Development of Various Quantitative and Analytical Methods for the Analysis of the Dynamics of Fish Populations: An Application to the Spotted Seatrout Population in Coastal Louisiana.

Presented in this dissertation are analytical and quantitative methods developed for an experimental gillnet sampling program for the analysis of the dynamics of fish populations, illustrated here on Louisiana\u27s spotted seatrout population. Chapter 1 presents a new method of estimating gillnet selectivity using a system of simultaneous equations and a non-linear iterative maximum likelihood approach. The model solution is a set of parameter estimates which mathematically describe the response surface of capture probabilities for fish of size-class j in mesh size i. As an extension to the nonlinear maximum likelihood gillnet selectivity model, Chapter 2 presents a second approach using the probability of capture to estimate the relative abundances of the various size-classes of fish in the population and develops a variance estimator for the relative abundances. The selectivity model and variance estimation procedures were applied to the experimental gillnet catches of spotted seatrout from 1988 to 1990. In Chapter 3, several multivariate statistical techniques were applied to the experimental gillnet catches of spotted seatrout to examine the distributional ecology of the population. Principal Components Analysis (PCA) revealed a two factor model which explained 78% of the variation in the covariance matrix of the original data. The Principal Component factor loadings were interpreted as recruit (juvenile) and spawner (Adult) abundance for factor 1 and factor 2, respectively. Linear regression analysis showed recruit and spawner abundance had a high positive correlation to salinity during the spawning season, but slopes between the two life history stages of seatrout varied significantly (p $\u3c$ 0.05). After the spawning season (September-December) recruit abundance showed a high negative correlation to salinity. Implications of the non-uniform spatiotemporal distributions of spotted seatrout abundance to management are discussed. Finally, in Chapter 4, a population level assessment is conducted on the spotted seatrout fishery in Louisiana to estimate fishing mortality at age, population size at age, and spawning potential ratios using a Monte Carlo-based Virtual Population Analysis (VPA). Application of the Monte Carlo based simulation (N = 3000) was used to characterize uncertainty in the VPA model output of spawning potential ratios which arise from uncertainty associated with input parameters of natural and terminal fishing mortality

The Iowa Homemaker vol.19, no.3

Cuisine, page 1 College With an Eye to a Job, page 2 Shoulder Arms Against Telltale Tarnish, page 3 Generosity with Spices, page 4 Grandmother’s Heirlooms, page 5 Greyed Pastels, page 6 Food Facts – or Fairy Tales, page 8 Les Menus, the American Nemesis, page 9 What’s New in Home Economics, page 10 From Panama to Paris, page 12 Spread-ucation, page 13 Behind Bright Jackets, page 14 Alums in the News, page 15 His Royal Highness, the Chef, page 16 New Zealand Cuisine, page 17 From Journalistic Spindles, page 18 A Frozen Art, page 19 Biography of a Home Economist, page 2

Bomb-produced radiocarbon validation of growth-increment crossdating allows marine paleoclimate reconstruction

The bivalve Pacific geoduck (Panopea generosa) has been used in the eastern North Pacific Ocean to create proxies for environmental factors such as temperature and oceanographic conditions. This type of research depends upon accurate age determination of Pacific geoducks, which historically was based on shell growth-increment counts. A recent study comparing age estimates generated by the dendrochronology (tree-ring science) procedure of crossdating to those estimated from growth-increment counts found a significant difference between the methods for geoduck older than 30 years. Compared to the traditional age determination method of counting growth increments, the crossdating method estimates a greater longevity in this species, with some individuals living in excess of 150 years. In the present study, the accuracy of each method was independently assessed using bomb-produced radiocarbon (C-14) techniques. Specimens whose birth years were estimated to be within the era of the bomb-produced marine C-14 increase and where the differences between ages estimated by the two methods were greatest were selected for C-14 analysis. The difference between age estimates from traditional growth-increment counts and those from crossdating was evaluated using their respective C-14 chronologies in comparisons to a reference chronology as a standard. The comparisons relied on Bayesian nonlinear models using Markov Chain Monte Carlo simulation. This method of analysis showed that with a 50% probability geoducks were aged correctly when using the crossdating method, compared to the growth increment counts which had a 50% probability of underestimating the age by 4 years. Therefore, the crossdated age estimates were found to be more accurate than increment counts. Furthermore, these results provide new confidence in using Pacific geoduck biochronologies for paleoclimate and paleoenvironmental reconstruction. Published by Elsevier B.V.Keywords: Age determination, Pacific geoduck, Bomb-produced radiocarbon, Bayesian models, Shell growth-increment counts, Crossdating, Panopea generos

Bayesian hierarchical modeling of Pacific geoduck growth increment data and climate indices

Growth increment widths from hard structures of marine and freshwater fish and bivalve species are increasingly used to model growth and elucidate relationships with environmental variability. Fully characterizing the intrinsic age-related growth variation among individuals within and between populations, while estimating the extrinsic environmental effects simultaneously, can be challenging. Using the long-lived bivalve Pacific geoduck (Panopea generosa), we develop an integrated approach to analyze the relationship between growth increment data and climate indices using Bayesian hierarchical methods. Fitting models to growth increment data from multiple individuals over two sites, we examined different covariance structures related to random individual effects, long- and short-term environmental effects and unexplained errors. The best fitting hierarchical model accounted for a site-specific mean growth response, individual growth variability through random parameter effects, and site-specific error variances. Extrinsic environmental effects on growth were also significant and included a random year effect and the Pacific Decadal Oscillation (PDO) as a predictor of mean growth across both individuals and sites. Once intrinsic age-related growth was accounted for. PDO accounted for 18% to total variability in growth increment data: geoduck shell size was predicted to increase as a function of larger PDO anomalies. However, the greatest variability in growth increment data was explained by random year effects (similar to 60-70%), and while largely unexplained, sea surface temperature (SST) is a likely determinant on geoduck growth rates showing a positive growth-SST response. Published by Elsevier B.V

Sub-sampling populations with spatially structured traits: a field comparison of stratified and random strategies

Scientific surveys are widely used for stock assessment, but the estimated population parameters are based on the size-at-age relationship and age structure derived from a small subsample of the catch that is aged. This calls for an assessment of subsampling strategies, especially when population’s life history traits are spatially structured. In the Eastern Bering Sea, Pacific cod (Gadus macrocephalus) size and age are spatially structured, with younger and smaller individuals being more abundant at shallower depths. We conducted parallel subsamplings during Pacific cod surveys to compare two contrasting subsampling strategies: length-stratified and random. Geographical heterogeneity of Pacific cod length resulted in divergent estimates of ages between subsampling strategies. When this spatial variability was taken into account to estimate population parameters, random strategy provided more accurate mean and modal size-at-age and estimated age structure. Bias in the length-stratified subsampling arises from the poor efficacy in capturing the geographical patterns of size observed in the population. However, combining age data samples from multiple years helps to minimize the divergences between the two strategies

A transformative approach to ageing fish otoliths using Fourier transform-near infrared spectroscopy (NIRS): a case study of eastern Bering Sea walleye pollock (Gadus chalcogrammus)

We investigated the use of Fourier transform-near infrared spectroscopy (FT-NIRS), which is a method of measuring light absorbance signatures, to derive ages from eastern Bering Sea walleye pollock (Gadus chalcogrammus) otoliths. This approach is based on a predictive model between near infrared spectra in the otolith and fish age, which is calibrated and validated. The advantage of FT-NIRS over traditional methods is the speed and repeatability with which age estimates are generated. The application of FT-NIRS to walleye Pollock otoliths yielded r2 values between 0.91 and 0.95 for the calibration models, and good validation performance (between 0.82 and 0.93). This approach can be expected to predict fish age within Âą 1.0 year of age 67% of the time. When comparing approaches, the FT-NIRS had as good or slightly better precision (75% agreement) than the traditional ageing (66% agreement), and showed little or no bias at age before 12 years of age. Once the predictive FT-NIR model is calibrated and validated, age-estimates using FT-NIRS can be done at 10 times the rate compared to traditional methods.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Spatial, interannual, and generational sources of trait variability in a marine population

Life-history traits of individuals in marine populations exhibit large sources of variability. In marine fish, variation of individual size at a given age has three main components: (1) spatial, correlated with the location in which individuals are caught, (2) temporal, correlated with the time when individuals are caught, and (3) generational, correlated with the year of birth of the examined individuals. These variations, if present, have practical implications for individual fitness as well as for sampling, survey design, and population assessment. Disentangling these variations and understanding their sources is hard, given the potentially correlated nature of their effects on individual traits. This study examines the size-at-age relationship of the Bering Sea Pacific cod, an economically and ecologically important groundfish. We used extensive records spanning 1994 to 2016 (inclusive) of 25,213 observations of both environmental variables and catch, lengths, and ages. We found that the average size of individuals of the same age could differ up to 7 cm. Notably, we found that the cohort composition of the sampled population explained >75% of the year effect and that individuals caught in the northwest and shallower portion of the sampling area were on average 5 cm smaller than individuals caught in the southern and deeper portion. We further found that northwest movement of young cod (age 1–5) as a result of warming places individuals in areas where we predict them to have smaller size at age. Smaller and less conditioned individuals are less fecund and may not be able to perform long migrations to return to their distant spawning grounds. Both the spatial distribution and water temperature experienced by Pacific cod in the Bering Sea are changing, and this study provides a mechanism for how these changes affect Pacific cod life-history traits and individual fitness.S

Spatial, interannual, and generational sources of trait variability in a marine population

Life-history traits of individuals in marine populations exhibit large sources of variability. In marine fish, variation of individual size at a given age has three main components: (1) spatial, correlated with the location in which individuals are caught, (2) temporal, correlated with the time when individuals are caught, and (3) generational, correlated with the year of birth of the examined individuals. These variations, if present, have practical implications for individual fitness as well as for sampling, survey design, and population assessment. Disentangling these variations and understanding their sources is hard, given the potentially correlated nature of their effects on individual traits. This study examines the size-at-age relationship of the Bering Sea Pacific cod, an economically and ecologically important groundfish. We used extensive records spanning 1994 to 2016 (inclusive) of 25,213 observations of both environmental variables and catch, lengths, and ages. We found that the average size of individuals of the same age could differ up to 7 cm. Notably, we found that the cohort composition of the sampled population explained >75% of the year effect and that individuals caught in the northwest and shallower portion of the sampling area were on average 5 cm smaller than individuals caught in the southern and deeper portion. We further found that northwest movement of young cod (age 1–5) as a result of warming places individuals in areas where we predict them to have smaller size at age. Smaller and less conditioned individuals are less fecund and may not be able to perform long migrations to return to their distant spawning grounds. Both the spatial distribution and water temperature experienced by Pacific cod in the Bering Sea are changing, and this study provides a mechanism for how these changes affect Pacific cod life-history traits and individual fitness