Differences in the response of a striped dolphin (Stenella coeruleoalba) and a harbour porpoise (Phocoena phocoena) to an acoustic alarm

Small cetacean bycatch in gillnet fisheries may be reduced by deterring odontocetes from nets acoustically. However, different odontocete species may respond differently to acoustic signals from alarms. Therefore, in this study a striped dolphin and a harbour porpoise were subjected simultaneously to sounds produced by the XP-10 experimental acoustic alarm. The alarm produced 0.3s tonal signals randomly selected from a set of 16 with fundamental frequencies between 9 and 15kHz, with a constant pulse interval of 4.0s (duty cycle 8%) and a Source Level range of 133-163dB re 1muPa (rms). The effect of the alarm was judged by comparing the animals' respiration rate and position relative to the alarm during test periods with those during baseline periods. As in a previous study on two porpoises with the same alarm, the porpoise in the present study reacted strongly to the alarm by swimming away from it and increasing his respiration rate. The striped dolphin, however, showed no reaction to the active alarm. Based on harbour porpoise audiograms and the specific audiogram of the striped dolphin in the present study, and the low background noise levels during the experiment, both animals must have heard the alarm signals clearly. This study indicates that cetacean species are not equally sensitive to human-made noise disturbance. Therefore, source levels of acoustic alarms should be adapted to the species they are supposed to deter. In addition, alarms should be tested on each odontocete species for which they are intended to reduce bycatch.     

Deterring effects of 8-45 kHz tone pulses on harbour seals (Phoca vitulina) in a large pool

The marine aquaculture industry suffers losses due to pinniped attacks which damage net enclosures and fish stocks. Acoustic harassment devices (AHDs) emit loud sounds which are intended to deter pinnipeds from approaching aquaculture enclosures. At present, many AHDs emit sounds in the 8-20 kHz frequency range. It is not known whether sounds of higher frequencies have a deterrent effect on seals. Therefore five captive harbour seals (Phoca vitulina) were subjected to four series of tone pulses together spanning a broad frequency range (8, 16, 32 and 45 kHz). Pulse duration was 250 ms and pulse interval was 5s. Each of the four sounds was made deterrent by increasing the amplitude. The seals reacted by swimming away from the sounds. The displacement effect of each sound was judged by comparing the animals' surface positions, and number of surfacings, during ten 45 min baseline periods with ten 45 min test periods per frequency (one frequency per day in rotation, 40 sessions in total). The seals were displaced by all four frequencies throughout the 40 trial days. The seals came to the surface more often when the test tones were produced than in the baseline periods. The initial displacement distances did not change over the 40 test days. This suggests that operating AHDs for only short periods will be more effective and less likely to result in habituation by the seals than operating them continuously. The discomfort threshold sound pressure level (SPL) was established for each of the four pulse frequencies. The acoustic discomfort threshold SPL is defined as the boundary SPL between the area that the animals generally occupied during the transmission of the sounds and the area that they generally did not enter during sound transmission. The discomfort threshold SPL may depend on the context.     

煤层气井历史拟合方法探讨

借鉴油藏的历史拟合方法,结合煤储层自身特征,概括了煤层气井历史拟合的原则和步骤。把该方法应用于新集煤层气井的拟合,取得良好效果。      

Multivariate analysis of Kenya's urban system

The study analyzes the structure, spatial interaction, and dimension of the post-colonial urban systems of Kenya using component factor analysis and based on selected socio-cultural, economic, and demographic variables. The study identified seven major dimensions of variation accounting for 72.0%. The analysis of the urban spatial variation is compared and intertwined with studies done in other countries to find out the regional variation of the loadings. Finally, a seven-order characteristics of Kenya urban systems is suggested, based on the study. The accurate knowledge of these salient characteristics of Kenya urban sub-systems is important before any viable spatial planning should be implemented.     

静应力变化对南加州地震位置的影响

地震引起邻近断层的静应力变化有推迟，加速，甚至触发以后的地震（ＤａｓａｎｄＳｃｈｏｌｚ，１９８１；ＳｔｅｉｎａｎｄＬｉｓｏｗｓｋｉ，１９８３；Ｈｕｄｎｕｔｅｔａｌ。，１９８９；Ｒｅａｓｅｎｂｅｒｇｅｔａｌ。，１９９２；ＤｕａｎｄＡｙｄｉｎ，１９９３；Ｈａｒｒｉｓｅｔａｌ。。，１９９２；Ｊｏｕｍｅｅｔａｌ。１９９２；Ｓｔｅｉｎｅｔａｌ。，１９９２；Ｓｉｍｐｓｏｎｅｔａｌ。，１９９４；Ｈａｒｒｉｓａｎ     

喜马拉雅碰撞早期含有机碳地层的剥蚀和全球变暖

印度和亚洲大陆碰撞早期新特提斯被动与活动大陆边缘上海相沉积物中含有机碳地层的剥蚀和氧化，可能影响到新世至早始新世海相碳酸盐中碳同位素比率向轻的比率转化，并通过温室效应导致全球性变暖。碰撞时间的最新确定和喜马拉雅沉积物源中有机碳含量的降低，允许我们估计古新世纯有机碳的输出。我们的计算表明，大陆碰撞通过含有机碳地层的剥蚀和埋藏，在全球碳旋回和气候变化中起着重要作用。     

Food intake and body measurements of Atlantic bottlenose dolphins (Tursiops truncates) in captivity

The food consumption (recorded in kg of individual fish species), body length and mass of 11 Atlantic bottlenose dolphins kept first at Windsor Safari Park, UK (1979-1993/1994), and later at Harderwijk Marine Mammal Park, The Netherlands (1993/1994-1995) are reported. This broad-scale, longitudinal study is based on historical data that were originally recorded for short-term husbandry purposes. The chemical composition and caloric value of the diet were variable and were not recorded. The food intake quantities should therefore be viewed as rough weight estimates of what wild conspecifics might eat (depending on their diet). The average annual food consumption of adult males and non-pregnant, non-lactating females was approximately 2000 kg of fish (estimated at 176 x 10(5) kJ). Food consumption showed little increase during gestation, but was 58-97% higher during lactation than during similar periods in non-reproductive years. All six calves began to eat solid food within a year of birth although suckling continued for 14-37 months after birth. The pattern of food intake of mothers and calves varied substantially between suckling periods. No seasonal changes in food consumption were detected, although there were small seasonal changes in water temperature. Births occurred at various times of year, since the timing of mating varied between years. The animals' body length increased rapidly during the first 3 years of life after which the growth rate decreased. Body length reached asymptote at approximately 270 cm. Adults of both sexes weighed around 260 kg. The relationship between standard body length (in cm) and body mass (in kg), although based on a small sample size (n = 16), can be expressed as body mass = 17.261e(0.0156(body length-100)). Animals weighing 155-225 kg consumed between 2 and 4% of their body mass per day.     

Detection distances of bottom-set gillnets by harbour porpoises (Phocoena phocoena) and bottlenose dolphins (Tursiops truncatus)

Many odontocetes die annually in gillnet fisheries. Why they become entangled is not yet clear. Maybe some species detect the nets too late to avoid collision. Therefore, the target strength of 11 types of bottom-set gillnets was measured under 0 and 45 degrees angles of incidence. From these target strengths and from knowledge on the echolocation abilities of two odontocete species (harbour porpoises, bottlenose dolphins), the detection ranges of the nets by these small cetaceans could be estimated. The 90% detection range by echolocating harbour porpoises, approaching the nets at right (perpendicular) angles under low noise level conditions, varied between 3 and 6 m depending on the net type. For bottlenose dolphins, under high noise conditions, the 90% detection range varied between 25 and 55 m. At other angles of approach, the estimated detection ranges are shorter. The study suggests that echolocating bottlenose dolphins can detect nets in time to avoid collision, whereas echolocating harbour porpoises cannot in most cases. Suggestions for future research to reduce small cetacean bycatch by improving the nets' detectability by echolocation are given.