Impact of the commercial fishery on the population of bait shrimp (Penaeus spp.) in Biscayne Bay, 1986

Monthly population size of bait shrimp in the Bay was estimated from December 1984 to July 1985. Growth rates for male and female P. duorarum showed that pink shrimp exhibit a mean residence time in the nursery area (Biscayne Bay) of approximately 21 weeks. Monthly mortality rates were determined for each sex of pink shrimp. It was estimated that 23% and 26% of the male and female monthly population size, respectively, was absorbed by both the fishery and ecosystem monthly. Monthly proportion of the standing stock expected to die exclusively through fishing was 6.5% and 6.0% for males and females respectively. Estimates of emigration rates showed that approximately 4.0% of the population was lost from the Bay system each month. This surplus production was about 50% of the average monthly catch by the fleet. Fishing mortality represents only 8 - 9% of the losses to the shrimp population. The biggest source of loss is emigration, suggesting that most shrimp beyond the size at recruitment (to the fishery) are not utilized for food while in the Bay. Thus, it appears that the direct impact of the fishery on the bait shrimp population is relatively small. (PDF contains 46 pages

Bait shrimp fishery of Biscayne Bay

A small but valuable live bait shrimp fishery has existed in Biscayne Bay since at least the early 1950s. In recent years there has been increasing pressure from recreational fishing and environmental groups to eliminate this fishery from the Bay because the fishing activity is generally thought to be deleterious to the environment and/or destructive to juvenile game fish. This study was initiated to update the existing knowledge of the bait shrimp fishery in Biscayne Bay and document historical trends in number of participants, fishing methods, fishing area, seasonality, total catch, catch-per-unit-effort, disposition of the catch, and economics of the industry. (21pp.

A Morning Coffee in Melbourne: Discussing the Contentious Spaces of Media Practice Research

This is a conversation that took place between three practitioner-academics one morning in Melbourne. All three work and practice in the field of the moving image: from screen production to audiovisual installation to screenwriting. Our conversation is underpinned by previous research we have undertaken in this field, namely the launching of a moving image journal, Sightlines, and a companion journal article on the process of setting it up, which focussed on the issues presented when trying to establish peer review protocols and guidelines for moving image works

Diffuse Interstellar Bands in z < 0.6 CaII Absorbers

The diffuse interstellar bands (DIBs) probably arise from complex organic molecules whose strength in local galaxies correlates with neutral hydrogen column density, N(HI), and dust reddening, E(B-V). Since CaII absorbers in quasar (QSO) spectra are posited to have high N(HI) and significant E(B-V), they represent promising sites for the detection of DIBs at cosmological distances. Here we present the results from the first search for DIBs in 9 CaII-selected absorbers at 0.07 < z_abs < 0.55. We detect the 5780Ang DIB in one line of sight at z_abs = 0.1556; this is only the second QSO absorber in which a DIB has been detected. Unlike the majority of local DIB sight-lines, both QSO absorbers with detected DIBs show weak 6284Ang absorption compared with the 5780Ang band. This may be indicative of different physical conditions in intermediate redshift QSO absorbers compared with local galaxies. Assuming that local relations between the 5780Ang DIB strength and N(HI) and E(B-V) apply in QSO absorbers, DIB detections and limits can be used to derive N(HI) and E(B-V). For the one absorber in this study with a detected DIB, we derive E(B-V) = 0.23mag and log[N(HI)] >= 20.9, consistent with previous conclusions that CaII systems have high HI column densities and significant reddening. For the remaining 8 CaII-selected absorbers with 5780Ang DIB non-detections, we derive E(B-V) upper limits of 0.1-0.3mag.Comment: 5 pages, 2 figures. Accepted to MNRAS Letter

The host galaxies of strong CaII QSO absorption systems at z<0.5

We present new imaging and spectroscopic observations of the fields of five QSOs with very strong intervening CaII absorption systems at redshifts z<0.5 selected from the Sloan Digital Sky Survey. Recent studies of these very rare absorbers indicate that they may be related to damped Lyman alpha systems (DLAs). In all five cases we identify a galaxy at the redshift of the CaII system with impact parameters up to ~24 kpc. In four out of five cases the galaxies are luminous (L ~L*), metal-rich (Z ~Zsun), massive (velocity dispersion, sigma ~100 km/s) spirals. Their star formation rates, deduced from Halpha emission, are high, in the range SFR = 0.3 - 30 Msun/yr. In our analysis, we paid particular attention to correcting the observed emission line fluxes for stellar absorption and dust extinction. We show that these effects are important for a correct SFR estimate; their neglect in previous low-z studies of DLA-selected galaxies has probably led to an underestimate of the star formation activity in at least some DLA hosts. We discuss possible links between CaII-selected galaxies and DLAs and outline future observations which will help clarify the relationship between these different classes of QSO absorbers.Comment: Accepted for publication in MNRAS, 14 pages, 9 figures. Version with full resolution images available at http://www.ast.cam.ac.uk/~bjz/papers/Zych_etal_2007a.pd

Between chaos and control: a practice-based investigation into the creative process of an improvised micro-budget screen production.

This PhD research has been conducted by project and, through the production of a 75 minute film called How To Change The World, has investigated screen production practice as research. In that context, the research question used to frame the project is the following:  How can a creative practice in screen production be transformed into a research practice, which integrates professional, cultural and academic experience? Using reflective practice as a methodology, the screen production project How To Change The World was developed to enable the consideration of this question, as well as building on themes and approaches explored in my prior filmmaking practice. I describe the film as a playful tapestry of stories exploring the world of a decaying neighbourhood pub. A significant feature of the project’s design was that it was a film made on a ‘micro’ budget. How To Change The World was also produced without a script and nearly all the dialogue was improvised. The film was designed to explore the significance of improvisation within the screen production process. This aspect of the research was initially focused on the performances of the actors but broadened in scope as its relevance to the central research question became more apparent. A significant focus of the research was on issues of identity and agency within the field of screen production. Within the broad framework of ideas proposed by Bourdieu in his work on the field of cultural production and drawing on related theorists such as Schön and cultural anthropologists Holland, Lachicotte, Skinner &amp;amp; Cain, I have argued that the screen production process for How To Change The World was a complex social, cultural and technical environment where I needed to negotiate multiple and often competing priorities in executing creative ideas, often under the pressure of time and resource constraints. The choices made in this improvisational environment were informed by both the history of my positions within the field, in both mainstream and marginal micro-budget sectors, as well as my dispositions to make certain types of films. These dispositions were, in turn, informed by a range of influences. I investigated the different ways that influences such as key films and prior production experiences can be seen to have an impact on the current creative production process. Like Schön’s ‘surfacing of tacit knowledge’, I investigated how my identity as a filmmaker informed the myriad creative and practical decisions made in the screen production process and whether a more explicit awareness of that identity enhanced my agency in the process, agency in this context being understood as the ability to act independently of the accepted and often internalised norms of the field

Potential role of methane-derived carbon as a food source for Daphnia in a North Carolina reservoir

Herbivorous zooplankton feed on seston, including algal, detrital, and bacterial components. However, many studies have found that Daphnia del13C is more depleted than seston del13C, and selective feeding on seston algal components has been hypothesized. We hypothesized that low zooplankton del13C was due to utilization of methane-derived carbon (MDC). Lake Brandt data indicated a strong seasonal effect on the del13C of Daphnia when compared to seston. During summer stratification, carbon signatures of Daphnia were more depleted than bulk seston, while during winter mixing Daphnia were more enriched. We conducted an experiment to assess utilization of MDC as a possible mechanism of depleted Daphnia del13C. At low methane concentrations, methane del13C was more enriched than at high concentrations, indicating isotopic fractionation by methanotrophs. Daphnia del13C was slightly enriched compared to seston at low methane concentrations, but was depleted compared to seston at high methane concentrations, consistent with incorporation of MDC. An antibiotic appeared to limit methanotrophs in the water column resulting in enriched Daphnia del13C. MDC contribution to the diet of Daphnia was estimated as almost 32% of assimilation. Our study provides strong evidence that assimilation of MDC resulted in depleted Daphnia del13C relative to seston. We suggest that this phenomenon is widespread in freshwater ecosystems, explaining the consistently light del13C of grazing zooplankton relative to bulk seston

Effect of Iodine Doping on Bi2_{2}Sr2_{2}Ca1_{1}Cu2_{2}Ox_{x}: Charge Transfer or Interlayer Coupling?

A comparative study has been made of iodine-intercalated Bi$_{2}$Sr$_{2}$Ca$_{1}$Cu$_{2}$O$_{x}$ single crystal and 1 atm O$_{2}$ annealed Bi$_{2}$Sr$_{2}$Ca$_{1}$Cu$_{1}$O$_{x}$ single crystal using AC susceptibility measurement, X-ray photoemission (XPS) and angle-resolved ultraviolet photoemission spectroscopy (ARUPS). AC susceptibility measurement indicates that O$_{2}$-doped samples studied have T$_{c}$ of 84 $^{o}$K, whereas T$_{c}$ of Iodine-doped samples studied are 80 $^{o}$K. XPS Cu 2p core level data establish that the hole concentration in the CuO$_{2}$ planes are essentially the same for these two kinds of samples. ARUPS measurements show that electronic structure of the normal states near the Fermi level has been strongly affected by iodine intercalation. We conclude that the dominant effect of iodine doping is to alter the interlayer coupling.Comment: LBL 9 pages, APS_Revtex. 5 Figures, available upon request. UW-Madison preprin