16 resultados para 180 days remaining
em Aquatic Commons
Resumo:
This dissertation: 1) determines the factor(s) responsible for spawning induction in NematosteJla vectensis; 2) isolates, describes, and documents the source of jelly from egg masses of N. vectensis; and 3) describes N. vectensis' early development. Namatostella vectensis were maintained on a 7-day mussel feeding/water change regime over 159 days. Within 36 hours of mussel feeding/water change. 69.1% of females and 78.5% of males spawned reliably. Through manipulation of feeding, water change, oxygen and nitrogenous waste concentrations, spawning induction was found to be triggered by the oxygen concentration associated with water change, and not by feeding. Ammonia, anemones' major waste product, inhibited this induction in a concentration-dependent manner. Female N. vectensis release eggs in a persistent jellied egg mass which is unique among the Actiniaria. The major component of this egg mass jelly was a positive periodic acid-Schiffs staining, 39.5-40.5 kD glycoprotein. Antibodies developed in rabbits against this glycoprotein bound to jelly of intact egg masses and to granules (~ 2.8 IJm in diameter) present in female anemone mesenteries and their associated filaments. Antibodies did not label male tissues. Nematostella vecfensis embryos underwent first karyokinesis -60 minutes following the addition of sperm to eggs. Second nuclear division took place, followed by first cleavage, 90-120 minutes later. Each of the 4 blastomeres that resulted from first cleavage contained a single nucleus. Arrangement of these blastomeres ranged from radial to pseudospiral. Embryonic development was both asynchronous and holoblastic. Following formation of the 4-cell stage, 71% of embryos proceeded to cleave again to form an 8-cell stage. In each of the remaining 29% of embryos, a fusion of from 2-4 blastomeres resulted in 4 possible patterns which had no affect on either cleavage interval timing or subsequent development. The fusion event was not due to ooplasmic segregation. Blastomeres isolated from 4-celled embryos were regulative and developed into normal planula larvae and juvenile anemones that were 1/4 the size of those that developed from intact 4-celled embryos. Embryos exhibiting the fusion phenomenon were examined at the fine structural level. The fusion phenomenon resulted in formation of a secondary syncytium and was not a mere compaction of blastomeres.
Resumo:
Details are given of a study carried out in Nigeria, to introduce the practice of fish-cum-rice culture, using Sarotherodon galilaeus. Two plots each measuring 360m super(2) were used for this study and were compared with the farmer's two plots measuring 300m super(2) and 350m super(2). The plots were modified and had two central canals. Rice seedlings were transplanted into the plots after 19 days using a planting distance of 20 x 20cm. Three rice seedlings were planted per hole, using rice variety FARO 40, and grown for 90 days. About 240 and 180 S. galilaeus fingerlings of mean weight of 30g and 26g were stocked in the two experimental plots, respectively. They were fed with pelleted feed of 25% C.P. and monitored for 100 days. A yield of 22.8kg was obtained in plot A while 15.66kg was obtained in plot B. A rice yield of 250kg (i.e 5 bags) was obtained in each of the plots. The results obtained were compared with plots with no fish
Resumo:
The surface temperature of Windermere has been recorded by the staff of the Freshwater Biological Association on every weekday (with a few minor exceptions) since 11 January 1933. This publication presents this information in a form which can easily be used by individual research workers. There are 43 tables (1 for each year, 1933-1975) which give the data, expressed as degree-days centigrade. The tables show for each month the number of degree-days above each temperature from 0 degree C to the highest recorded, at 1 degree C intervals. Mean temperatures are obtained by dividing the number of degree-days over 0 degree C by the relevant number of days. The advantage of degree-days rather than mean temperatures is that degree-days are additive so data for any desired periods may be combined quickly and simply. Seasonal results for spring, summer, autumn and winter are presented in tabular form, as are selected totals for comparisons between years. Further tables give the mean temperature in each month of the year, and the frequency distributions of monthly mean temperatures.
Resumo:
Navigation and surveying formed a connecting link, as it were, between what was getting to be called the “Old Navy” and what was soon to take shape as a “New Navy.” Seamanship, as an art of special character, was beginning to change its form with the passing of sail power and its supersession by the steam engine; while requiring in its new form no less ability and practiced judgment in the handling of large ships, it offered a diminished field for expertness in craft of only moderate size and speed among officers doing simple watch duty not in company with other ships; and, therefore, it was threatened with a materially lessened regard.
Resumo:
A reoccurring goal listed during the creation of Marine Protected Areas (MPAs) is to return the region to a former state. However, limited data is available that describes or characterizes this former condition. Data collected from ecosystems with comparatively limited anthropogenic impacts, can provide invaluable information in suggesting what former states may have looked like. One example is the Flower Garden Banks National Marine Sanctuary which is located 180 kilometers off the coast of Texas. These relatively isolated and pristine banks are capped by substantial scleractinian coral communities, forming excellent habitat for over 200 species of fish. While fishing is permitted, it is limited by difficulty of access. In 2006, NOAA’s Biogeography Branch, in collaboration with the Sanctuary, initiated the first quantitative assessment of fish resources throughout the diveable portions of the Sanctuary. The sampling design and methodologies employed were identical to those that the Branch has utilized in other more impacted regions of the US Caribbean. Initial analyses reveal that fish density and species richness at the Sanctuary were almost two times greater than that found within the US Caribbean and biomass was approximately six times higher. This was due in large part to the presence of sizeable piscivores of the genera Mycteroperca and Dermatolepis. The Sanctuary is one of few minimally impacted locations remaining within the Tropical Western Atlantic. As such, these findings should be considered when attempting to establish a former state or evaluate effectiveness of an MPA in meeting its management goals.
Resumo:
We have studied the reproductive biology of the goldlined seabream (Rhabdosargus sarba) in the lower Swan River Estuary in Western Australia, focusing particularly on elucidating the factors influencing the duration, timing, and frequency of spawning and on determining potential annual fecundity. Our results demonstrate that 1) Rhabdosargus sarba has indeterminate fecundity, 2) oocyte hydration commences soon after dusk (ca. 18:30 h) and is complete by ca. 01:30−04:30 h and 3) fish with ovaries containing migratory nucleus oocytes, hydrated oocytes, or postovulatory follicles were caught between July and November. However, in July and August, their prevalence was low, whereas that of fish with ovaries containing substantial numbers of atretic yolk granule oocytes was high. Thus, spawning activity did not start to peak until September (early spring), when salinities were rising markedly from their winter minima. The prevalence of spawning was positively correlated with tidal height and was greatest on days when the tide changed from flood to ebb at ca. 06:00 h, i.e., just after spawning had ceased. Because our estimate of the average daily prevalence of spawning by females during the spawning season (July to November) was 36.5%, individual females were estimated to spawn, on average, at intervals of about 2.7 days and thus about 45 times during that period. Therefore, because female R. sarba with total lengths of 180, 220, and 260 mm were estimated to have batch fecundities of about 4500, 7700, and 12,400 eggs, respectively, they had potential annual fecundities of about 204,300, 346,100 and 557,500 eggs, respectively. Because spawning occurs just prior to strong ebb tides, the eggs of R. sarba are likely to be transported out of the estuary into coastal waters where salinities remain at ca. 35‰. Such downstream transport would account for the fact that, although R. sarba exhibits substantial spawning activity in the lower Swan River Estuary, few of its early juveniles are recruited into the nearshore shallow waters of this estuary.
Resumo:
An experiment was conducted for a period of 28 days using 7-day old C. batrachus larvae of initial total length (±S.D.) of 7.4 ± 0.49 mm and weight (±S.D.) of 2.8 ± 0.75 mg. Five test diets viz. diets I, II, III, IV and V were prepared. Diet I was formulated using 30% fish meal (FM), 20% soybean meal (SM) and 20% Baker's yeast (BY), diet III using 15% FM, 20% SM, 15% cotton seed meal and 30% BY and diet IV using 20% FM, 30% BY and 30% powdered milk. The remaining two diets (diets II and V) were prepared using minced clam meat (96%) and BY (90%) respectively as the sole source of protein. Three replications were used for each treatment. The larvae fed on diet II exhibited significantly (P<0.05) better length gain and specific growth rate (SGR) than those of the larvae fed on diet III and there was no significant difference among the length gain and SGR of the larvae fed on diet I,II,IV and V. The larvae fed on diet II also showed significantly better weight gain and survival than those of the larvae fed on other diets. There was no significant difference between the condition factor of the larvae fed on diet II and IV. However, the larvae fed on diet II showed better condition factor than those of the larvae fed on other diets.
Resumo:
Four zoeal stages and one megalopal stage were identified in laboratory reared semiterrestrial mangrove sesarmine crab Chasmagnathus convexus. At an average salinity and temperature of 20±1% and 19.2±0.2°C, the megalopa was attained 24 days after hatching. Morphologically, the first zoae of C. convexz1s is very similar to those of other species of the genus Chasmagnathus as well as species of the genus Helice, in that view all share the following characteristics: lateral spine on the carapace, three pairs of setae on the posterior margin of the telson furca, one plus five setae on the endopod of the maxillule, and two plus two setae on the endopod of the maxilla. The differences between the first zoea and megalopa of and those of its congeners are discussed.
Resumo:
Studies were undertaken to evaluate the quality changes in freshwater giant prawn, Macrobrachium rosenbergii during various storage conditions of handling and preservation and producing safe and quality products. The samples kept in ice immediately after catch with head-on and head-less condition were found to be acceptable for 6 days and 7 days, respectively. Delaying of icing considerably shortened the shelf-life. The pH value increased from 6.36 to 8.0 after 10 days in ice. The initial average TVB-N value of sample increased from below 10 mg/100 g to 25 mg/100 g with the lapse of storage period. The Ca++ ATPase activity in presence of 0.1M KCl slightly decreased at the end of 10 days of ice storage. Immediately after harvest, initial aerobic plate count (APC) was 2.88x10^6 CFU/g which gradually increased to 1.12x10^8 CFU/g after 6 days in ice storage and showed early signs of spoilage. Initial bacterial genera in the prawn iced at 0 hours were comprised of Coryneform (22.21 %), Bacillus (7.40%), Micrococcus (11.11 %), Achromobacter (48.14%), Flavobacterium/Cytophaga (7.40%), Pseudomonas (3.70%) and Aeromonas (3.70%). During ice storage Coryneforms and Bacillus were always dominating along with less prominent ones - Micrococcus, Achromobacter and Flavobacterium. Studies were conducted on the stability of myofibrillar protein of M. rosenbergii under different storage and pH conditions. The influence of a wide range of pH on the remaining Ca++ ATPase activity of M. rosenbergii muscle myofibrils after storage at -20°C for 2 days, at 0°C for 2 days and at 35°C for 30 minutes demonstrated that ATPase activities were lower in acidic and alkaline pH regions and the activity remained relatively high. Mg++ ATPase activities both in presence and absence of Ca++ remained high at neutral pH compared to those of acidic and alkaline region. The solubility of myofibrillar protein decreased gradually both in acidic and alkaline pH regions. The study also examined the bacteriological quality of freshly harvested M. rosenbergii, pond sediment and pond water from four commercial freshwater prawn farms at Fulpur and Tarakanda upazilas in the district of Mymensingh. The study included aerobic plate count (APC), total coliform count, detection, isolation and identification of suspected public health hazard bacteria and their seasonal variation, salt tolerance test, antibiotic sensitivity test of the isolates and washing effect of chlorinated water on the bacterial load in the prawn samples. APC in sediment soil and water of the farm and gill and hepatopancreas of freshly harvested prawns varied considerably among the farms and between summer and winter season. The range of coliform count in water, gill and hepatopancreas ranged between 6 - 2.8x10^2 CFU/ml, 1.2x10^2 - 3.32x10^2 CFU/g and 1.43x10^2 - 3.89 x10^3 CFU/g, respectively. No coliform was detected in pond sediment sample. Suspected health hazard bacteria isolated and identified from pond sediment, water, gill and hepatopancreas included Streptococcus, Bacillus, Escherichia coli, Klebsialla, Salmonella, Staphylococcus, Pseudomonas and Aeromonas. Bacillus, Salmonella and Staphyloccus [sic], and were found to be highly salt tolerant and capable of growing at 10% NaCl. The antibiotic discs with different concentration of antibiotics were used for the sensitivity test. The organisms were found to be most sensitive against Tetracyclin and Gentamycin.
Resumo:
The first spawnings were obtained 12 days after ablation with 4 spawners yielding 784,000 eggs and a harvest of 250,000 P SUB-10 fry. Survival of females after 1 month was approximately 30%. Mortalities were mostly due to handling stress during the regular ovarian samplings as well as disease frm the accumulated excess feeds on the bottom of the tank. Male survival could not be recorded because of transfers to other tanks and addition of new stocks. Development seemed to peak 3 weeks after ablation. The average number of eggs per ablated spawner was 120,000. However, many of the partially spawned females were removed from the spawning tanks the following day so that remaining eggs released in the next 2 to 3 days could not be recorded. Estimate of the average number of eggs per ablated spawner is 120,000-150,000 in contrast to 500,000 per wild spawner. However, the low production cost more than compensates for the difference. Fry reared in the Wet Laboratory were used for experiments, mostly on feeding. Therefore, survival at harvest is not to be taken as a reflection of stock quality. Although fewer in number, larvae from ablated prawns are as healthy in terms of vigor in swimming and feeding as those from wild females. Most mortalities are due to inability to molt caused by lower water temperatures and inadequate feeding.
Resumo:
To what extent spent P. monodon females can remature and spawn successive broods is an important question in terms of recycling spawners in a commercially viable operation. Corollary to this is the quantity and quality of fry from rematured females in comparison to those from first spawning. Of 347 experimental females, only 10.1% had a second spawning, and 1.4% a third spawning. To a large degree the low rate of rematuration is due to high spawner mortality - average survival period after spawning was only 6 days in a sample of 176 spawners. It took an average of 23 days after ablation for a prawn with undeveloped ovaries to mature and spawn. An ablated female may have another spawning in as little as 5 days after the previous one. Average fecundity was 180,000 eggs per second spawning, and 140,000 eggs per third spawning. The average number of eggs from first spawning ablated females was 110-120,000. Hatching rate was lower for rematuration: 44% for second spawnings, and 35% for third spawnings, as compared to 64% for first maturation.
Resumo:
A study was undertaken to find out the impact of ten days fishing ban in the major spawning grounds of hilsa during October to December. The study revealed a positive impact of fishing ban during spawning season on reproduction success of hilsa. Proportionate distribution of male and female hilsa also showed a significant level of distribution in and around the spawning grounds where the ratio was 35:65. Percent of oozing hilsa during fishing ban period in the spawning grounds was observed 1.61%. About 5% spent hilsa was observed in the fish landing centers and was compared with the data of Global Environment Facility (GEF) and Bangladesh Fisheries Research Institute (BFRI) studies and was found about 2.80-3.57 times higher than that of the findings of 2002 and 2003. Estimated egg production value showed about 46,800 Kg of eggs could have been produced that indicating a positive impact of 10 days fishing ban in spawning season. Abundance of higher percentages of gravid hilsa was found which were not available in the same quantity and condition in the non-fishing ban period. During the present investigation, fairly higher amount of spent hilsa and juveniles were also observed in the spawning grounds. Along with the jatka fry, spawn and fries of other fishes were also found in higher quantity than the previous years and thus it is assumed that fishing ban also might have positive impact on the successful breeding of other fishes. Overall, the fishing ban was found effective for successful breeding of hilsa.
Resumo:
The acute toxicity and effects of diazinon on some haematological parameters of kutum (Rutilus frisii kutum, Kamensky, 1901) weighing 613.33 g±157.06 g were studied under static water quality conditions at 15°C ± 2ºC in winter and spring 2009. The effective physical and chemical parameters of water were pH= 7-8.2, dh= 300mg/L (caco3), DO= 7 ppm and T= 15°C±2ºC. The first test was primarily to determine the effects of acute toxicity (LC5096 h) of the agricultural toxicant diazinon (emulsion 60%) on kutum male brood stocks. For this purpose, 4 treatments were used to test toxicity; each treatment was repeated in 3 tanks with 9 fish per treatment and with 180 litres water capacity. After obtaining the final results, the information was analysed statistically with Probit version 1.5 (USEPA, 1985), and we determined the LC10, LC50 and LC90 values at 24 hours, 48 hours, 72 hours and 96 hours; the maximum allowable concentration value (LC5096 h divided by 10) (TRC, 1984); and the degree of toxicity. The second stage of testing consists of four treatments: LC0= 0 as experimental treatment, treatment A with a concentration of LC1= 0.107 mg/L, treatment B with concentration of LC5= 0.157 mg/L, treatment C with concentration of MAC value= 0.04 mg/L. Male brood stocks of kutum were treated with these concentrations for 45 days. Experiments were carried out under static conditions based on the standard TRC, 1984 method over 45 days. Our results show that long-term exposure to diazinon causes a decrease in the erythrocyte count (RBC), haemoglobin (Hb), haematocrit (PCV), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), leucocyte count (WBC), lymphocyte, testosterone, iron (Fe), sodium (Na), lactate dehydrogenase (LDH), and cholinesterase (CHeS). In addition, diazinon also causes an increase in prolymphocyte, aspartate aminotransferase (AST), cholesterol, alkaline phosphatase (ALP) and adrenaline (P<0.05). There are no significant effects on monocyte, eosinophil, magnesium (Mg), chloride (Cl), glucose (BS), urea (BUN), uric acid (U.A), triglyceride (TG), calcium (Ca), albumin (Alb), total protein (TP), cortisol, noradrenaline and high density lipoprotein (HDL) levels in kutum male brood stocks (P>0.05). Pathology results showed toxin diazinon no effect on average weight and fish body length, the average weight of heart, brain, spleen, liver, kidney and liver index but caueses decrease of gonad weigth and gonad index and also, cause complications of tissue necrosis, vascular congestion, inflammation in the liver, a sharp reduction in the number of glomeruli, necrosis, vascular congestion and haemorage in the kidney, capsule thickening and fibrosis, atrophy, vascular congestion, macrophages release increased, increasing sediment Hemosiderine and thickening of artery walls in the spleen, atrophy, fibrosis and necrosis in testis , vascular congestion, increased distance between the myocardium and fibrous string in heart and neuronal loss, vascular congestion and edema in the brain of kutum male brood stocks.