Chlorophyll blooms induced by tropical cyclone Vardah in the Bay of Bengal

The present study documented the formation of surface and subsurface chlorophyll a (Chla) blooms after the passage of tropical cyclone Vardah in the Bay of Bengal, using remote sensing and Bio-Argo float data. Surface Chla bloom occurred in the cyclonic eddy waters and lasted for three weeks, longer than the surface and subsurface Chla blooms in the anti-cyclonic eddy waters (lasted for two weeks). Thickness of the subsurface Chla bloom and depth-integrated Chla increased after the Vardah passage. Analysis shows that Vardah-induced upwelling and vertical mixing transported nutrients to the upper layer and supported the Chla bloom. The fast translation speed and pre-existed anti-cyclonic eddy were the reason of the relatively weak subsurface Chla bloom compared with other studies

Chlorophyll blooms induced by tropical cyclone Vardah in the Bay of Bengal

1383-1390The present study documented the formation of surface and subsurface chlorophyll a (Chla) blooms after the passage of tropical cyclone Vardah in the Bay of Bengal, using remote sensing and Bio-Argo float data. Surface Chla bloom occurred in the cyclonic eddy waters and lasted for three weeks, longer than the surface and subsurface Chla blooms in the anti-cyclonic eddy waters (lasted for two weeks). Thickness of the subsurface Chla bloom and depth-integrated Chla increased after the Vardah passage. Analysis shows that Vardah-induced upwelling and vertical mixing transported nutrients to the upper layer and supported the Chla bloom. The fast translation speed and pre-existed anti-cyclonic eddy were the reason of the relatively weak subsurface Chla bloom compared with other studies

Population dynamics of Randall’s threadfin bream <i>Nemipterus randalli </i> from Pakistani waters, Northern Arabian Sea

551-561The N. randalli fish data consist of 1141 pair of length weight relationship and 24312 length frequencies were measured during 2009 - 2010 survey. The maximum length and weight were 25 cm and 251 g, respectively. The length-weight relationship were a = 0.035, b = 2.744 and R2 = 0.972. The asymptotic length (L∞) and growth coefficient (K) were estimated to 26.25 cm and 0.320 year-1, respectively. The total mortality (Z) was 1.25 year-1. The natural mortality (M) was 0.863, hence the fishing mortality (F) was Z–M = 0.387 year-1 for N. randalli. The yield per recruit analysis indicated that when tc was assumed to be 2, Fmax was estimated at 1.3 and F0.1 at 1.3; while tc was assumed to be 1, Fmax was estimated at 1.1 and F0.1 at 0.95. Currently age at first capture is about 1 year and Fcurrent was 0.387, therefore, Fcurrent was smaller than F0.1 and Fmax. The results during present study indicate that current fishery stock is in sustainable state. However, it is suggested that take some management steps to maintain the stock of N. randalli in Pakistani waters, Northern Arabian Sea

Growth and mortality parameters of Indian squid Uroteuthis (Photololigo) duvaucelii (D'Orbigny,1835) from Pakistani waters(Arabian Sea) based on length frequency data.

1598-1603Present study was carried out to understand the Growth and Mortality parameters of commercially important Indian Squid Uroteuthis Duvauceli (D’ Orbigny.1985) based on length frequency data from Pakistani waters. The pooled n=1138 pair length-weight data of both sexes combined were used to calculate the length weight relationship as: W=0.278*L2.122 (R2=0.9520) length frequency data n=10008 were used to estimate VBGF growth parameters as =26.25(ML-cm) and K= 0.270 year-1 with goodness of fit model were estimated at Rn=0.335. The t0 value was calculated at t0=-0.442. Length converted catch curve analysis gave a Z value of 1.14 year-1. Natural mortality (M) obtained from Srinath’s method using empirical formula M = 0.4603+1.4753K, M=0.853 year-1. Fishing mortality was calculated as F=Z-M = 0.287 year and the exploitation rate (E) was calculated from F/Z = 0.251 year because the exploitation rate in present study is lower than 0.5

Examining the Impact of Tropical Cyclones on Air-Sea CO2 Exchanges in the Bay of Bengal Based on Satellite Data and In Situ Observations

The impact of tropical cyclones (TCs) on the CO2 partial pressure at the sea surface (pCO(2sea)) and air-sea CO2 flux (F-CO2) in the Bay of Bengal (BoB) was quantified based on satellite data and in situ observations between November 2013 and January 2017. The in situ observations were made at the BoB Ocean Acidification mooring buoy. A weak time-mean net source of 55.78 +/- 11.16 mmol CO2 m(-2) year(-1) at the BoB Ocean Acidification site was estimated during this period. A wide range in increases of pCO(2sea) (1.0-14.8 mu atm) induced by TCs occurred in postmonsoon (October-December), and large decreases of pCO(2sea) (-14.0 mu atm) occurred in premonsoon (March-May). Large vertical differences in the ratio of dissolved inorganic carbon (DIC) to total alkalinity (TA) in the upper layer (Delta DIC/TA) were responsible for increasing pCO(2sea) in postmonsoon. Relatively small values of Delta DIC/TA were responsible for decreasing pCO(2sea) in premonsoon. Five TCs (Hudhud, Five, Kyant, Vardah, and Roanu) were considered. Hudhud significantly enhanced CO2 efflux (18.49 +/- 3.70 mmol CO2/m(2)) in oversaturated areas due to the wind effect during the storm and wind-pump effects after the storm. Vardah insignificantly changed F-CO2 (1.22 +/- 0.24 mmol CO2/m(2)) in undersaturated areas because of the counteraction of these two effects. Roanu significantly enhanced CO2 efflux (19.08 +/- 3.82 mmol CO2/m(2)) in highly oversaturated conditions (Delta pCO(2) > 20 mu atm) since the wind effect greatly exceeded the wind-pump effects. These five TCs were estimated to account for 55 +/- 23% of the annual-mean CO2 annual efflux, suggesting that TCs have significant impacts on the carbon cycle in the BoB

<span style="font-size:15.0pt;line-height:115%;font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";mso-bidi-font-family:"Times New Roman"; mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA" lang="EN-US">Estimation of growth, mortality and exploitation of <span style="font-size:15.0pt;line-height:115%;font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";mso-bidi-font-family:"Times New Roman"; mso-ansi-language:EN-GB;mso-fareast-language:EN-US;mso-bidi-language:AR-SA" lang="EN-GB">lesser tiger toothed croaker <i style="mso-bidi-font-style:normal"><span style="font-size:15.0pt;line-height:115%;font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";mso-bidi-font-family:"Times New Roman"; mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA" lang="EN-US">Otolithes cuvieri</span></i><span style="font-size:15.0pt;line-height:115%; font-family:"Times New Roman";mso-fareast-font-family:"Times New Roman"; mso-bidi-font-family:"Times New Roman";mso-ansi-language:EN-US;mso-fareast-language: EN-US;mso-bidi-language:AR-SA" lang="EN-US"> (Trewavas. 1974)<i style="mso-bidi-font-style: normal"> </i><span style="font-size:15.0pt;line-height:115%; font-family:"Times New Roman";mso-fareast-font-family:"Times New Roman"; mso-bidi-font-family:"Times New Roman";mso-ansi-language:EN-GB;mso-fareast-language: EN-US;mso-bidi-language:AR-SA" lang="EN-GB">in Pakistan</span></span></span></span>

63-68Four demersal trawl surveys were carried out in Pakistani marine waters in 2009-2010.  Length frequency data of 3219 individuals were used to estimate growth, mortality and exploitation, whereas data of 671 individuals were used to estimate length weight relationship in Otolithes cuvieri (Trewavas, 1974).  Length ranges from 3 - 35cm and weight ranges from 1 - 208g.  Length weight relationship parameters were computed as a = 0.014, b = 2.870 and R2 = 0.952. Using the ELEFAN routine of the FiSAT computer package, the calculated von Bertalanffy growth function parameters were L∞= 36.75cm, K= 0.300/year. Total mortality were computed using length-converted catch curve analysis at Z=1.26/year, whereas natural M=0.740/year and fishing mortality F=Z-M= 0.52/year were calculated. The exploitation ratios (E) were computed as Emax = 0.412, E10 = 0.355, E50 = 0.278. The yield per recruit analysis showed that when tc was 1, Fmax was calculated at 0.5 and F0.1 at 0.4. When biological reference point of Fopt was `M (0.740), current fishing mortality rate of 0.52 is smaller than the target biological reference point

Growth, mortality and exploitation rate of <i>Sardinella longiceps</i> (Valenciennes, 1847) from Pakistani waters based on length frequency distribution data

1693-1703The computer software FiSAT package was used to analyze the growth and mortality parameters of S. longiceps. Length weight relationship parameters of both sexes combined were at W= 0.0179xb2.8583 (R2 = 0.819). ELEFAN method was used to estimate the von Bertalanffy growth function (VBGF) parameters and were estimated as L∞ = 25.20 cm (FL), K = 1.4 year-1 and t0 value was calculated by Pauly’s formula as -0.929, hence the total mortality was estimated using length converted catch curve analysis as Z = 4.84 year-1 at 95% confidential interval between (CI = 3.32-6.37). Natural mortality was calculated as M = 2.255year-1 using an average sea surface temperature of 26 oC from Pakistani waters, hence the fishing mortality was obtained by F=Z-M = 2.560 year-1. Exploitation rate (E) was E = F/Z = 0.534 year-1. Present study results indicate that the stock of S. longiceps from Pakistani waters is in overexploitation state

Applications of CEDA (catch effort data analysis) computer software in estimation of Maximum Sustainable Yieldof the Black Pomfret <i>Parastromateus niger</i>Fishery from Pakistani Waters

576-581The surplus production models of Fox, Schaefer and Pell-Tomlinson with three error assumptions of normal, log-normal and gamma were used to analyze the catch and effort data of Black PomfretParastromateus niger fishery from Pakistani waters using the computer software package CEDA (catch effort data analysis).When using initial proportion of 0.4 (because the initial catch was roughly 40% of the maximum catch) the estimated maximum sustainable yield (MSY) were about 2000-2300t, the coefficient determinationR2 were about 0.20-0.31. Gamma error assumption often showed minimization failure. The estimated MSY from CEDA is smaller than most recent catch of the fishery which indicates that the fishery of P.niger in Pakistani waters may not be in a sustainable condition

Carapace length-weight and carapace width-weight relationship of <em>Portunus pelagicus</em> (Linnaeus, 1758) in Pakistani waters northern Arabian Sea

890-896The carapace length-weight and carapace width-weight relationship of Portunus pelagicus analysis were conducted from Pakistani waters. Total of 897 specimen of both sexes combined were measured in which 478 female and 419 male specimen during January to November 2015. The carapace length-weight of both sexes combined were calculated as W = 0.2888*2.73 (R2 = 0.860). However the carapace width-weight of both sexes were as W = 0.1198*2.79 (R2 = 0.870). The carapace length-weight of separate sexes (male and female) of P. pelagicus were also calculated as W = 0.967*2.91(R2 = 0.874) and carapace width-weight were as W = 0.8138*2.95 (R2 = 0.882). While the carapace width-weight and length-weight of male were calculated as W = 0.967*2.44 (R2 = 0.795), W = 0.204*2.56 (R2 = 0.809), respectively. The present study shows that the growth of P. pelagicus is isomateric from Pakistani waters