Fish intake mortality at power stations the problem and its remedy

Summary Fish larvae and juveniles are not strong enough to maintain in the water flow occurring at cooling water intakes of power stations. Therefore, they are drawn into the cooling water system and show considerable mortality mainly due to mechanical causes. In this paper several measures are discussed which may lead to a reduction of this problem. Special emphasis is laid on site selection in low productive areas, reduction of the volume of cooling water, careful removal and transport from the screens and preventing fish from entering the intake. Illumination of the intake area during night appears to be an effective means in decreasing the large nocturnal fish inflow. It is suggested to modify the current cooling water standards in order to diminish the intake fish mortality.     

Fish impingement at power stations situated along the rivers Rhine and Meuse in The Netherlands

Summary Substantial numbers of predominantly O⁺ fish were impinged on the cooling water screens of Harculo, Gelderland, Merwedehaven and Amer power stations. Low numbers were impinged at the two stations located on the river Meuse (Maas and Claus). Two possible reasons for this difference are suggested,viz. a low fish density in the river Meuse and the deep position of the cooling water intakes. In comparison with Bergum power station situated on a lake the impingement rate at the river stations was more than ten times as low.Most fish were impinged during the summer months when large numbers of juvenile fish are present in the rivers. Dominating species impinged were roach, pikeperch, bream and perch. The abundance of pikeperch in the screensamples, points to a recent increase in the population of pikeperch in the rivers. The growth pattern of O⁺ pikeperch and O⁺ roach during summer seemed very similar for power stations located at different rivers. Thirty fish species and four crustacean species were collected, among whichOrconectus limosus was quite abundant at Maas and Claus power stations.     

Comparison of fish impingement by a thermal power station with fish populations in the Ems Estuary

On an annual basis >10 million individuals of c . 35 fish species are impinged at the EC20 unit of the Eems power station located on the Ems Estuary. The most abundant are: herring Clupea harengus , gobies ( Gobiidae ), Nilsson's pipefish Sygnathus rostellatus , three-spined stickleback Gasterosteus aculeatus and sprat Sprattus sprattus . The impingement shows a seasonal pattern which reflects the presence of the fishes in the estuary. The results are compared with other impingement studies at power stations on the Belgian and Dutch estuaries.
In 1995, the cooling water entrance was displaced from the shoreline to 300 m off the coast at the edge of the tidal channel. The effect of this relocation on the level of fish impingement, determined by comparing the ratio of fish density in the cooling water and in the estuary before (1992–1993) and after (1996–1997) the relocation of the intake canal is discussed.     

Fish entrapment in the seawater intake of a power plant at Karachi coast

Synopsis The study deals with the entrapment of fishes in the intake of Karachi Nuclear Power Plant. A total of 62 species of marine fishes belonging to 43 genera were observed entrapped in the seawater intake. Therapon puta, Liza waigiensis, Abudefduf septemfasciatus, and Lagoceptalus inermis were the most common. Mass mortalities of the juveniles of Sardinella sindensis were recorded in September and October of 1974, 1975, and 1977. Commercially important fishes such as sardines, mullets and anchovies, were entrapped in the intake of the power plant in considerable numbers at various times of the year. The majority of fishes removed from the screen washes of the power plants were killed by impingement.     

Overfishing and the Replacement of Demersal Finfish by Shellfish: An Example from the English Channel

The worldwide depletion of major fish stocks through intensive industrial fishing is thought to have profoundly altered the trophic structure of marine ecosystems. Here we assess changes in the trophic structure of the English Channel marine ecosystem using a 90-year time-series (1920–2010) of commercial fishery landings. Our analysis was based on estimates of the mean trophic level (mTL) of annual landings and the Fishing-in-Balance index (FiB). Food webs of the Channel ecosystem have been altered, as shown by a significant decline in the mTL of fishery landings whilst increases in the FiB index suggest increased fishing effort and fishery expansion. Large, high trophic level species (e.g. spurdog, cod, ling) have been increasingly replaced by smaller, low trophic level fish (e.g. small spotted catsharks) and invertebrates (e.g. scallops, crabs and lobster). Declining trophic levels in fisheries catches have occurred worldwide, with fish catches progressively being replaced by invertebrates. We argue that a network of fisheries closures would help rebalance the trophic status of the Channel and allow regeneration of marine ecosystems.     

Combining Telephone Surveys and Fishing Catches Self-Report: The French Sea Bass Recreational Fishery Assessment

Fisheries statistics are known to be underestimated, since they are mainly based on information about commercial fisheries. However, various types of fishing activities exist and evaluating them is necessary for implementing effective management plans. This paper assesses the characteristics and catches of the French European sea bass recreational fishery along the Atlantic coasts, through the combination of large-scale telephone surveys and fishing diaries study. Our results demonstrated that half of the total catches (mainly small fish) were released at sea and that the mean length of a kept sea bass was 46.6 cm. We highlighted different patterns of fishing methods and type of gear used. Catches from boats were greater than from the shore, both in abundance and biomass, considering mean values per fishing trip as well as CPUE. Spearfishers caught the highest biomass of sea bass per fishing trip, but the fishing rod with lure was the most effective type of gear in terms of CPUE. Longlines had the highest CPUE value in abundance but not in biomass: they caught numerous but small sea bass. Handlines were less effective, catching few sea bass in both abundance and biomass. We estimated that the annual total recreational sea bass catches was 3,173 tonnes of which 2,345 tonnes were kept. Since the annual commercial catches landings were evaluated at 5,160 tonnes, recreational landings represent 30% of the total fishing catches on the Atlantic coasts of France. Using fishers'' self-reports was a valuable way to obtain new information on data-poor fisheries. Our results underline the importance of evaluating recreational fishing as a part of the total amount of fisheries catches. More studies are critically needed to assess overall fish resources caught in order to develop effective fishery management tools.     

Landings of whale sharks Rhincodon typus Smith, 1828 in Indian waters since protection in 2001 through the Indian Wildlife (Protection) Act, 1972

Since 28^th May 2001, Whale shark Rhincodon typus Smith, 1828 have received the highest protected status for an animal in India through the Indian Wildlife (Protection) Act, 1972 Schedule-1. However, landings have still been recorded off the Indian coast since 2001, mostly as incidental bycatch in commercial fishing operations, and other sightings have also been reported. In the 1990’s, a targeted whale shark fishery existed off the Gujarat coast following increased demand for the flesh in some other Asian countries. Since the ban, landings of whale sharks have decreased substantially with only 79 recorded between 2001 and 2011. Landings were recorded in each year and in each month of the year with the highest landings in January and February. Between 2001 and 2011, the smallest specimen reported from Indian waters was a 94 cm TL individual and the largest was a 13.7 m TL individual, with most individuals recorded in the 4–6 m TL size class. Small juveniles of less than 3 m TL are rarely recorded in the literature and appear to be rarely observed globally. Between 2006 and 2011, seven juveniles of less than 3 m TL were recorded from two landing sites. Despite the continued landing of whale sharks along the Indian coasts since 2001, the protection of this species appears to have substantially reduced the catches with only incidental landings and strandings now evident. The protection status of whale sharks in India is generally well understood by fishers, but still there is need for further education regarding the current national legislation and vulnerability of the species.     

Biology of the sand-smelt (Atherina presbyter Valenciennes) around Fawley power station

Past studies of fish impingement at Fawley power station have shown that sand-smelts, Atherina presbyter Valenciennes, are susceptible to impingement and may be a useful species for examining effects of impingement mortalities on population size and structure. A 21 month study of populations in the vicinity of Fawley power station was carried out to obtain data on the biology of the species for future population dynamics modelling studies. Aspects included in the study were growth, sex ratio, reproduction, survival and mortality rates and diet. Differences in apparent and true rates of growth indicated some size-selective mortality towards younger age groups, possibly caused by the power station. A seasonallyoscillating von Bertalanffy growth equation is given to predict mean length-at-age. Most female sand-smelts (73%) matured at the end of their first year of life, fecundities ranging on average from 1394 eggs per female for 1+ group fish to 6872 for III+ fish. The sex ratio was even (1 : 1). An annual survival rate of 10–8% was estimated for mature fish, and the consequent age structure of the population indicates that the bulk of egg production lies with the smaller (1+ group) fish. Since smaller fish are generally more vulnerable to impingement this factor may render populations sensitive to impingement mortalities. Gut content analysis indicated that sand-smelts probably actively select zooplankters from the general plankton when young and, once larger than 104 mm in length, increasingly feed upon natant macrofaunal species.     

中国海域海洋生物的营养级指数变化特征

利用联合国粮农组织(FAO)1950-2011年渔获物捕捞量资料, 分析了我国海域(包括大陆海域、台湾海域、香港海域和澳门海域)129种渔获物的营养级指数变化特征。研究表明, 1950-1974年我国海洋营养级指数在3.45左右波动, 1975-1978年下降至3.35左右, 1982-1987年急剧下降到3.25并维持到1996年, 1997-2011年平稳回升至3.34。与全球海洋营养级指数相比, 1984年之前我国高于全球水平, 而1984年之后则低于全球水平。就生物类群而言, 鱼类对我国海洋营养级指数的贡献最大, 达73.1-85.8%; 甲壳动物次之, 为9.2-15.5%; 软体动物较小, 为3.3-11.6%; 其他无脊椎动物的贡献最小, 不超过1.8%。过度捕捞使我国部分渔获物由原来的长寿命、高营养级的底层鱼类变为现在的短寿命、低营养级的无脊椎动物和中上层鱼类。渔业捕捞许可管理制度、禁渔期和禁渔区制度、海洋捕捞产量“零增长”和“负增长”计划、增殖放流、扩大海洋保护区面积等措施的实施可能是我国海洋营养级指数回升的主要原因。     

Catch and discards from experimental trawl and longline fishing in the deep water of the Rockall Trough

Comparative bottom trawl and longline surveys were carried out on two chartered commercial fishing vessels in the deep waters (350-1300 m) of the Rockall Trough, an area subjected to heavy commercial exploitation. The species composition, catch rates and length distributions from each survey were very different and reflected the fundamental difference in the two types of fishing operations. Bottom-trawled catches produced greater species diversity and higher discard rates. Longline catches produced larger specimens of teleost fish and were dominated by squalid shark. Trawl discards, expressed as kgs of discards per tonne of roundnose grenadier Coryphaenoides rupestris landed, were calculated for a broad range of the most abundant species taken in the catch. First estimates of total international discarding from deep-water trawling operations in the Rockall Trough area (7530 tonnes; 26.5 million individuals) were made by raising the discard rates using international grenadier landings for 1995. The outlook for the continued exploitation of the deep-water fish resource in the Rockall Trough and possible management options are discussed.     

The effect of size on juvenile green sturgeon (<Emphasis Type="Italic">Acipenser medirostris</Emphasis>) behavior near water-diversion fish screens

Anthropogenic water management projects and facilities that alter the local and regional hydrology of riverine environments greatly influence the behavior, physiology, and survival of native fishes. To mitigate for losses of native fishes at these structures, many are outfitted with fish-exclusion screens to reduce entrainment. The effect of fish size and age on behavior near fish screens, however, is largely unknown. Therefore, we tested two size classes of juvenile green sturgeon (Acipenser medirostris; small, early juveniles: 9.2 ± 0.2 cm fork length [FL], 6.9 ± 0.3 g; intermediate juveniles: 18.8 ± 0.2 cm FL, 36.9 ± 0.8 g) near fish-exclusion screens in a laboratory swimming flume. Although size was a significant factor influencing the way in which fish contacted the screens (i.e., proportion of body contacts, p = 2.5 × 10^?9), it did not significantly influence the number of times fish contacted screens or the amount of time fish spent near screens. We also compared the performance of these two size classes to that of older and larger sturgeon that were tested previously (29.6 ± 0.2 cm FL, 147.1 ± 3.1 g), and documented a clear difference in the behavior of the fish that resulted in disparities in how the large fish contacted screens relative to small- or intermediate-sized juveniles (p = 0.005, 5.4 × 10^?4, respectively). Our results further our understanding of how ontogeny affects fish behavior near anthropogenic devices, and are informative for managers seeking to identify the most susceptible size and age class of juvenile green sturgeon to water-diversion structures to potentially develop size-specific conservation strategies.     

Fishery, seasonal abundance and mortality of grey mullets (Pisces: Mugilidae) in Negombo Lagoon, Sri Lanka

The seasonal abundance and instantaneous natural and fishing mortalities of six species of grey mullets, namely Liza subviridis, L. macrolepis, L. tade, Mugil cephalus, Valamugil buchanani and V. cunnesius were studied as a prelude for the management of their fishery in Negombo lagoon (7°10′N and 79°50′E). L. subviridis was the most abundant of the grey mullet species in the commercial catches and accounted for 37% of the total grey mullet catch. M. cephalus was the least abundant and constituted 6%. The annual catch of grey mullets was estimated to be around 23 000 kg (5.67 kg/ha); about 40 % of the total fish landings of the lagoon. The seasonal variation in the catch of different species of grey mullets appear to be related to their breeding seasons and spawning migrations. The highest value for instantaneous natural and fishing mortalities, which were 1.04 and 0.94 respectively were obtained for V. cunnesius. The lowest values for instantaneous natural and fishing mortalities which were 0.51 and 0.19 respectively were obtained for M. cephalus. The exploitation ratios calculated were less than 0.5 for all species other than L. tade which suggest that the grey mullet populations excluding L. tade in this lagoon may presently be underexploited.     

A preliminary survey of the artisanal fishery on coral reefs of the Tulear Region (southwest Madagascar)

Fish catches from the coral reefs of the Tulear region (southwest Madagascar), are analyzed based on fish landings. This region of the island consists of two barrier reefs, two coral banks, three lagoon reefs and a fringing reef. The total reef area studied was 190 km². Of the whole fishing area, the reef flat was the most frequently used by fishermen. Line catches per unit efort (CPUE) were stable throughout the eight month sampling period (6 to 8 kg/trip to sea), whereas gillnet and seine catches showed differences between the cold period and the warm period. These results appear to be representative of the artisanal fishery catches in the southwest Indian Ocean. Annual fish yield was estimated at 12 t km^-2 yr^-1. Comparable yields have been recorded in certain regions of the Indo-Pacific, that have similar ratios of coral reef area to adjacent shallows and similar fishing practices. Reef species (Lethrinidae, Siganidae) dominated the catches. At present, coastal waters of the Tulear region are heavily fished, and the fishermen report a progressive decrease in the average size of fish caught over the last 15 years. Management measures are suggested, based on preliminary findings.     

Biological characteristics of European Atlantic sturgeon, Acipenser sturio, as the basis for a restoration program in France

The European Atlantic Sturgeon, Acipenser sturio, has received increased attention in France because of population declines due to overfishing and deterioration of spawning grounds. Conservation of this species requires many actions, including publicizing the necessity to protect this fish and its habitats, investigations on catches and probable spawning grounds, and on artificial reproduction, which is still in an experimental stage. During its sea life, European Atlantic sturgeon occur from the Bay of Biscay to the Bristol Channel and North Sea. Presently, the number of young fish in the Gironde Estuary during summertime is low and the population has a unimodal age structure. At the time this paper was written, the last recorded reproduction of sturgeon in the Gironde system occurred in 1988 (new evidence of reproduction was discovered in 1995). Growth of young fish from the 1988 cohort was faster than that previously determined for others cohorts. Over our study period (1980–1994), the availability of wild broodfish declined. Successful artificial reproduction of wild-caught females requires an optimal physiological state; any delay decreases their reproductive potential. Acclimatization of wild-caught juveniles to fresh water was most successful when fish were transported and held upon arrival in low salinity water. For such wild-caught juveniles, the first food intake usually occurs several months after capture, but remains irregular. These findings will be used to improve ongoing efforts to restore A. sturio.     

The effect of various Aeromonas bestiarum vaccines on non-specific immune parameters and protection of carp (Cyprinus carpio L.)

Aeromonas bestiarum is one of the causal agents of motile aeromonad infection/motile aeromonad septicemia (MAI/MAS) in fish. Infections of the bacterium is an increasing problem in commercial carp (Cyprinus carpio L.) farmed in Poland. Non-specific immune response of the fish, vaccinated with oil-emulsified experimental vaccines containing formalin killed whole cells (WCs), formalin killed whole culture (WCt) or crude LPS (50 or 1250 microg per fish) were studied on days 7 and 30 after vaccination. Fish vaccinated for 30 days were challenged with the pathogen and mortalities recorded over 14 days. The cumulative mortalities were 10%, 0%, 20% and 20% in WCs, WCt, LPS-1250 and LPS-50 groups, respectively, whereas 70% fish died in the control group. Vaccinated fish showed significant increase of phagocytic activity (PA) and phagocytic index (PI). The total serum Ig (TSIg) level was significantly higher in most vaccinated fish groups than in control. Moreover, WCs and WCt induced significant increase of mucus lysozyme level in vaccinated fish.     

Approach velocity and impingement duration influences the mortality of juvenile Golden Perch (Macquaria ambigua) at a fish exclusion screen

Globally, the extraction and diversion of water from river systems has had substantial impacts on aquatic ecosystem health and ecological processes. One such impact is the entrainment of fish at pump offtakes that can result in vast quantities of fish being permanently removed from rivers. Exclusion screens to prevent fish entrainment at pump offtakes are therefore an important management consideration. In this study, impingement and subsequent injury and mortality of a juvenile freshwater perciform, Golden Perch (Macquaria ambigua), was assessed in the laboratory using a simulated fish exclusion screen under a range of velocities and impingement durations. A 2 mm wedge‐wire screen eliminated the entrainment of 44‐day‐old Golden Perch that were exposed to approach velocities between 0.05 and 0.3 m/s. However, impingement rates of Golden Perch increased significantly with increased approach velocities and rates of injury and mortality increased with impingement duration. Results from this study indicate the primary mechanisms to reduce fish loss at pump offtakes are to design pump offtakes, fitted with fish exclusion screens, which limit approach velocities or impingement duration. Further studies are required to examine a range of species with varying swimming ability at early life‐history stages. Such data will contribute to the growing body of knowledge that supports adaptive management plans to prevent fish loss at water offtake pumps.     

The relevance of size parameters as indicators of fishery exploitation in two West African reservoirs

Fish communities living within the artificial reservoirs of Manantali and Selingue in Mali are compared after the monitoring of small-scale fishery landings over 13 months (May 2002–June 2003). The fishing pressure constitutes the main difference of these two similar reservoirs. The effects of fishing on the structure of the fish communities are analyzed by using fish size spectra and derived indicators. In Selingue Reservoir, the fishing gears mostly target smaller species (mean length of 165 mm) than in Manantali Reservoir (mean length of 210 mm). Unlike in Selingue, the size structure does not change between seasons in Manantali. In Selingue, fishing practices that target the fish recruitment of the year constitute a structuring factor of the fish sizes observed in the catches. In spite of similar values of the slopes of the global fish communities’ size spectra between the two reservoirs, they clearly display an intense exploitation at Selingue. Then, size-based spectra indicators represent a potential tool for assessing the impact of fishing on fish communities in small-scale fisheries.     

应用鱼类完整性指数(FAII)评价长江口沿岸碎波带健康状况

基于2006年11月-2007年10月在长江口的13个站点的周年调查,探索了鱼类完整性指数（FAII）在河口水域鱼类栖息地环境评价中的应用。结果显示各站点FAII值介于0-46之间,表明碎波带健康状况全年处于一般到极差的水平。系统聚类（Hierarchical Cluster）将所有站点分为四组,第一组St.1,Sts.12-13;第二组为Sts.2- 3,St.5;第三组为St.6,St.11;第四组为St.4,Sts.7- 10。健康状况差的站点FAII值全年波动较大,由于夏季水温升高,部分站点出现大量的洄游性和海洋性种类,FAII值出现季节性的升高;其中河口外段的St.1,St.11-St.13的完整性等级分别在7月和8月达到一般水平。St.4,St.10因位于水源保护区外侧,St.9位于西沙湿地公园,受人为影响较小,这三个站点的FAII值相对比较稳定且在所有站位点中处于较高水平。FAII与Margalef丰富度指的周年变化有一定的相似性,但与Shannon-Wiener多样性指数的变化却有很大的差异。     

A holistic look at minimizing adverse environmental impact under Section 316(b) of the Clean Water Act

Section 316(b) of the Clean Water Act (CWA) requires that "the location, design, construction, and capacity of cooling water intake structures reflect the best technology available for minimizing adverse environmental impact." As the U.S. Environmental Protection Agency (EPA) develops new regulations to implement Section 316(b), much of the debate has centered on adverse impingement and entrainment impacts of cooling-water intake structures. Depending on the specific location and intake layout, once-through cooling systems withdrawing many millions of gallons of water per day can, to a varying degree, harm fish and other aquatic organisms in the water bodies from which the cooling water is withdrawn. Therefore, opponents of once-through cooling systems have encouraged the EPA to require wet or dry cooling tower systems as the best technology available (BTA), without considering site-specific conditions. However, within the context of the broader scope of the CWA mandate, this focus seems too narrow. Therefore, this article examines the phrase "minimizing adverse environmental impact" in a holistic light. Emphasis is placed on the analysis of the terms "environmental" and "minimizing." Congress chose "environmental" in lieu of other more narrowly focused terms like "impingement and entrainment," "water quality," or "aquatic life." In this light, BTA for cooling-water intake structures must minimize the entire suite of environmental impacts, as opposed to just those associated with impingement and entrainment. Wet and dry cooling tower systems work well to minimize entrainment and impingement, but they introduce other equally important impacts because they impose an energy penalty on the power output of the generating unit. The energy penalty results from a reduction in plant operating efficiency and an increase in internal power consumption. As a consequence of the energy penalty, power companies must generate additional electricity to achieve the same net output. This added production leads to additional environmental impacts associated with extraction and processing of the fuel, air emissions from burning the fuel, and additional evaporation of freshwater supplies during the cooling process. Wet towers also require the use of toxic biocides that are subsequently discharged or disposed. The other term under consideration, "minimizing," does not equal "eliminating." Technologies may be available to minimize but not totally eliminate adverse environmental impacts.     

Distribution,abundance and food of commercial fish in the Black Volta and the Volta man-made lake in Ghana during its first period of filling (1964–1966). I. Mormyridae

Summary As analysed from fish landings for different parts of the Volta Lake, mormyrids have not established themselves in the new lacustrine environment during the first two years after the formation of the Lake. While they form a substantial part of the fish catches in the Black Volta, especially during the dry season, in the Lake they occur regularly in low numbers, only in the northern parts influenced by the river waters. The major factor limiting the establishment of mormyrids in the Volta Lake may be the deoxygenation of the deep water layers, but other factors may also be involved.All mormyrids from the Black Volta are insectivorous and this tendency has not substantially changed in the Lake. Species utilizing to any great extent rheophilic bottom fauna in the Black Volta have an especially low occurrence in Volta Lake catches.