Pennellid copepod Peniculus fistula fistula (Nordmann, 1832) (Synonym: Peniculus fistula Nordmann, 1832, Aphia ID: 745880), a worldwide distributed species, has been recovered from at least 19 teleost families. The present paper reports for the first time from the Malabar coast (South India), not only the existence of a new host family, Clupeidae, hosting this parasitic copepod species (P. fistula fistula) but also their season dependent hosting. A total of 123 marine fish species, belonging to 77 genera and 38 families surveyed along the Malabar coast, only the clupeid, Anadontostoma chacunda (Hamilton, 1822) was shown to be infected by this copepod species; all the recovered (copepod) parasites were invariably found attached at the mid portion of the caudal fin lobes and lying parallel to the host body, indicating the strict site-specific parasitisation. There is a discrete seasonality in the prevalence (P<0.05) as the sign of infection was noticed during the period from September to May with relatively high prevalence during winter months (November–January). During the monsoon months (June–August), the host fish was found completely free from Peniculus infection. Interestingly, all the 229 recovered specimens (P. fistula fistula) were gravid females having paired uniserrate egg sacs with the length more than its own body length.

In the present study, we report N₂ fixation rate (¹⁵N isotope tracer assay) and the diazotroph community structure (using the molecular method) in the western tropical North Pacific Ocean (WTNP) (13°–20°N, 120°–160°E). Our independent evidence on the basis of both in situ N₂ fixation activity and diazotroph community structure showed the dominance of unicellular N₂ fixation over majority of the WTNP surface waters during the sampling periods. Moreover, a shift in the diazotrophic composition from unicellular cyanobacteria group B-dominated to Trichodesmium spp.-dominated toward the western boundary current (Kuroshio) was also observed in 2013. We hypothesize that nutrient availability may have played a major role in regulating the biogeography of N₂ fixation. In surface waters, volumetric N₂ fixation rate (calculated by nitrogen) ranged between 0.6 and 2.6 nmol/(L·d) and averaged (1.2±0.5) nmol/(L·d), with <10 μm size fraction contributed predominantly (88%±6%) to the total rate between 135°E and 160°E. Depth-integrated N₂ fixation rate over the upper 200 m ranged between 150 μmol/(m²·d) and 480 μmol/(m²·d) (average (225±105) μmol/(m²·d). N₂ fixation can account for 6.2%±3.7% of the depth-integrated primary production, suggesting that N₂ fixation is a significant N source sustaining new and export production in the WTNP. The role of N₂ fixation in biogeochemical cycling in this climate change-vulnerable region calls for further investigations.

This paper reports the distribution of natural radionuclides of ^{224, 223}Ra in the surface water and stratified waters of the Luzon Strait and its adjacent waters during the cruises of September 2015 and May 2016. To understand the impact of the Fukushima nuclear accident, the artificial radionuclide ¹³⁷Cs in the waters was also analyzed. The results showed that the activities of ^{224, 223}Ra and ¹³⁷Cs were all within the natural radioactive background levels of the marine environment in the South China Sea. ²²⁴Ra had a higher activity level in the water of the north South China Sea to the west of the Luzon Strait, and a lower activity level in the oceanic Philippine Sea to the east. The ¹³⁷Cs activity had no obvious spatial trends. Based on the vertical trends of ²²⁴Ra, ¹³⁷Cs, and water temperature and salinity at three stations (LS3, LS5 and LS8), the distinct characteristics of the activity levels and gradients of ²²⁴Ra and ¹³⁷Cs among the tropical surface water, subsurface water and mid-deep water were revealed. Typhoon Rainbow event reversed the overall circulation of the Luzon Strait and its adjacent area. A huge amount of western Pacific water characterized by low ²²⁴Ra activities flooded into the South China Sea, reducing the activity level of ²²⁴Ra in the waters. However, there were no significant differences of ¹³⁷Cs activity between the West Pacific and the north South China Sea, and ocean current changes had no effect on the ¹³⁷Cs activity levels of the water bodies.

Iranian nesting populations of the critically endangered hawksbill turtle (Eretmochelys imbricate) are some of the most important in the Indian Ocean. In this study, four of the most important hawksbill nesting grounds in the Persian Gulf, situated within three Iranian marine protected areas, were surveyed during nesting season, including Nakhiloo, Ommolgorm and Kharko Islands and the mainland beaches of the Naiband Marine-Coastal National Park (NMCNP). We present GIS maps of these key nesting grounds and describe sand texture of key nesting zones, along with conservation recommendations. About 9.2 (28.3%) out of 32.5 km of all shores surveyed in this study were used by nesting hawksbill turtles follows: Nakhiloo: 1.4 km (52% of potential nesting area); Ommolgorm: 1.94 km (40%); Kharko: 3.4 km (28%), and NMCNP: 2.46 km (18.9%). The average nesting density was calculated as 131 nests/km at Nakhiloo, 76 nests/km at Ommolgorm, 7 nests/km at Kharko, and 15 nests per km at NMCNP. Highest nesting density was observed in Nakhiloo and Ommolgorm. It is thought that high hawksbill nesting density in these islands seems likely a result of limiting adequate nesting shores rather than the size of population, and also low density in Kharko and NMCNP more related to past and current pressures and low population density. With the exception of Ommolgorm Island, sands at the nesting grounds were well sorted. Grain size indicated that female hawksbill turtles in the Iranian Persian Gulf nest in sands that are generally mixed, with mean grain size ranging from coarse sands (0.4Φ; ~0.5–1 mm) to fine sands (2Φ; ~0.25 mm). We provide and discuss conservation recommendations and suggestions for future.

The existing study was taken to represent the current information in order to develop a mass-balanced ecosystem model within the resettled maritime boundary area of the Bay of Bengal (BoB), Bangladesh from July 2016 to June 2017 through ECOPATH approach covering over 90 000 km². A total of 19 functional groups were considered representing all trophic levels in the foodweb where estimated trophic interactions between the groups were varied from 1 (primary producers and detritus) to 3.45 (sharks). The ecotrophic efficiency (EE) of most of the consumers was greater than 0.80; symbolizing a largely exploited ecosystem and high energy transfer from lower to higher trophic levels. Moreover, the gross efficiency (0.001 8) and transfer efficiency (11.12%) of the whole system symbolizes the “Developing Systems” with somewhat maturity currently. Ecosystem’s overhead (64.6) and ascendancy (35.4) also designate the ecosystem’s stability. Thus, this study determines that the resettled maritime area of BoB reserves significant backup strength to face stress situations having capacity to rapid restoration to the original states.

Various population structures or spatial heterogeneities in population distribution have been an important source of model misspecification and have had an impact on estimation performance in fisheries stock assessment. In this study, we simulated the Indian Ocean albacore spatial heterogeneity in age-structure using Stock Synthesis according to the stage-dependent migration rate and region-dependent fishing mortality rate and generated the stock assessment data. Based on these data, we investigated the performances of different spatial configurations, selectivity curves and selections of CPUE (catch per unit effort) indices of the assessment models which were used to account for spatial heterogeneity. The results showed: (1) although the spatially explicit configurations, which exactly matched the operating model, provided unbiased and accurate estimates of relative spawning biomass, relative fishing mortality rate and maximum sustainable yield in all simulation scenarios, their performance may be very poor if there were mismatches between them and the operating model due to gaps in knowledge and data; (2) for spatially explicit assessment configuration, the correct boundary was required, but for non-spatially explicit assessment configuration, it seemed more important for analysts to partition the area to properly reflect the transition in field data and to effectively account for the impacts of ignoring the spatial structure by using the additional spatially referenced parameters; (3) although the areas-as-fleets methods and flexible time-varying selectivity curves could be used as better alternative approaches to account for spatial structure, these configurations could not completely eliminate the impacts of model misspecification and the quality of estimates of different quantities from the same assessment model may be inconsistent or the performance of the same assessment configuration may fluctuate significantly between simulation scenarios; (4) although the worst estimates could generally be avoided by using multiple CPUE indices, there were no best solutions to select or regenerate the CPUE indices to account for the impacts of the ignored spatial structure to obviously improve the quality of stock assessment. Compared with the results of assessment model configurations which are used to account for the spatial structure by different modelers, the performances of the configurations are always case-specific except for spatially explicit configurations which exactly match the operating model. In this sense, our study will not only provide some insights into the current Indian Ocean albacore stock assessment but also enrich existing knowledge regarding the performance of assessment configurations to account for spatial structure.

An enhanced ARTSIST Sea Ice (ASI) algorithm is presented based on a data fusion method of calculating total sea ice concentration from high-frequency microwave data. Algorithms that use low-frequency data to calculate total sea ice concentration are less affected by atmosphere, but their spatial resolutions tend to be lower. In contrast, algorithms using high-frequency data have higher spatial resolution but are significantly influenced by atmosphere. Although errors can be eliminated using weather filters, the concentration of mixed pixels cannot be modified. Here, an enhanced ASI algorithm uses the 19 GHz polarization difference to modify the 91 GHz polarization difference, which is substituted into the ASI algorithm to calculate total sea ice concentration. Arctic total sea ice concentration results are obtained based on Special Sensor Microwave Imager Sounder (SSMIS) data on January 3, from 2008 to 2017. Total sea ice area and average concentration using the enhanced ASI algorithm are compared to traditional ASI and NASA Team results. In the Marginal Ice Zone, there is a considerable difference between the enhanced and traditional ASI algorithm results, with the former much closer to the NASA Team results. The proposed algorithm effectively modifies the concentration of the mixed pixels in the marginal zone.

The Subei Shoal is a special coastal area with complex physical oceanographic properties in the Yellow Sea. In the present study, the distribution of phytoplankton and its correlation with environmental factors were studied during spring and summer of 2012 in the Subei Shoal of the Yellow Sea. Phytoplankton species composition and abundance data were accomplished by Utermöhl method. Diatoms represented the greatest cellular abundance during the study period. In spring, the phytoplankton cell abundance ranged from 1.59×10³ to 269.78×10³ cell/L with an average of 41.80×10³ cell/L, and Skeletonema sp. and Paralia sulcata was the most dominant species. In summer, the average phytoplankton cell abundance was 72.59×10³ cell/L with the range of 1.78×10³ to 574.96×10³ cell/L, and the main dominant species was Pseudo-nitzschia pungens, Skeletonema sp., Dactyliosolen fragilissima and Chaetoceros curvisetus. The results of a redundancy analysis (RDA) showed that turbidity, temperature, salinity, pH, dissolved oxygen (DO), the ratio of dissolved inorganic nitrogen to silicate and SiO₄-Si (DIN/SiO₄-Si) were the most important environmental factors controlling phytoplankton assemblages in spring or summer in the Subei Shoal of the Yellow Sea.

The morphology of seven specimens of Chrysaora chinensis (Scyphomedusae, Semaestomae) obtained from four sites off the coast of Peninsular Malaysia was examined. Morphological characteristics of C. chinensis that encompasses structures such as the bell, tentacles, oral arms, stomach, manubrium, radial canals and gonads were described in detail. A total of 107 specimens that represented C. chinensis populations of four coastal areas of Peninsular Malaysia (East-Central, East-North, West-Central, and West-North) were also analysed for shape variation using geometric morphometric analysis. Procrustes superimposition, Principal Component Analysis (PCA) and Canonical Variate Analysis (CVA) were applied to the images of gastrovascular pouches of C. chinensis to extract the shape information. Independent contrasts were used for comparisons between shapes. There were no significant differences in shape variation between all the specimens based on the PCA results. However, CVA results showed shape variations between specimens taken from the four areas of Peninsular Malaysia, especially with higher magnitudes of Mahalanobis distances between the east and west coast areas, including between East-Central and East-North, but lower magnitudes were detected between the West-Central and West-North.

The response of glutathione S-transferase (GST) in Zostera marina to temperature variation was analyzed at molecular level by cloning the microsomal GST gene and texting the microsomal GST expression regularity under different temperature. Specific speaking, express ZmGST in Escherichia coli, then purify the recombinant protein and make the thermal stability analysis. Therefore, the experiments were carried out to provide a theoretical basis for the further elaboration to the population degradation mechanisms of Z. marina. In conclusion, the thermostability and the response of ZmGST gene to temperature changes can determine its temperature tolerance range, and affect its resilience in turn.