Evaluating impacts of pulse fishing on the effectiveness of seasonal closure

Seasonal fishing closures are often used in fisheries management to conserve overfished stocks.As one of the unintended consequences,fishermen often contend for maximizing catches immediately after reopening fisheries.The resultant large catch landings in a short time period(i.e.,pulse fishing)may undermine the benefit of closure.We implemented an end-to-end model OSMOSE-JZB(Object-oriented Simulator of Marine ec OSystem Exploitation OSMOSE)modelling ecosystem in the Jiaozhou Bay located in China to evaluate the impact of pulse fishing on the effectiveness of seasonal closure at levels of fish community,population,and individual.Our study demonstrated that the three-month closure was successful in conserving fish stocks.There were small variations on ecological indicators(i.e.,total biomass of the community,mean trophic level of the community,mean trophic level of the catch,and Shannon-Wiener biodiversity index)when pulse fishing occurred.Pulse fishing seemed not to result in a great shift in community structure.Compared to other species,the biomass of two large predatory fishes were more susceptible to pulse fishing.Pulse fishing could change the pressure of predators to fish stocks via food webs,especially for young individuals.Our simulations indicate that we can improve the effectiveness of seasonal closure by managing pulse fishing.Although the results derived in this study may be specific to the target ecosystem,the general approach is applicable to other ecosystems when evaluating fishing impacts.     

Application of the ALE technique for underwater explosion analysis of a submarine liquefied oxygen tank

The design of submarines has continually evolved to improve survivability. Explosions may induce local damage as well as global collapse to a submarine. Therefore, it is important to realistically estimate the possible damage conditions due to underwater explosions in the design stage. The present study applied the Arbitrary Lagrangian–Eulerian (ALE) technique, a fluid–structure interaction approach, to simulate an underwater explosion and investigate the survival capability of a damaged submarine liquefied oxygen tank. The Lagrangian–Eulerian coupling algorithm, the equations of state for explosives and seawater, and the simple calculation method for explosive loading were also reviewed. It is shown that underwater explosion analysis using the ALE technique can accurately evaluate structural damage after attack. This procedure could be applied quantitatively to real structural design.     

Status of butyltin pollution along the coasts of western Japan in 2001, 11 years after partial restrictions on the usage of tributyltin

Restrictions on the use of tributyltin (TBT) in aquaculture and on boats in coastal regions, except for ocean-going vessels, have been in place in Japan since 1990 due to the strong toxic effects of TBT on marine organisms. However, TBT pollution along the Japanese coasts has been reported after this legislation was enacted. In order to elucidate the present status of contamination by butyltin (BT) compounds, we measured the levels of BTs [monobutyltin (MBT), dibutyltin (DBT) and TBT] in seawater and Caprella spp. samples obtained from the western part of Seto Inland Sea, Uwa Sea and Uranouchi Bay in western Japan during March to September, 2001. Butyltins were detected in more than 90% of the seawater samples (n = 59), with average concentrations of 8.2 ± 9.2 (SD) ng MBT L⁻¹, 3.3 ± 3.0 ng DBT L⁻¹ and 9.0 ± 7.0 ng TBT L⁻¹. Among 41 stations situated on coastal lines, a sufficient number of Caprella organisms for chemical analysis could be collected from only 16 stations. The butyltin concentrations in seawater and Caprella samples from Uwa Sea and Uranouchi Bay, in which the dominant industry in both waters is aquaculture, showed significantly higher than or no significant differences from those samples from the western part of Seto Inland Sea, a major heavy-industry area in Japan. As the TBT concentration in seawater increased, the number of Caprella organisms collected decreased. The mean TBT concentration among the seawater samples was above the estimated lowest observable effect concentration (LOEC) that reduces the survival rate of Caprella danilevskii. Thus, the present study indicates that TBT is still a potential ecological hazard to the survival of marine invertebrates inhabiting coasts along western Japan, even 11 years after the partial ban on TBT usage was implemented.     

Space/Time Features of the Secular Variation in 1951–1998 Northern 500-hPa Height

Summary  This paper presents a trend coefficient as a characteristic index with which to investigate the 1951–1998 secular trend variation (STV) of northern 500-hPa height on a seasonal basis. Evidence suggests that low (high) latitude 500 hPa geopotential height displays a remarkably positive (negative) trend; the positive anomaly of the height is maintained over NW Africa, the western Mediterranean Sea and North Africa, mid-Pacific at lower latitudes, Lake Baikal and area to the east and NW North America; the height drops significantly over the Aleutians and North Pacific, the area to the south of the Greenland and NE North America and the sector to the north of the Arabian Sea. Further, analysis of abrupt change shows that the 500-hPa circulations experience noticeable sudden change twice, once around the early 1960s and again in 1976, during which period the height exhibits great differences between the Pacific and Atlantic. In the first period it drops (rises) over the mid-Atlantic at lower latitudes (NW Africa); in the second period the height rises (drops) over the mid-Pacific at lower latitudes and Lake Baikal (the North Pacific). Statistical tests indicate that in the 1976 case the low-latitude positive abrupt change is even more noticeable compared to the negative of the North Pacific, thus representing a large-scale jumping event of the northern 500-hPa height. Received April 9, 1999/Revised October 15, 1999     

Behavior of sand–rubber particle mixtures: experimental observations and numerical simulations

A series of laboratory experiments and numerical simulations are conducted to explore the characteristics of mixtures composed of sand and rubber particles of the same median diameter. The mixtures are prepared with different volumetric sand fractions (sf = V_sand/V_total). The experiment focuses on assessing the strain level on the characteristics of the mixture with the volume fraction of each component. Numerical simulations using the discrete element method are performed to obtain insight into the microscale behavior and internal mechanism of the mixtures. The experimental results show that the behavior of the mixtures is dependent on the relative sand and rubber particles composition with variation in the strain levels. The numerical simulation reveals the effect of the soft rubber particle inclusion in the mixture on the micromechanical parameters. In low sand fraction mixtures, a high shear stress along the contact is mobilized, and the stress state is driven to a more anisotropic condition because of the relatively high particle friction angle of the rubber. The rubber particles play different roles with the strain level in the mixture, including increasing the coordination number and controlling plasticity of the mixture in a small strain, preventing buckling of the force chain in an intermediate strain, and leading to contractive behavior in a large strain. Copyright © 2014 John Wiley & Sons, Ltd.     

Retrieval of the single scattering albedo of Asian dust mixed with pollutants using lidar observations

The vertical distribution of single scattering albedos （SSAs） of Asian dust mixed with pollutants was derived using the multi-wavelength Raman lidar observation system at Gwangju （35.10°N,126.53°E）.Vertical profiles of both backscatter and extinction coefficients for dust and non-dust aerosols were extracted from a mixed Asian dust plume using the depolarization ratio from lidar observations.Vertical profiles of backscatter and extinction coefficients of non-dust particles were input into an inversion algorithm to retrieve the SSAs of non-dust aerosols.Atmospheric aerosol layers at different heights had different light-absorbing characteristics.The SSAs of non-dust particles at each height varied with aerosol type,which was either urban/industrial pollutants from China transported over long distances at high altitude,or regional/local pollutants from the Korean peninsula.Taking advantage of independent profiles of SSAs of non-dust particles,vertical profiles of SSAs of Asian dust mixed with pollutants were estimated for the first time,with a new approach suggested in this study using an empirical determination of the SSA of pure dust.The SSAs of the Asian dust-pollutants mixture within the planetary boundary layer （PBL） were in the range 0.88-0.91,while the values above the PBL were in the range 0.76-0.87,with a very low mean value of 0.76 ± 0.05.The total mixed dust plume SSAs in each aerosol layer were integrated over height for comparison with results from the Aerosol Robotics Network （AERONET） measurements.Values of SSA retrieved from lidar observations of 0.92 ± 0.01 were in good agreement with the results from AERONET measurements.     

Effect of ultraviolet irradiation on the production and composition of fatty acids in plankton in a sub-Antarctic environment

We investigated the effects of ultraviolet-B (UV-B) radiation on the natural phytoplankton assemblage in Marine Cove on King George Island, Antarctica, in December 2005. The amount of newly synthesized phytoplankton polyunsaturated fatty acids (PUFAs) was lower with exposure to full irradiation (PAR+UV-A+UV-B) than without such exposure (exposed instead to PAR+UV-A radiation) in an in situ incubation under the light conditions in two different types of incubation bottles: quartz bottles transmitting all light wavelengths including UV-B and polycarbonate bottles with no UV-B transmission and 20 % reduced PAR compared to the quartz bottle. However, the amount of newly synthesized saturated fatty acids was greater with than without UV-B radiation. Thus, UV-B radiation may have a significant influence on fatty acid synthesis in phytoplankton. In particular, the production of eicosapentaenoic acid [20:5(n-3)] and docosahexaenoic acid [22:6(n-3)] was reduced during incubation under the natural solar radiation including UV-B. To understand the indirect influence of UV-B on herbivores (the secondary producer), we conducted feeding experiments with amphipods fed in situ on the natural phytoplankton assemblage. The amphipods fed on the phytoplankton with the low PUFA values also exhibited a low PUFA accumulation rate, which could negatively affect their growth, development, and reproduction. Consequently, the diminished rate of essential fatty acid synthesis [especially 20:5(n-3) and 22:6(n-3)] in primary producers caused by UV-B exposure could affect the structure and function of the Antarctic marine ecosystem.