养蟹苗。河蟹在库内生长良好，体大肥腴，取得了良好的社会、经济和生态效益。     

大港水库养殖河蟹纤毛虫病防治取得明显效果

大港水库地处沧州东北部，面积533．33hm^2，水草繁茂，已养殖河蟹多年，2005年暴发了河蟹纤毛虫病，造成河蟹行动缓慢，摄食减少。不蜕壳，生长缓慢。严重的造成河蟹大量死亡，大港区水产服务中心同专家共同深入调查研究、进行了多次防治试验，最后确定采取施用治疗纤毛虫病的有效成分硫酸锌、硫酸铜、硫酸亚铁合剂配方，根据水量分布，病害程度，全水库泼洒药液，该配方治疗效果显著，3d后河蟹纤毛虫开始脱落死亡，蟹体变得干净。     

大型工厂化河蟹育苗技术

大型工厂化河蟹育苗技术东辛农场位于黄海之滨，具有丰富的海水资源，南与２０４国道毗邻，交通便利，完全适合河蟹的人工育苗。近些年河蟹苗种价格飞涨，江苏省农垦总公司和东辛农场，瞄准市场，看准行情，共同投资６００多万元在东辛农场建造了一座大型工厂化河蟹育苗中...     

中小型水库河蟹增养殖技术

河蟹学名中华绒螫蟹,其肉味鲜美,营养价值高,深受人们喜爱。安徽省滁州市位于江淮丘陵地区,境内水库众多,中小型水库1209座,面积50多万亩。水库河蟹增养殖从80年代中期开始起步,因其技术操作简便,经济效益显著,深受广大养殖户欢迎。到1998年底,全市水库河蟹养殖面积达4467公顷,河蟹产量达200多吨,产值2000多万元,每公顷产蟹10-75kg。发展水库养蟹对调整优化水库养殖品种结构,提高水库渔业的经济效益起到了积极的促进作用。     

中小型水库河蟹增养殖技术

河蟹学名中华绒毛蟹 ,其肉味鲜美 ,营养价值高 ,深受人们喜爱。安徽省滁州市位于江淮丘陵地区 ,境内水库众多 ,中小型水库12 0 9座 ,面积 5 0多万亩。水库河蟹增养殖从80年代中期开始起步 ,因其技术操作简便 ,经济效益显著 ,深受广大养殖户欢迎 ,得到了较快发展 ,到 98年底 ,全市水库河蟹养殖面积达 446 7ｈａ ,河蟹产量达 2 0 0多吨 ,产值 2 0 0 0多万元 ,每ｈａ产蟹 10 - 75ｋｇ。发展水库养蟹对调整优化水库养殖品种结构 ,提高水库渔业的经济效益起到了积极的促进作用。1　养蟹水库的选择应选择平原地区或丘陵地区中小型水库 ,水库面积从…     

黄河三角洲平原水库大规格河蟹养殖关键技术

黄河三角洲地区淡水资源相对匮乏，为保障生产生活用水，该地区以黄河为水源，修建了大量平原型水库。水库具有水质清新，水草丰茂，受风面积大，溶氧充足，天然饵料较丰富的资源优势，适于发展河蟹生态养殖。该地区以培育黄河口大闸蟹为突破口，实施生态渔业、品牌渔业发展战略，但由于河蟹养殖规格小，养殖效益低，养殖积极性不高，严重影响黄河口大闸蟹品牌的营销与推广，因此推广水库大规格河蟹养殖关键技术，提高河蟹养殖规格和品质，实现渔业增效、渔民增收是发展品牌渔业的关键。     

水库网围生态养殖河蟹试验

为促进河蟹养殖的可持续发展，2001～2002年我们承担了河南省科委“水库网围生态养殖无公害河蟹技术研究”试验项目，取得了显著的经济、生态和社会效益。现将主要技术方法介绍如下：     

The shadow of the Balbina dam: A synthesis of over 35 years of downstream impacts on floodplain forests in Central Amazonia

1. The Balbina hydropower dam in the Central Amazon basin, established in the Uatumã River in the 1980s, is emblematic for its socio-environmental disaster. Its environmental impacts go far beyond the reservoir and dam, however, affecting the floodplain forests (igapó) in the downstream area (dam shadow), which have been assessed using a transdisciplinary research approach, synthesized in this review.
2. Floodplain tree species are adapted to a regular and predictable flood pulse, with high- and low-water periods occurring during the year. This was severely affected by the operation of the Balbina dam, which caused the suppression of both the aquatic phase at higher floodplain elevations and the terrestrial phase at lower floodplain elevations (termed the ‘sandwich effect’).
3. During the period of construction and reservoir fill, large-scale mortality already occurred in the floodplains of the dam shadow as a result of reduced stream flow, in synergy with severe drought conditions induced by El Niño events, causing hydraulic failure and making floodplains vulnerable to wildfires.
4. During the operational period of the dam, permanent flooding conditions at low topographical elevations resulted in massive tree mortality. So far, 12% of the igapó forests have died along a downstream river stretch of more than 125 km. As a result of flood suppression at the highest elevations, an encroachment of secondary tree species from upland (terra firme) forests occurred.
5. More than 35 years after the implementation of the Balbina dam, the downstream impacts caused massive losses of macrohabitats, ecosystem services, and diversity of flood-adapted tree species, probably cascading down to the entire food web, which must be considered in conservation management.
6. These findings are discussed critically, emphasizing the urgent need for the Brazilian environmental regulatory agencies to incorporate downstream impacts in the environmental assessments of several dam projects planned for the Amazon region.

     

Migration pattern of silver eel (Anguilla anguilla, L.) in an obstructed river system

Abstract –  The downstream migration of European silver eels in the River Frémur was examined to determine the potential effects of the numerous migration barriers that exist on waterways in western France. The Frémur has a 14 m high dam which creates a 3 × 10⁶ m³ water supply reservoir, 6 km from tidal limit. Based on 8-year records (1996–2004) of migrant silver eels captured in a Wolf trap located about 1 km below the dam, the influence of this dam on the migration was examined. These records indicate that 91% of silver eels were captured when the dam was overtopped (i.e. when the water reservoir was full). The timings of the overflow periods varied greatly between years mainly because they are function of the duration of the filling period which in turn is dependent on the level of summer water abstraction and annual hydrological conditions. Consequently, migration periods occurred at variable dates (between November and April) which is late in comparison with nonobstructed European river systems (generally between August and December). During overflow periods the migration of silver eels increased markedly during rain events (increasing river flow). This indicates that flow flushes, are essential so that settled silver eels can orientate themselves and pass over the dam. The hypothesis of a 'dam effect' that could stop temporarily or permanently some of silver eels in the reservoir is discussed. Finally, the influence of the migration delays on the condition of silver eels is considered.     

Downstream effects of hydroelectric dam operation on thermal habitat use by Brook Trout (Salvelinus fontinalis) and Slimy Sculpin (Cottus cognatus)

Hydroelectric dams can alter downstream water temperatures, impacting thermal habitat available for fishes. Decreases in river water temperatures resulting from hydroelectric dam operations may be beneficial to coldwater species and could potentially offset warming resulting from climatic trends. We used two coldwater fish species, Slimy Sculpin (Cottus cognatus) and Brook Trout (Salvelinus fontinalis) to assess the impact of a cool water draw below a 15 MW hydroelectric dam on fish thermal habitat use relative to a nearby naturally flowing river. Cooler water temperatures below the dam corresponded with significantly cooler mean growth season temperature use for Slimy Sculpin, but not Brook Trout, relative to the natural river. As well, mean growing season temperature use by Slimy Sculpin was significantly cooler relative to Brook Trout in both rivers, and significantly different amongst studied sites in the regulated river. Fish condition was significantly correlated with temperature use for Slimy Sculpin in the naturally flowing river only. Our results indicate that manipulating river water temperatures through hydroelectric dam operations to benefit multiple fish species will be difficult given the complexity of riverine thermal habitat and species‐specific differences in thermal preferences and behaviour.     

Genetic effects and growth performance in pure and hybrid strains of rainbow trout, Oncorhynchus mykiss (Walbaum) (Order: Salmoniformes, Family: Salmonidae)

Progeny from a cross of two strains of rainbow trout, Oncorhynchus mykiss (Walbaum), displayed about 7% heterosis in their growth rate. Variance component analysis showed that dams accounted for 20.3% to 65.8% variability in growth while sires accounted for none. Maternal effects were significant, but showed a diminishing trend over the study period. Additive genetic effects were nonsignificant. The Mount Lassen strain was better in maternal ability which indicated that source of dam was important. Interactions between sires and dams were significant with source of dam being important. Heritability for weight based on half-sib sire component of variance was estimated at 0.020 ± 0.001 and 0.269 ± 0.016 based on the dam component. Heritability for growth rate was 0.27 ± 0.04 based on the sire component and 0.88 ± 0.35 based on the dam component. Fulton's condition factor was lower in the hybrids. Egg size was correlated with fish size in the early growth phase. It was concluded that crossbreeding of rainbow trout strains could be advantageous owing to the display of hybrid vigour in the progeny.     

Genetic effects on carcass-quality traits in hybrid striped bass (Morone chrysops♀×Morone saxatilis♂)

A 10 × 10 factorial mating design was used to examine the genetic effects on various carcass‐quality traits in hybrid striped bass (Morone chrysops♀×Morone saxatilis♂). A total of 448 offspring were raised in a ‘common‐garden’ environment and carcass‐quality traits were assessed at 389 days post fertilization; parentage of each fish was inferred from genotypes at 5–10 nuclear‐encoded microsatellites. There was a significant effect of dam and sire on body weight and fillet weight and a significant effect of dam on viscera weight and condition factor. When carcass‐quality traits were standardized to body weight, there was a significant effect of dam, sire and dam × sire interaction on viscera percentage (proportion of viscera weight to body weight). Phenotypic correlations between body weight and non‐standardized carcass‐quality traits were high (r_p=0.80–0.92), whereas phenotypic correlations between body weight and standardized carcass‐quality traits were low (r_p=0.13–0.19). Genetic correlations between body weight and fillet weight (dams and sires), and body weight and viscera weight (dams only) were significant and positive, while the genetic correlations between body weight and viscera percentage (dams and sires) were significant and negative. Significant general combining ability values for favourable carcass‐quality traits in the same breeder (dam or sire) occurred only in one or two of 20 (dams and sires) used in this study, suggesting that simultaneous improvement in multiple traits in hybrid striped bass may require evaluation of large numbers of candidate breeders. The effect of sex on body weight and all non‐standardized carcass‐quality traits was significant and appeared to be due to faster growth in females. These results indicate that selection for faster growth of hybrid striped bass would lead to a correlated increase in fillet weight and viscera weight but not necessarily to an increase in the proportion of fillet and waste product generated. The significant dam, sire and dam × sire interaction effects on viscera percentage and the negative genetic correlations between body weight and viscera percentage indicate that selection for reduced proportion of viscera relative to body weight might be feasible.     

Effects of small dam condition and drainage on stream fish community structure

Low‐head dams are ubiquitous in eastern North America, and small dam removal projects seek to improve habitat conditions for resident and migratory fishes. Effects of small dams of varying status on local fish communities are poorly documented, and recent work suggests benefits of maintaining fragmentation. We sampled fish at 25 dams (9 breached, 7 relict, 9 intact) in three river basins in North Carolina, USA. Fishes were sampled at three reaches/dam from 2010 to 2011. Study reaches were located upstream (free‐flowing reaches), downstream (tailrace) and >500 m downstream of dams (n = 75 reaches). Analyses revealed significantly elevated fish CPUE, taxa richness and percentage intolerant taxa in intact dam tailraces suggesting small dams may improve conditions for resident taxa. Breached dam tailrace reaches exhibited lower fish CPUE, taxa richness and percentage intolerant taxa relative to upstream reference reaches. Relict dams exhibited no between‐reach differences in fish community metrics. Nonmetric multidimensional scaling revealed drainage‐specific stream fish responses across study drainages. Tar and Roanoke drainage streams with intact and relict dams supported fish assemblages indicative of natural communities, whereas Neuse Drainage streams with intact and breached dams contained disturbed habitats and communities. These data demonstrate fish community responses to dam condition are drainage specific but communities in streams with intact and relict dams are largely similar. Additionally, breached dams may warrant higher removal priorities than intact dams because they negatively influence fish communities. The variability in response to some dams indicates managers, regardless of region or country, should consider holistic approaches to dam removals on a case‐by‐case basis.     

Fish and lamprey passage in a combined Denil and vertical slot fishway

A fishway (fish pass), consisting of vertical slot and Denil sections, was constructed at the lowest dam on the River Kemijoki, northern Finland, in 1993. The river was one of the best salmon rivers in Europe until 1949, when the dam and the hydropower plant were completed close to the river mouth. From 1993 to 1995, nearly 1000 adult salmonids passed through the fishway despite heavy fishing below the dam. Of environmental variables measured, water temperature, headwater level, and discharge through the power plant in relation to season changes explained most of the variation in Baltic salmon, Salmo salar L., numbers. They had a minor effect on trout, Salmo trutta L. Migratory whitefish, Coregonus lavaretus (L.), entered the fishway but were not observed in its uppermost pool. River lamprey, Lampetra fluviatilis (L.), passed through the vertical slot section of the fishway after plastic bristles were fastened into the bottom of the slots.     

Hydroacoustic survey of fish density,spatial distribution,and behavior upstream and downstream of the Changzhou Dam on the Pearl River,China

Hydroacoustic surveys were conducted to understand the relationship between fish density, spatial distribution, and behavior upstream and downstream of the Changzhou Dam on the Pearl River, China, and the condition (open/closed) of the spillways. When the spillways were open on 24 June 2010, numerous fish were observed to be densely distributed in the forebay upstream of the dam, with an average fish density was 0.22 fish m⁻³. When the spillways were closed on 25 June 2010, the fish upstream of the dam dispersed, and the average fish density decreased to 0.007 fish m⁻³. Prior to operating the spillways on 24 May 2010, the average fish density downstream of the dam was 0.28 fish m⁻³; in comparison, on 26 June, immediately following closure of the spillways, the average fish density downstream of the dam was 0.08 fish m⁻³. Fish were more active on June 24 than on 25 June: they swam faster and their positions in the water column varied greatly. On 26 June, fish did not to swim as freely in the water column as those measured on 24 May. Based on these observations, we conclude that a large number of fish are able to swim to the upstream side of the dam while the spillways are open.