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1.
An analysis of the food of 274 specimens of Tilapia aurea (Steindachner), which had been collected in Lake Kinneret, showed that this species is mainly a zooplankton consumer.A study of the quantitative dynamics of the food components in the course of a year has proved that the species in question feeds more intensely in spring, this being the time when zooplankton forms are more abundant in the water of the lake. Vegetable detritus, mixed with plankton and benthos forms, served as additional and alternative food.The lack of clearly positive degree of food component selectivity, as well as the low values of the intestine repletion index and of the condition coefficient, account for the slowness in growth of Tilapia aurea in Lake Kinneret.The low values of the growth and feeding indices are due, according to the authors, to the pressure brought to bear by the other local fish species, which are competitors for the same food. 相似文献
2.
Pepietta Spataru 《Aquaculture (Amsterdam, Netherlands)》1978,14(4):327-338
Analysis of the gut content of 329 specimens of T. zillii (Cichlidae) collected from Lake Kinneret, has shown great variation in the sorts of food.A study of seasonal dynamics has proved the prevalence in the food of Chironomida pupae (Diptera) in winter and spring and of zooplankton forms in summer and autumn. The additional food consisted of the various groups of algae, the most frequently found being Cyanophyta (100%) and Pyrrophyta (64.16%). An extremely voraceous species, it consumes — while searching for its preferred food — anything that comes its way in the water: algae, scraps of macrophytes, autochthonous and allochthonous insects, and forms of benthic origin, such as Nematoda, Ostracoda, Porifera and Chironomida (larvae).The satiation index is high (between 4.08 and 5.63), in contradiction to the low values of the coefficient of condition (between 3.05 and 3.51), and with the slow rate of growth in Lake Kinneret. The main food of Tilapia zillii, consists of arthropod species with a chitin content (which is eliminated unchanged) of more than 50% of the total weight, and this may account for the poor exploitation of the trophic base.This species of fish may be considered as being detrimental to others (i.e. commercially important species) because of its successful competition for food, and not, as is often incorrectly assumed, because it is an aggressive consumer of their spawn and fry. 相似文献
3.
M. Bar-Ilan 《Aquaculture (Amsterdam, Netherlands)》1975,5(1):85-89
As early as 1962, two mugil species were introduced into Lake Kinneret, in annual quantities of about 1.5·106 fry, taken from rivulets flowing into the Mediterranean. These were collected by means of specially devised beach seines. Stocking activity of mugil reached its peak in 1967, when 5.6·106 fry were introduced into the Lake.The total number of mugil fry introduced in these 11 years, was 19·106 specimen.The result was a yield of nearly 1 800 tons of mugil during this time, consisting of only two species: Mugil capito and Mugil cephalus. The fish reached a weight of 1–4 kg. Costs incurred in the stocking activity were less than 10% of the revenue of the yield.Up to the present, each million of small mugil fry, produced 100 tons of mugil catch, and large schools of mugil are as yet living and growing in the lake, so that additional large yields of mugil in the catch can be expected.Pollution of rivulets and great competition over the remaining fry, concentrating in the few rivulets left unpolluted, decrease the expectation for large quantities of fry for restocking. The main solution to this problem is induced spawning. 相似文献
4.
The total catch of prawns from the Egyptian Mediterranean waters decreased substantially from 7.23 thousand t in 1962 to 1.06 thousand t in 1976. To compensate for this loss, Lake Quarun, an inland closed saline basin in Middle Egypt, was selected for seeding and culture of prawn fry.The bionomics of Penaeus kerathurus, such as composition and distribution of the catch, growth, length-weight relationship, maturity stages of the females, and food, were investigated to confirm the suitability of Lake Quarun for marine prawns. The study showed that P. kerathurus have an approximate monthly growth rate of 10.0 mm for females and 5.0 mm for males (condition factor 0.62 and 0.58, respectively). The growth rates and condition factors in Lake Quarun did not vary much from those observed for stocks in the Mediterranean Sea. P. kerathurus became abundant in the southwest section of Lake Quarun. Futther studies are recommended to increase prawn propagation in the lake, but the preliminary results indicate that an inland lake fishery for marine prawns can be established. 相似文献
5.
The waters of Lake Quarun have undergone severe chemical changes in the last 50 years. Salinity has increased progressively and is now 38‰ in some regions of the lake. Tilapia zillii is the only species that has not been affected by the salinity increase. Mullet fry have been stocked in the lake since 1928. There has been a progressive increase in the average total production of mullet from 0.45 tons (1929–1932) to 128.25 tons (1966–1969), and to 291.67 tons (1975/76–1978/79). Length and age composition of mullets in Lake Quarun were studied. The growth in length and weight of Mugil cephalus showed that the fish were in better condition in Lake Quarun than in other coastal areas of Egypt.It is recommended that studies should continue to improve survival of transplanted mullet fry into the lake, and on the artificial propagation of mullets on site. 相似文献
6.
Bartosz Mysłowski Remigiusz Panicz Jacek Sadowski Paulina Hofsoe 《Aquaculture International》2013,21(4):739-750
The aim of this study was to characterize whitefish and peled populations in Miedwie Lake by means of the genetic analysis of ND-1 (NADH dehydrogenase 1) gene and the ITS-1 (internal transcribed spacer 1) region in order to distinguish native forms from whitefish/peled hybrids. In the analysis, archival specimens of Coregonus lavaretus maraena from the Berlin Museum für Naturkunde were used. Genetic analysis performed with the aid of MEGA 4.0 software explicitly indicated that samples from Miedwie Lake belonged entirely to a native (rapidly growing) form of whitefish. Furthermore, the conducted research has also provided crucial information for a C. lavaretus management program for Miedwie Lake. 相似文献
7.
1. Economic development in arid regions is closely linked to efficient use of limited water resources. As such, management and conservation of these water resources requires concurrent optimization of the interrelationships between supply quantity and resource quality. 2. Multiple uses of water resources generate conflicting needs within management, with different uses requiring objective characterization of quality for different management scenarios and goals. 3. A sound management programme needs close interactions between water policy makers, managers, users, engineers and limnologists, and thus needs a common language that can transcend the boundaries of the individual fields. 4. This paper describes a system of water quality indices and standards designed for conservation and sustainable management of Lake Kinneret (Sea of Galilee), Israel, based on observed variability in various chemical and biological parameters during a 25‐year period (1969–1992). Such a system can form a common language which can then be used as a tool for optimal management. 5. This system of water quality indices (a) includes both traditional limnological parameters (plant nutrients, chlorophyll, primary production) and engineering parameters (coliform bacteria, turbidity), (b) is acceptable to all parties involved in lake management, and (c) is easily adaptable to different management scenarios and to management‐induced changes in ecosystem functioning. 6. Analysis of variability in these water quality parameters in Lake Kinneret during 1994–1999 when the lake was showing signs of destabilization highlights the usefulness and limitations of this system. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
8.
Lake Taihu is the third largest freshwater lake in China and has provided local communities with valuable fisheries for centuries. However, we have only a limited knowledge of its ecosystem. In this study, a trophic model was constructed for the Lake Taihu ecosystem. This model was used to evaluate and analyze the food web structure and other properties of this ecosystem using data covering the period from 1991 to 1995. Using the model, we evaluated the impacts on local fisheries of various management scenarios comprising two basic management regimes: (1) setting fishing mortality for the top predator (large culters, Erythroculter mongolicus and Erythroculter ilishaeformis) to 0, 0.3, 0.6, 0.9 and 1.2, and (2) adjusting overall fishing effort to 0.25, 0.5, 0.75 and 1.25 times the current level. For both scenarios, fishery profit and cost were evaluated to provide an understanding of how components of the ecosystem interact. We identified possible causes of fishery overexploitation in the lake ecosystem and described the necessity of developing ecosystem-based management. The results showed that Lake Taihu had six theoretical trophic levels (TLs), with the trophic flows primarily occurring through the first five TLs. System properties such as transfer efficiency, Finn's index, Finn's mean length, connectance index, system omnivory index, primary production/respiration ratio, and net primary production all indicated that Lake Taihu was an immature, fairly simple ecosystem in which a relatively low fraction of total primary production was utilized. At the same time, the ecosystem was also experiencing high fishing pressure. Yet despite this, the low ascendency index (25.9%) and high system overhead ratio (74.1%) indicated that the system was highly developed and relatively stable, a condition that might result from the high degree of recycling in the system. Among the harvesting strategies considered, a strategy of either decreasing the fishing mortality of the top predator (large culters) to 0.3 or, alternatively, reducing the overall effort on the system by a factor of 0.75 appeared to be most effective at increasing the efficiency of the fisheries. 相似文献
9.
Thea M. Edwards Hilary D. Miller Gunnar Toft Louis J. Guillette Jr. 《Fish physiology and biochemistry》2013,39(5):1165-1180
Sixteen monthly collections of adult male Gambusia holbrooki (eastern mosquitofish) were obtained from two lakes in central Florida, USA. Lake Woodruff and Lake Apopka are 36 miles apart, but differ in several environmental parameters. Compared with Lake Woodruff, Lake Apopka is warmer, more shallow in sampling areas (particularly during drought conditions; approximately 15–90 cm in Lake Apopka versus 60–120 cm in Lake Woodruff), more turbid, and more heavily contaminated with nutrients and industrial and agricultural chemicals. Here, we present detailed information on seasonal reproduction patterns in mosquitofish in their native range and compare patterns between fish from the two lakes. Male mosquitofish were reproductively active from spring through fall. Spermatogenesis, which is regulated in part by 11-ketotestosterone, ceased in October, and fish stored spermatozoa through the winter for immediate fertilization of offspring in the spring. Compared with Lake Woodruff, fish from Lake Apopka tended to be larger and have longer gonopodia and greater gonado- and hepato-somatic indices (GSI and HSI). High GSI in Apopka fish correlated with greater spermatid production, but fewer mature spermatozoa and either the same or lower sperm counts and sperm viability. Taken together, these observations suggest that differentiation of spermatids to spermatozoa is disrupted in Apopka fish, leading to reductions in fertility in some months. Delivery of sperm to females could also be affected in Apopka fish, which exhibit lower prevalence of efferent duct tissue in the testes during the summer. 相似文献
10.
Ahmet R. Oğuz 《Fish physiology and biochemistry》2018,44(1):227-233
Lake Van is one of the largest alkaline lakes worldwide and Lake Van Fish (Alburnus tarichi Güldenstädt, 1814) is the only vertebrate species inhabiting it. Lake Van Fish is an anadromous species that migrates to the streams (salinity 0.02%, pH 8.42) flowing into Lake Van (salinity 0.22%, pH 9.8) during the spawning period (April–July). Following spawning, fish return to Lake Van while larvae remain in fresh water. This study examined the development of osmoregulatory organs and the distribution of ionocytes in Lake Van Fish larvae adapting to the highly alkaline water characterizing the lake. Ionocytes were marked immunohistochemically and observed in whole mounts with immunofluorescence staining using the Na+/K+ ATPase antibody. Ionocytes were first identified in the yolk sac membrane and skin, and then in the gills, digestive tract, and kidneys of larvae. The number of ionocytes on yolk sac membrane and skin decreased during larval development, indicating ionocytes on these tissues have a role in larvae osmoregulation. Larvae hatched from eggs in stream waters die when transferred to Lake Van water but survived in lake water diluted with deionized water. Thus, larvae need to go through certain alterations at the cellular and organ levels in order to adapt to the conditions of Lake Van water, indicating they do not enter this lake immediately after hatching. 相似文献
11.
《Fisheries Research》2007,83(1-3):304-318
In 1986 a motorised, commercial gillnet fishery was introduced in Lake Tana, Ethiopia's largest lake (3050 km2) in addition to the artisanal, predominantly subsistence fishery conducted from reedboats. The three main species groups targeted by this fishery are a species flock of endemic, large Labeobarbus spp., African catfish (Clarias gariepinus) and Nile tilapia (Oreochromis niloticus). The commercial gillnet fisheries was monitored during 1991–1993 and in 2001 (CPUE, effort allocation, catch composition, yield) and the development of the stocks of the three species groups was determined using an experimental trawl program during 1991–1993 and 1999–2001.In 1991–1993 the vast majority of fishing activities took place in the southern Bahar Dar Gulf (71%). Each species group contributed roughly one third to the total catch. In 2001, 41% of the effort was allocated to the north-eastern shores of Lake Tana. Both the CPUE and the contribution of O. niloticus to the total catch had doubled. However, the proportion of large specimen (>50 cm TL C. gariepinus; >20 cm FL O. niloticus) in the trawl surveys decreased significantly. A three-fold decline in abundance of the anadromous Labeobarbus species occurred. The 15 large labeobarb species are long-lived, ecologically specialised endemics. The seven riverine spawning Labeobarbus species form aggregations in the river mouths in August–September, during which period they are targeted by the commercial gillnet fishery.A sharp decrease in abundance by ca. 75% of the migratory riverine spawning Labeobarbus species in the sublittoral and pelagic zones of the lake, areas where no fishing takes place and the collapse of juvenile Labeobarbus (between 5 and 18 cm FL: by 90%) during the 1990s suggest recruitment-overfishing. To prevent the possible extinction of the unique Labeobarbus species flock all fishing effort should be severely restricted near the river mouths and on the upstream spawning areas during August–September (peak breeding period) to protect the vulnerable spawning aggregations. 相似文献
12.
Triangle sail mussel (Hyriopsis cumingii) is the most important mussel species commercially exploited for freshwater pearl culture in China. Its genetic diversity
was studied among populations from the five largest freshwater lakes of China, Poyang Lake (PY), Dongting Lake (DT), Taihu
Lake (TH), Hongze Lake (HZ), and Chaohu Lake (CH), by the polymorphism of the inter-simple sequence repeats (ISSRs). Polymerase
chain reaction (PCR) detections showed that a total of 62 loci were amplified from eight primers; of those, 31.88%, 31.15%,
31.03%, 27.27% and 26.92%, respectively, were polymorphic in each of the five populations across all genotypes tested. The
average heterozygosities were 0.4747, 0.3274, 0.2366, 0.2099 and 0.2018 in each of these populations from PY, TH, DT, CH and
HZ, respectively. Phylogenic analyses showed that PY and TH populations clustered with CH and HZ and formed a group, while
the DT population on its own formed a separated branch. The smallest distance (0.0404) was scored between PY and TH populations,
indicative of their closest relationship; the biggest distance (0.2438) was found between PY and DT populations, suggesting
their greatest divergence. The present study provided genetic basis for managing mussel stocks from these lakes separately
to best preserve the genetic diversity of H. cumingii. On the other hand, since the population in PY displayed the highest genetic diversity, it may be used preferably in future
selective breeding to improve pearl yield and quality. 相似文献
13.
John Wimbush Marc E. Frischer Joseph W. Zarzynski Sandra A. Nierzwicki‐Bauer 《水产资源保护:海洋与淡水生态系统》2009,19(6):703-713
- 1. Since their introduction to North America, zebra mussels (Dreissena polymorpha) and quagga mussels (Dreissena rostriformis bugensis) have rapidly colonized North American fresh waters. Strategies for limiting the economic and ecological impacts of zebra mussels exist, but there are few examples where once zebra mussels have invaded a natural body of water they have been removed or managed without the use of ecologically destructive methods. The first successful attempt to eradicate a colonizing population of zebra mussels using SCUBA is reported here. Studies were conducted in Lake George, NY.
- 2. Since zebra mussel larvae had been detected prior to the discovery of adults in Lake George, a comprehensive management programme for zebra mussels was in place when mussels were found in 1999, at a single location in the southern part of the Lake (Lake George Village site). Efforts were quickly launched to remove as many mussels as possible by SCUBA with the intent of minimizing the risk of the population reproducing and establishing a permanent presence in the Lake.
- 3. Population size at the discovery site was initially estimated at fewer than 30000 animals. Between 1999 and 2007 more than 21000 animals were removed from the site, over 90% of them shortly after the colony was discovered. Continued monitoring of the site for larvae, recruitment, and growth suggests that the animals have not successfully reproduced since the project began. Since detection at the Lake George Village site, six separate colonizing populations at other locations in the lake were found and similar removal efforts appear to be having comparable success.
- 4. This study demonstrates that the combination of early detection, suboptimal habitat, proactive establishment of a rapid response and management plan, and cooperation of a comprehensive network of stakeholders can prevent a successful zebra mussel invasion.Copyright © 2009 John Wiley & Sons, Ltd.
14.
The expression of selected genes linked to metabolic homeostasis in obese pansteatitis‐suffering Mozambique tilapia,Oreochromis mossambicus (Peters) 
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下载免费PDF全文 J C Truter J H van Wyk P J Oberholster A‐M Botha W J Luus‐Powell 《Journal of fish diseases》2016,39(1):69-85
The Oreochromis mossambicus (Peters) population inhabiting Lake Loskop, South Africa, is characterized by a high incidence of obesity and pansteatitis. We investigated potential links between the impaired health of Lake Loskop O. mossambicus and the endocrine system by assessing the expression of selected genes associated with the thyroid and adrenal endocrine axes as well as peroxisome proliferator‐activated receptor gamma (pparg). Moreover, contaminant‐induced thyroid and/or metabolic modulation in Lake Loskop water was evaluated using juvenile O. mossambicus in laboratory exposures. The expression of thyroid hormone receptor alpha (thra) and type 2 deiodinase (dio2) was higher in Lake Loskop O. mossambicus than fish from another population, suggesting a degree of thyroid disruption. The altered gene expression may be a consequence, rather than cause of obesity. Expression of dio2 and pparg was higher in juvenile O. mossambicus exposed to unfiltered compared to filtered lake water, and our data suggest fasting as causative factor. Micro‐organism abundance can therefore be a confounding factor in studies applying molecular markers to test for thyroid modulation by environmental waters. Pansteatitis was not a significant source of variance in the expression of any of the genes investigated, suggesting that the disease is not associated with disrupted endocrine signalling. 相似文献
15.
The phytoplanktivorous silver carp is an important biomanipulation fish to control cyanobacterial blooms and is also a food fish with the greatest production in China. The accumulation of the hepatotoxic microcystins (MCs) determined by LC-MS in various organs of silver carp was studied monthly in Lake Taihu dominated by toxic Microcystis aeruginosa. Average recoveries of spiked fish samples were 78% for MC-RR and 81% for MC-LR. The highest content of MCs was found in the intestine (97.48 μg g− 1 DW), followed by liver (6.84 μg g− 1 DW), kidney (4.88 μg g− 1 DW) and blood (1.54 μg g− 1 DW), and the annual mean MC content was in the order of intestine > liver > kidney > blood > muscle > spleen > gallbladder > gill. Silver carp could effectively ingest toxic Microcystis cells (up to 84.4% of total phytoplankton in gut contents), but showed fast growth (from 141 g to 1759 g in 1 year in mean weight). Silver carp accumulated less microcystins in liver than other animals in the same site or other fish from different water bodies at similar level of toxin ingestion. There was possible inhibition of the transportation of the most toxic MC-LR across the gutwall. Muscle of silver carp in Lake Taihu should not be consumed during period of dense Microcystis blooms while viscera were risky for consumption in more months. 相似文献
16.
Estimating rates of mortality is important for assessing stocks and for effectively managing seafood resources. This study reports the first estimates of rates of instantaneous fishing mortality (F) and natural mortality (M) for the commercially important school prawn, Metapenaeus macleayi. Replicated tag-recapture experiments were conducted on two stocks (Clarence River and Wallis Lake) to estimate the catchability coefficient (q) and F, whilst M was estimated from meta-analyses. Experiments were conducted across spatial and temporal scales to consider variability between stocks and variability between fisheries targeting this resource. The catchability coefficient was fitted to tag-recapture data in a population model across a range of M values (0.001-0.025 per day) and average daily F values were calculated. Values of q ranged between 2.03E−04 and 5.43E−02 and, 1.29E−04 and 3.41E−03 for the Clarence River and Wallis Lake stocks, respectively. Average daily F ranged between 2.86E−03 and 1.69 for the Clarence stock and 1.71E−03 and 3.44E−02 for the Wallis stock. With one exception (the November 2004 experiment) there were no differences in q and F values between experiments conducted on the Wallis Lake stock. For the Clarence stock values of q and F varied between years and within years. Factors thought to contribute to this variability were changes in prawn behaviour, differences in sizes of prawns tagged between experiments and differences in the survival of tagged prawns. The catchability coefficient for the Clarence River stock was weakly correlated to greater rates of river discharge. Estimates of F for the Wallis stock, the Clarence stock in 2004-05 and estimates of M were comparable to those reported for other penaeid fisheries world wide. There was no consistent pattern in comparisons of q and F values between the predominantly trawling operation of the Clarence River fishery and the seine netting of the fishery in Wallis Lake. 相似文献
17.
Nile tilapia, Oreochromis niloticus (L.), and channel catfish, Ictalurus punctatus (Rafinesque), were experimentally infected by immersion with three isolates (Lake, DL8O5 and MS91452) of Streptococcus sp. from diseased fish. To enhance infection, the lateral body surface of each fish was scraped prior to bacterial exposure. The Lake and DL8O5 isolates caused exophthalmia, ocular opacity and ocular haemorrhage in some tilapia. Histopathology of these fish revealed; meningitis; polyserositis of heart, liver, spleen, ovary and kidney; splenitis; ovaritis; and myocarditis. Isolate MS91452 induced only mild granulomas in spleen, kidney and ovary of tilapia. The Lake and DL8O5 isolates induced endophthalitis, Channel catfish infected with the Lake and DL805 isolates developed similar eye lesions to tilapia. Histologic lesions caused by all three isolates in channel catfish consisted of meningoencephalitis, mild myocarditis, splenitis and ovaritis, but these lesions were not as severe as in Nile tilapia. 相似文献
18.
19.
Success of the Introduction of the Fresh Water Clupeid Limnothrissa miodon (Boulenger) in Lake Kivu 总被引：1，自引：0，他引：1
The freshwater clupeid Limnothrissa miodon was transplanted with success from Lake Tanganyika to Lake Kivu during 1958–1960. An artisanal fishery to exploit the clupeid stock started in the beginning of 1980. Based on the results of this artisanal fishery a minimum sustained yield of 4,000 tons/year was estimated for the Rwandese territorial waters of Lake Kivu. Biological research revealed information about growth rate, condition factor K, fat content, migration, distribution and reproduction of Limnothrissa. An obvious relation was found between fat content and sexual activity with the seasonal fluctuations of plankton production. The main spawning peak coincided with a plankton bloom caused by the turnover of the lake at the end of the dry season in September. At that time a small percentage of the clupeids had fat in their body cavity. It is stated that horizontal migration is mainly induced by reproduction, while the vertical migration is determined by feeding habits. Socio-economic benefits of the artisanal fishery using trimarans and lift nets were compared with those of the semi-industrial purse seining. 相似文献
20.
The effects of crab aquaculture on the water and sediment quality and the pelagic and macrobenthic community of the adjacent reclamation area of Guchenghu Lake, Jiangsu Province were evaluated over two consecutive crop cycles from April 2010 to November 2011. The results indicated that most of the nutrient concentrations in both the water column and the sediment varied temporally and showed significant spatial differences. The peak values of most of the physico-chemical parameters measured were obtained during the summer or autumn, whereas the opposite result was observed for suspended solids. A higher zooplankton density and lower phytoplankton biomass were observed in ponds than in other sampling sites, whereas Cyanophyta (80 %), with Planktothrix rubescens as the dominant taxon, was predominant in the canal closest to the ponds. The benthic community was dominated by Bellamya aeruginosa in the ponds. Limnodrilus hoffmeisteri was the predominant species in the canal. Comparative analysis of the impact of crab culture showed that it produced a relatively low level of disturbance but introduced large quantities of nutrients and organic matter into the canal around the farming ponds. The introduction of these substances increased the risk that Guchenghu Lake would be affected by pollution. 相似文献