General and specific combining abilities of larval and juvenile growth and viability estimated from natural oyster populations

Diallel crosses of oysters from three geographically isolated natural populations were produced to evaluate the relative importance of genetic, maternal, and environmental effects on larval and juvenile growth and viability. Significant additive genetic effects were observed only in larval viability at Day 12 and larval shell length at Day 2. The presence of significant male and female mean square for larval viability (suggesting non-additive genetic variance) is consistent with fitness related characters. Important maternal effects were observed for the larval and juvenile shell length and viability characters. These female mean squares are probably affected by both real and spurious maternal effects and potential contributing influences are discussed. The performance of the crosses can be largely explained by two factors: parental performance and the heterotic gene effects. This is based on an apparent positive correlation of mean values between the parental populations and their crosses. The crosses' mean viability at the end of the larval phase was 14.0% lower than the pure matings and support a previous observation of lower heterozygote viability in the larval phase (Mallet and Haley, 1983b).     

Effects of deodorants on treatment of boat holding-tank waste

A literature search and survey of Virginia, USA, campgrounds with RV pump-out stations were used to determine whether boat holding-tank deodorant chemicals would have deleterious effects on marina septic systems or package treatment plants. Laboratory studies reported in the literature indicate that these chemical additives could affect septic system function in three ways: (1) active ingredients in the additives can impair sewage degradation in septic tanks, causing sludge buildup and overflow of solids into the drainfield, (2) additive chemicals might enter the drainfield and, in high enough concentrations, reduce the drainfield's ability to degrade waste, or (3) toxic additive chemicals might migrate from the drainfield to ground or surface water. Laboratory studies also show that some ingredients added to holding tanks interfere with functioning of activated sludge treatment process. Experience in the field and in other laboratory studies suggests that factors such as dilution of treated waste with untreated waste and the characteristics of the sewage to be treated can reduce the possibility of damage to septic and activated sludge systems. The campground owners surveyed indicated that they have few problems with their septic systems in spite of the presence of chemical additives in the RV waste. However, most of them practice good septic system maintenance and have devised other means of ensuring that their systems function efficiently. In addition, the survey indicates that most Virginia campgrounds get only seasonal use (as would marinas in Virginia), allowing their systems to recover between peak seasons.     

Effects of Timber Harvesting on Southern Appalachian Salamanders

We compared the species richness and abundance of salamanders on six recent clearcuts (< 10 years old) with that of salamanders on 34 mature forest stands (>50 years old) in southern Appalachian forests in western North Carolina, U.S.A. Catches of salamanders from plots in mature forest stands were about five times higher than those on recent clearcuts. Almost all species and major taxonomic groups of salamanders were adversely affected by timber removal. Mean number of species collected per plot was about twice as great in mature forest stands as in clearcuts. Analyses of stand age versus salamander catch for 47 plots indicate that 50–70 years are required for populations to return to predisturbance levels following cutting. We conservatively estimate that clearcutting in U.S. national forests in western North Carolina results in a loss of nearly 14 millton salamanders annually. It also is chronically reducing regional populations by more than a quarter of a billion salamanders (9%) below that which could be sustained if mature forests were not cut.     

Resource-holding power asymmetries,the prior residence effect,and reproductive payoffs in male northern elephant seal fights

The effect of resource-holding power (RHP) and prior residency asymmetries on fight outcome and subsequent seasonal copulatory success was analyzed for fights between marked male northern elephant seals (Mirounga angustirostris). RHP asymmetries were measured as differences in estimated mass and prior residency asymmetries were measured as differences in beach tenure prior to the fight. The principal results were: (a) Neither differences in mass nor differences in beach tenure had any effect on fight outcome as separate factors. (b) Mass and tenure differences had an interactive effect on fight outcome; fight winners were either heavier males present for shorter periods (intruders) or lighter males present for longer periods (prior residents). (c) Winners of fights copulated more often than losers after a fight throughout the breeding season; this difference was smallest for low-ranking males, larger for high-ranking males in short fights, and greatest for high-ranking males in long fights. (d) Prior resident males who won long fights obtained significantly more copulations after a fight than the males they defeated, but this was not true for intruder males who won long fights. These results suggest that male northern elephant seals will incur greater contest costs (i.e., fight for longer periods and/or against heavier males) for higher reproductive payoffs. They also imply that, at least for males in long fights, differences in prior residence represent payoff asymmetries, with higher reproductive payoffs for winning prior residents than for winning intruders.     

Genetics of larvae and spat growth rate in the oyster Crassostrea virginica

The heritability of oyster (Crassostrea virginica) larval growth rate was estimated to be in the range of 0.25 to 0.50 and a significant part of this genetic variation is of the additive type. Larval growth rate and spat growth rate were found to be highly correlated. These results suggest that a selection program for faster growing larvae and spat would be successful.     

Taking the bait: species taking oral rabies vaccine baits intended for raccoons

Raccoon rabies in eastern USA is managed by strategically distributing oral rabies vaccine (ORV) baits. The attractiveness, palativity, density, and non-target species bait take affect ORV effectiveness. We examined raccoon and non-target species differences in investigating/removing fish-meal polymer and coated sachet baits applied to simulate two aerial bait distribution densities. Bait densities of 150 baits/km² and 75 baits/km² were evaluated, respectively, in zones expected to have high and low raccoon densities. Three primary non-target species visited baits: coyotes, white-tailed deer, and feral swine. The proportion of bait stations visited by raccoons during 1 week observation periods ranged from 50 to 70%, exceeding non-target species visitation. Raccoon take rates for visited baits averaged from 59 to 100%. Raccoon visitation was similar for both bait densities, indicating a proportionally greater quantity of baits were taken in the higher bait density zone. Coyote visitation rates ranged from 16 to 26%, with take rates for visited baits between 46 and 100%. Coyotes were expected to take baits intended for raccoons, because similar baits are applied to vaccinate coyotes. Deer regularly investigated but rarely took baits. Feral swine were in low abundance in the high bait density zone (higher human density) and visited ≤?1% of baits there but visited baits at frequencies similar to coyotes and deer in the low-density zone and were likely to take encountered baits (63–100%). Non-target bait consumption could be a concern in some circumstances for achieving sufficient raccoon sero-conversion rates.

     

A comparison of SEM-EDS with ICP-AES for the quantitative elemental determination of estuarine particles

Suspended particulate matter (SPM) is a key component regulating the biogeochemistry of natural and contaminant moieties in estuaries. Individual particle analyses can complement conventional bulk analyses of SPM, but are rarely undertaken. This study used scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS) of particles to quantify a range of elements in the reference estuarine sediment PACS-2. This approach was compared with a bulk SPM analysis based on inductively coupled plasma-atomic emission spectrometry (ICP-AES). The median concentrations of Al, Fe, Mg, and Ca for the two approaches were similar, and accuracy for both methods was good. SEM-EDS analysis was also satisfactory for K. Agreement was poorer for Mn and Ti, which were present at trace concentrations. Increasing the number of particles examined by SEM-EDS should improve the analysis. SEM-EDS analysis of SPM from the Tamar Estuary, UK, revealed marked geochemical differences between particle sub-populations.Selected article from 6th European Meeting on Environmental Chemistry, Belgrade, 2005, organised by Prof. Dr. Branimir Jovancicevic and the European Association of Chemistry and the Environment (ACE, www.research.plymouth.ac.uk/ace)