东洞庭湖鱼类资源保护对策探讨

东洞庭湖是现存洞庭湖面积最大的本底湖，总水面１７．７万公顷，有淡水鱼１１８种。但是，东洞庭湖的淡水鱼类，在近几十年人类活动和环境变迁等因素的综合影响下，鱼类总体资源明显下降，部分种类已呈濒危。２０世纪９０年代东洞庭湖平均年捕捞产量约为１９０２８吨，２００１年约为１４３７６．９吨，２００２年略有增加，为１５７９８．８５吨，但总体仍呈逐年下降趋势；９０年代前，东洞庭湖的渔获物中，“四大家鱼”等江河半洄游性鱼类总量组成占３２％，鲤、鲫、鲶等湖泊定居性鱼类约占６３％，刀鲚等咸淡水洄游性鱼类占５％。９０年…     

日本养鱼用配合饲料的生产使用

日本的养殖鱼类，海水鱼中主要是鰤鱼、鰤鱼，淡水鱼中主要是鳗、鲤、香、虹鳟、鲫鱼等。七十年代初，鰤鱼占海水养殖产量的98％以上，其后因养鲷业发展，至1977年的比例降为92．4％，但其养殖产量仍比1968年增加2．62倍，达115，098吨。淡水鱼中鳗鱼养殖产量居首位，     

美国太平洋沿岸渔业产量上升

据不完全统计，1987年美国合资企业的渔获量比1986年上升16％，达150万吨。阿拉斯加水域的渔获量占总渔获量的94％，阿拉斯加狭鳕为104．2万吨，鲽鱼224，000吨，鳕鱼为60，000吨。国内加工的阿拉斯加鱼类的美国份额比去年翻了一番，达296，000吨。     

俄罗斯共和国扩大池塘鱼类的生产

目前，俄罗斯联邦共和国的淡水鱼产量已占苏联全国内陆水域(包括池塘养鱼场在内)总渔获量的41％。1981年，池塘总面积达6万公顷，鱼产量已从每公顷4～5公担，据统计，1981年仅以池塘养殖鱼类为内容的养殖面积已扩大到59．4万公顷，比1965年高5倍。其主要养殖对象为鲤鱼，其次为草、鲢、鳙等鱼，其产量已占养殖鱼类总产量的25％。     

低值鱼和水产废弃物在调味料生产中的利用

资源潜力巨大 1984年，全世界总渔获量8，631．4万吨，其中暖水性中上层低值鱼鲲鱼、沙丁鱼类，占15．4％，达1，332．8万吨。这一年日本的鲲鱼、沙丁鱼渔获量459万吨，占其海洋渔获1，129万吨的41％。     

水丰水库渔获变化和鱼类资源现状及小型经济鱼虾种间关系分析

水丰水库的渔获量1961－1980年间变化于47－300t,1981-1984年增长到740－1321t,1985-2000年为2270－4926t。渔获物组成中以亚洲公鱼为主，1980－2000年亚洲蚣鱼占总渔获的29．6％－93．0％，平均为65．6％。鲁鲫鱼占6．2％－16．4％，鲢鳙鱼占8．1％－13．3％，鳊鲂占1．8％－11．3％，虾占5．9％－16．1％，其它鱼类占2．4％－9．3％。2000年大银鱼占总渔获的2．8％。1985－2000年水库鱼类资源相对稳定。亚洲公鱼、青虾和大银鱼三种小型经济鱼虾的种间关系表现为互利共生，竞争和残敌关系，可能向种间形成平衡调节方向发展。     

世界各国鱼类和其它水生生物的加工现状

八十年代前半期世界渔获量进一步增长，从1980年7，200万吨增至1984年8，000万吨。近几年来世界渔获量的增长速度每年不超过1-2％。1975-1983年世界渔获量的种类组成结构发生很大变化，部分有价值的传统经济鱼类逐渐减少，而部分非鱼类捕捞对象相应的增加，世界渔获量中上层鱼类的比重占三分之二，其中灯笼鱼科和钻光鱼科的中上层鱼类占优势，它是当今发展海洋渔业的极大潜力，     

25年来世界渔业生产

总渔获量全世界渔获量，1960年3，950万吨，1985年增至8，400万吨，1972年首次剧降，由于智利、秘鲁鳀鱼剧减，世界总渔获量6，160万吨，中上层鱼类的渔获量，从1960年1，290万吨增为1984年的3，200万吨(同期底层鱼类从860万吨增至1，890万吨)，在世界总渔获量中所占比率，以70年代中期的28％为最高，     

冰岛的渔业

冰岛水域资源丰富，渔场每年提供大约150万吨渔获量，其中一半是中层鱼类，大多数用于生产鱼糜。现在冰岛的鱼产品年出口总值超过1亿美元，约占该国外汇收入的55％，占商品出口额的70—80％。冰岛水域最重要的鱼种是鳕科鱼类，即：鳕、黑线鳕和绿青鳕。鲈、马舌鲽、鲱鱼、毛鳞鱼和长额对虾也是非常重要的品种。     

日本养殖鱼虾类饲料的发展概况

一、养殖鱼虾类产量和饲料应用情况 日本海淡水鱼类养殖，从50年代中后期开始。海水鱼类养殖以鳞鱼、鲷鱼为主，现在已成为沿岸渔业的重要支柱。1984年的养殖产量为192，392吨，其中鰤鱼占79．26％，其次是鲷类，占13．74％，其它如鲹类、鲆鲽、河鲀类、对虾等占7％。近年来，由于养殖过密，渔场老化，饵料鱼营养等方面存在的缺点，病害多，产量下降，     

Fishing down or fishing up in Chinese freshwater lakes

Changes in mean trophic level (MTL) of catches have been widely used to reflect the impact of industrial fisheries on aquatic ecosystems because this measure represents the relative abundance of fished species across the trophic level spectrum. In this study, fisheries data from six important freshwater lakes at the middle‐lower Yangtze River and Huaihe River reach of Southern China from 1949 to 2009 were used to evaluate changes in catch MTL. After fishery markets opened at 1985, fish catches increased significantly in all the lakes. Lakes Poyang and Dongting, which were dominated by omnivores and connected to the Yangtze River, showed no significant change in catch MTL before and after 1985. Catch MTL in lakes Taihu and Hongze increased significantly due to an increase in the proportion of pelagic zooplanktivorous. Catches in Lake Chaohu were dominated by zooplankton‐feeding lake anchovy, Coilia ectenes Temminck & Schlegel and icefish, Neosalanx taihuensis Chen, while Lake Donghu was dominated by phytoplanktivorous carps. Due to low biodiversity, catch MTL of these two lakes showed no significant change before and after 1985. Both fisheries‐based and human activities‐based drivers influenced the structure and catch MTL of fisheries in Chinese freshwater lakes.     

Fisheries management based on ecosystem dynamics and feedback control

Recently, ecosystem management has become popular for forestry, agriculture and fisheries management. Carrying capacity and maximum sustainable yield for a particular species definitely depend on population sizes of other species in the same ecosystem. Natural stock fluctuations of sardine, anchovy and chub mackerel are well known examples of large, natural fluctuations. There is a negative correlation among their fluctuations. In accordance with the cyclic advantage hypothesis for replacement of pelagic fish species (Matsuda et al., 1992), we can predict the next dominant species, despite an uncertainty in the year of the next replacement. We recommend that commercial fisheries should switch their target to the next dominant species before the stock of the present dominant species collapses. Whilst total allowable catch (TAC) of the present dominant species can be as large as we can consume, TAC after the species collapses should be much smaller than the present catch level.     

Fisheries by-catch and processing waste meals as ingredients in diets for Nile tilapia, Oreochromis niloticus

Digestibility, feeding and growth studies were conducted with Nile tilapia using diets containing fishery by‐catch and processing waste meals. Three meals manufactured from sorted fisheries by‐catch (MBM, from mixed benthic species, SPM, from small pelagic species, CAM, from mixed catfish species) one from tuna cannery waste (TCW) and one commercial anchovy meal (COM) were tested. By‐catch and processing waste meals had lower protein, lower lipid and higher ash contents than anchovy meal. The meals were all highly digestible and no significant differences (P≥0.05) were observed between apparent protein digestibility measurements. Five feeds, containing fish meal as the major protein ingredient, were formulated and fed to triplicate groups of 30 juvenile tilapias for 9 weeks. Survival, weight gain, specific growth rate (SGR), feed conversion ratio, protein efficiency ratio, phosphorus retention and whole body proximate composition were compared. Weight gain and SGRs were similar for each treatment group and compared favourably with the results obtained from juvenile tilapia elsewhere. Growth was the highest for CAM (P≤0.05), which contained both the highest essential amino acid levels and the highest ash content. Phosphorus retention was significantly lower in fish fed with high ash meals, MBM, CAM and TCW (P≤0.05) than in fish fed with the lower ash meals COM and SPM. Overall, the fisheries by‐catch and processing waste meals evaluated in this study are suitable protein ingredients for juvenile tilapia feeds.     

Long-term effects of human influence on fish community structure and fisheries in Berlin waters: an urban water system

Commercial catch and fisheries monitoring data were compared with hydrological and water course characteristics conditions to identify the cause of changes in fisheries production in Berlin water courses since the 1950s. The urban parts of Berlin are densely populated, and the waters are under pressure from shipping, hydraulic engineering, pollution and recreation use. Most Berlin waters are polytrophic or hypertrophic, with an annual nutrient input of 595 t of total phosphorous and 8640 t of total nitrogen. A total of 34 fish species were recorded, eight of which were introduced. According to historical records, seven native fish species are extinct or missing. At present, the fish community is dominated by a few eurytopic species, i.e. roach, Rutilus rutilus (L.), common bream, Abramis brama (L.), silver bream, Blicca bjoerkna (L.), and perch, Perca fluviatilis L., which contribute 85% of all individuals caught. Two 'faunal breaks' were identified. The first was the changing of river character from a barbel to bream zone caused by damming and river regulation. This started in the thirteenth century and ended at the beginning of the twentieth century with the extinction of anadromous fishes. The second break was during the 1960s and 1970s, with the eutrophication of Berlin waters and the near total loss of submerged macrophytes. All phytophilic fish species declined greatly and a mass development of eurytopic species started. The catch of pike, Esox lucius L., common carp, Cyprinus carpio L., and tench, Tinca tinca (L.), became negligible, and at present, eel, Anguilla anguilla (L.), and pikeperch, Stizostedion lucioperca (L.), are the main commercial fish species. Concomitantly, the profitability of the fisheries declined and was linked to a decrease in the number of people employed in fisheries by more than 75% compared with 1950.     

祟明东滩团结沙鱼类群落多样性与生长特性

研究了长江口祟明东滩团结沙5~8月间的鱼类多样性和生长特性。初步调查表明,祟明东滩团结沙共有鱼类9目19种,以鲤形目最多,鲻形目次之。这些鱼类分为4个主要生态类型,包括河口性鱼类4种、近海鱼类3种、江海洄游型鱼类4种和淡水鱼类8种。鱼类群落多样性较低,以个体数为单位计算的Shannon-Wiener多样性指数H′为2.790,Simpson优势度指数λ为0.198,Pielou种类均匀度指数J′为0.657。主要优势鱼类为窄体舌鳎、刀鲚、长蛇鮈、鲻、鲫、中国花鲈和中华鲟等7种,个体都较小。这7种鱼中窄体舌鳎、刀鲚、长蛇鮈、鲻、鲫和中华鲟呈等速生长,而中国花鲈为异速生长,肥满度最大的是鲫,最小的是刀鲚。5~8月间每个月渔获物的种类与数量组成有一定差异。为了更好地保护长江口祟明东滩的鱼类资源,应加强长江口渔业生态环境的综合治理,加大增殖和保护鱼类资源的力度,充分发挥长江口中华鲟自然保护区的保护功能。     

长江口定置张网渔业调查

本文报导了1982年和1988年长江口(E121°10′～122°15′;N31°00′～31°42′)定置张网渔业调查情况。调查表明: (1)长江口定置张网包括深水张网、高仓张网、插网、挑网四种渔具。作业范围主要在潮间带和潮下带水深8米以内的四个区域;①自崇明岛北四滧河口到佘山西北一带;②由白龙港至老港以及九段沙、铜沙一带;③从浏河口外到宝钢码头之间;④长兴、横沙两岛的南、北港水道和吴淞口外。作业期一般从2月至11月。 (2)渔获物种类组成共有61种,分属鱼类、甲壳类、水母类,头足类和哺乳类。其中主要经济种类有:长颌鲚、凤鲚、前颌间银鱼、安氏白虾、中华绒螯蟹和海蜇。 (3)据崇明、宝山、川沙和上海四县,1971年—1982年资料统计:年平均投网数达 4189顶。年平均渔获量为7.6万担,其中毛鲚约占43.4％。 鉴于长江口渔业资源因遭受酷渔滥捕、水质污染、渔场浅滩局部变迁和航道拓宽等因素的影响而开始衰退,建议结合渔民生计,尽快制定对定置张网采取限制、调整等“繁保”管理措施,使渔业资源得到保护和合理利用。     

长江南京江段长颌鲚生境履历的反演研究

利用电子探针显微分析技术(EPMA),对2009年和2014年采自长江南京段的长颌鲚耳石微化学进行了研究,反演了其生境履历.结果显示,这些长颌鲚耳石上元素Sr/Ca值的动态可分为两类.一类Sr/Ca值出现显著波动,不仅具有对应淡水生境的低值(1.87±0.36),而且有对应于河口半咸水生境的较高值(4.80±0.80),甚至出现了外海高盐度生境的高值(7.85±0.57),反映了溯河洄游的生境履历特征.另一类Sr/Ca值稳定3.0以下(14NJC09和14NJCE10),仅反映出在淡水生境中生活的履历.上述结果均得到了耳石Sr面分布的验证.上述“反演”的结果首次发现,传统上认为的一定是溯河洄游的长颌鲚,也可能存在有淡水定居个体.单纯利用上颌骨的长短并不能作为有效判别长江刀鲚资源群体中溯河洄游个体和淡水定居个体的标准.     

Identification and evaluation of shark bycatch in Georgia’s commercial shrimp trawl fishery with implications for management

Abstract Many US states have recreational and commercial fisheries that occur in nursery areas occupied by subadult sharks and can potentially affect their survival. Georgia is one of few US states without a directed commercial shark fishery, but the state has a large, nearshore penaeid shrimp trawl fishery in which small sharks occur as bycatch. During our 1995–1998 investigation of bycatch in fishery‐dependent sampling events, 34% of 127 trawls contained sharks. This bycatch totalled 217 individuals from six species, with Atlantic sharpnose shark, Rhizoprionodon terraenovae (Richardson), the most common and finetooth shark, Carcharhinus isodon (Müller & Henle) and spinner shark, Carcharhinus brevipinna (Müller & Henle), the least common. The highest catch rates for sharks occurred during June and July and coincided with the peak months of the pupping season for many species. Trawl tow speed and tow time did not significantly influence catch rates for shark species. Gear configurations [net type, turtle excluder device (TED), bycatch reduction device] affected catch rates for shark species. Results of this study indicate gear restrictions, a delayed season opening, or reduced bar spacing on TEDs may reduce shark bycatch in this fishery.     

太湖敞水区鱼类种间关系现状

太湖敞水区鱼类群落组成，除人工放流的种类外，河湖洄游性鱼类已基本消失，以湖鲚、银鱼、虾类和小型鲤科鱼类种群占绝对优势。８种优势种种间协调系数显示，湖鲚、银鱼类，白虾，似鲚、九州稣箴等相互关系较为密切，其中太硝新银鱼和寡齿新银鱼之间除产卵期有先后外，时空分布和食饵对象基本一致。