Estimating Sustainable Bycatch Rates for California Sea Lion Populations in the Gulf of California

Abstract:  Commercial and subsistence fisheries pressure is increasing in the Gulf of California, Mexico. One consequence often associated with high levels of fishing pressure is an increase in bycatch of marine mammals and birds. Fisheries bycatch has contributed to declines in several pinniped species and may be affecting the California sea lion ( Zalophus californianus ) population in the Gulf of California. We used data on fisheries and sea lion entanglement in gill nets to estimate current fishing pressure and fishing rates under which viable sea lion populations could be sustained at 11 breeding sites in the Gulf of California. We used 3 models to estimate sustainable bycatch rates: a simple population-growth model, a demographic model, and an estimate of the potential biological removal. All models were based on life history and census data collected for sea lions in the Gulf of California. We estimated the current level of fishing pressure and the acceptable level of fishing required to maintain viable sea lion populations as the number of fishing days (1 fisher/boat setting and retrieving 1 day's worth of nets) per year. Estimates of current fishing pressure ranged from 101 (0–405) fishing days around the Los Machos breeding site to 1887 (842–3140) around the Los Islotes rookery. To maintain viable sea lion populations at each site, the current level of fishing permissible could be augmented at some sites and should be reduced at other sites. For example, the area around San Esteban could support up to 1428 (935–2337) additional fishing days, whereas fishing around Lobos should be reduced by at least 165 days (107–268). Our results provide conservation practitioners with site-specific guidelines for maintaining sustainable sea lion populations and provide a method to estimate fishing pressure and sustainable bycatch rates that could be used for other marine mammals and birds .     

机械卷载和余氯对渔业资源损失量评估初探

火(核)电厂、液化天然气(LNG)接收站排放余氯水和取水机械卷载效应均对渔业资源带来影响.本文以LNG接收站工程为例,依据2004年5、8、11月和2005年5月评价水域渔业调查资料,采用渔业资源尾数密度(包括鱼卵、仔鱼生长形成的部分)、受影响的面积和鱼类商品体重的乘积作为计算模式,评估机械卷载和余氯对渔业资源的损失量.结果表明,LNG接收站余氯和机械卷载引起的渔业资源损失量为176.0t/a.本文所采用的评估方法,有助于解决海洋工程影响渔业资源数量评估的实践问题,对渔业资源物损评价标准的制定有一定的参考价值.     

安全与危险纠缠理论创建及其研究

针对安全概念不统一,安全科学与技术发展相对滞后,重特大安全事故频发等问题,通过借鉴量子纠缠理论,提出了安全与危险纠缠理论学说。建立了安全与危险纠缠理论模型,阐述了其纠缠机制,明确了一个系统中的安全与危险在不同时段内存在的方式和状态:通常人们所认知的安全或危险均是系统在过去时段内以“一显一隐”的方式塌缩成确定的状态,而在现在与未来时段,它们分别是以“显性”、“隐性”的方式纠缠为不确定的状态;若该系统的“安全与危险纠缠”状态向安全方向塌缩时,系统则表现为安全,若向危险转化时,则系统表现为事故。同时,分析了“安全与危险纠缠”理论建立的对安全科学及安全生产实际意义与理论价值,及其未来展望和存在问题。     

Assessment of Management to Mitigate Anthropogenic Effects on Large Whales

United States and Canadian governments have responded to legal requirements to reduce human‐induced whale mortality via vessel strikes and entanglement in fishing gear by implementing a suite of regulatory actions. We analyzed the spatial and temporal patterns of mortality of large whales in the Northwest Atlantic (23.5°N to 48.0°N), 1970 through 2009, in the context of management changes. We used a multinomial logistic model fitted by maximum likelihood to detect trends in cause‐specific mortalities with time. We compared the number of human‐caused mortalities with U.S. federally established levels of potential biological removal (i.e., species‐specific sustainable human‐caused mortality). From 1970 through 2009, 1762 mortalities (all known) and serious injuries (likely fatal) involved 8 species of large whales. We determined cause of death for 43% of all mortalities; of those, 67% (502) resulted from human interactions. Entanglement in fishing gear was the primary cause of death across all species (n = 323), followed by natural causes (n = 248) and vessel strikes (n = 171). Established sustainable levels of mortality were consistently exceeded in 2 species by up to 650%. Probabilities of entanglement and vessel‐strike mortality increased significantly from 1990 through 2009. There was no significant change in the local intensity of all or vessel‐strike mortalities before and after 2003, the year after which numerous mitigation efforts were enacted. So far, regulatory efforts have not reduced the lethal effects of human activities to large whales on a population‐range basis, although we do not exclude the possibility of success of targeted measures for specific local habitats that were not within the resolution of our analyses. It is unclear how shortfalls in management design or compliance relate to our findings. Analyses such as the one we conducted are crucial in critically evaluating wildlife‐management decisions. The results of these analyses can provide managers with direction for modifying regulated measures and can be applied globally to mortality‐driven conservation issues. Evaluación del Manejo para Mitigar Efectos Antropogénicos sobre Ballenas Mayores     

动态安全系统理论的研究与应用

将量子纠缠理论引入安全理论中,提出安全与危险纠缠机制;指出人们当前所处的“安全”的状态,实质上是“安全与风险叠加”的状态,是不确定的;而相对于当前的状态,之前的状态实质上是安全的,是确定的,由此重新给出了安全的新认知。再以安危纠缠和安全新认知为理论基础,建立了动态安全系统理论,给安全管理与事故预防提供了新思想和新方向。然后借由塔吊生产系统,展示了动态安全系统理论的应用,定量分析系统内部安全程度,从而使安全管理步入动态的定量化管理阶段。     

Antepartum rupture of the intertwin-dividing membrane in monochorionic diamniotic twins: a case report and review of the literature

We report a case of monochorionic diamniotic twin gestation confirmed by ultrasound visualization of the thin intertwin-dividing membrane at 32 weeks' gestation. Ultrasound at 36 weeks failed to demonstrate the thin dividing membrane. The pregnancy ended a few days later with spontaneous vaginal delivery of the first twin. The second twin was in transverse lie with no membranes that could be felt around. Severe fetal heart rate deceleration developed, prompting delivery by emergency caesarean section. Cord entanglement was noted at the time of delivery, which resulted in severe perinatal morbidity of the second twin. The antepartum rupture of the dividing membrane must have happened some time between 32 and 36 weeks. The etiology for this intrauterine disruption is unknown. A review of the literature about the antepartum rupture of the intertwin-dividing membrane is described, along with its possible causes and complications. In addition, we discuss possible causes of incorrect amnionicity determination, and thus how to minimize these pitfalls. We conclude that antepartum disruption of the intertwin-dividing membrane is more common than previously thought. Moreover, prenatal ultrasonographic visualization of a dividing membrane in a diamniotic twin pregnancy does not rule out future change in this environment to a monoamniotic one, with all its perinatal morbidity and mortality complications, which result mainly from cord entanglement. This suggests a modification in the method and frequency of the prenatal fetal well-being follow-up, as well as the time and mode of delivery. Copyright © 2005 John Wiley & Sons, Ltd.