Observed oceanic response to tropical cyclone Jal from a moored buoy in the south-western Bay of Bengal

Upper oceanographic and surface meteorological time-series observations from a moored buoy located at 9.98°N, 88°E in the south-western Bay of Bengal (BoB) were used to quantify variability in upper ocean, forced by a tropical cyclone (TC) Jal during November 2010. Before the passage of TC Jal, salinity and temperature profiles showed a typical BoB post-monsoon structure with relatively warm (30 °C) and low-saline (32.8 psu) waters in the upper 30- to 40-m layer, and relatively cooler and higher salinity (35 psu) waters below. After the passage of cyclone, an abrupt increase of 1 psu (decrease of 1 °C) in salinity (temperature) in the near-surface layers (up to 40-m depth) was observed from buoy measurements, which persisted up to 10–12 days during the relaxation stage of cyclone. Mixed layer heat budget analysis showed that vertical processes are the dominant contributors towards the observed cooling. The net surface heat flux and horizontal advection together contributed approximately 33 % of observed cooling, during TC Jal forced stage. Analysis showed the existence of strong inertial oscillation in the thermocline region and currents with periodicity of ∼2.8 days. During the relaxation stage of the cyclone, upward movement of thermocline in near-inertial frequencies played significant role in mixed layer temperature and salinity variability, by much freer turbulent exchange between the mixed layer and thermoclin

Metazoan parasites of the Indian mackerel, Rastrelliger kanagurta (Scombridae) of Visakhapatnam coast, Bay of Bengal

The metazoan parasite fauna of the Indian mackerel Rastrelliger kanagurta of Visakhapatnam coast, Bay of Bengal comprised 15 species including three species of Monogenea, seven species of Digenea and five species of Crustacea. Digeneans were the dominant members in the parasite spectrum while infections with ectoparasitic monogeneans and crustaceans were rare. The digeneans Opechona bacillaris and Lecithocladium angustiovum which occurred with high prevalence and mean intensity are the typical parasites of the mackerel. The parasitic fauna in general is found to be a reflection of the planktonivorous diet of the host. Except for two species of digeneans, Lecithocladium angustiovum and Aponurus laguncula, all the remaining species of metazoans showed narrow specificity to R. kanagurta, indicating a high degree of host specialization. The parasitological data may prove useful for differentiating stocks of R. kanagurta