A complete sample of radio sources in the North Ecliptic Cap, selected at 38 MHz -- III. further imaging observations and the photometric properties of the sample

Further imaging observations of a sample of radio sources in the North Ecliptic Cap are presented and a number of new identifications are made. Using redshifts from spectroscopic data presented in a companion paper (Lacy et al.\ 1999b), the photometric properties of the galaxies in the sample are discussed. It is shown that: (1) out to at least z~0.6 radio galaxies are good standard candles irrespective of radio luminosity; (2) for 0.6~<z~<1 a large fraction of the sample have magnitudes and colours consistent with a non-evolving giant elliptical, and (3) at higher redshifts, where the R-band samples the rest-frame UV flux, most objects have less UV luminosity than expected if they form their stellar populations at a constant rate from a high redshift to $z\sim 1$ in unobscured star-forming regions (assuming an Einstein -- de Sitter cosmology). The consequences of these observations are briefly discussed.Comment: 10 pages, 6 figures, accepted by MNRA

A portable, low-cost approach for photographing fluid preserved snake specimens- Recommendations with comments on optimizing specimen photography in Natural History collections

Access to preserved specimens in museum collections is one of the key needs of those engaged in systematics research (e.g., Bi et al. 2013; Rocha et al. 2014; McLean et al. 2016). Yet, sometimes the constraints of research budgets and time prevent the optimal use of this critical resource, resulting in project delays, incomplete information, or flawed scientific conclusions. With many natural history museums now digitizing information related to specimens in their collections, imaging of specimens is a logical next step, and one of critical importance to make holdings available electronically to a broader audience (Baird 2010; Lister et al. 2011; Knight-Davis et al. 2015; Page et al. 2015). A complete 2D image library of all specimens in a collection may appear utopian at the moment, given the millions of specimens and lack of financial support for collections (e.g., Paknia et al. 2015). However, outside of visiting each collection to study individual specimens, or requesting loans of unique and valuable specimens, the lack of suitable specimen images means that some data may simply remain unavailable to researchers who cannot afford to obtain them. We wish to emphasize that the approach we advocate herein in no way negates the need to maintain and make accessible physical specimens in a collection. Although in rare cases where the lack of specimens is unavoidable (e.g., Marshall and Evenhuis 2015; Pape et al. 2016), there is no replacement for examining a well-preserved specimen. Our method should be regarded as an ancillary technique, useful when it is necessary to obtain preliminary data or when it is not possible to examine the specimen in person, and for archival purposes

Commercial and non-target species of deep water trawled muddy habitats on the Maltese continental shelf

Prior to joining the European Union, Malta operated a 25nm Exclusive Fishing Zone that was retained as a Fisheries Conservation Zone (FCZ) following EU membership. The present study was conducted in this FCZ as part of the ongoing MEDITS trawl survey programme. Otter trawl samples were collected from muddy bottoms at depths of 100-300m. The catch from each haul was sorted into commercial and non-commercial components, and fauna were identified and counted. Samples for analyses of infauna and sediment characteristics were collected using a 0.0625m² capacity box-corer. Macrofaunal abundance data for the stations were analysed using ordination techniques (nMDS) and relationships between environmental variables and faunal assemblages were explored by superimposing individual variables on the two-dimensional nMDS plots. The analyses clearly separated the commercial species into two distinct groups of assemblages that seemed to be defined principally by depth: those from inshore and south-eastern stations (depth range 100-250m) and those from north-western stations (depth range 250-300m). The non-commercial species showed a similar pattern with assemblages from inshore stations grouping together; however, the offshore stations had a greater variability in non-target species composition, especially for infauna. For the offshore stations, geographical position seemed to be important since stations off the north-western coast of the Maltese islands grouped separately from those off south-eastern Malta.peer-reviewe

Fishers’ perception of a 35-year old exclusive Fisheries Management Zone

Fishers’ attitudes and perceptions are critical for the success of fisheries protection areas with their associated biota, and a failure to understand fishers’ behaviour may undermine the success of such fisheries management measures. In this study, we examine fishers’ perception of a long-established exclusive fisheries zone around Malta and to investigate if the perceptions depend on fishers’ demographic, economic, social characteristics and fishing activity of the fishers. A questionnaire survey was undertaken to evaluate the demographic characteristics, economic situation (costs and revenue) and fishers’ activity and behaviour, together with their perception of the Fisheries Management Zone (FMZ). A total of 241 interview responses were analysed which was a response rate of 60%. The perception of most fishers was that the establishment of the FMZ has had an overall negative impact on their fishing activity and that the zone is not important for the protection of local fish stocks. When asked about the beneficial effect of the zone for fishers, most fishers from all backgrounds said that the zone does not benefit commercial fishers, but benefits mainly recreational fishers. The most evident differences in the perceptions and attitudes were between the full-time, part-time and recreational fishers. Fishers that have been fishing for more than 35 years and fishers from the main fishing village also had different attitudes from other fishers towards the FMZ. The results of this study suggest that the proportion of individual income derived from fishing was the strongest factor that influenced attitudinal differences, with home port and fishing experience having less important effects. The main differences in attitude among fishers were related to the protection and conservation effects of the zone, enhancement of resources and conflicts among user groups. The heterogeneity among fishers’ attitudes revealed by the present study has important implications for the implementation of spatial closures. Some sectors of stakeholders may require additional incentives to accept restrictions on access if spatial management is to achieve its intended objectives.peer-reviewe

Using radio galaxies to find super-structures

Radio galaxies are excellent at tracing large-scale structure due to their high bias. We present new results from the TONS08 radio galaxy redshift survey. We find unequivocal evidence for a huge (at least 80 x 80 x 100 Mpc^3) super-structure at redshift z=0.27, confirming tentative evidence for such a structure from the 7C redshift survey (7CRS). A second, newly discovered super-structure is also tentatively found at redshift 0.35 (of dimensions at least 100 x 100 x 100 Mpc^3). Out of the total sample size of 84 radio galaxies, at least 25 are associated with the two super-structures. We use quasi-linear structure formation theory to estimate the number of such structures expected in the TONS08 volume if the canonical value for radio galaxy bias is assumed. Under this assumption, the structures represent ~ 4-5 sigma peaks in the primordial density field and their expected number is low (10^{-2}-10^{-4}). Fortunately, there are several plausible explanations (many of which are testable) for these low probabilities in the form of potential mechanisms for boosting the bias on large scales. These include: the association of radio galaxies with highly biased rich clusters in super-structures, enhanced triggering by group/group mergers, and enhanced triggering and/or redshift space distortion in collapsing systems as the growth of super-structures moves into the non-linear regime. Similar structures could have been missed in previous surveys because of the effects of Poisson-sampling fluctuations.Comment: 6 pages, 3 figures. To appear in "Radio galaxies: past, present and future", eds M. Jarvis et al., Leiden, Nov 200

Differences in demersal community structure and biomass size spectra within and outside the Maltese Fishery Management Zone (FMZ)

We examined the protection effect of a long-established fisheries protection zone by studying the demersal communities and the biomass size spectra of specific taxonomic groups. The results and the relevant management implications of the community analysis are discussed within the context of the MEDITS trawl survey program, from which the data was derived. The demersal fishery resources on the muddy bottoms of Maltese trawling grounds were found to be stratified in four main depth ranges: 83 to 166 m (outer continental shelf), 140 to 230 m (shelf break), 270 to 440 m (shallow slope), and 466 to 701 m (deep slope). Significant differences were detected between the inside and outside zones of the outer continental shelf. Stations from this stratum inside the protected zone had twice as much biomass as those outside as well as larger individuals of some species (e.g. elasmobranchs). The depth strata identified do not coincide with those sampled in existing trawl survey programmes in the Sicilian Channel, which were set up without reference to demersal assemblage structure and its relation to depth. It is therefore clear that characterisation of the biotic assemblages is important in order to obtain a better sampling representation of each depth-stratum/assemblage type, and this should be considered in the survey design.peer-reviewe

Redshift-Space Enhancement of Line-of-Sight Baryon Acoustic Oscillations in the SDSS Main-Galaxy Sample

We show that redshift-space distortions of galaxy correlations have a strong effect on correlation functions with distinct, localized features, like the signature of the baryon acoustic oscillations (BAO). Near the line of sight, the features become sharper as a result of redshift-space distortions. We demonstrate this effect by measuring the correlation function in Gaussian simulations and the Millennium Simulation. We also analyze the SDSS DR7 main-galaxy sample (MGS), splitting the sample into slices 2.5 degrees on the sky in various rotations. Measuring 2D correlation functions in each slice, we do see a sharp bump along the line of sight. Using Mexican-hat wavelets, we localize it to (110 +/- 10) Mpc/h. Averaging only along the line of sight, we estimate its significance at a particular wavelet scale and location at 2.2 sigma. In a flat angular weighting in the (pi,r_p) coordinate system, the noise level is suppressed, pushing the bump's significance to 4 sigma. We estimate that there is about a 0.2% chance of getting such a signal anywhere in the vicinity of the BAO scale from a power spectrum lacking a BAO feature. However, these estimates of the significances make some use of idealized Gaussian simulations, and thus are likely a bit optimistic.Comment: 17 pages, 27 figures. Minor changes to match final version accepted to Ap

Role of environmental variables in structuring demersal assemblages on trawled bottoms on the Maltese continental shelf

Demersal assemblages from trawl surveys made at depths of 45-800m in trawled areas within the 25NM Fisheries Management Zone round the Maltese Islands were related to environmental characteristics on the seabed. Depth, temperature, and mean grain size all affected the structure of the demersal assemblages but depth and temperature gradient were overall the most important in that order; while mean grain size seemed more important for relatively shallow bottoms (<80m) than for deep ones.peer-reviewe

Dynamic Microclimate Boundaries across a Sharp Tropical Rainforest–Clearing Edge

As landscapes become increasingly fragmented, research into impacts from disturbance and how edges affect vegetation and community structure has become more important. Descriptive studies on how microclimate changes across sharp transition zones have long existed in the literature and recently more attention has been focused on understanding the dynamic patterns of microclimate associated with forest edges. Increasing concern about forest fragmentation has led to new technologies for modeling forest microclimates. However, forest boundaries pose important challenges to not only microclimate modeling but also sampling regimes in order to capture the diurnal and seasonal dynamic aspects of microclimate along forest edges. We measured microclimatic variables across a sharp boundary from a clearing into primary lowland tropical rainforest at La Selva Biological Station in Costa Rica. Dynamic changes in diurnal microclimate were measured along three replicated transects, approximately 30 m in length with data collected every 1 m continuously at 30 min intervals for 24 h with a mobile sensor platform supported by a cable infrastructure. We found that a first-order polynomial fit using piece-wise regression provided the most consistent estimation of the forest edge, relative to the visual edge, although we found no best sensing parameter as all measurements varied. Edge location estimates based on daytime net shortwave radiation had less difference from the visual edge than other shortwave measurements, but estimates made throughout the day with downward-facing or net infrared radiation sensors were more consistent and closer to the visual edge than any other measurement. This research contributes to the relatively small number of studies that have directly measured diurnal temporal and spatial patterns of microclimate variation across forest edges and demonstrates the use of a flexible mobile platform that enables repeated, high-resolution measurements of gradients of microclimate