Sex-change rules, stock dynamics, and the performance of spawning-per-recruit measures in protogynous stocks

Predicting and under-standing the dynamics of a population requires knowledge of vital rates such as survival, growth, and reproduction. However, these variables are influenced by individual behavior, and when managing exploited populations, it is now generally realized that knowledge of a species’ behavior and life history strategies is required. However, predicting and understanding a response to novel conditions—such as increased fishing-induced mortality, changes in environmental conditions, or specific management strategies—also require knowing the endogenous or exogenous cues that induce phenotypic changes and knowing whether these behaviors and life history patterns are plastic. Although a wide variety of patterns of sex change have been observed in the wild, it is not known how the specific sex-change rule and cues that induce sex change affect stock dynamics. Using an individual based model, we examined the effect of the sex-change rule on the predicted stock dynamics, the effect of mating group size, and the performance of traditional spawning-per-recruit (SPR) measures in a protogynous stock. We considered four different patterns of sex change in which the probability of sex change is determined by 1) the absolute size of the individual, 2) the relative length of individuals at the mating site, 3) the frequency of smaller individuals at the mating site, and 4) expected reproductive success. All four pat-terns of sex change have distinct stock dynamics. Although each sex-change rule leads to the prediction that the stock will be sensitive to the size-selective fishing pattern and may crash if too many reproductive size classes are fished, the performance of traditional spawning-per-recruit measures, the fishing pattern that leads to the greatest yield, and the effect of mating group size all differ distinctly for the four sex-change rules. These results indicate that the management of individual species requires knowledge of whether sex change occurs, as well as an understanding of the endogenous or exogenous cues that induce sex change

A prior for steepness in stock-recruitment relationships, based on an evolutionary persistence principle

Priors are existing information or beliefs that are needed in Bayesian analysis. Informative priors are important in obtaining the Bayesian posterior distributions for estimated parameters in stock assessment. In the case of the steepness parameter (h), the need for an informative prior is particularly important because it determines the stock-recruitment relationships in the model. However, specifications of the priors for the h parameter are often subjective. We used a simple population model to derive h priors based on life history considerations. The model was based on the evolutionary principle that persistence of any species, given its life history (i.e., natural mortality rate) and its exposure to recruitment variability, requires a minimum recruitment compensation that enables the species to rebound consistently from low critical abundances (Nc). Using the model, we derived the prior probability distributions of the h parameter for fish species that have a range of natural mortality, recruitment variabilities, and Nt values

Regulatory Mechanisms and Information Processing in Uncertain Fisheries

We study the effects on fisherman decision processes of periodic (e.g., weekly) individual quotas. In the model, the fisherman must choose at the start of each week which of two grounds to fish on. The catch per week on each ground is a random variable and the fisherman does not know with certainty the parameters of the distribution of that variable. He does have estimates on each parameter and can improve these estimates by Bayesian updating. The choice of a fishing ground takes into account the expected catch on that ground and the expected improvement in information from fishing on that ground. Our study is concerned with the effect of weekly quotas on the joint production of information and fish. Various policy implications are discussed, and the results are compared with the policy analysis of Clark (1980) in the deterministic case. We show that the quota affects the value of Information and that if quotas are transferable, then the quota may limit its own value.Environmental Economics and Policy, Research Methods/ Statistical Methods, Resource /Energy Economics and Policy, Risk and Uncertainty,

Evolution of size-dependent flowering in Onopordum illyricum: A quantitative assessment of the role of stochastic selection pressures

We explore the evolution of delayed, size-dependent reproduction in the monocarpic perennial Onopordum illyricum, using a range of mathematical models, parameterized with long-term field data. Analysis of the long-term data indicated that mortality, flowering, and growth were age and size dependent. Using mixed models, we estimated the variance about each of these relationships and also individual-specific effects. For the held populations, recruitment was the main density-dependent process, although there were weak effects of local density on growth and mortality Using parameterized growth models, which assume plants grow along a deterministic trajectory, we predict plants should flower at sizes approximately 50% smaller than observed in the field. We then develop a simple criterion, termed the "1-yr look-ahead criterion," based on equating seed production now with that of next year, allowing for mortality and growth, to determine at what size a plant should flower. This model allows the incorporation of variance about the growth function and individual-specific effects. The model predicts flowering at sizes approximately double that observed, indicating that variance about the growth curve selects for larger sizes at flowering. The 1-yr look-ahead approach is approximate because it ignores growth opportunities more than 1 yr ahead. To assess the accuracy of this approach, we develop a more complicated dynamic state variable model. Both models give similar results indicating the utility of the 1-yr look-ahead criterion. To allow for temporal variation in the model parameters, we used an individual-based model with a generic algorithm. This gave very accurate prediction of the observed flowering strategies. Sensitivity analysis of the model suggested that temporal variation in the parameters of the growth equation made waiting to flower more risky, so selected for smaller sizes at flowering. The models clearly indicate the need to incorporate stochastic variation in life-history analyses

Harmonization of Private Law and the destiny of overriding mandatory provisions: The Example of Consumer Protection under The Common European Sales Law

The CESL is not quite as “complete” a sales law as its name suggests. It cannot, in the opinion of this author, be considered “hard core” contract law as it has substantial gaps, which need to be filled by the national laws of the member states.5 As the objectives of the CESL are consumer protection and also the removing of obstacles in the internal market, it is needless to say that a balance had to be struck. Therefore, the CESL does not contain the highest degree of consumer protection possible, albeit the allegations of the European Commission that it does achieve a level of protection that is on average higher than that which the member states’ laws have to offer.6 Member states have on top of that lost the power to impose their own mandatory provisions, which protect the consumer, as the CESL imposes its own mandatory rules, when chosen by the parties. The relationship of the CESL and the Regulation on the law applicable to contractual obligations will be the subject of this paper. Special attention will be paid to the application mechanism, which, as the drafters argue will make Article 6 Rome I superfluous where parties have chosen the CESL to govern their contract, which will however not make the application of all other PIL rules applicable to the contract

How to Prepare for Your College Advising Appointment

This video informs students how to prepare for their appointment with their college academic advisors. It is about understanding the role of your advisor, the importance of showing up on time, examples of great questions to ask, and why you should stay connected to them. Relating to the Appreciative Education framework, this video can help students feel more disarmed and prepared when meeting with their advisor

Pest science in Pasteur’s Quadrant

More than 25 years ago, Donald Stokes argued that we must move beyond the false dichotomy of basic or applied research and suggested that when considering a program of scientific research it is important to ask whether (i) the work is motivated by use and (ii) if there is a search for fundamental understanding. Giving yes/no answers to these questions allows us to characterize research more fully, replacing the “or” of “basic or applied” by a richer understanding of the process of science. Stokes proposed that research that was motivated by a consideration of use and sought fundamental understanding be called research in Pasteur’s Quadrant. One advantage of such work is that the search for fundamental understanding means that the problem-solving tools are more likely to be transferrable. After reviewing Stokes’s formulation of research, I illustrate it with examples from the control of tephritid flies and the use of insect parasitoids for biological control. Thinking about one’s work within Stokes’s framework has many advantages for individual scientists, including guidance for journal selection, how to organize and conclude papers and seminars, and the “elevator speech.” Furthermore, since research in Pasteur’s Quadrant has the characteristic of simultaneously increasing our understanding of how the world works and improving applications, it will more likely benefit the community of pest scientists.publishedVersio

Operational analysis for COVID-19 testing: Determining the risk from asymptomatic infections

Testing remains a key tool for managing health care and making health policy during the coronavirus pandemic, and it will probably be important in future pandemics. Because of false negative and false positive tests, the observed fraction of positive tests—the surface positivity—is generally different from the fraction of infected individuals (the incidence rate of the disease). In this paper a previous method for translating surface positivity to a point estimate for incidence rate, then to an appropriate range of values for the incidence rate consistent with the model and data (the test range), and finally to the risk (the probability of including one infected individual) associated with groups of different sizes is illustrated. The method is then extended to include asymptomatic infections. To do so, the process of testing is modeled using both analysis and Monte Carlo simulation. Doing so shows that it is possible to determine point estimates for the fraction of infected and symptomatic individuals, the fraction of uninfected and symptomatic individuals, and the ratio of infected asymptomatic individuals to infected symptomatic individuals. Inclusion of symptom status generalizes the test range from an interval to a region in the plane determined by the incidence rate and the ratio of asymptomatic to symptomatic infections; likelihood methods can be used to determine the contour of the rest region. Points on this contour can be used to compute the risk (defined as the probability of including one asymptomatic infected individual) in groups of different sizes. These results have operational implications that include: positivity rate is not incidence rate; symptom status at testing can provide valuable information about asymptomatic infections; collecting information on time since putative virus exposure at testing is valuable for determining point estimates and test ranges; risk is a graded (rather than binary) function of group size; and because the information provided by testing becomes more accurate with more tests but at a decreasing rate, it is possible to over-test fixed spatial regions. The paper concludes with limitations of the method and directions for future work.publishedVersio

Through Me Tell the Story : A New Historical Analysis of Bob Dylan as a Nobel Laureate

Bob Dylan\u27s receipt of the Nobel Prize for Literature in 2016 for for having created new poetic expressions within the great American song tradition is perhaps the strongest validation for New Historicism as a method of literary analysis. The individual puzzle pieces of Dylan\u27s postmodern rock poems are themselves little bits of history, but combined within the context of the massive paradigm shifts of the 1960s, they become something new and entirely relevant to the nonstop turmoil of contemporary life in America