International Journal of Aquatic Biology
Volume:1 Issue: 3, Jun 2013

Skeletal deformities are a common problem in fish hatcheries and commercial farms that affect growth, development and survival as well as the market value of the final product. Among the nutritional components, phosphorus (P) and calcium (Ca) are of special interest as they are directly involved in the development and maintenance of the skeletal system. Hence, the present study was carried out to investigate the effects of dietary P and Ca on the skeletal deformity, growth and carcass composition the Caspian roach (Rutilus rutilus caspicus) larvae. In this study, six semi-purified diets were formulated. The diets A, B, C, D and E were supplemented with 0.0, 0.4, 0.8, 1.2 and 1.6% available P supplied as a 1:1mixture of NaH2Po4/KH2Po4. These five diets were supplemented with 1% Ca, supplied as CaCo3. Diets F was Ca-free and supplemented with 0.8% available P served as control level of P. Each diet was randomly assigned to triplicate groups of fish, and each group was stocked with 30 larvae and fed three times a day for 60 days. At the end experiment, there was no significant effect of dietary P (0 to 1.6%) or Ca (0 or 1%) supplementation on growth performance such as weight gain and FCR, carcass moisture, P and Ca. However, a significant difference found between treatments in carcass ash. Analysis of length, height and area of vertebrae in two regions of the vertebral column showed no significant difference between the dietary treatments. The skeletal abnormalities were highest incidence in the Caspian roach fed with a low P. Kyphosis placement of vertebrae was the most frequent abnormality.

Eutrophication is known as the most common problem in water bodies, caused by high concentrations of different nutrients leading to unbalanced growth of aquatic plants, among other symptoms. Hence, the possibility of eutrophication prediction can be beneficial to the sustainable management of these natural resources and create an opportunity to control their trophic conditions over time. A software package applied for generating these predictions is PAMOLARE with its different models (layers). The 1-Layer model of this method was selected to investigate the trophic condition of hypertrophic Zaribar lake. Prior to 2012, water samples were collected from six stations over a seven-year period. During the last year of this period, sediment samples were also collected. The concentrations of N and P were measured in the samples. The initial results showed that the Zaribar Lake is a hypertrophic water body. Applying the PAMOLARE 1-Layer model showed that this model was not powerful enough to predict the trophic changes in this hypertrophic water body and suggested that other models should be examined and modified for use in these ecosystems. Alternatively, it is necessary to improve the software for the prediction of eutrophication in hypertrophic water bodies.

Compensatory growth response and body composition of male sailfin molly, Poecilia latipinna subjected to short-term starvation and subsequent feeding were studied for 54 days. Four feeding schedules were used in this study: C, Control (were fed to apparent satiation throughout the experiment); T1, Treatment 1 (3 days Starvation and 6 days refeeding); T2, Treatment 2 (6 days Starvation and 12 days refeeding); T3, Treatment 3 (9 days Starvation and 18 days refeeding). At the end of the experiment, the starved fish gained a body weight comparable to that of the control fish. There were no differences in condition factor, specific growth rate and weight gain between the starved and control fish at the end of the experiment. Daily feed intake was significantly higher in T3 than that in the control. Short-term starvation did not influence protein, lipid and ash contents. Moisture content of T2 and T3 fish were significantly higher than those of T1 and control one. The results indicated that complete compensation occurred in the starved fish and that this species can tolerate to short term starvation without any significant effects on growth and feeding performance.

The present study investigated the efficiency of semi-closed incubator for hatching the Persian Sturgeon (Acipenser persicus) eggs. The incubator was basically designed according to Vase apparatus equipped with collector vessel, recirculation pump and aerator. 50% of water was changed every day. Triplicate groups of Persian Sturgeon (50 g) fertilized eggs were stocked in the incubators. Water flow rate was set not to harm the eggs and only circulating the eggs. The mortality of embryos and larvae at gasterula stage, formation of S-type heart stage, before hatching and hatching percent were recorded. Our results showed that semi-closed incubator circulated eggs completely and the probability of fungal infections was lower than that of flow through incubators. Since water used in semi-closed incubator is far less than that of flow through systems, thus semi-closed incubator may be a proper alternative for flow-through incubated systems in future.

Eight medicinal plants were assessed for antimicrobial activity against Lactococcus garvieae isolate obtained from diseased Oncorhynchus mykiss collected from rainbow trout fish farms in Iran. Lactococcus garvieae is among the major pathogens of a large number of fish species cultured in fresh and marine recirculating and net pen production systems. The antibacterial activity of the medicinal plants against L. garvieae was evaluated using disc diffusion, well diffusion and minimum inhibitory concentration. Results showed that the extracts and essential oils had a relatively high antibacterial activity against L. garvieae. Of the plants studied, the most active extracts were those from the methanol extract of Peganum harmala, the essential oil of Satureja bachtiarica, the ethanol extract of Juglans regia and Trachyspermum copticum with minimum inhibitory concentration (MIC) of 105, 126, 510 and 453 μg/ml, respectively. Conversely, some of the extracts such as Quercus branti Lindley andGlycyrrhiza glabra L. had lower activity against L. garvieae with MIC values of 978 and 920 μg/ml, respectively. Plant extracts as natural and environment-friendly compounds can be an important source of antibacterial agents against L. garvieae. They may be used for disinfection of instruments and rainbow trout raceways or treatment of the fish.

Pattern of feeding and reproduction of Amblypharyngodon mola (Hamilton, 1822) was studied in two floodplain lakes of North 24 Parganas districts of West Bengal in India during 2011. Results indicated that the fish exhibited a predominantly herbivorous diet with algae as the main content of gut. A long, thin walled, coiled gut and closely packed filamentous gill racker suited this feeding habit. Feeding intensity of the fish fluctuated throughout the year, males showing maximum intensity in June and females showing maximum intensity in February and November. Females outnumbered males (1.9:1) and were found as highly fecund with a calculated fecundity factor of 1445 ova g-1 of body weight. From the peak of gonado-somatic index and ova diameter it was revealed that A. mola apparently spawned only once during July in these floodplain lakes. It was concluded that improvement of ecosystem health of these two lakes were necessary to ensure spawning of the fish.

In the present study, the age- and sex-specific changes of various haematological and blood serum biochemical parameters of Beluga (Huso huso) were investigated. Blood samples were collected from 4-, 6-, 7-, and 8-year-old beluga (n = 7 for each sex and age). The specimens were fed at a rate of 0.5-3% body weight per day. AST and LDH levels in 7- and 8-year-old fish of both sexes were significantly higher (P<0.05) than those in 4- and 6-year-old individuals. The mean ALT were significantly different (P<0.05) in both sexes of 4-, 6-, and 7-year-old sturgeon. However, the 6-, 7-, and 8-year-old female sturgeon had higher ALP levels (P<0.05). Additionally, mean RBC, PCV, and Hb values were significantly higher (P<0.05) in 7- and 8-year-old females and males than the others. Two-tailed Pearson’s correlation between the biochemical and haematological parameters obtained for beluga sturgeon indicated significant positive correlations between AST and ALP, AST and LDH, ALP and LDH, RBC and Hb, RBC and PCV, Hb and PCV, MCH and MCHC, and MCV and MCH. However, significant negative correlations were found between RBC and MCV and MCH. These results suggest that the blood parameters of beluga are influenced by age- and sex-specific factors.

Diazinon and deltamethrin are common useful agricultural pesticides in the world. The present research compared the acute toxicity of diazinon and deltamethrin to tench larvae and fingerling. LC50 of 24 h, 48-h, 72 h and 96 h were determined using a probit. Fish samples (21 fish in each test group) were exposed to different concentrations of diazinon and deltamethrin (diazinon: for fingerling between1-20 ppm and larvae 0.25-2 ppm, deltamethrin: for fingerling between 0.01-0.2 ppm and larvae 0.0025-0.02) for 96 h and mortality were recorded. The LC50 96 h of diazinon for fingerlings and larvae were 6.77 and 0.63, respectively. The LC50 96 h of deltamethrin for fingerlings and larvae were 0.07 and 0.005 ppm, respectively. According to the results, larvae are more sensitive than fingerlings, LC50 values indicated that deltamethrin is more toxic than diazinon to Tinca tinca, so we suggest to use diazinon instead of deltamethrin in agriculture.