东海区鱼类资源变化GIS时空分析

以东海区分小渔区分天分网型的捕捞量统计数据为样本数据 ,计算出资源密度的时空分布数据 ,并结合地理信息系统技术对这一时空数据进行时空分析。对东海区的中上层鱼类资源和底层及近底层鱼类资源的空间展布作分析 ,可以看到资源分布的块状和带状特征 ,以及资源分布与水文环境的关系。最后 ,对每个渔区 1 1年的资源密度进行趋势分析发现 ,1 1年来大部分渔区的资源密度呈下降趋势 ,小部分渔区的资源密度呈上升趋势。

美国海洋渔业捕捞份额管理--兼论其对中国海洋渔业管理的启示

为了解决近海渔业资源衰退、海洋渔业过度捕捞问题,美国在20世纪70年代后期出台了包括《马格努森·史蒂文斯渔业养护和管理法案》在内的一系列海洋渔业管理法案,其中以总捕捞量控制为先决条件的捕捞份额制度最为核心。近年来,中国也面临着近海渔业资源衰竭、过度捕捞等一系列问题。本文通过美国海洋渔业捕捞配额制度的研究,深入探讨、分析美国渔业捕捞制度的实施背景、目标、内容、份额分配方式及制度实施效果,就此进一步结合中国海洋渔业管理中的"捕捞限额"管理探讨其对中国海洋渔业管理的借鉴与启示。

Evaluating the Ryman-Laikre effect for marine stock enhancement and aquaculture

The Ryman-Laikre （R-L） effect is an increase in inbreeding and a reduction in total effective population size （NET） in a combined captive-wild system, which arises when a few captive parents produce large numbers of offspring. To facilitate evaluation of the R-L effect for scenarios that are relevant to marine stock enhancement and aquaculture, we extended the original R-L formula to explicitly account for several key factors that determine NeT, including the numbers of captive and wild adults, the ratio of captive to wild Ne/N （β）, productivity of captive and wild breeders, and removal of individuals from the wild for captive breeding. We show how to provide quantitative answers to questions such as： What scenarios lead to no loss of effective size？ What is the maximum effective size that can be achieved？ and What scenarios insure that NeTWill be no smaller than a specified value？ Important results include the following： （1） For large marine populations, the value of β becomes increasingly important as the captive contribution increases. Captive propagation will sharply reduce NeT unless the captive contribution is very small or β is very large （～10^3 or higher）. （2） Very large values of β are only possible if wild Ne/N is tiny. Therefore, large wild populations undergoing captive enhancement at even modest levels will suffer major reductions in effective size unless wild Ne is a tiny fraction of the census size （about 10 4 or lower）.

An ecosystem-based approach to marine risk assessment

Risk assessments quantify the probability of undesirable events along with their consequences.They are used to prioritize management interventions and assess tradeoffs,serving as an essential component of ecosystem-based management(EBM).A central objective of most risk assessments for conservation and management is to characterize uncertainty and impacts associated with one or more pressures of interest.Risk assessments have been used in marine resource management to help evaluate the risk of environmental,ecological,and anthropogenic pressures on species or habitats including for data-poor fisheries management(e.g.,toxicity,probability of extinction,habitat alteration impacts).Traditionally,marine risk assessments focused on singular pressure-response relationships,but recent advancements have included use of risk assessments in an EBM context,providing a method for evaluating the cumulative impacts of multiple pressures on multiple ecosystem components.Here,we describe a conceptual framework for ecosystem risk assessment(ERA),highlighting its role in operationalizing EBM,with specific attention to ocean management considerations.This framework builds on the ecotoxicological and conservation literature on risk assessment and includes recent advances that focus on risks posed by fishing to marine ecosystems.We review how examples of ERAs from the United States fit into this framework,explore the variety of analytical approaches that have been used to conduct ERAs,and assess the challenges and data gaps that remain.This review discusses future prospects for ERAs as EBM decision-support tools,their expanded role in integrated ecosystem assessments,and the development of next-generation risk assessments for coupled natural-human systems.

Principles for managing marine ecosystems prone to tipping points

As climatic changes and human uses intensify,resource managers and other decision makers are taking actions to either avoid or respond to ecosystem tipping points,or dramatic shifts in structure and function that are often costly and hard to reverse.Evidence indicates that explicitly addressing tipping points leads to improved management outcomes.Drawing on theory and examples from marine systems,we distill a set of seven principles to guide effective management in ecosystems with tipping points,derived from the best available science.These principles are based on observations that tipping points(1)are possible everywhere,(2)are associated with intense and/or multifaceted human use,(3)may be preceded by changes in earlywarning indicators,(4)may redistribute benefits among stakeholders,(5)affect the relative costs of action and inaction,(6)suggest biologically informed management targets,and(7)often require an adaptive response to monitoring.We suggest that early action to preserve system resilience is likely more practical,affordable,and effective than late action to halt or reverse a tipping point.We articulate a conceptual approach to management focused on linking management targets to thresholds,tracking early-warning signals of ecosystem instability,and stepping up investment in monitoring and mitigation as the likelihood of dramatic ecosystem change increases.This approach can simplify and economize management by allowing decision makers to capitalize on the increasing value of precise information about threshold relationships when a system is closer to tipping or by ensuring that restoration effort is sufficient to tip a system into the desired regime.

A review of potential conservation and fisheries benefits of breaching four dams in the Lower Snake River(Washington,USA)

Abundances of important and imperiled fishes of the Snake River Basin continue to decline.We assessed the rationale for breaching the four lower Snake River Basin dams to prevent complete loss of these fishes,and to maximize their likelihood of recovery.We summarize the science surrounding Sockeye Salmon(Oncorhynchus nerka),Chinook Salmon(O.tshawytscha),steelhead(O.mykiss),Bull Trout(Salvelinus confluentus),White Sturgeon(Acipenser transmontanus),and Pacific Lamprey(Entosphenus tridentatus).From this,we drew ten conclusions:(1)development of the Columbia River System(including the Snake River Basin)has converted mainstem rivers into reservoirs,altering fish behavior and survival;(2)most populations currently record their lowest abundance;(3)the Columbia River System dams reduce productivity of diadromous fishes in the highest-quality spawning grounds that could buffer against future climate dynamics;(4)past actions have done little to reduce impacts or precipitate recovery;(5)the Columbia River System constrains survival and productivity of salmon,steelhead and Bull Trout;(6)Snake River Basin salmon and steelhead remain at high extinction risk;(7)eliminating migration impediments and improving mainstem habitats are essential for maintaining genetic diversity and improving Bull Trout persistence;(8)the lower Snake River Basin dams preclude passage of adult White Sturgeon,constraining gene flow and recruitment;(9)the lower Snake River Basin dams impede dramatically passage of adult and juvenile Pacific Lamprey,and(10)Snake River Basin Pacific Lamprey is at high risk of extirpation.Breaching the four lower Snake River Basin dams is an action likely to prevent extirpation and extinction of these fishes.Lessons from the Columbia River System can inform conservation in other impounded rivers.

Movements and diving behavior of internesting green turtles along Pacific Costa Rica

Using satellite transmitters,we determined the internesting movements,spatial ecology and diving behavior of East Pacific green turtles(Chelonia mydas)nesting on Nombre de Jesús and Zapotillal beaches along the Pacific coast of northwestern Costa Rica.Kernel density analysis indicated that turtles spent most of their time in a particularly small area in the vicinity of the nesting beaches(50%utilization distribution was an area of 3 km^(2)).Minimum daily distance traveled during a 12 day internesting period was 4.6±3.5 km.Dives were short and primarily occupied the upper 10 m of the water column.Turtles spent most of their time resting at the surface and conducting U-dives(ranging from 60 to 81%of the total tracking time involved in those activities).Turtles showed a strong diel pattern,U-dives mainly took place during the day and turtles spent a large amount of time resting at the surface at night.The lack of long-distance movements demonstrated that this area was heavily utilized by turtles during the nesting season and,therefore,was a crucial location for conservation of this highly endangered green turtle population.The unique behavior of these turtles in resting at the surface at night might make them particularly vulnerable to fishing activities near the nesting beaches.

Providing refuges for adult Pacific lamprey Entosphenus tridentatus inside fishways

Fishways at hydroelectric dams are unnatural environments that typically present fish with channels of uniform depth,variable water velocity,and lack of cover.Fish retention and overall passage success may be improved by providing rest and sheltering areas inside fishways.We examined adult Pacific lamprey Entosphenus tridentatus use of two specially designed fishway refuges at Bonneville Dam on the Columbia River(northwestern USA).These relatively small boxes(1.1 m×0.4 m×0.2 m)provided low-velocity,dark refuge from predation for Pacific lamprey,a largely nocturnal species.Refuge boxes were equipped with antennas to detect entry of lamprey tagged with passive integrated transponder(PIT)tags.We PIT tagged and released 3,247 lamprey,including 599 that were double-tagged with a PIT and a radio transmitter,over three study years(2012-2014).In each year,PIT-tagged lamprey detected at nearby fishway exits had used a refuge:12%in 2012,28%in 2013,and 36%in 2014.Median residence time of PIT-tagged lamprey in the refuges for each year was 20.3 h,16.6 h,and 13.1 h.Lamprey entrance into refuges peaked at 0300-0500 PDT,and they typically exited at around 2000 PDT,suggesting that refuges primarily functioned as shelter from daylight.Probability of refuge use increased with a morphological indicator of sexual maturity(distance between dorsal fins).In the radio-tagged group,refuge users were equally likely to pass Bonneville Dam as non-users.However,refuge users were less likely than non-users to be detected at sites upstream from the dam,perhaps owing to their maturation status or longer mean passage time through our study area(2.0 vs.0.6 d for non-users).Refuges show promise for improving fish retention in fishways,particularly for nocturnal and/or small-bodied species that seek shelter from light or predation.