Effectiveness of a Rigid Grate for Excluding Pacific Halibut, Hippoglossus stenolepis, From Groundfish Trawl Catches

A rigid grate was installed in a groundfish trawl to test its effectiveness in excluding Pacific halibut, Hippoglossus stenolepis, from commercial flatfish catches in the Gulf of Alaska. The grate was located ahead of the trawl codend to direct halibut toward an escape opening while allowing target species to pass through toward the codend. In an experimental fishery, the escape rate of halibut was estimated at 94%, while 72% of the Dover sole, Microstomas pacificus, 67% of the rex sole, Glyptocephalus zachirus, and 79% of the flathead sole, Hippoglossoides elassodon, were retained

Feeding habits of the arrowtooth flounder, Atheresthes stomias, from the northeast Gulf of Alaska

Thesis (M.S.) University of Alaska Fairbanks, 1980The feeding habits of Atheresthes stomias from the northeast Gulf of Alaska were studied. Analysis of 558 specimens indicated that fishes, shrimp, and euphausiids were the dominant prey items. Fishes occurred in 42% of the specimens found to be feeding and contributed nearly 90% of the total prey volume. Shrimp, primarily Pandalidae, contributed approximately 6% of the total prey volume and were found in 28% of the feeding specimens. Euphausiids occurred in nearly 26% of the feeding specimens, but contributed less than 3% of the total prey volume. Feeding habits were influenced by the size of the flounder; larger specimens preyed more heavily on fishes than on crustaceans. Depth also affected the feeding habits of A. stomias. Flounders taken from depths of 150 m or less were feeding more intensively than those from deeper water. Marked differences in the diet of specimens from different sample locations were observed

Handling Non-detects with Imputation in a Nested Design: A Simulation Study

In this paper, a simulation study was conducted to assess whether it is ideal to address the issue of non-detects in data using a traditional substitution approach for non-detects, imputation, or a non-imputation based approach. Simulated data used were simple nested designs motivated by a real-life data in a study of bumble bee activity in a commercial cherry orchard by Kuivila et al. (2021). The simulated data were generated at different thresholds or censoring levels and at different effect sizes. For each simulated data, seven popular existing techniques to handle non-detects were applied: (i) Zero substitution, (ii) Substitution with half Limit of Detection (LOD/2), (iii) Substitution with LOD/√ 2, (iv) Multiple Imputation (MI), (v) Regression on Order Statistics (ROS) (Imputation approach), and (vi) Maximum Likelihood Estimation (MLE) (likelihood estimation approach) and (vii) Kaplan-Meier (KM). Multiple Imputation (MI) was not applicable as the design of the simulated data violated the assumption of having a multivariate distribution. By comparative analysis of the simulated data, substituting with LOD/2 seemed appropriate for the design simulated, as it outperformed the other techniques (i.e ROS, MLE, KM, LOD/√ 2, and zero substitution) by yielding a lower Type I error, lower bias, and a better power across increasing effect sizes

Philosophical Agents

Abstraction is the technique we use to deal with complexity. What is the proper kind and level of abstraction for complex software agents? We think it would be reasonable to endow agents with a philosophy. Then, by understanding their philosophies, we can use them more effectively. To endow agents with ethical principles, developers need an architecture that supports explicit goals, principles and capabilities, as well as laws and ways to sanction or punish miscreants. All of the ethical approaches described in this article are single-agent in orientation and encode other agents implicitly

Response of blackberry cultivars to nematode transmission of Tobacco ringspot virus

A study was conducted on eight cultivars of blackberry (‘Apache’, ‘Arapaho’, ‘Chester’, ‘Chickasaw’, ‘Kiowa’, ‘Navaho’, ‘Shawnee’, and ‘Triple Crown’), of which four plants of each were previously determined in the fall of 2001 to have root, but not leaf, infection with Tobacco ringspot virus (TRSV). The objectives of our study were to determine virus effects on plant vigor and the spread of virus infection in the plants. Eight plants of each cultivar, four infected and four free of infection, were grown in pots on a gravel pad for the 2002 growing season, and samples of primocane and floricane leaves were taken to determine if TRSV had moved to the above-ground portion of the plants. TRSV infection was determined by ELISA tests. At the end of the growing season (October), the plants were harvested and dry weights determined for floricanes, primocanes, and roots to determine virus effects on plant vigor. In all plants that had been shown to have root TRSV infection, the virus was shown to have moved into the top portion of the plants as evidenced by positive ELISA tests on primocane and floricane leaf tissue. Dry-weight results indicated no significant interaction of virus infection and cultivar, or any main effects of virus on cane or root growth, as all dry weights were similar for infected and non-infected plants. No dramatic leaf symptoms of virus infection were observed on infected plants in our study at any time during the growing season. Further research should focus on possible virus effects on plants that have been infected for a longer period of time to determine if in fact the virus has any effect on plant growth or productivit

Complex Adaptive Systems: Adapting and Managing Teams and Team Conflict

Complexity comes from dramatic structural changes to organizations and governments such as globalization, global competition, workforce diversity, and continual innovations. Complex adaptive systems (CAS) are organizations that are a composite of the interconnected whole. Teams must manage and operate in emerging ecosystems, understand factors that lead to team effectiveness when managing and facilitating teams and team conflict, and understand the development of conflict models. This chapter provides an overview of teams, CAS, conflict stages, and conflict models. This chapter presents adaptive leadership as one leadership style that offers organizations with the capabilities of reacting to changing environments quickly. Adaptive leadership offers a prescriptive approach for managers and leaders to follow when dealing with organizational conflict while operating in today’s complex and global environment

Mathematical modelling of tissue-engineering angiogenesis

We present a mathematical model for the vascularisation of a porous scaffold following implantation in vivo. The model is given as a set of coupled non-linear ordinary differential equations (ODEs) which describe the evolution in time of the amounts of the different tissue constituents inside the scaffold. Bifurcation analyses reveal how the extent of scaffold vascularisation changes as a function of the parameter values. For example, it is shown how the loss of seeded cells arising from slow infiltration of vascular tissue can be overcome using a prevascularisation strategy consisting of seeding the scaffold with vascular cells. Using certain assumptions it is shown how the system can be simplified to one which is partially tractable and for which some analysis is given. Limited comparison is also given of the model solutions with experimental data from the chick chorioallantoic membrane (CAM) assay