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The spatial and seasonal variability in finfish availability in the tropical Kali Estuary, in Karwar was studied from January 2017- May 2019 at three stations. A total of 26 species belonging to 9 orders and 20 families were recorded from the Kali Estuary and the order Perciformes with 16 species dominated the group (62%) followed by order Mugilliformes and Pleuronectiformes (8%). Maximum abundance was observed during the pre-monsoon season in all the stations. Excluding Ambassis ambassis which was abundant in all the stations, Caranx ignobilis dominated in all the stations. Truly marine and estuarine species of fishes recorded dominated than the freshwater estuarine ones like Etroplus suratensis, Scatophagus argus, Aplocheilus lineatus. Number of species recorded at each station during the study ranged from 11 to 25 and it was significantly different between stations. The Shannon- Wiener diversity index ranged from 2.0 to 4.6, the minimum in station 1 and maximum in station 3. The seasonal analysis of diversity also showed minimum value during the monsoon season in station 1 and maximum value in station 3. The minimum value (2.2) of Margalef richness index was also recorded in Station 1 during monsoon season and maximum value (4.2) in Station 2. When comparing the relative abundance using Pielou’s evenness index (J’) the values were in the range of 0.92 to 0.99 which was closer to one, indicating evenness in distribution. There was similarity in species composition according to different seasons except for monsoon season in Station 1. The same pattern was also evident in the MDS plot where seasonal aggregation was observed between the stations. In addition to the diversity studies, the surveys also threw light on the abundance and seasonality of candidate species suitable for mariculture like C. ignobilis, Lutjanus spp., Etroplus spp., etc. Judicious exploitation of the species could help brackishwater fish farmers.

A study was conducted to investigate the histological changes in the gills of orange-spotted grouper infested with flukes of Dactylogyrus spp. Several histological changes were observed in the gill which included complete fusion of secondary lamellae, dilatation of the venous sinus at the middle of the primary lamellae, oedema and complete loss of secondary lamellae, etc

Development of aquaculture facilities like cages has led to rise in submerged structures which provide ample substratum to biofoulers which could greatly interfere with culture operations. An attempt was made to study the biofouling communities and succession of macro foulers on the cage culture net installed in the open sea. The main objective of the present study is to reveal the succession pattern of the biofouling communities on the panels of cage culture sites to find out seasonal settlement pattern, Dominant species and Climax community. A long-term study on the succession pattern of the cage farm experimental-net-panels revealed results as Hydroids-Gastropods-Hydroids-Barnacles-Modiolus-Green mussels. Hydroids were initial communities on the net panels and green mussels (Perna viridis) formed the climax community, also dominating on the cage culture nets. Different succession patterns were observed in two sites as well as in culture nets studied. The net panels of the cage were loaded with hydroids in the initial months and the peak fouling was during May. So frequent net cleaning was required during summer and during the spat settlement period of green mussel (September, October and November). Modiolus settlement during February month on the culture nets can be avoided by net exchange immediately after spat fall in this month. This attempt was made to study the ecological succession on the panels, in cages installed in Karwar, which is the first attempt, since the open sea cage culture was initiated in India. Looking at vast opportunities for further development in biofouling research, the aim of this investigations was to obtain the baseline information about the ecological succession pattern of biofouling organisms in fish cage sites. More research on biofouling in mariculture is essential to ensure the profitability of the aquaculture operations with environmental safety measures as a prime criteria

A new species of Apocyclops Lindberg (Cyclopoda: Cyclopoida: Cyclopidae) is described based on specimens collected from marine waters of Karwar, Karnataka, India. At present, there are 11 valid and accepted species excluding one extinct species (fossil) in this genus which are widely distributed in fresh and brackishwater areas in the tropics and subtropics. Five valid species of Apocyclops are reported from the Asian region, including two species from India. The new species is closer to the previously reported Indian species, A. royi (Lindberg) and A. dengizicus dengizicus (Lepeshkin). Apocyclops cmfri sp. nov. differs from these in the size of caudal rami, in the characteristic shape of disto-medial part of coxa and basis of first to fourth pleopods (P1-P4) and in the presence of a single broad spinous expansion with a pointed tip in between exopod and endopod in basis of P1 to P4. Only one terminal spine is present in the second segment of endopod of P1. In P2 to P4, both exopod and endopod terminate in a spine and a seta of almost equal size. Maxillule highly dentate and maxilla basis form a large dentate claw with inner serration. All these characters form distinct identification features of the new species in comparison with the 12 accepted species under the genus. A key to all the species of the genus including the newly described species is proposed here. Molecular identification of the new species was carried out by mitochondrial cytochrome c oxidase 1 (CO1) gene sequencing and the sequence was submitted to NCBI, GenBank. Genetic differentiation and divergence between A. cmfri sp. nov. and species belonging to other closely related genera; Thermocyclops, Mesocyclops and Eucyclops were compared using CO1 gene sequences. The new species belonging to Apocyclops showed significant divergence from Apocyclops borneoensis with K2P value of 10.2% and from species under the genera Mesocyclops, Thermocyclops and Eucyclops with K2P values of 26.6, 27.5and 34.9% respectively.

An experimental study was carried out to evaluate the efficacy of three commercially available probiotics P1, P2 and P3 consisting of mainly Bacillus spp. and nitrifying bacteria against Vibrio loads in mass culture tanks of the rotifer Brachionus plicatilis. Triplicate tanks were maintained for each of the probiotic treatment as well as for control group. All the tanks were inoculated with 50 rotifers ml-1 and were fed with Nannochloropsis oculata at a density of 1 x 107 cells ml-1. Every alternate day, all the experimental tanks were treated with probiotics at a concentration of 1 x 104 cfu ml-1 and the experiment was carried out for one week. The study showed a significant increase in rotifer density (p

Effect of marine microalgal diet on filtration and ingestion rates of Brachionus plicatilis was studied. Marine microalgae viz., Nannochloropsis oculata, Isochrysis galbana, Chaetoceros calcitrans and a combination of N. oculata and I. galbana (Nanno+Iso) at different cell concentrations were selected for the experiment and triplicates were maintained for each feed. Significant difference (p

Growth rates of cage cultured Asian seabass Lates calcarifer (Bloch, 1790) and cobia Rachycentron canadum (Linnaeus, 1766) in relation to the water and sediment quality of marine farm at Karwar for two consecutive crops (2012-13 and 2013-14) were analysed. No significant variation was observed in the specific growth rate (SGR) of both the species between the crops. But within a crop, variations were observed in the SGR and absolute growth rate (AGR) of both the species (p

Investigations were carried out on the bacterial flora of water and the quality of rotifers in outdoor mass culture tanks. Brachionus plicatilis and B. rotundiformis were cultured in 10 numbers of 1 tonne tanks and the physico-chemical parameters and microbial loads of water, and total bacterial and Vibrio loads of microalgae and rotifers, during the period 2014-15, were studied. The study revealed a significant variation of the ammonia levels and total bacterial loads with different diets (P < 0.05). A positive correlation was observed between the total bacterial loads of algal concentrations and loads of rotifers, but no correlation was observed between Vibrio loads of water and rotifers. The prevalence of Vibrio loads of rotifers was low in tanks fed with Nannochloropsis oculata and maximum Vibrio loads were recorded in Chaetoceros calcitrans fed rotifers. The Vibrio loads significantly varied with days of culture and also with the algal diets. A positive correlation was observed between the total Vibrio loads of water and rotifers.