Seasonal stratification in fish culture and irrigation reservoirs: potential dangers for fish culture

Dual-purpose reservoirs for field irrigation and fish culture are characterized by the simultaneous (a) increase in standing crop biomass and feeds during the fish culture period and (b) decrease of water level due to irrigation. This management practice affects stratification, which in turn affects water quality and may affect the fish stocked. To study the limnology of dual-purpose reservoirs, an extensive sampling programme including automatic continuous recording and manual water sampling in deep and shallow reservoirs was carried out. This paper describes limnological changes during the week in which a 3 month long seasonal stratification ended and fish kills occurred. Management implications of stratification are also discussed. The data presented are the first continuous records of this process in this particular type of water body.     

Water quality and freshwater fish culture intensification: the Israeli example

Abstract. During the development of freshwater fish culture in Israel there has been a trend toward intensification, which has been accelerated in the last years with the introduction of new culture systems: deep reservoirs, fish cages and mechanically stirred ponds. In the present paper, the main processes affecting water quality variability in outdoor systems with increasing fish culture intensification levels are presented. The analysed systems are semi-intensive shallow ponds with different organic loading, semi-intensive shallow ponds with different fish species combinations, semi-intensive deep reservoirs, and intensive mechanically stirred ponds. The examples are from experiments conducted at the Fish and Aquaculture Research Station Dor and from follow-ups at fish farms.     

黄河三角洲水质污染对淡水鱼类多样性的影响

1993-1997年对黄河三角洲8条河流、3个水库和1个湖泊水质连续5年进行了监测，1996-1997年对淡水鱼类多样性开展了同步系统调查，水质评价结果：6条河流为重污染，2条河流为严重污染，2个水库轻污染，麻大湖严重污染，淡水鱼类共鉴定出102种和亚种，隶属于9目17科65属，占山东省炎水鱼类总种数的89%。水质污染已志致鱼类多样性减低，少数河流鱼类绝迹。     

生物操纵技术在西北地区水库水体富营养化防治应用前景

西北地区是我国最干旱的地区,水库在西北地区的工农业生产、渔业养殖、水利调度、防洪以及气候调节等方面发挥着极为重要的作用。外源污染的过量输入、来水量下降和补水不足、气温升高、生态系统受损是西北地区水库水体富营养化的成因。应对西北地区不同类型水库进行基础调查,了解水库水质状况和营养水平,有针对性的实施投放鱼食性鱼类或人工控制浮游动物食性鱼类、投放滤食性鱼类、投放螺、蚌、贝类等水生动物和人工调控水生植被等生物操纵技术。     

Trophometric index: a predictor for fish density, biomass and production in Mediterranean reservoirs in Spain

Abstract  A trophometric index (TMI) is proposed to estimate fish density, biomass and production in Mediterranean reservoirs. It consists of simple and integrated environmental variables such as the form index ( IF  =  S / V ), the volume percentage of water with sufficient oxygen to sustain fish life, conductivity, chlorophyll a concentration and perimeter, the synergic effect of which explains the fish structure and accounts for the functioning of the ecosystems. This index was tested in eight reservoirs in the Guadalquivir River basin, showing a good fit with a potential model for fish density and a linear model for fish biomass and production ( P  < 0.01; r ² > 0.8). The TMI is a valuable tool for evaluating fishery production in Mediterranean reservoirs and allows these to be classified by type for better management and evaluation in the framework of the European Water Directive.     

Hydroacoustical parameters of fish in reservoirs with contrasting levels of eutrophication

Hydroacoustical estimation of fish abundance and distribution is performed in three reservoirs that are characterised by different levels of eutrophication. The Biosonics 101 dual beam echosounder with a frequency of 420 kHz and the ESP software for acoustical data analyses are used. A clear dependence between fish density and the level of eutrophication is observed. In the mesotrophic Solina reservoir, fish abundance is over an order of magnitude lower than that in the eutrophic Dobczyce and Sulejów reservoirs. Fish length distributions have different shapes in the three reservoirs, which indicates the changes in fish size structure due to eutrophication; however, the mean target strength of fish does not differ significantly. These results suggest that hydroacoustically collected data may help to assess the ecological state of inland waters and may be used together with other methods in monitoring the water quality.     

A low prevalence of mycobacteria in freshwater fish from water reservoirs, ponds and farms

A survey of the occurrence of mycobacteria was conducted from 717 freshwater fish (25 species) in two water reservoirs, five ponds and two farms in the Czech Republic. A total of 2182 tissue samples from these fish were examined using the conventional culture method. Thirteen mycobacterial isolates were obtained from 12 (1.7%) fish belonging to nine species. Isolates were identified using sequence analysis of the 16SrRNA gene as: Mycobacterium algericum, M. fortuitum, M. gordonae, M. insubricum, M. kumamotonense, M. nonchromogenicum, two isolates of M. peregrinum, M. terrae and M. triplex. Mycobacteria were isolated more frequently from fish skin and gills than from internal organs or muscles.     

Fisheries and cage culture of three reservoirs in west Java, Indonesia; a case study of ambitious development and resulting interactions

Abstract The interactions between cage culture and wild fishery activities in three Indonesian reservoirs, Saguling, Cirata and Jatiluhur, of the greater Ciratum watershed, West Java, were evaluated using historical data and interviews with cage culture operators. In all three reservoirs, cage culture of common carp, Cyprinus carpio L., and later of common carp and Nile tilapia, Oreochromis niloticus (L.), were encouraged as an alternative livelihood for persons displaced by the impoundment. Currently, a two‐net culture system, locally known as ‘lapis dua’, in which in the inner cage (7 × 7 × 3 m) is used for common carp culture and the outer cage (7 × 7 × 5/7 m) is stocked with Nile tilapia, is practised. On average each cage is stocked with approximately 100 kg fingerlings each of common carp and Nile tilapia. The numbers of cages and production of cultured fish has increased in the reservoirs, but total and per cage production began to decline from about 1995 in Saguling from 2200 kg cage^?1 in 1989 to <500 kg cage^?1 in 2002, and in Cirata from a peak of approximately 2300 kg cage^?1 in 1995 to approximately 400 kg cage^?1 in 2002. In Jatiluhur, which has a considerably lower cage density, total fish production and production per cage has increased since 2000, and currently is approximately 4000 kg cage^?1, close to production in the early years of cage culture activities. The cage culture operations also resulted in substantial nutrient loading, estimated at 3.2, 15.2 and 3.1 t of nitrogen and 134, 636 and 128 kg of phosphorous per year in the maximum years of production for Saguling, Cirata and Jatiluhur reservoirs, respectively. In later years, when cage culture production was high, fish kills occurred in the cages, and in Jatiluhur reservoir coincided with a dramatic decline in wild fishery catches. An attempt is made to determine the maximum number of cages for each of the reservoirs that will bring long‐term sustainability of cage culture operations and the wild fisheries in the three reservoirs.     

Aquacultureagriculture systems integration: an Australian prospective

The concept of integrating aquaculture with irrigated farming systems was evaluated in three projects in the GoulburnMurray Irrigation District (GMID) in south-eastern Australia. (1) Semi-intensive cage culture trials using silver perch, Bidyanus bidyanus (Mitchell), were undertaken in a range of irrigated farming systems: irrigation supply channels; groundwater supplies; and on-farm storage dams. Survival and growth of fish under these conditions were comparable to fish reared in conventional aquaculture ponds. However, poor water quality at some sites reduced survival and growth. (2) A study was undertaken to assess the feasibility of the cage culture of silver perch and rainbow trout, Oncorhynchus mykiss (Walbaum), in three irrigation water storage reservoirs. Conditions within each reservoir, particularly water quality, wind and wave action, and cage fouling, varied considerably, and influenced fish growth and survival. (3) Mariculture trials were undertaken in two saline groundwater evaporation basins, which were part of an integrated agriforestry and salt reclamation system. The species tested included two oyster, two prawn and nine fish species. Some species exhibited exceptional survival and growth rates under trial conditions. These projects indicate that the concept of integrating aquaculture with existing irrigated farming systems has the potential to enhance productivity, water use efficiency and overall environmental sustainability in the GMID.     

Small tropical reservoirs and fish cage culture: a pilot study conducted in Machakos district,Kenya

The findings of this study provide useful insights into the key aspects of fish cage farming to be considered during setting and overall management of multi-purpose water resources so as to maximise their aquacultural potential. The study was conducted in Machakos District, Kenya, to characterise limnochemistry and algal composition of three small man-made reservoirs Ngeki, Ngei and Kavovi, used for cage culture of Nile tilapia (Oreochromis niloticus). In Ngeki, the open water was compared with areas in between the cages and significant differences in dissolved oxygen were found. For N, P and chlorophyll-a, no differences were noticed. In all the reservoirs, temporal variations were noticed for all parameters except NO₃N and NH₄N. Peak concentrations of nutrients occurred during the rainy season with lower values in the dry season (below detectable limits for SRP). All reservoirs were classified as hyper-eutrophic with a strong positive correlation between chlorophyll-a and TP. Algal abundances changed with season. Chlorophyta dominated at the start of the rainy season, while cyanobacteria prevailed at the onset of thermal stratification. Diatoms prevailed in the dry season but were notably absent in the rainy season. It was concluded that all the reservoirs are suitable for cage culture of Nile tilapia, but this should be undertaken with caution considering critical periods when anoxic conditions may occur.     

The culture-based fisheries in small, farmer-managed reservoirs in two Provinces of northern Vietnam: an evaluation based on three production cycles

In this paper the results of a study conducted on the culture‐based fisheries in small (ranging from 2 to 160 ha), farmer‐managed reservoirs in YenBai and ThaiNguyen Provinces in the northern highland region of Vietnam, for the production cycles of 1997/98, 98/99 and 99/00 are presented. The small reservoirs are leased to small farmers by the provincial authorities for fishery activities, and all lessees adopt culture‐based fisheries when fingerlings of grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix), bighead carp (Aristichthys nobilis), common carp (Cyprinus carpio) and mrigal (Cirrihinus mrigala) are stocked between March and mid‐April each year and harvested, using large seine nets, after approximately 11–12 months. The mean yields from reservoirs in YenBai and ThaiNguyen Provinces in 97/98, 98/99 and 99/00 production cycles were 251, 332 and 253, and 331, 372 and 210 kg ha^?1 respectively. There were major differences in the fish productivity in the reservoirs in the two Provinces, and in a reservoir between culture cycles. The stocking strategies appeared to be rather ad hoc, being determined by the availability of seed stock and the financial status of the lessees. Accordingly, there was no apparent consistent trend in the improvement of yields from the culture‐based fishery practice throughout the growth cycles. The fish yields in reservoirs in each Province were significantly related to reservoir area (exponentially) and to mean weight of stocked fish and conductivity (logarithmically). Of the stocked fish, the highest returns were obtained with mrigal and bighead carp, which collectively contributed > 50% to the harvest. The return from common carp was the lowest. The mean growth rate of grass carp (2.7 g day^?1), followed by bighead carp (2.0 g day^?1) was the highest in reservoirs in YenBai Province, bighead carp (4.0 g day^?1) followed by grass carp (3.2 g day^?1) was the highest in ThaiNguyen Province. The seed stocked on average accounted for 65% and 48% of the total operating costs in YenBai and ThaiNguyen Provinces, and the mean cost:benefit ratio of the culture‐based fishery in the two Provinces was 0.35 and 0.37 respectively. The culture‐based fishery on average contributed about 28% to the gross income of a farmer lessee.     

Carrying capacity and potential environmental impact of fish farming in the cascade reservoirs of the Paranapanema River,Brazil

The objective of this study was to simulate changes in water quality standards caused by the installation of aquaculture parks for caged fish farming in the eight large artificial reservoirs in the Paranapanema River according to the different scenarios of technical and legal limitations: (i) occupancy of 1% of the total surface of the reservoirs and (ii) occupancy according to the environmental carrying capacity. For water quality modelling, these two scenarios were simulated to determine the trophic state index (TSI) of each reservoir. Based on the total area of all reservoirs in the first scenario, the fish farm facilities would occupy 18.3 km² and have an annual fish production of an estimated 513 thousand MT. However, because of limitations in the carrying capacity, the annual production in the second scenario would be 98 thousand MT and the fish farm facilities would occupy 3.5 km². Simulating the TSI for the first scenario, approximately 75% of the total area of all reservoirs was estimated to change from oligo or mesotrophic conditions to eutrophic, supereutrophic and hypereutrophic conditions, and four reservoirs may become completely eutrophic (Canoas 2, Canoas 1, Taquaruçu and Rosana). For the second scenario, however, eutrophic areas accounted for less than 30% of the total, although the Taquaruçu and Rosana reservoirs were still at risk of total eutrophication. These results indicate as well‐intentioned legislation can have unintended environmental consequences in dynamic social–ecological aquaculture systems as in the case of large reservoirs in the Paranapanema River.     

Chronological age and reservoir characteristics as predictors of trait composition in Neotropical reservoir fish assemblages

One of the main impacts on aquatic environments is the alteration of flow regime, usually caused by dam construction. This impact changes the dynamics and functioning of the environment. We aimed to evaluate changes in the composition of functional traits of fish assemblages from 29 reservoirs of different chronological ages. We assessed if there were any alterations in trophic state of these reservoirs according to their ages (chronological variable). Then, we evaluated the relationship between functional traits and environmental/chronological variables. Results showed that reservoir age is a predictor of fish assemblage functional traits composition. In older reservoirs, there was a predominance of omnivorous species, with multiple spawning and parental care. However, herbivorous species, with total spawning and medium size, had their abundance reduced. Also, it was possible to identify the influence of depth and water retention time on the composition of functional traits. By showing that although age has an influence on composition, the intrinsic characteristics of each reservoir are very important in evaluating the impacts of these projects. Therefore, the findings presented provide insights into what may happen to functional traits of fish assemblages with ageing of reservoirs.     

Factors contributing to the outcome of stocking programmes in Cuban reserviors

Abstract In less-developed countries, fisheries enhancement using stocking is a common practice to manage reservoirs for biomass production. In many cases, there appears to be little control over whether the stocking activity is appropriate or necessary. Cuban reservoir fisheries have been usually managed to maximize fish biomass. Blue tilapia have been introduced and supplemented in reservoirs, and Chinese carp are introduced and maintained in reservoirs throughout the entire island. Supplemental stocking with introduced fish species is a usual practice to manage large and medium-sized reservoirs. Small and very small reservoirs have been managed as semi-intensively enhanced fisheries with carp and tilapia stocking. The main purposes of the present paper are to study the factors contributing to the outcome of stocking programmes in reservoirs and to test the hypotheses that supplementary stocking for self-sustained fish populations usually cannot contribute to increase fish yield. Yield and stocking data by groups of fish species were available for Cuban reservoirs. Total fish yield was only slightly related to total fish stocking density for the complete set of reservoirs. However, this result was mainly because of the relationship between total yield and cyprinid stocking for semi-intensively-used reservoirs. Tilapia yield was not significantly related to tilapia stocking for both extensively and semi-intensively-used reservoirs. However, yield and stocking for cyprinids were highly related for both reservoir subsets. Therefore, cyprinid stocking was effective in certain reservoirs, but tilapia stocking was not effective in any reservoir. Moreover, tilapia stocking was a superfluous activity for reservoirs where tilapia have an adequate natural reproduction cycle.     

Food Production and Water Conservation in a Recirculating Aquaponic System in Saudi Arabia at Different Ratios of Fish Feed to Plants

An indoor aquaponic system (i.e., the integration of fish culture with hydroponic plant production in a recirculating setup) was operated for maximizing water reuse and year-round intensive food production (Nile tilapia, Oreochromis niloticus , and leaf lettuce) at different fish feed to plants ratios. The system consisted of a fish culture component, solid removal component, and hydroponic component comprising six long channels with floating styrofoam rafts for holding plants. Fish culture effluents flowed by gravity from the fish culture component to the solid removal component and then to the hydroponic component. Effluents were collected in a sump from which a 1-horsepower in-line pump recirculated the water back to the fish culture tanks at a rate of about 250 L/min. The hydroponic component performed as biofilter and effectively managed the water quality. Fish production was staggered to harvest one of the four fish tanks at regular intervals when fish attained a minimum weight of 250 g. Out of the total eight harvests in 13 mo, net fish production per harvest averaged 33.5 kg/m³ of water with an overall water consumption of 320 L/kg of fish produced along with the production of leaf lettuce at 42 heads/m² of hydroponic surface area. Only 1.4% of the total system water was added daily to compensate the evaporation and transpiration losses. A ratio of 56 g fish feed/m² of hydroponic surface effectively controlled nutrient buildup in the effluents. However, plant density could be decreased from 42 to 25–30 plants/m² to produce a better quality lettuce.     

天津大银鱼仔、幼鱼的食性

１９９５年３月至５月对天津地区北塘、黄港二库、东丽水库的大银鱼仔、幼鱼的食性进行了分析研究。成鱼为肉食性鱼类,但在仔、幼鱼阶段主要摄食浮游生物中的原生动物,肠道中未找到枝角类,仔、幼鱼阶段的食性不是专一的,随水体中饵料生物组成的变化而变化。     

梯级开发下金沙江下游鱼类群落结构特征及环境驱动因子

为了探明梯级电站开发下金沙江下游鱼类群落的结构特征及主要环境驱动因子,于2017年对春季和秋季金沙江下游尚未建成的乌东德和白鹤滩水电站江段以及已下闸蓄水的溪洛渡和向家坝水电站江段应用多网目复合刺网进行了鱼类群落定量研究,同时运用多种统计分析方法分析了鱼类多样性特征以及鱼类群落与环境因子的关系。研究发现仍保持正常流水未成库区的乌东德和白鹤滩江段鱼类群落与已成库区的溪洛渡和向家坝江段有着明显的差异。在仍为峡谷激流型生境的江段,鱼类组成以土著特有鱼类为主,优势种为喜流水的圆口铜鱼C. guichenoti、泉水鱼P. procheilus、犁头鳅L. fimbriata;而在已蓄水的库区江段,鱼类组成多为长江中下游常见种类,优势种为喜静水缓流的?H. leucisculus、飘鱼P. sinensis、似鱎T. wwinhonis。应用典范对应分析对鱼类群落与环境因子做了相关分析,发现影响金沙江下游鱼类群落的主要环境驱动因子包括水深、总固体悬浮物、电导率、pH和水温等。这些研究结果为制定金沙江下游鱼类种质资源和生物多样性保护的相关管理政策提供了基础与支撑。     

Culture-based fisheries in non-perennial reservoirs in Sri Lanka: production and relative performance of stocked species

Abstract In Sri Lanka, there is a great potential for the development of culture-based fisheries because of the availability of around 12 000 non-perennial reservoirs in the dry zone (<187 cm annual rainfall) of the island. These reservoirs fill during the north-east monsoonal period in October to December and almost completely dry up during August to October. As these non-perennial reservoirs are highly productive, hatchery-reared fish fingerlings can be stocked to develop culture-based fisheries during the water retention period of 7–9 months. The present study was conducted in 32 non-perennial reservoirs in five administrative districts in Sri Lanka. These reservoirs were stocked with fingerlings of Indian (catla Catla catla Hamilton and rohu Labeo rohita Hamilton) and Chinese (bighead carp Aristichthys nobilis Richardson) major carps, common carp Cyprinus carpio L., genetically improved farmed tilapia (GIFT) strain of Nile tilapia, Oreochromis niloticus (L.) and post-larvae of giant freshwater prawn, Macrobrachium rosenbergii De Man, at three different species combinations and overall stocking densities (SD) ranging from 218 to 3902 fingerlings ha⁻¹, during the 2002–2003 culture cycle. Of the 32 reservoirs stocked, reliable data on harvest were obtained from 25 reservoirs. Fish yield ranged from 53 to 1801 kg ha⁻¹ and the yields of non-perennial reservoirs in southern region were significantly (P < 0.05) higher than those in the northern region. Naturally-recruited snakehead species contributed the catches in northern reservoirs. Fish yield was curvilinearly related to reservoir area (P < 0.05), and a negative second order relationship was evident between SD and yield (P < 0.05). Chlorophyll-a and fish yield exhibited a positive second order relationship (P < 0.01). Bighead carp yield impacted positively on the total yield (P < 0.05), whereas snakehead yield impact was negative. Bighead carp, common carp and rohu appear suitable for poly-culture in non-perennial reservoirs. GIFT strain O. niloticus had the lowest specific growth rate among stocked species and freshwater prawn had a low return.