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1.
Abstract

This study assessed the potential to increase sales of farm‐raised tilapia through domestic restaurants in Nicaragua. Direct personal interviews were conducted with 118 restaurant managers. Information was collected on tilapia and other seafood sales, restaurant and market characteristics, attitudes towards tilapia characteristics, and willingness to add tilapia to the menu. The results from logit analyses suggest that the most promising restaurant markets for tilapia are older restaurants that offered a variety of food and those that served steaks. Larger restaurants that considered tilapia to be a high‐quality product and that offered “ceviche” (fish marinated in lime juice) on the menu were those that tended to sell tilapia. Tilapia farmers and processors in Nicaragua will need to guarantee and ensure the flavor, quality, and safety of their product, and promote these attributes.  相似文献   

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4.
With this study, we aimed to assess the safety of using Curcuma longa in fish feed. Juvenile Astyanax aff. bimaculatus (0.83 ± 0.04 g) were kept in 24 80‐L aquaria, at a density of 0.5 fish L?1 for 60 days. Six diets supplemented with 0.0, 20.0, 40.0, 60.0, 80.0 and 100.0 g kg?1 were evaluated. Histopathological analysis of the gills showed that there was an increasing linear effect of turmeric on the frequency of lamellar aneurysm, hypertrophy of mucous cells, oedema and necrosis. There was a quadratic effect of turmeric supplementation on the frequency of fusion and disruption of secondary lamellae, vacuolation and hypertrophy of the epithelial cells, and the estimated values to minimize these variables were 4.63, 25.93 and 24.46 g kg?1 respectively. There was a quadratic effect of turmeric on the gills index (IBRA), and the estimated value to minimize this index was 30.23 g kg?1. No effect of turmeric on the frequency of histopathological changes and organ index in fish liver was observed. Thus, we conclude that turmeric is not hepatotoxic for A. aff. bimaculatus; however, its use is safe at concentrations up to 30.23 g kg?1 diet as a function of its gill toxic effect at higher doses.  相似文献   

5.
Denitrification reactors have proven their functionality in commercial recirculation aquaculture systems (RAS). Nevertheless, clogging occurs due to the low hydraulic loads necessary to accomplish anoxic conditions for a successful denitrification process in RAS, which hampers the adjustment of stable working conditions within fixed bed denitrification reactors. Reactors working on the basis of activated sludge demand careful hydraulic control and/or complex configurations for sludge retention.To develop a low-maintenance denitrification reactor, an enclosed moving bed filter, driven by recirculation of the inherent, oxygen poor gas was designed. A Self cleaning Inherent gas Denitrification reactor (SID-reactor) of 0.65 m3, which offered a moving bed volume of 0.39 m3 was connected with a RAS of semi-industrial scale for pike perch (Sander lucioperca) production. This species indicates suboptimal environmental conditions (as e.g. NO3-N concentrations above approximately 68 mg l−1) by prompt reduction of the feed intake. In different experimental series, the SID-reactor was operated with denatured ethanol, methanol, acetic acid or glycerin as carbon sources and changing operational modes.Clogging was prevented by a 40 second inherent gas recirculation twice an hour, which provided continuous, maintenance free operation with marginal energy demand. With inlet (RAS) and outlet NO3-N concentrations in the range of 49 mg l−1 and 12 mg l−1, mean denitrification rates of 199 g to 235 g NO3-N per m3 moving bed volume and day were determined for all tested carbon sources. Negative effects on the feed intake of the reared pike perch were detected with all carbon sources except methanol. Changing the mode of operation to continuous circulation of the filter bed at inlet NO3-N concentrations of 26 mg l−1, the denitrification performance reached 451 g NO3-N per m3 moving bed volume and day. The SID-reactor allowed for the reduction of freshwater exchange in the pike perch RAS from 600 l to 70 l (−88%) and the sodium bicarbonate buffer from 182 g to 31 g (−83%) per kg of administered food. The easy and reliable operation of the SID-reactor could help to establish controlled denitrification as a routine purification step in RAS.  相似文献   

6.
One method of increasing the value of aquacultured product is to produce fillets that are fortified with minerals that are beneficial to human health – that is enhance the functionality of an already healthy product. A good candidate mineral in this regard is selenium (Se) which is of vital importance to normal metabolism in humans. In order to evaluate the dose response and tissue accumulation of supplemental dietary Se, a study was undertaken with hybrid striped bass (HSB). Animals were fed diets supplemented with either organic (0–3.2 mg kg?1 as SelPlex®) or inorganic (0.2 and 0.4 mg kg?1 as sodium selenite) Se for 6 weeks. Because basal fishmeal‐based diets contained 1.22 mg Se kg?1, doses of Se delivered equated to 1.22–4.42 mg kg?1. At trial end, greatest weight gain was observed in fish receiving 0.2 mg Se kg?1, irrespective of form (organic/inorganic). Se accumulation in HSB liver and fillet revealed a classical dose‐response once a threshold level of 0.2 mg Se kg?1 was surpassed. Greatest tissue accumulation of Se was observed in fish fed the 3.2 mg Se kg?1 level (P > 0.0001). A 100 g portion of Se‐enhanced HSB fillet would contain between 33 and 109 μg Se, amounting to a dietary intake of between 25 and 80 μg Se; a level that would satisfy present daily intake recommendations. Comparison of tissue Se levels indicated that the muscle provides a more conspicuous gauge of dietary Se dose‐response than does liver. Dietary treatments of between 0.4 and 1.6 mg organic Se kg?1 reduced (P < 0.024) plasma glutathione peroxidase (GSH‐Px) activity. No differences were observed in ceruloplasmin, lysozyme or GSH‐Px activities between organic and inorganic Se when delivered at the 0.2 mg Se kg?1 level. Ceruloplasmin, lysozyme and GSH‐Px levels were elevated (P ≥ 0.025) in fish fed the diet containing 0.4 mg inorganic Se kg?1.  相似文献   

7.
The proximity of many Pacific countries to seafood markets in Asia, the high value of species associated with coral reefs, and the increased demand for marine aquarium species, has prompted many nations in the region to investigate opportunities for coastal aquaculture. There are, however, several constraints to consider throughout much of the Pacific, including, transport problems, fragile ecosystems, lack of suitable sites, limited economies, and the effects of customary marine tenure on access to growout sites. To overcome these problems, coastal aquaculture in the Pacific will need to focus either on species of high value, or those that yield non-perishable products. Valuable industries have been established for pearl oysters, penaeid shrimps, and the microalgae, Spirulina, in tropical Australia, the French territories and Hawaii, whereas enterprises for cultured giant clams, milkfish (Chanos chanos) as tuna bait, the macroalgae, Eucheuma, and sponges are emerging in the small island developing states. Species demanded by the aquarium trade, groupers for live reef fish markets, tropical abalone (Haliotidae), mangrove crabs (Scylla spp.) and a variety of invertebrates as sources of bioactive compounds are promising new species for intensive farming. Aquaculture technology is being applied to the restocking and stock enhancement of valuable, sedentary species low in the food chain, and there are active programmes in several small island developing states to assess the scope for releasing cultured giant clams, trochus, green snail and sea cucumbers to replenish and enhance wild stocks. There is a growing awareness that the potential benefits of increased aquaculture, restocking and stock enhancement need to be balanced by the risks associated with culturing additional species, i.e. introduction of diseases, dilution of gene pools and increased biological interactions with other species, and that sustainable aquaculture, restocking and stock enhancement are most likely to be achieved with responsible application of technology and the use of indigenous species.  相似文献   

8.
The recent decreasing worldwide supplies of marine oils have forced the aquaculture industry to investigate alternative lipid sources for use in marine fish feeds. The aim of this study was to determine the impact of dietary replacement of fish oil by vegetable oils on gilthead seabream (Sparus aurata) growth performance, nutritive utilization, body composition, and fatty acid profile as well as feed cost. Two dietary vegetable oil (VO) mix blends (VO1 and VO2) in which: sunflower (SO), cottonseed (CO) and linseed (LO) for VO1 or soybean oil (SBO) for VO2, were tested as 60% fish oil (FO) substitutes versus the 100% FO control or reference diet (FO). Three iso-proteic (46% CP) and iso-lipidic (18%) experimental diets were hand fed, twice a day, 6 days a week to apparent visual satiety to triplicate groups of seabream growers (average initial weight, 130.9 ± 3.44 g), until fish reached market size (300–400 g/fish) after 20 weeks at mean ambient temperature 27.0 ± 1.8°C. All experimental diets were well accepted by seabream growers regardless of the different lipid sources used, as overall mean feed intake (FI) and daily intake (DFI) were not significantly different (P > 0.05) among dietary treatments. In terms of growth performance, fish fed VO1 diet (with LO) exhibited a relatively lower, but significant (P < 0.05), total weight gain (WG) than fish fed all FO diet (FO). However, mean value of WG of fish fed either vegetable oil-tested diet was nonsignificantly different. Feeding seabream growers vegetable oil (VO) diets (VO1 or VO2) had no significant effect on specific growth rate (SGR), daily weight index (DWI), or feed conversion ratio (FCR) among dietary treatments. Consumption of VO for 20 weeks did not significantly alter the major nutrient composition of fish, but the muscle fatty acid (FA) profile was significantly altered compared to the reference FO diet. Comparatively reduced levels of eicosapentaenoic acid (EPA) and docosahexaenoic acids (DHA), as well as elevated levels of linoleic and linolenic acids (LA and LNA) compared with fish fed the FO were noticed. In terms of economics, 17 or 20% reduction in Kg feed cost was obtained for diets VO1 or VO2, respectively. In terms of growth performance and cost, VO2 diet showed slight relative superiority over VO1 diet. However, in terms of liver structure morphology, VO1 diet (with LO) has resulted in less fat-infiltration and altered hepatic cells than VO2 (with SBO). As these traits do not affect yield or the price paid for the fish, VO2 diet has therefore been considered better than VO1 as complementary lipid sources for gilthead seabream grower diets.  相似文献   

9.
  • 1. Recently, the snails Hinia reticulatus, Cyclope neritea and Cerithium rupestre and the hermit crabs Diogenes pugilator and Clibanarius erythropus from warm European coastal waters have started to be commercially collected and traded.
  • 2. The average number (± standard deviation) of specimens captured per hour, by collectors were 475±237 for H. reticulatus, 363±112 for C. neritea, 384±173 for C. rupestre, 302±121 for D. pugilator and 210±54 for C. erythropus.
  • 3. All species survived well during transportation, were popular among aquarium hobbyists and attained high retail values, ranging from €0.90 to €4.00 per specimen.
  • 4. The collection and trade of these novel commercial species can either become a sole economic activity or an additional one for traditional fishermen and aquaculturists.
  • 5. Although no destructive collection techniques are employed, the lack of population biology studies and legislation regulating the capture of these species is a major problem in ensuring the sustainable use of these highly valuable marine resources.
  • 6. These species are currently mainly collected from natural parks areas protected by Portuguese and European Union designations.
Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

10.
Lake trout Salvelinus namaycush, lake whitefish Coregonus clupeaformis and cisco Coregonus artedi are salmonid fishes native to the Laurentian Great Lakes that spawn on rocky substrates in the fall and early winter. After comparing the locations of spawning habitat for these species in the main basin of Lake Huron with surficial substrates and the hypothesized locations of fast‐flowing Late Wisconsinan paleo‐ice streams, we hypothesize that much of the spawning habitat for these species in Lake Huron is the result of deposition and erosion by paleo‐ice streams. This hypothesis may represent a new framework for the identification and protection of spawning habitat for these native species, some of which are currently rare or extirpated in some of the Great Lakes. We further suggest that paleo‐ice streams may have been responsible for the creation of native salmonid spawning habitat elsewhere in the Great Lakes and in other glaciated landscapes.  相似文献   

11.
The River Bush (Northern Ireland) is an index river for the estimation of Atlantic salmon, Salmo salar L., stock size, population dynamics and marine survival rates. Marine survival estimates are based on the number of smolts counted at a trap 3.5 km upstream of the river outlet. The survival from release to coastal inshore waters for acoustic‐tagged smolts released at the Bushmills trap varied between 32% and 68%, with both year and brightness during river exit playing a significant role in explaining the variations in survival. This constitutes an important survival bottleneck. Contrary to true marine mortality, this significant loss of smolts in the river and nearshore environments could be reduced by focused management actions. More studies on other rivers, where smolts are enumerated above the head of tide, could further partition smolt and post‐smolt mortality, help differentiate true marine survival and help understand fluctuations in adult returns.  相似文献   

12.
Models of coccidiosis-monitoring known from literature are described. A suitable alternative of determining the coccidia status in a broiler population is the "modified Johnson-Reid method". This method makes a standardization of diagnostic finding and evaluation possible as well as a differentiated intestinal localization and the determination of coccidia incidence severity. In addition to the microscopic screening of the caecum contents--as described by Johnson-Reid--it appears necessary to take also swabs from parts of the duodenum and jejunum (near the Meckel's diverticulum). Subsequently this method is an important help for veterinarians working with broiler production, for diagnostic institutions as well as producers of anticoccidial agents, especially in regard to its documentation rate and the resulting consequences. In this way other diagnostic efficiency data in broiler production are significantly completed.  相似文献   

13.
Fish populations may spawn a vast number of offspring, while only a small and highly variable fraction of a new cohort survives long enough to enter into the fisheries as recruits. It is intuitive that the size and state of the spawning stock, the adult part of the fish population, is important for recruitment. Additionally, environmental conditions can greatly influence survival through vulnerable early life stages until recruitment. To understand what regulates recruitment, an essential part of fish population dynamics, it is thus necessary to explain the impact of fluctuations in both spawning stock and environment, including interactions. Here, we examine if the connection between the environment and recruitment is affected by the state of the spawning stock, including biomass, mean age and age diversity. Specifically, we re-evaluate the hypothesis stating that recruitment from a spawning stock dominated by young fish and few age classes is more vulnerable to environmental fluctuations. We expand upon earlier work on the Barents Sea stock of Atlantic cod, now with data series extended in time both backwards and forwards to cover the period 1922–2019. While our findings are correlative and cannot prove a specific cause and effect mechanism, they support earlier work and strengthen the evidence for the hypothesis above. Furthermore, this study supports that advice to fisheries management should include considerations of environmental status.  相似文献   

14.
The aim of this study was to evaluate the addition of artificial substrates in biofloc technology systems that are used for the intensive production of Litopenaeus vannamei. The experiment lasted 35 days. Tanks each with a useful volume of 800 L were filled with water containing bioflocs (25 % of the total volume) and filtered seawater. Three treatments with three replicates each were compared: (1) Ctrl (control), i.e., without the addition of artificial substrate, (2) 200 and (3) 400, with added artificial substrate equivalent to 200 and 400 % of the lateral area of the tanks, respectively. The shrimp with initial weight of 0.40 ± 0.15 g were stocked at a density of 300 shrimp/m2. Feed (Guabi/38 Active, Brazil) was supplied two times per day. The water quality parameters were suitable for the production of L. vannamei. The settleable solids (SS) were higher in the Ctrl treatment (82.1 ± 19 mL L?1) and differed statistically from the 200 and 400 treatments that presented average SS values below 10 mL L?1. The reuse of water with bioflocs accelerated nitrification in the tanks, and no significant differences were shown between tanks. The presence of biofilm did not interfere with ammonium or nitrite levels, but it did serve as a food source that optimized shrimp performance, as shown by higher final weights. More studies are needed to evaluate the circulation and mixing intensity effects of the substrates on water throughout the production cycle.  相似文献   

15.
ABSTRACT

A feeding experiment was conducted for 100 days to evaluate the suitability of soybean flour (SBF) as a partial or complete substitute for the protein supplied by herring fish meal (HFM) in diets for growth of red tilapia, Oreochromis niloticus ×O. mossambicus, fingerlings (mean weight of 0.65 g/fish) grown outdoors in concrete tanks. Five isonitrogenous and isocaloric diets containing 35% crude protein and 3.36 kcal of digestible energy (DE)/g of diet were formulated in which SBF replaced 0%, 25%, 50%, 75% and 100% of the protein supplied by HFM. Results demonstrated that SBF has good potential as a substitute protein source for up to 75% of the protein supplied by HFM (diet 4) in red tilapia diets with no significant (P>0.05) adverse effects on growth, feed efficiency, body composition, and apparent digestibility of protein compared to the HFM-based control diet. The highest growth performance and best economic efficiency of fish weight gain were obtained with fish fed diet contained 50% of the protein from HFM and the other 50% from SBF. Fish fed this diet had the highest weight gain (11.95 g/fish), percent increase in weight (1838%) and growth rate (0.120 g/day) among fish fed all the other test diets. The lowest feed efficiency and growth performances were shown in the fish fed diet containing SBF as a complete substitute for protein supplied by HFM. Fish fed this diet had the lowest weight gain (4.70 g/fish), percent increase in weight (723%) and growth rate (0.047 g/day) among fish fed all the other test diets. Survival of fish was not statistically different (P>0.05) among all treatments. The apparent protein digestibility values showed wide variation between diets, ranging from 70.13% to 82.12% and the values were remarkably high in fish fed SBF-based diets. At the conclusion of the study, substituting HFM-protein with SBF-protein in diets for red tilapia did not affect the final fish protein, ash and moisture contents, but lipid content was significantly higher (P <0.05) in fish fed diets in which SBF substituted for 50% or more of the protein supplied by HFM. Hematological characteristics of red tilapia were examined at the end of the study and the results showed that all the blood parameter values were within normal values for fish. Economic analysis of diets suggested the possibility of using SBF as an alternative source of protein in red tilapia diets.  相似文献   

16.
  • 1. The vegetation of disused and occasionally used navigation canals with acknowledged botanical conservation value was compared with that of major land‐drainage channels with potential conservation interest.
  • 2. Aquatic plant taxa and their abundance were recorded in 500‐m lengths of watercourses in East Yorkshire, north‐east England.
  • 3. There was substantial overlap between canals and drains in the aquatic plant species recorded (42 out of 66 taxa were found in both canals and drains) and ordination analysis (DECORANA) showed that there were not two distinct vegetation types: one for canals and one for drains.
  • 4. The aquatic plants recorded in both canals and drains probably largely originated from an eighteenth‐ and nineteenth‐century pre‐drainage marshland flora that has since been lost.
  • 5. The conservation value of the aquatic vegetation at canal sites (assessed as diversity, rarity and naturalness) was not significantly greater than at the drain sites.
  • 6. The canals are potentially threatened by restoration of navigation or increase in boat usage; a simplistic interpretation of the results is that potential losses in the conservation value of canals would be substituted by the flora of the drains.
  • 7. A more measured interpretation, however, is that the canals and drains should be regarded as parallel conservation resources. This is because some aquatic plant taxa with limited distribution at local, regional or national level were found only in canals while others were found only in drains.
  • 8. The results emphasize that evaluation of the botanical conservation value of artificial watercourses should include drains as well as canals; disused and lightly used navigation canals are widely recognized as of high conservation value whereas drains, being utilitarian landscape features, are more likely to be overlooked.
Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

17.

18.
Stock assessment modeling provides a means to estimate the population dynamics of invasive fishes and may do so despite data limitations. Blue catfish (Ictalurus furcatus) were introduced to the Chesapeake Bay watershed to support recreational fisheries but also consume species of conservation need and economic importance. To assess management tradeoffs, managers need to understand the current status of the population and anticipate future population abundance and trends. A Bayesian size-based stock assessment model was used to estimate blue catfish abundance, fishing mortality, and size structure over time (2001–2016) in the tidal James River. The model estimated population size increases until around 2006, with declines in total abundance after 2011 and large blue catfish (≥80 cm total length) after 2001. These first estimates of blue catfish population dynamics in the Chesapeake Bay region provide inputs for projection models to evaluate prospective management actions and identify monitoring needs.  相似文献   

19.
《水生生物资源》1999,12(5):335-342
Bioassays were carried out with the `blue diatom' Haslea ostrearia Simonsen, which is responsible for oyster greening during the fattening period of Crassostrea gigas Thunberg in oyster ponds. Samples of seawater were taken from two oyster ponds: one without oysters and the other with 20 oysters per m[sup2 ], maximal density allowed by the French AFNOR norm for `refinement'. The aims were to clarify the nutrient requirements of this diatom, also to elucidate the eventual influence of C. gigas at this density on the seawater fertility and to envisage the mass production of this diatom by pond fertilization. Examination of cell numeric densities at the end of bioassays allows us to conclude that silicate was the first limiting nutrient, closely followed by phosphate. Chlorophyll a concentrations led to different conclusions: phosphate was the first limiting factor, but after the seawater storage period in ponds, seawater quality evolved to a deficiency of nitrogen. Silicate addition increased cell division rate, and silicate depletion increased chl a synthesis for this species. Examination of nutrient assimilation ratios confirms that H. ostrearia requires a large amount of silicon. From these results, it was possible to prepare a N + P + Si simplified medium which has been tested in laboratory and field mesocosm conditions. In both conditions, similar results were observed: a significant increase in H. ostrearia cell concentrations and consequently an evolution up to the greening stage. Applications of this work are numerous; the principal permits us to envisage the production of this species in 25-m3 ponds, with the aim of allowing constant production of the greening phenomenon.  相似文献   

20.
Enhancement release has been proven effective in natural resources recovery of Chinese shrimp Fenneropenaeus chinensis in the last several decades in China,however,to assess the effectiveness of enhancement release,we still need to develop a high-efficient and easy-operational method to replace those physical-tagging release method with labor intensive,size-and number-limited.In the present study,single(with maternal known)parentage identification using eight simple sequence repeat(SSR)markers genotype fingerprint was used to trace Chinese shrimp released in Bohai Bay in2013.A total of 884 shrimp spawners were collected from two hatcheries in Tianjin City respectively after enhancement release of shrimp larvae in May 2013.A total of 844 shrimp samples were recaptured around the release location approximately 4 months after the shrimp larvae were released into the natural sea.Genotype data of 8 SSR loci of the 1,726 samples were used for maternal-offspring parentage identification using CEervus 3.0 software.The allele number in each locus ranged from 8 to 68 with an average value of 33.25,which produced the cumulative exclusion probability with one parent known of all these sight loci up to 99%.Among the 844 recaptured shrimp samples,448(♂:♀=212:232,gender information was lost for 4 samples)were successfully traced to their 337 maternal parents using a logarithm of odds(LOD)3.0 threshold.Among these 337 maternal parents,253 had a single offspring,62 had two offspring,18 had three offspring,3 had four offspring,and 1 had five offspring.For the first time,a large number of released shrimp were identified from recapture samples,and this study showed that it is possible to trace all released Chinese shrimp without using any type of physical tag in enhancement release activities.This not only means more precise recapture ratio assessment than ever expected,but also this method demonstrates an effective method for large-scale hatchery release as well as for organisms used in hatchery enhancement which are not suitable for physical tagging.  相似文献   

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