Temporal trends (2000–2011) and influences on fishery-independent catch rates for loggerhead sea turtles (Caretta caretta) at an important coastal foraging region in the southeastern United States

Seasonal trawling was conducted randomly in coastal (depths of 4.6–17 m) waters from St. Augustine, Florida, (29.9°N) to Winyah Bay, South Carolina (33.1°N), during 2000–03, 2008–09, and 2011 to assess annual trends in the relative abundance of sea turtles. A total of 1262 loggerhead sea turtles (Caretta caretta) were captured in 23% (951) of 4207 sampling events. Capture rates (overall and among prevalent 5-cm size classes) were analyzed through the use of a generalized linear model with log link function for the 4097 events that had complete observations for all 25 model parameters. Final models explained 6.6% (70.1–75.0 cm minimum straight-line carapace length [SCLmin]) to 14.9% (75.1–80.0 cm SCLmin) of deviance in the data set. Sampling year, geographic subregion, and distance from shore were retained as significant terms in all final models, and these terms collectively accounted for 6.2% of overall model deviance (range: 4.5–11.7% of variance among 5-cm size classes). We retained 18 parameters only in a subset of final models: 4 as exclusively significant terms, 5 as a mixture of significant or nonsignificant terms, and 9 as exclusively nonsignificant terms. Four parameters also were dropped completely from all final models. The generalized linear model proved appropriate for monitoring trends for this data set that was laden with zero values for catches and was compiled for a globally protected species. Because we could not account for much model deviance, metrics other than those examined in our study may better explain catch variability and, once elucidated, their inclusion in the generalized linear model should improve model fits.

Learning optimal adaptation strategies in unpredictable motor tasks.

Picking up an empty milk carton that we believe to be full is a familiar example of adaptive control, because the adaptation process of estimating the carton's weight must proceed simultaneously with the control process of moving the carton to a desired location. Here we show that the motor system initially generates highly variable behavior in such unpredictable tasks but eventually converges to stereotyped patterns of adaptive responses predicted by a simple optimality principle. These results suggest that adaptation can become specifically tuned to identify task-specific parameters in an optimal manner.

Developing alternative shoreline armoring strategies: the living shoreline approach in North Carolina

This paper reviews the scientific data on the ecosystem services provided by shoreline habitats, the evidence for adverse impacts from bulkheading on those habitats and services, and describes alternative approaches to shoreline stabilization, which minimize adverse impacts to the shoreline ecosystem. Alternative shoreline stabilization structures that incorporate natural habitats, also known as living shorelines, have been popularized by environmental groups and state regulatory agencies in the mid-Atlantic. Recent data on living shoreline projects in North Carolina that include a stone sill demonstrate that the sills increase sedimentation rates, that after 3 years marshes behind the sills have slightly reduced biomass, and that the living shoreline projects exhibit similar rates of fishery utilization as nearby natural fringing marshes. Although the current emphasis on shoreline armoring in Puget Sound is on steeper, higher-energy shorelines, armoring of lower-energy shorelines may become an issue in the future with expansion of residential development and projected rates of sea level rise. The implementation of regulatory policy on estuarine shoreline stabilization in North Carolina and elsewhere is presented. The regulatory and public education issues experienced in North Carolina, which have made changes in estuarine shoreline stabilization policy difficult, may inform efforts to adopt a sustainable shoreline armoring strategy in Puget Sound. A necessary foundation for regulatory change in shoreline armoring policy, and public support for that change, is rigorous scientific assessment of the variety of services that natural shoreline habitats provide both to the ecosystem and to coastal communities, and evidence demonstrating that shoreline armoring can adversely impact the provision of those services.

Examination of the foraging habits of Pacific harbor seal (Phoca vitulina richardsi) to describe their use of the Umpqua River, Oregon, and their predation on salmonids

The increase in harbor seal (Phoca vitulina richardsi) abundance, concurrent with the decrease in salmonid (Oncorhynchus spp.) and other fish stocks, raises concerns about the potential negative impact of seals on fish populations. Although harbor seals are found in rivers and estuaries, their presence is not necessarily indicative of exclusive or predominant feeding in these systems. We examined the diet of harbor seals in the Umpqua River, Oregon, during 1997 and 1998 to indirectly assess whether or not they were feeding in the river. Fish otoliths and other skeletal structures were recovered from 651 scats and used to identify seal prey. The use of all diagnostic prey structures, rather than just otoliths, increased our estimates of the number of taxa, the minimum number of individuals and percent frequency of occurrence (%FO) of prey consumed. The %FO indicated that the most common prey were pleuronectids, Pacific hake (Merluccius productus), Pacific stag-horn sculpin (Leptocottus armatus), osmerids, and shiner surfperch (Cymatogaster aggregata). The majority (76%) of prey were fish that inhabit marine waters exclusively and fish found in marine and estuarine areas (e.g. anadromous spp.) which would indicate that seals forage predominantly at sea and use the estuary for resting and opportunistic feeding. Salmonid remains were encountered in 39 samples (6%); two samples contained identifiable otoliths, which were determined to be from chi-nook salmon (O. tshawytscha). Because of the complex salmonid composition in the Umpqua River, we used molecular genetic techniques on salmonid bones retrieved from scat to discern species that were rare from those that were abundant. Of the 37 scats with salmonid bones but no otoliths, bones were identified genetically as chinook or coho (O. kisutch) salmon, or steelhead trout (O. mykiss) in 90% of the samples.

根茎克隆植物羊草分株种群对去叶干扰的生长对策

克隆植物具有多种不同于非克隆植物的生长和繁殖策略。本研究首先综述了这些生长与繁殖策略之中，与我们的实验研究相关的尤其是对于去叶干扰适应策略的四个方面，包括克隆整合、克隆分株大小与密度之权衡( tradeoff)过程、碳水化合物贮备与利用、营养繁殖和芽种群(bud population)调节等。预测克隆植物选择什么样的对策以及某种对策发生作用的条件及程度如何，对克隆植物生态学研究者来说，将是富有挑战意味的课题。 羊草(Leymus chinensis (Trin,) Tzvel.)是禾本科的一种多年生根茎型克隆植物，常常处于由放牧或刈割造成的去叶干扰( defoliation)的胁迫下。在我们的第一个实验（2002年）中，考察了去叶干扰和根茎切割( rhizome severing)是否影响根茎本身和分株地上部分的生长、以及营养繁殖芽的数量特征。同时我们检验如下的假设：直接受到去叶干扰的分株除了会受益于可能的补偿作用之外，还会受益于克隆整合作用，即与之保持根茎联系的未受去叶处理的分株将转移碳水化合物或养分给受去叶干扰的分株，使之得以尽快恢复光合组织。实验结果显示：单次去叶干扰影响根茎生长和芽的产生，而对地上部分的生长影响甚微。只有重度去叶干扰才显著影响营养繁殖芽的产生，而轻度去叶干扰作用不明显。所以，当去叶强度不大时，补偿作用机制将弥补植物由于去叶干扰而受到的损失。我们的实验并未检测到克隆整合的发生，可能的原因是本实验持续的时间不足够长或者是由于根茎中的碳水化合物贮备在去叶干扰发生后发挥了作用，缓解了去叶干扰对羊草分株生长及芽生产的所造成的冲击。 在第二个实验（200 3年）中，为了考查相继数次的去叶干扰是否能够启动羊草分株间的克隆整合，以及启动克隆整合所需达到的去叶干扰的频次，我们将实验样方设计为两部分：核心区( Core section)和外围区(Periphery section)。不同频次的去叶处理（0去叶，作为对照; 1次去叶;3次去叶;5次去叶）仅施加于实验样方的核心区。结果表明，经历3次和5次去叶处理的样方外围区的生物量及水溶性碳水化合物( wsc)含量均明显少于经历1次去叶处理及0去叶处理的样方外围区，这意味着克隆整合在3次去叶和5次去叶两种处理中发生了，而在其它两种处理中没有发生。此外，分株的大小一数目之权衡可能在基株(genet)水平上发生，因此，一个克隆植物基株，当部分分株受到去叶干扰后，将增加其分株数目，但优先增加未受到去叶干扰部分的分株数目。我们将羊草的这种行为视为克隆基株试图逃避干扰的“逃逸行为”( escaping behavior)。 同时在实验中，我们监测了实验样方核心区分株的wsc浓度，目的是查明羊草枝条与根茎中wsc浓度随时间的变化格局及其对去叶干扰的响应，意在发现羊草枝条地上、地下部分和根茎中wsc浓度的时间变化之间的联系。在生长旺季，对照处理（即O去叶处理）的wsc浓度显著降低，这是由于植物在此时期的高生长速率和高呼吸速率所致;相比之下，其它经历去叶干扰的三个处理中羊草wsc浓度降低不如对照处理那么明显和迅速，甚至在高频次去叶处理中还有所上升，其原因大概是由于去叶而使叶面积减小，引起枝条的总呼吸下降所致。羊草枝条中最终的wsc浓度没有受到单次去叶处理的显著影响，却很可观地受到相继数次去叶干扰（3次和5次去叶处理）的影响。去叶干扰可能加速了碳水化合物在气温降低时自地上向地下的转移。枝条的地下部分wsc浓度比地上部分更稳定。在地上部分受到去叶干扰后，根茎中的wsc必然向上输出到地上枝条，而强烈的生长会消耗wsc，但可能的克隆整合（通常在相对频繁的去叶干扰条件下发生）将在一定程度上缓解这种wsc消耗。 在此实验中，我们还监测了羊草平均每分株所拥有的芽的数目，包括每分株分蘖节芽（tiller bud）数目和根茎芽(thizomatous bud)数目。从平均每分株芽数目的时间动态来看，各种去叶处理之间的差异程度不大，这主要是羊草在受到去叶干扰后补偿作用的贡献。与对照处理相比，受不同频次去叶干扰的三个处理的根茎芽具有相对于分蘖节的更强的增长优势。去叶干扰对根茎芽生长的促进作用大于对分蘖节芽的促进作用。我们认为这种反应是羊草克隆基株的一种逃避干扰的适应性努力，可视为一种“逃逸行为”，也可看作克隆植物觅养行为(foraging behavior)的一种特殊形式。芽的增长在中等频度的去叶干扰条件下最强，似乎同样符合中度干扰理论。有趣的是，特定频度的去叶干扰可能会造成芽种群中两大类型芽之间比例（根茎芽／分蘖节芽）的振荡现象（Oscillation）。 最后展望了对于羊草今后应继续开展的工作主要集中在两大方面：一是有性繁殖与无性繁殖之间在不同生境或不同干扰条件下的权衡关系;二是处于不同斑块对比度( patch contrast)的生境中的羊草克隆分株之问的生理整合，及其强度与斑块对比度的定量关系。

Coping with excess salt in their growth environments: osmoregulation and other survival strategies deployed by the mangroves

Mangroves are defined as a collection of woody plants and the associated fauna and flora that use a coastal depositional environment. Here the specific effects of salinity changes in mangroves have been examinated.

Niche measures and feeding strategies of Barbodes gonionotus Bleeker and Oreochromis spp. from a ricefield in Bangladesh

Intra-and interspecific virtual niche measures and feeding strategies of Barbodes gonionotus and Oreochromis spp. were studied from a rice field in Bangladesh. Appropriateness and ease of interpretation of different indices were evaluated. Small sizes of both species had a relatively wider dietary breadth and used many of the resource categories available to them than the large size groups, though none were generalist feeder. The dietary overlap of large B. gonionotus on the small was greater than the reverse, but biologically insignificant. While the dietary overlap of large Oreochromis spp. on the small was significantly greater. Interspecific dietary width was relatively broader for B. gonionotus than Oreochromis spp. and overlap of B. gonionotus on Oreochromis spp. was significantly greater than the reverse. Evidence of significant intraspecific dietary overlap between the two sizes of tilapia reflects strong competition and cautions for mixed-size stocking in rice-fish system. Besides, there seem fewer opportunities for habitat segregation between B. gonionotus and Oreochromis spp., due to the significant interspecific dietary overlap of the former on the latter in rice-fish system. Tilapia specialized on periphytic detrital aggregate while silver barb tended to consume aquatic macrophytes and molluscs. Small sizes of B. gonionotus should be preferred for rice-fish integration over the Oreochromis spp. due to their broader niche width and pronounced ontogenetic dietary shifts with the aging of the stock.

Investigation of anti-lock braking strategies for heavy goods vehicles

An articulated lorry was instrumented in order to measure its performance in straight-line braking. The trailer was fitted with two interchangeable tandem axle sub-chassis, one with an air suspension and the other with a steel monoleaf four-spring suspension. The brakes were only applied to the trailer axles, which were fitted with anti-lock braking systems (ABS), with the brake torque controlled in response to anticipated locking of the leading axle of the tandem. The vehicle with the air suspension was observed to have significantly better braking performance than the steel suspension, and to generate smaller inter-axle load transfer and smaller vertical dynamic tyre forces. Computer models of the two suspensions were developed, including their brakes and anti-lock systems. The models were found to reproduce most of the important features of the experimental results. It was concluded that the poor braking performance of the steel four-spring suspension was mainly due to interaction between the ABS and inter-axle load transfer effects. The effect of road roughness was investigated and it was found that vehicle stopping distances can increase significantly with increasing road roughness. Two alternative anti-lock braking control strategies were simulated. It was found that independent sensing and actuation of the ABS system on each wheel greatly reduced the difference in stopping distances between the air and steel suspensions. A control strategy based on limiting wheel slip was least susceptible to the effects of road roughness.

Management strategies for exploitation of Uganda fisheries resources

Fisheries legislation in Uganda has not been feasibly applicable to all Uganda water bodies and species therein. Failure to make appropriate legislation to regulate fishing gears and methods has led to the decline or near collapse of some fisheries. Most fisheries have been damaged by destructive fishing gears and methods. Selectivity characteristics of several gears and fishing methods were therefore examined for different commercially important fish species in major and minor lakes and recommendations made on suitable types of gears, gear sizes and fishing methods for exploitation of the fisheries resource.