Variability Of Biological Parameters Research Articles

Exploring the Use of a Size‐Based Egg‐per‐Recruit Model for the Red Abalone Fishery in California

AbstractEggs‐per‐recruit (EPR) models are widely used for management of invertebrate fisheries to provide guidance to managers about the magnitude of egg production for a given level of instantaneous annual fishing mortality (F). We constructed a deterministic size‐based EPR model that utilizes size‐specific natural mortality rates and egg production for red abalone Haliotis rufescens in California. We analyzed the sensitivity of the model to alterations in biological parameters, modeled the effect of incidental mortality of sublegal individuals on EPR, and modeled the effects of various management actions, including incorporation of a slot size limit, incorporation of a harvest refugium, and alternative legal minimum size limits. Model results were more sensitive to alterations in growth parameters and lower mortality estimates than to changes in upper mortality estimates or fecundity parameters. When F increased from 0.0 to 0.1 per year, EPR exhibited a large decline from 100% to 70%. Only the incorporation of a harvest refugium and an increase in the minimum size limit produced increases in the percent of maximum EPR. Implementing a slot limit of 152.4–203.2 mm maximum shell length (MSL) decreased the EPR value, indicating the importance of egg production by red abalone that are smaller than the current minimum size limit of 177.8 mm MSL. Because of the sensitivity of model predictions to changes in certain biological parameters, we recommend caution when applying EPR models to management, particularly for regions without spatially explicit parameter values. Despite this sensitivity, EPR models provide a heuristic framework for exploring the potential impacts of proposed fishery management strategies (e.g., harvest refugia), establishing biological reference points, examining how spatial and temporal variability in biological parameters affects egg production, and providing a guide for prioritizing research to improve data quality used for red abalone management.

IMRT optimization including random and systematic geometric errors based on the expectation of TCP and NTCP

The purpose of this work was the development of a probabilistic planning method with biological cost functions that does not require the definition of margins. Geometrical uncertainties were integrated in tumor control probability (TCP) and normal tissue complication probability (NTCP) objective functions for inverse planning. For efficiency reasons random errors were included by blurring the dose distribution and systematic errors by shifting structures with respect to the dose. Treatment plans were made for 19 prostate patients following four inverse strategies: Conformal with homogeneous dose to the planning target volume (PTV), a simultaneous integrated boost using a second PTV, optimization using TCP and NTCP functions together with a PTV, and probabilistic TCP and NTCP optimization for the clinical target volume without PTV. The resulting plans were evaluated by independent Monte Carlo simulation of many possible treatment histories including geometrical uncertainties. The results showed that the probabilistic optimization technique reduced the rectal wall volume receiving high dose, while at the same time increasing the dose to the clinical target volume. Without sacrificing the expected local control rate, the expected rectum toxicity could be reduced by 50% relative to the boost technique. The improvement over the conformal technique was larger yet. The margin based biological technique led to toxicity in between the boost and probabilistic techniques, but its control rates were very variable and relatively low. During evaluations, the sensitivity of the local control probability to variations in biological parameters appeared similar for all four strategies. The sensitivity to variations of the geometrical error distributions was strongest for the probabilistic technique. It is concluded that probabilistic optimization based on tumor control probability and normal tissue complication probability is feasible. It results in robust prostate treatment plans with an improved balance between local control and rectum toxicity, compared to conventional techniques.

Spatial patterns in the biology of the chokka squid, Loligo reynaudii on the Agulhas Bank, South Africa

Although migration patterns for various life history stages of the chokka squid (Loligo reynaudii) have been previously presented, there has been limited comparison of spatial variation in biological parameters. Based on data from research surveys; size ranges of juveniles, subadults and adults on the Agulhas Bank were estimated and presented spatially. The bulk of the results appear to largely support the current acceptance of the life cycle with an annual pattern of squid hatching in the east, migrating westwards to offshore feeding grounds on the Central and Western Agulhas Bank and the west coast and subsequent return migration to the eastern inshore areas to spawn. The number of adult animals in deeper water, particularly in autumn in the central study area probably represents squid spawning in deeper waters and over a greater area than is currently targeted by the fishery. The distribution of life history stages and different feeding areas does not rule out the possibility that discrete populations of L. reynaudii with different biological characteristics inhabit the western and eastern regions of the Agulhas Bank. In this hypothesis, some mixing of the populations does occur but generally squid from the western Agulhas Bank may occur in smaller numbers, grow more slowly and mature at a larger size. Spawning occurs on the western portion of the Agulhas Bank, and juveniles grow and mature on the west coast and the central Agulhas Bank. Future research requirements include the elucidation of the age structure of chokka squid both spatially and temporally, and a comparison of the statolith chemistry and genetic characterisation between adults from different spawning areas across the Agulhas Bank.

Biological variation between two Brazilian geographical isolates of Echinostoma paraensei

The biological behaviour and morphometric data from two allopatric isolates of Echinostoma paraensei (Rio Bonito - RB and Sumidouro - SU) collected from naturally infected Nectomys squamipes from two secluded Atlantic Forest fragments were studied. Mice that had been experimentally infected with ten encysted metacercariae of each isolate were monitored weekly in two trials to analyse worm burden and the kinetics of worm distribution along the intestine. The total number of uterine eggs, wet weights and measurements of the worms and body, acetabulum, testes and ovaries were also analysed. The RB isolate showed a higher worm burden, 7.7+/-0.8, and a longer life span, 16 weeks, compared to a worm burden of 5.8+/-1.1 and life span of 9 weeks for the SU isolate. Worms of the RB isolate were clustered in the duodenum and in the bile duct while the SU isolate worms were dispersed along the small intestine of infected mice. Both isolates developed similarly as regards morphometric data and wet weight, although the total number of uterine eggs was greater in RB. The degree of intraspecific variation observed in the worm distribution along the intestine, worm burden and life span raises questions regarding the use of these criteria for species differentiation. These findings suggest that variation in biological parameters found between the E. paraensei isolates could result from geographical isolation and, in particular, the environmental conditions of transmission. Further studies on E. paraensei polulations from different forest fragments will contribute towards an understanding of the speciation of this parasite.

Single cell resolution in regulation of gene expression

Single cell resolution in regulation of gene expression

Variation in biological parameters of Trichogramma spp. purchased from commercial suppliers in the United States

The efficacy of biological controlobtained through releases of commerciallysupplied Trichogramma is influenced by bothabiotic conditions in the field during andfollowing release and an array of biologicalattributes of the released Trichogramma. Thisstudy was undertaken to assess the degree ofvariation that existed among commerciallysupplied Trichogramma in an array of biologicalparameters that potentially may influence thelevel of control that can be expected in aTrichogramma release program. Shipments ofTrichogramma were obtained from 12 commercialsuppliers of beneficial insects over a 2-yearperiod and the following parameters weremeasured: percentage of emergence duringshipping, total percentage of emergence,percentage of females, percentage ofbrachypterous females, percentage ofbrachypterous males, adult female longevity,and species composition. In addition, weestimated the percentage of macropterousfemales that had not emerged prior to the timethe shipment was received, based on the firstfour parameters. Results indicate a high levelof variation in each of these parameters amongsuppliers of Trichogramma and among shipmentsby individual suppliers. The proportion ofnon-emerged macropterous female wasps was lowfor all suppliers (range 2.5–27.7%). Thiswas primarily attributable to the highincidence of brachyptery among female wasps. However, variation among suppliers in theincidence of emergence during shipping and theproportion of female wasps in a shipment alsocontributed to the low proportion ofnon-emerged macropterous female wasps. Inaddition, in 11 of 24 shipments received duringthe 2-year study, the Trichogramma speciesdiffered from that specified by the shipper orthe shipment contained a mixture ofTrichogramma species.

Pacific warm pool and divergence: temporal and zonal variations on the equator and their effects on the biological pump

The equatorial Pacific consists of two regions that have distinct hydrological features and ecosystem dynamics: the warm pool to the west and the Pacific Equatorial Divergence (PEQD). The two regions are separated by well-defined fronts in salinity, pCO2, and macronutrients. Both the input of macronutrients in the two regions and their zonal extension are influenced primarily by the El Niño Southern Oscillation (ENSO) variability, which may be depicted by the Southern Oscillation Index (SOI). Thus, a quantitative relationship can be established between the longitude of the front and the SOI (Geophys. Res. Lett. 23 (1996) 1781–1784), allowing an assessment of the zonal extension of the two regions. In the PEQD, equatorial transects have shown that there is much temporal and spatial stability of biomass and fluxes of the biological pump, regardless of variations in macronutrient concentrations. This is a consequence of the High Nutrient Low Chlorophyll (HNLC) status of the waters, where primary production is not limited by the input of macronutrients. Moreover, the lack of an E–W gradient in the biological parameters supports the view that micronutrient inputs also should be more or less constant with longitude along the equator. A review of temporal variability on scales ranging from ENSO cycles to diel cycles leads to the conclusion that much of the biomass and flux variations along equatorial transects may be ascribed to temporary meridional transport by Tropical Instability Waves (TIW). In the warm pool, primary production is regulated by the input of macronutrients to the photic zone. These inputs from the deep nutricline depend on the ENSO cycle and temporary events. However, primary production is less than in the PEQD. A monthly estimate of the biological pump was made for the period 1980–2000 and the 1°N–1°S band of the divergence, west of the Galapagos Islands, on the assumption that: the longitude of the front was directly related to the SOI; there were no zonal variations in biological parameters; and mean rate values could therefore be used for primary production, new production, particle sinking and fluxes due to diel migration. The average longitude of the front was 178°W, and mean new production was 106–134 Mt C yr−1; it was 76–96 Mt C yr−1 during strong El Niño years and 114–144 Mt C yr−1 during other years. These variations between the two ENSO situations are less than those of published CO2 fluxes to the atmosphere, a result that can be ascribed to the particularly stable HNLC system.

Genetic variance of adolescent growth in stature

The aim of this study is to quantify the genetic and environmental variation in biological parameters of the adolescent growth in stature in both sexes, using structural equation models. Standing height was measured in 99 twin pairs from the Leuven Longitudinal Twin Study. Subjects were seen at semi-annual intervals between 10 and 16 years and at 18 years. Preece-Baines model I was fitted to the individual data and biologically meaningful parameters were derived. Path models were fitted to these parameters and a gender heterogeneity analysis was performed. A model including additive genetic and specific environmental factors (AE-model), allowing for a difference in total variance or in genetic/environmental variance components in males and females best explains most of the growth characteristics. For the timing and velocity of the adolescent growth spurt, no gender heterogeneity was observed, and the genetic (0.89 to 0.93) and specific environmental (0.07 to 0.11) contributions were equal in both sexes. For stature at take-off, stature at peak height velocity and for adult stature, gender heterogeneity was observed and different models appeared to result in the best fit for boys and girls. For height at PHV and adult stature, the significant contribution of a common environmental (0.39 to 0.56) factor in boys was noteworthy. For percentage of adult stature and distances between relevant time points of the growth curve, a non-scalar effect was observed, indicating that different genes affect these characteristics in boys and girls. It is concluded that most characteristics of the growth spurt in stature are under strong genetic control. Gender heterogeneity is present for stature and for a number of derived growth characteristics.

Lotka-Volterra prey-predator model with harvesting and environmental perturbations

The authors considered the two-species Lotka-Volterra prey-predator system where both species are subjected to combined harvesting effort. The system is studied by taking into account time-periodic variations in biological parameters and harvesting effort. The significant results are discussed.

Sequential Decision Plans in Monitoring Benthic Macroinvertebrates: Cost Savings, Classification Accuracy, and Development of Plans

Sequential decision plans provide a statistical approach that can reduce the number of benthic sample units needed to classify a site as impacted or unimpacted, thus reducing the cost of using benthic macroinvertebrates in water quality assessment programs. These plans require information about unimpacted and impacted conditions, the mathematical distribution of the data, and acceptable risks of classification error. A large benthic data set (n = 55) was used for simulations that created and tested sequential decision plans. Using 10–60% reductions in species richness, mayfly (Cinygmula) population density, and species diversity as definitions of impact in the simulations, the average number of sample units processed for identification of the unimpacted reference site was reduced (compared with fixed sample-size methods that are commonly used) by 50–64% for species richness, 59–79% for density estimates, and 51–55% for species diversity. Unimpacted data sets were initially classified as representing impacted conditions in 0–5% of the cases. If classifications are to be interpreted properly, sampling error and spatial and temporal variation in biological parameters must be considered when sequential decision plans are created.