The Early Life-History of King George Whiting (Sillaginodes punctatus: Perciformes) in South Australia’s Gulf System

The life-history of many marine fish species involves a pelagic larval stage that connects spatially segregated spawning grounds and nursery areas. The dispersal of larvae in marine ecosystems is heavily influenced by physical oceanographic processes, which provide the potential for large-scale transport and mixing between groups of larvae that originated from different spawning grounds. Understanding the connectivity between these different populations identifies the spatial scale over which the life-history operates, and is necessary to delineate populations into the appropriate stock structure. This biological information underpins the development of effective fishery management strategies. King George whiting (Sillaginodes punctatus; Perciformes) is a demersal marine finfish species endemic to temperate coastal waters of southern Australia, and conforms to the general bi-partite life-history cycle of most demersal fishes. South Australia is at the geographic centre of its distribution and supports the highest abundances and its most significant fishery. However, in recent years, commercial catches and estimated biomass in South Australia’s gulfs have declined to record lows, and the populations were subsequently classified as ‘transitional depleting’. Despite extensive research into the life-history of this species, there remains considerable uncertainty about the spawning sources, population connectivity and early life-history processes that ultimately culminate in recruitment. As such, the aim of this study was to understand the early life-history of King George whiting in South Australia’s gulf system, and specifically, to investigate the connectivity between coastal spawning grounds and inshore nursery areas. King George whiting is a multiple batch spawning species that produces large numbers of pelagic eggs throughout a protracted spawning season (ca. 4 months). Larvae that hatch at different times are exposed to different physical and ecological conditions during ontogeny that influence survivorship and subsequent recruitment. To investigate the temporal nature of recruitment throughout the settlement season, recently-settled larvae were collected fortnightly between July and November at a significant nursery area in Gulf St. Vincent. These larvae hatched between March and July, although a three week spawning period in May was responsible for >50% of recruitment. Throughout the settlement season, the recently-settled larvae progressively decreased in size (range: 16.1-25.3 mm SL) but increased in age (range: 92-184 d). As such, smaller, slower-growing larvae that experienced a longer pelagic phase were responsible for the majority of recruitment. In addition, otolith chemistry related to the natal origin of these larvae differed significantly between those that hatched from March to May, and those that hatched from May to July. There are two primary hypotheses to explain this: Either (1) within-season environmental change at a single spawning ground; or (2) the contribution of two different spawning grounds to recruitment at different times of the settlement season. For demersal fish species, understanding connectivity during the larval phase is necessary to determine the spatial scale over which the life-history operates, as this is the spatial scale at which populations are considered ecologically discrete. To evaluate spatial connectivity and stock structure, recently-settled larvae were collected from nursery areas throughout Spencer Gulf and Gulf St. Vincent. Regional differences in the natal otolith chemistry of larvae that hatched at the same time indicated that the two regions are replenished by different spawning populations, and provide empirical support for the hypothesis that the populations of King George whiting in Spencer Gulf and Gulf St. Vincent represent discrete sub-populations. The only recognised spawning area for King George whiting in south-eastern Australia is throughout southern Spencer Gulf and Investigator Strait. The otoliths of larvae collected throughout the recognised spawning area were examined to determine if the large spawning area represented a single spawning population or multiple discrete spawning grounds. The spatial distribution of larvae was broadly divisible into two groups – those in southern Spencer Gulf and those in Investigator Strait. There were no spatial differences in the sizes (3.0-5.0 mm SL), ages (5-21 d), hatch dates (7-24 Apr) or growth rates (0.09-0.21 mm d-1) of larvae. However, otolith chemistry differed significantly between the two groups, providing empirical evidence that southern Spencer Gulf and Investigator Strait represent two independent spawning grounds. Having determined that larvae which settled to nursery areas in Spencer Gulf and Gulf St. Vincent had originated from different spawning grounds, and that the recognised spawning area is comprised of two discrete spawning grounds, connectivity between them was investigated by simulating larval dispersal using a biophysical model. The model was seeded with particles according to the distribution and abundance of eggs throughout the spawning area and dispersal was simulated using three increasingly complex behavioural models. Predicted settlement was highest to nursery areas only short distances from regional spawning grounds, which indicated that population processes were localised within each gulf. However, the model also predicted that later in the spawning season, larvae originating in southern Spencer Gulf contributed to recruitment in Gulf St. Vincent. The within-season change in dispersal pathways corresponded to the breakdown of a thermohaline frontal system at the entrance of each gulf in early May, which is consistent with spatial and temporal patterns in the otolith chemistry of larvae. Consequently, the most parsimonious explanation is that the populations of King George whiting in South Australia’s gulf system constitute a single, panmictic stock. The population connectivity identified in this study has implications for the understanding of stock structure, and subsequently, the spatial scale at which fishery management should be applied.Thesis (Ph.D.) -- University of Adelaide, School of Biological Sciences, 202

An Efficient Irrigation Technology for Alfalfa Growers

A trial on the suitability of subsurface drip irrigation (SDI) for alfalfa (Medicago sativa L) was conducted on a producer\u27s field. The soil is sandy loam. The treatments included drip tape spacing of 60, 40, and 30 inches, placed at 18- and 12-inch depth. A nearby center pivot sprinkler irrigated plot was seeded to alfalfa as a control. Seedling emergence and yield was adversely affected at 60-inch spacing. The depth of placement of drip tapes (18 and 12 inch) showed no effect. The site served for Extension education and allowed comparison between SDI tape spacing and center pivot system

Proceedings of the 24th annual Central Plains irrigation conference

Presented at Proceedings of the 24th annual Central Plains irrigation conference held on February 21-22 in Colby, Kansas.Includes bibliographical references

Using the K-State center pivot sprinkler and SDI economic comparison spreadsheet - 2008

Presented at the 2008 Central Plains irrigation conference on February 19-20 in Greeley, Colorado.Includes bibliographical references

Wavefront sensing and control performance modeling of the Thirty Meter telescope for systematic trade analyses

We have developed an integrated optical model of the semi-static performance of the Thirty Meter Telescope. The model includes surface and rigid body errors of all telescope optics as well as a model of the Alignment and Phasing System Shack-Hartmann wavefront sensors and control algorithms. This integrated model allows for simulation of the correction of the telescope wavefront, including optical errors on the secondary and tertiary mirrors, using the primary mirror segment active degrees of freedom. This model provides the estimate of the predicted telescope performance for system engineering and error budget development. In this paper we present updated performance values for the TMT static optical errors in terms of Normalized Point Source Sensitivity and RMS wavefront error after Adaptive Optics correction. As an example of a system level trade, we present the results from an analysis optimizing the number of Shack-Hartmann lenslets per segment. We trade the number of lenslet rings over each primary mirror segment against the telescope performance metrics of PSSN and RMS wavefront error

Systems engineering of the Thirty Meter Telescope for the construction phase

This paper provides an overview of the system design, architecture, and construction phase system engineering processes of the Thirty Meter Telescope project. We summarize the key challenges and our solutions for managing TMT systems engineering during the construction phase. We provide an overview of system budgets, requirements and interfaces, and the management thereof. The requirements engineering processes, including verification and plans for collection of technical data and testing during the assembly and integration phases, are described. We present configuration, change control and technical review processes, covering all aspects of the system design including performance models, requirements, and CAD databases

Wavefront sensing and control performance modeling of the Thirty Meter telescope for systematic trade analyses

We have developed an integrated optical model of the semi-static performance of the Thirty Meter Telescope. The model includes surface and rigid body errors of all telescope optics as well as a model of the Alignment and Phasing System Shack-Hartmann wavefront sensors and control algorithms. This integrated model allows for simulation of the correction of the telescope wavefront, including optical errors on the secondary and tertiary mirrors, using the primary mirror segment active degrees of freedom. This model provides the estimate of the predicted telescope performance for system engineering and error budget development. In this paper we present updated performance values for the TMT static optical errors in terms of Normalized Point Source Sensitivity and RMS wavefront error after Adaptive Optics correction. As an example of a system level trade, we present the results from an analysis optimizing the number of Shack-Hartmann lenslets per segment. We trade the number of lenslet rings over each primary mirror segment against the telescope performance metrics of PSSN and RMS wavefront error

Planet Hunters VII. Discovery of a New Low-Mass, Low-Density Planet (PH3 c) Orbiting Kepler-289 with Mass Measurements of Two Additional Planets (PH3 b and d)

We report the discovery of one newly confirmed planet ($P=66.06$ days, $R_{\rm{P}}=2.68\pm0.17R_\oplus$) and mass determinations of two previously validated Kepler planets, Kepler-289 b ($P=34.55$ days, $R_{\rm{P}}=2.15\pm0.10R_\oplus$) and Kepler-289-c ($P=125.85$ days, $R_{\rm{P}}=11.59\pm0.10R_\oplus$), through their transit timing variations (TTVs). We also exclude the possibility that these three planets reside in a $1:2:4$ Laplace resonance. The outer planet has very deep ($\sim1.3$), high signal-to-noise transits, which puts extremely tight constraints on its host star's stellar properties via Kepler's Third Law. The star PH3 is a young ($\sim1$ Gyr as determined by isochrones and gyrochronology), Sun-like star with $M_*=1.08\pm0.02M_\odot$, $R_*=1.00\pm0.02R_\odot$, and $T_{\rm{eff}}=5990\pm38$ K. The middle planet's large TTV amplitude ($\sim5$ hours) resulted either in non-detections or inaccurate detections in previous searches. A strong chopping signal, a shorter period sinusoid in the TTVs, allows us to break the mass-eccentricity degeneracy and uniquely determine the masses of the inner, middle, and outer planets to be $M=7.3\pm6.8M_\oplus$, $4.0\pm0.9M_\oplus$, and $M=132\pm17M_\oplus$, which we designate PH3 b, c, and d, respectively. Furthermore, the middle planet, PH3 c, has a relatively low density, $\rho=1.2\pm0.3$ g/cm$^3$ for a planet of its mass, requiring a substantial H/He atmosphere of $2.1^{+0.8}_{-0.3}$ by mass, and joins a growing population of low-mass, low-density planets.Comment: 21 pages, 10 figures, 5 tables, accepted into Ap