Harvesting at the Cohort and Population Levels

This chapter explores dynamical behaviors that go beyond globally stable outcomes to include alternate stable states, and non-equilibrium behaviors. The possibility of multiple equilibria emerges quite readily in models with non-linear harvesting functions. In practice, most fisheries management protocols at least implicitly assume that harvested populations have well-behaved stable equilibrium properties. If this is not the case, then sudden changes (including collapse) can occur and be totally unanticipated. This chapter describes the spectrum of single-species harvesting models from biomass dynamics models that do not include age or size structure, to delay–difference models with a simple demographic structure, to full age-structured models. Dynamic-pool models combine yield per recruit and egg-per-recruit with a stock-recruitment model to obtain an equilibrium yield curve. These single-species models are used to estimate biological reference points with which to assess stock status.

Material screening for two-step thermochemical splitting of H2S using metal sulfide

Associated with the rise in energy demand is the increase in the amount of H2S evolved to the environment. H2S is toxic and dangerous to life and the environment, thus, the need to develop efficient and costeffective ways of disposing of the H2S gas has become all-important. To this end, a two-step thermochemical H2S splitting cycle is proposed in this work which does more than just getting rid of the toxic gas but has the potential to produce valuable H2 gas as well as store the solar heat energy. Studies have proved that the type of material used, such as metal sulfides, is critical to the efficiency of this thermochemical splitting process. As follows, this study focuses on establishing a criterion to aid in selecting favorable metal sulfides for application and further development in the H2S thermochemical decomposition sphere. Using a computational approach, via the HSC Chemistry 8®, evaluations such as the equilibrium yield from the sulfurization and decomposition reaction steps, the temperature required for reaction spontaneity, and the Reversibility Index were determined. Investigations proved that sulfides of Zirconium, Niobium, and Nickel were auspicious candidates for the thermochemical decomposition.

Muskellunge Management: Fifty Years of Cooperation Among Anglers, Scientists, and Fisheries Biologists

<em>Abstract</em>.—The current Lake St. Clair Great Lakes Muskellunge <em>Esox masquinongy </em>fishery is entirely self-sustaining and dominated by a catch-and-release ethic. Catch rates of Lake St. Clair Muskellunge are among the highest documented for this species, and angler catches of trophy Muskellunge are considered relatively commonplace. The proximity of Lake St. Clair to many potential new Muskellunge anglers, interest among some anglers in restoring a long-prohibited winter spear fishery, and warming temperatures associated with climate change pose potential threats to the quality of this fishery. We developed an age-structured equilibrium yield model to project the likely effects of altered size and harvest limits, increased angling effort, establishment of a winter spearing season, or warming temperatures on open-water angling catch rates of three size-classes of Lake St. Clair Muskellunge (all fish ≥ age 1, legal-sized fish > 107 cm, and trophy-sized fish > 127 cm). Our modeling indicated that changes in regulations in the Lake St. Clair Muskellunge fishery were unlikely to result in substantial changes to catch rates of Muskellunge of any size-class. Similarly, the current high rate of voluntary release would largely buffer catch rates of all size-classes of Lake St. Clair Muskellunge from increases in fishing effort. Our simulation of a winter spearing fishery indicated that only high levels of spearing effort and harvest would reduce open-water catch rates to a degree that would likely be objectionable to anglers. In contrast, the predicted catch rates of legal-and trophy-sized fish were highly sensitive to modeled reductions in growth. As such, the major threat to this trophy Muskellunge fishery appears largely outside the traditional toolbox of fisheries managers, hastening the need for development of resilient management and monitoring plans for this valuable fishery.

Poly(ethylene glycol) based bis-diol as a functional medium for highly efficient conversion of urea and methanol to dimethyl carbonate

Poly(ethylene glycol) based bis-diol/ZnO is an excellent catalytic system for the reaction of urea and methanol to produce DMC. The equilibrium yield of DMC in the reaction can be ten times higher than that of the conventional method.