International Journal of Aquatic Biology
Volume:8 Issue: 5, Oct 2020

The study aimed to investigate the feeding ecology of a vulnerable freshwater puffer fish, Carinotetradon travancoricus from the Chalakudy river of Kerala, Western Ghats, a biodiversity hotspot of India. Fishes were sampled from October 2018 to September 2019. Stomach condition of the fishes showed the percentage of empty gut to be significantly higher during all seasons (P< 0.01). Feeding intensity depicted the fish to follow an ‘active’ feeding strategy (31.59±10.32%) during premonsoon season. Diet composition and relative length of gut analysis indicated that the fish during its early stages relied on an omnivorous diet however preferring autochthonous food materials such as insects (27.91%) and crustaceans (25.30%) during its adult stages. A perceptible variation in the feeding strategy associated with the spawning season of C. travancoricus was also noticed. During their spawning season (May-August), a greater preponderance towards animal matter (52.18%) was noticed in their diet. The results of gastrosomatic index indicated that feeding activity of C. travancoricus is considerably reduced (2.99) during the spawning period. The present study provides the baseline information on the feeding ecology of C. travancoricus which could be helpful to aquarists for breeding and rearing of this species in captivity and thereby reducing their fishing pressure in wild.

This study was undertaken to evaluate the effects of apple cider vinegar on growth performance and non-specific immune parameters of skin mucus (alkaline phosphatase, lysozyme and total protein) in common carp fingerlings. For this purpose, a total of 240 fish were stocked in twelve tanks for four treatment with three replications and fed by diets supplemented with 0, 1, 2 and 4 % apple cider vinegar for 60 days. The result showed that there was no significant difference in body weight increase (BWI), feed conversion ratio (FCR), specific growth rate (SGR) and condition factor (CF) among the treatments (P>0.05). The results revealed that there is no significant difference among skin mucus alkaline phosphatase of fish in all treatments. Although skin mucus lysozyme activity and total protein significantly increased by apple cider vinegar in comparison with the control group. The highest and lowest skin mucus lysozyme activity and total protein in common carp fingerlings were observed at 2% apple cider vinegar and control group, respectively. Therefore, apple cider vinegar improves skin mucus lysozyme activity and total protein and can be a good candidate for antibiotic replacement in common carp fingerlings.

This work provides the revised and updated checklist of the seagrass, Sri Lanka based on primary and secondary information. It is indeed to be an update the list of Seagrass species in Sri Lanka prepared by Abeywickrama and Arulgnanam (1991), which now been nearly three decades back. Further, several species names have been changed and there is concern that the nomenclature and distribution data are no longer accurate. Therefore, it is critical to identify the correct seagrasses species which are recorded in Sri Lanka in line with the updated global systematic records. More than forty (40) published pieces of literature, herbarium sheets in the National Herbarium and author’s personal observations since 2011 were reviewed. Sri Lanka belongs to the Indo-Pacific bioregion and 14 species have been recorded so far representing seven genera. They are Enhalus acoroides, Halophila beccarii, H. decipiens, H. ovalis, H. minor, H. ovata, H. stipulacea, Thalassia hemprichii, Cymodocea rotundata, C. serrulata, Halodule uninervis, H. pinifolia, Ruppia maritima, and Syringodium isoetifolium with the estimated extend to be 37,137 ha. Lack of evidences to cross check the identification of H. minor (only recorded in Negombo Lagoon) and H. ovata are main drawback. The composition and distribution of seagrasses along the coastal zone of Sri Lanka is yet to be established covering the entire coastline, which mainly due to a 30-year long civil conflict. Therefore, island wide comprehensive and systematic research studies could be positively contributed to fulfil the data gaps in future.

Fish epidermis functions as the first defense barrier against physical, chemical, and biological stressors. However, the effects of hand-stripping on fish mucosal immune responses have been hardly investigated. The present study investigated the effects of stripping procedures on skin mucosal immune responses of rainbow trout (Oncorhynchus mykiss) breeders. The skin mucus was sampled from six male and six female trout before and one week after the stripping handling. The results showed that stripping had significant effect on all parameters except protease activity, but gender had a significant effect only on the mucosal protease and alkaline phosphatase activity. The results did not show any effect of the interaction between stripping and gender on mucosal lysozyme activity. The data revealed that enzymatic activities of alkaline phosphatase, lysozyme, esterase, as well as the total immunoglobulin level and bactericidal activity were significantly reduced in the skin mucus of fish one week after the stripping. The reduction of immune parameters in the skin mucus could be related to immunosuppression caused by stripping stress which, in turn, might have made the fish more susceptible to microbial infections and diseases. Therefore, care should be taken during stripping to minimize the manipulation stress.

The role of different weight groups of the red tilapia on nutrient uptake of the feed supply was investigated in a recirculating aquaculture system (RAS). Five weight groups of red Tilapia viz. 20 (200.0), 40 (39.70.44), 80 (80.380.41), 120 (113.621.92), and 180 (177.671.81) g in triplicate treatments were designed. The studied nutrients uptake rates by red tilapia were significantly different (P<0.05) between the treatments. It was found that the red tilapia could assimilate 11.46% Fe, 13.43% Zn, 6.81% Mn, 3.55% Cu, 26.81 Ca %, 20.29% Mg, 32.53% N, 7.16% K and 15.98% P content of the feed supply during three weeks culture period. The specific growth rate (SGR) and food conversion ratio (FCR) indices showed significant differences (P<0.05) between the treatments. The highest growth rate was recorded in 120 g treatment. It was concluded that nutrient requirements of the red tilapia are changed in different growth stages.

Climate change particularly global warming unceasingly imposes a selective pressure in many organisms that results in phenotypic plasticity particularly by expressing different adaptive phenotypes to shifting environmental conditions. The present study was, therefore, conducted to explore the phenotypic responses of male guppy (Poecilia reticulata), a popular model fish, to an ambient (28±0.91°C), high (32±0.12°C) and low (22±0.17°C) rearing temperature. Almost equal sized juvenile males were collected from the wild and reared up to 30 days maintaining necessary conditions similar among treatments except the water temperature. The findings revealed that high-temperature reared fish had significantly lower number of courtships, reduced survival, decreased body size, deformed body shape, limited colour patterns and reduced sperm bundle number than the ambient- and low-temperature groups. On the other hand, low-treatment males performed significantly higher number of courtships than ambient-temperature group, while ambient-temperature reared males possessed significantly higher body size and iridescent colour area than low- temperature treatment. Interestingly, the findings also revealed some trade-offs between traits under thermal-induced stressed conditions (i.e. both high and low temperatures). These findings elicit further information about the thermal condition dependent expression of phenotypic traits of fishes which infer about how fish species will adapt in the predicted changing aquatic environments because of unprecedented climate change.

Marine forests are experiencing a severe decline in many Mediterranean areas. One of the major causes of the loss of the canopy-forming species is the overgrazing by herbivorous fishes. In the present study, the status of Treptacantha ballesterosii and Carpodesmia zosteroides populations was checked in two areas located along the central-eastern sector of Sicily. In addition, impact of herbivorous fishes, native or alien, on canopy-forming species was realized during monitoring of fish communities. It was observed that T. ballesterosii and C. zosteroides populations are in regression, particularly T. ballesterosii. Probably, the growth of this latter species may be limited by a strong herbivores’ pressure. During the monitoring period, the highest number of fish species has been observed at the depths where there are T. ballesterosii thalli. Moreover, an expansion of Sparisoma cretense populations has been observed that seems to be more competitive than the other herbivorous fish Sarpa salpa. Furthermore, the parrotfish has been observed several times in the bathymetric range where there is T. ballesterosii. Therefore, it may be hypothesized that in these areas the herbivorous fish which mostly hinder the development and growth of T. ballesterosii is S. cretense.

The present study was carried out to determine the distribution of Najas marina, an invasive floral species in the Ramsar site of Madu Ganga Estuary in Sri Lanka using ASTER satellite data. Cloud free ASTER imageries of Madu Ganga Estuary with 15 m resolution were atmospherically corrected using the FLAASH in ENVI software. The NDVI was calculated and unsupervised classification was applied for the study site for each image and the distribution maps of N. marina were developed from 2007 to 2014. Methodology was validated using in situ data, which were collected in 2014 with monthly intervals parallel to ASTER overpass. The derived distribution maps indicated that N. marina was distributed in about 31% of the estuary in April 2014. The highest densities were mostly found in bay areas and peripheral areas. Maps developed for December 2007, December 2009 and December 2013 indicated that there is a temporal variation in the distribution of N. marina over the years. The overall distribution of N. marina has decreased from December 2007 to December 2009 and increased from December 2009 to April 2014. Low water levels and stagnation of water appears to be conducive for the variation of this species. These factors should be taken into consideration when managing the invasion of N. marina in this economically and ecologically important estuary.