A note on mesh selection and sampling efficiency in benthic studies

Gillnets are a widely used fishing gear in Kenya’s artisanal fisheries, yet their mesh sizes are inadequately monitored or regulated. This study evaluated the impacts of gillnets of seven stretched-mesh sizes, through comparative analysis of species-related metrics and catch per unit effort (CPUE), to inform Kenya’s small-scale fisheries regulations. Data were collected from June 2014 to May 2015. Three mesh-size groups were identified from catch composition data using non-metric multidimensional scaling and comprised small (1.3, 5.1 and 7.6 cm), medium (10.2 and 15.2 cm) and large (20.3 and 25.4 cm) mesh. The dominant species (and their mean lengths) that were caught in the small, medium and large mesh sizes, respectively, were whitespotted rabbitfish Siganus sutor (21.7 cm [SD 5.3]), mackerel tuna Euthynnus affinis (40.8 cm [SD 9.1]) and honeycomb stingray Himantura uarnak (87.3 cm [SD 37.4]). Values of length at first capture (L 50) for S. sutor and E. affinis caught with the small and medium mesh sizes were below length at maturity (L m). Catches of juveniles were proportionately high in the small meshes (61.3–74.2%) and lower in the medium (38.3–50.9%) and large (9.1–36.2%) mesh sizes. Catches with small mesh tended to be species categorised as Least Concern on the IUCN Red List, in contrast to catches with large mesh which tended to be Near Threatened or Vulnerable species. Biomass CPUE differed between mesh-size groups, with the small sizes recording low CPUE. The medium sizes caught mid- to high-trophic-level species with high-income returns, displayed moderate CPUE, and had the lowest juvenile retention and capture of threatened species. Medium mesh sizes are therefore recommended for artisanal fisheries, given low trade-offs between ecological impact and fishery returns.

Size selectivity and catch efficiency of four codends were tested and compared for mantis shrimp (Oratosquilla oratoria) in demersal trawl fisheries of the South China Sea (SCS). These codends were differing in mesh shapes, diamond mesh (T0) and diamond-mesh turned 90° (T90) with mesh sizes of 30 and 35 mm, respectively. The results demonstrated that the T0 codend with a lower mesh size, 30 mm, presented poorer selective properties for the target species, while size selectivity would be significantly improved with the mesh size increasing to 35 mm, or substituting the T0 codend with the T90 codend. For the T90 codend with a larger mesh size, 35 mm, the size selectivity was the highest, whereas the loss of the legal individuals was also significantly considerable. Considering the trade-off between releasing undersized individuals and maintaining the legal ones, the T0 codend with 35-mm mesh size or the T90 codend with 30-mm mesh size might be a better choice to target mantis shrimp in demersal trawl fisheries of the SCS.

Mathematical models were used to generate numerical results by (1) combining the growth and mortality curves of a hypothetical lake whitefish (Coregonus clupeaformis) population to yield a length-frequency distribution, (2) calculating the number of fish caught by different mesh sizes and at different rates of exploitation by means of a gill-net selectivity model, and (3) subtracting the fish caught from the unexploited population. Assumptions on some population parameters and the choice of gill-net selectivity curves were verified against field data from the James Bay area. Results indicate that the use of a mix of mesh sizes (76.2-127 mm) is more compatible with the natural population structure than the use of one large mesh size alone, provided that the fishing intensity is controlled. These findings suggest a change in management policy from primarily regulating the mesh size to regulating the fishing intensity.

Genetically modified Bacillus thuringiensis Berliner (Bt) maize (Zea mays L.) expressing Cry toxins against various target pests is now grown on more than 16 million hectares worldwide, but its potential effects on the soil ecosystem need to be further investigated. In an 8-month field study, we investigated the effects of Bt maize expressing the Cry1Ab protein on both the soil community and maize residue decomposition. We used litterbags with three different mesh sizes (20, 125, and 5,000 μm) to investigate potential effects of different soil organism groups on the decomposition processes. Litterbags were incorporated into the soil in fall into a field that had previously been planted with non-Bt maize and subsamples were removed monthly. The dry weight of the remaining residue was measured for all bags. Bt and non-Bt maize decomposed similarly in large mesh bags, which allowed the whole soil organism community to enter and interact with each other. In contrast, Bt maize decomposed significantly faster than non-Bt maize at some sample dates in winter in bags with small and medium mesh sizes. At the end of the experiment in late spring, however, there was no significant difference in the amount of maize plant residues remaining for any of these three mesh sizes. Additionally, soil organisms from bags with the largest mesh size were identified. The most frequent taxa extracted were collembolans (Isotomidae, Tullbergiidae, Entomobryidae), mites (Gamasina, Oribatida), and annelids (Enchytraeidae). Three of these taxa were extracted in higher numbers from non-Bt than Bt residue (Tullbergiidae, Gamasina, Enchytraeidae), while there was no difference in the number of individuals extracted for the remaining three taxa. Our results do not show major changes in the decomposition of Bt maize residue and in the composition of the soil organism community. However, further studies are needed that assess the impact of the continuous release of Cry1Ab via root exudates and plant biomass on the soil ecosystem.

King's ships built on the North-East Coast of England Get access M. H. Dodds M. H. Dodds Search for other works by this author on: Oxford Academic Google Scholar Notes and Queries, Volume CLXV, Issue aug19, 19 August 1933, Page 124, https://doi.org/10.1093/nq/CLXV.aug19.124c Published: 19 August 1933

Matrices for tissue engineering-scaffold structure for a bioartificial liver support system

Nanostructured hydrogels based on "smart" polymer conjugates of poloxamers and protein molecules were developed in order to form stimulus-responsive materials with bioactive properties for 3-D cell culture. Functionalized Pluronic F127 was covalently attached to a fibrinopeptide backbone and cross-linked into a structurally versatile and mechanically stable polymer network endowed with bioactivity and temperature-responsive structural features. Small angle X-ray scattering and transmission electron microscopy combined with rheology were used to characterize the structural and mechanical features of this biosynthetic conjugate, both in solution and in hydrogel form. The temperature at which the chemical cross-linking of F127-fibrinopeptide conjugates was initiated had a profound influence on the mechanical properties of the thermo-responsive hydrogel. The analysis of the scattering data revealed modification in the structure of the protein backbone resulting from increases in ambient temperature, whereas the structure of the polymer was not affected by ambient temperature. The hydrogel cross-linking temperature also had a major influence on the modulus of the hydrogel, which was rationally correlated to the molecular structure of the polymer network. The hydrogel structure exhibited a small mesh size when cross-linked at low temperatures and a larger mesh size when cross-linked at higher temperatures. The mesh size was nicely correlated to the mechanical properties of the hydrogels at the respective cross-linking temperatures. The schematic charts that model this material's behavior help to illustrate the relationship that exists between the molecular structure, the cross-linking temperature, and the temperature-responsive features for this class of protein-polymer conjugates. The precise control over structural and mechanical properties that can be achieved with this bioactive hydrogel material is essential in designing a tissue-engineering scaffold for clinical applications.

Gel microstructure regulates proliferation and differentiation of MC3T3-E1 cells encapsulated in alginate beads

The study explores the impacts of varying gillnet mesh size and fishing level on yield per recruit (Y/R), escapement spawning stock (ESS) and mega‐spawners (MS) of three widely distributed freshwater fishery target species. Y/R is maximised when the optimal length of capture (Lcap) is above the size of maturity (L50). However, the unimodal shape of gillnet selectivity results in lower impacts to ESS and MS with both smaller and larger mesh sizes. Under conditions of moderate exploitation, the fraction of MS was significantly larger if small meshed gillnets were used. This is due to the relatively smaller cumulative vulnerability from small mesh sizes through time, as they target a smaller size range of fish, which also grow more quickly through the vulnerable window due to higher growth rates. Therefore, unlike trawls and beach seines, which select all size classes beyond the minimum length of capture (Lc), small meshed gillnets are not necessarily destructive and may rather promote sustained production by allowing a higher proportion of the spawning biomass to remain in the stock. The work also helps to explain the observation of sustained fish production in many developing countries despite the persistent use of gillnets of small mesh size that target small, under‐sized individuals.

In order to prepare spherical salbutamol sulfate particles of adjustable size, a Nano Spray Dryer B-90 was employed. A 33 full-factorial design was used to investigate the influence of process parameters (mesh size, feed concentration, and drying air temperature) on particle size (median size and width of the particle size distribution), amount of product produced per time, and product yield. The median particle size was significantly influenced by all three factors of the statistical design. Within the design space studied, particle sizes of 1.0 to 6.4 µm were obtained. The width of the particle size distribution (span) increased with increasing mesh sizes. All particles with a particle size greater than 2.4 µm showed a bimodal particle size distribution. Generally, larger mesh sizes as well as higher concentrations led to an increase in the amount of product prepared per time. The corresponding values observed were from 0.4 to 75.8 mg/min. The product yield was independent of the process parameters studied. All products were amorphous after spray drying and were stable up to a relative humidity of 60% at a temperature of 25°C.

Landings by the multi-gear coastal fleet operating off the Portuguese continental coast include about 300 species, from which only a few are the object of management plans. In this study, daily landings (kg trip-1) are used, along with an effort indicator, vessel length overall (LoA), to obtain landings per unit of effort (LPUE) as a proxy for the species relative abundance, for a total of 48 species. LPUE indices were used as a response variable in linear models where year (2012–2016), season, region (north and south) and NAO index were explanatory variables. Seasonal and regional effects were found to significantly affect species abundance for a total of 41 and 40 species respectively, while year trends were found to be significant for 19 species, and the NAO index for 3 species. LPUE density maps are presented for several selected species and a subsample of trips, where VMS records were available. It is proposed that geographic and seasonal changes in LPUE can be used to understand trends in abundance and obtain information that can be used in support regional management plans.

1. In an experiment conducted with eight pairs of monozygous twin heifer calves aged from 7 to 9 months, it was shown that the mean haemoglobin concentration of those reared on a high plane of nutrition was higher than the corresponding value of those reared on low-plane rations.2. The relative anaemia of the low-plane animals was microcytic but normochromic in type. Its cause must await further investigation, but these features would not be inconsistent with a deficiency of iron.3. For this type of haematological study, monozygous twins proved more efficient than unrelated animals, as shown by the smaller variability within than between pairs.4. Day-to-day variation in the same animal must be considered an important possible source of sampling error.

Accurate population estimates can reveal trends that are fundamental to detecting species’ declines and to designing and assessing conservation strategies. We compared spotlighting, diurnal line transects and thermal drone flights for detecting koalas in a rural landscape and evaluated a time series of data at our site to test sampling error and understand the influence of survey type and temporal variability on population estimates. Historically, diurnal koala detections were biased toward searches with a southerly view suggesting aspect with relation to the sun was a source of sampling error. No method detected all koalas, with drone flights, diurnal surveys and spotlighting transects detecting on average 79%, 48% and 43% of koalas respectively across repeated surveys, but detection differences were nonsignificant. Estimates of koala population density based on diurnal surveys had large confidence intervals. Combining techniques enhanced detection: a combination of drone and daytime surveys detected an average of 88% of koalas present. We conclude that, where possible, drone detection is currently the most effective way to detect koalas, but by combining methods, accuracy is improved.

In addition to the initial thermal conductivity value, the thermal conductivity of closed-cell foamed plastics over long periods of time depends to a large degree on the gas exchange processes between the blowing agent and the ambient air. It is very important to know and to show whether the cell gas remains in the foam for a short time or, to a large extent, for the whole lifetime of the foam material. A lifetime of between c.20 to 50 years is assumed for thermal insulation materials in construction, and it will be shown that blowing agents remain to a large extent in the foam material over such periods. The method most extensively applied for measuring cell-gas composition is to take a sample using a gas-tight syringe and then analyse by gas chromatography. In addition to the measuring method, possible sources of sampling errors and measuring uncertainty are indicated. In order to show the relationship between thermal conductivity and cell-gas composition, thermal conductivity curves for PUR rigid foam materials blown with CFC 11 over a period of 30 years, and PUR foam materials blown with HCFC 141b or pentane over a period of 9 years are presented, with the corresponding measured values for cell-gas composition. Cell-gas measurement continues to be applied as proof of the blowing agent used for consumers and official bodies, and also for compliance with regulations.

Riparian alder fens — source or sink for nutrients and dissolved organic carbon? — 2. Major sources and sinks