During the third week of November 2022, bloom of Noctiluca

scintillans (Macartney, 1810) was observed in multiple

locations along the coastal waters off Thiruvananthapuram.

Noctiluca bloom is commonly called as 'sea sparkles, as

it produces blue bioluminescence at nigh

Ambarish, Gop P

Anil, M K

Hussain, Tanveer

Menon, Nandini

Shalini, O

Sudarsan, K S

Surya, S

CMFRI Digital Repository

locals, including members of the SC and ST communities to initiate fish farming and local Panchayat and State Fisheries Department officials too have agreed to further the interest of the weaker sections with the proven cage farming technology of ICAR-CMFRI.The availability of seeds especially good quality seeds of cultivable marine finfish species has always remained a challenge for aquafarmers. Presently, because all the marine finfish hatcheries are located along the east coast, transportation and timely procurement of sufficient number of seeds has deterred the large-scale adoption of finfish farming along Karnataka coast. The successful breeding and the seed production of snubnose pompano at the Vizhinjam Regional Centre, Kerala has to a large extent solved the availability of fin fish farmers along the Karnatakaand Kerala coasts. Finfish farming in coastal Karnataka was mainly focussed in Udupi and Uttara Kannada districts and the present programme done in Dakshina Kannada has ensured the horizontal expansion of the cage farming to the third coastal district. This is also the first-time pompano seeds have been stocked and reared to marketable size in cages for Karnataka which has confirmed the suitability of the species for profitable farming.ReferenceDineshbabu, A. P. et at., 2019. Customized indigenous finfish cages developed fo r fish farmers o f coastal Karnataka.Gopakumar, G. et a l, 2012. Indian J. Fish., 59 (1): 53-57.Jayakumar, R. et a t, 2014. Indian J. Fish., 61 (3): 58-62.Kalidas, C. et a t, 2012. Indian J. Fish., 59 (3): 95-98.Brief CommunicationNoctiluca scintillans bloom and measures to protect marine hatcheriesAm barish P. Gop1, M. K. Anil1, N. Nandini M enon2, H. Tanveer1, S. Surya1, K. S. Sudarshan1 and O. Shalin i11Vizhinjam Regional Centre of ICAR-Central Marine Fisheries Research Institute, Vizhinjam P. O., Thiruvananthapuram -  695 521, Kerala2Nansen Environmental Research Centre India, KUFOS Am enity Centre, Madavana Junction, K och i--682 506.*E-mail: gopidas.ambarish@gmail.comDuring the third week of November 2022, bloom of Noctiluca scintillans (Macartney, 1810) was observed in multiple locations along the coastal waters off Thiruvananthapuram. Noctiluca bloom is commonly called as 'sea sparkles, as it produces blue bioluminescence at night. In the present bloom in Vettucaud, Shanghumukham, Valiyathura, Vizhinjam, Azhimala and Pullivila areas along the Thiruvananthapuram coast, N. scintillanswas identified as the causative organism. This bloom was also observed at the seawater intake point of the Vizhinjam Hatchery complex which put the staff on alert. Even though the dinoflagellate is considered non-toxic, it has been reported to cause 'fish kill,' associated with anoxia during the crashing phase of the bloom. Hence, to protect the fish larvae and broodstock in the rearing systems, precautions were taken to ensure the quality of seawater taken for the N octiluca scin tillans-m icroscop ic  v iewIC A R -C M F R I | M a r in e  F ish e rie s  In fo rm a tio n  S e rv ic e  T e ch n ic a l &  E x te n s io n  S eries  No. 256, 2023 20hatchery. A new offshore intake well was constructed, and the 6-inch PVC pipe w ith 22 mm-sized holes which is primarily used for the seawater input system was covered w ith two layers of foot valve protecting boring mesh (200 microns mesh size) for effective filtration of the pumped seawater. The stored seawater was aerated to ensure oxygenation of the water. Water quality parameters such as Dissolved oxygen (DO) and amm onia were m onitored daily since the detection of the bloom so as to confirm that the levels are normal (DO between 4.04 to 5.1 ppm; total ammonia nitrogen less than 0.001). The precautionary measures were continued for a week after the bloom started crashing which happened three days after the detection of the peak bloom on 16 November 2022.N. scintillans blooms have reportedly become a regular feature in the coastal waters of the Arabian Sea and Bay of Bengal during the w inter monsoon period of October -  February. Fish kills associated w ith these blooms are also increasing. Mixotrophic behaviour of the dinoflagellate helps in the sustenance of the bloom in low-nutrient waters as well as in low prey-dense waters. Therefore, w ith a view to closely monitor the sustenance and spread of the bloom, Sentinel 2 level 1 image were obtained from Copernicus open access HUB and processed using Case-2 regional coast colour processor to derive chl-a concentration for the coastal waters of Thiruvananthapuram. Due to cloud cover, clear chlorophyll images were not available across the region. Hence a mosaic of three S2-A scenes during the first week of November 2022 (1-7) was used for Chl-a extraction, wherein the chl-a concentrations were greater than 4 mg C n r2,Sentine l 2 im age o f 7 N ovem ber 2022 show ing  high ch lo ro p hy ll in the  coastal waters o ff Th iruvananthapuramindicating bloom condition. This points to the fact that the bloom was initiated much earlier than it was visible in the form of green discolouration and bioluminescence on 16th November 2022. Timely identification of the bloom and the interventions taken to prevent the intake of contaminated water into the hatchery served to protect the broodstock and fish larvae, and in turn, avoid economic loss.ICAR-CMFRI | M a rine  Fisheries In fo rm a tion  S erv ice  Techn ica l &  E xtension Series No. 256,2023 21

Noctiluca scintillans bloom and measures to protect marine hatcheries

http://eprints.cmfri.org.in/17699/1/MFIS%20256_2023_Ambarish%20P%20Gop.pdf

Noctiluca scintillans bloom and measures to protect marine hatcheries

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