Jury et al.Fine-scale measurement of gasoline vapors, major gases (O 2 , CO 2 , and Baehr, 1996; Anderssen et al., 1997; Anderssen and N 2 , and CH 4 ), residual nonaqueous phase liquid (NAPL) gasoline, Markey, 1997; Bekins et al., 1998;Johnson et al., 1999; and soil physical properties has allowed detailed assessment of the role of soil layering and seasonal variability on hydrocarbon vapor Turczynowicz and Robinson, fate and biodegradation. In this study we conducted coring and static 2001), some in combination with field studies (Barber depth profile monitoring at the end of summer and end of winter for and Davis, 1991aand Davis, , 1991bÖ hman, 1999;Hers et al., 2000). a layered sandy vadose zone in Perth, Western Australia. Transient Despite the modeling efforts and related work, there on-line monitoring of vapors and O 2 was also performed with in situ are still only limited field data sets with sufficient detail multilevel volatile organic compound (VOC) and O 2 probes. For high for evaluating vapor processes in impacted soil profiles soil moisture contents at the end of winter, vapors were shown to and for model validation. Additional well-documented accumulate beneath a compacted, cemented layer approximately 0.3 m studies are required (Johnson et al., 1999). Also, changes below the ground surface, and O 2 penetrated only to depths of 0.4 m in soil moisture distribution and soil layering have been below ground. At the end of summer, when soil moisture was lower, reported to impact vapor behavior and lead to complica-O 2 penetrated to depths of up to 1.5 m, and hydrocarbon vapors remained at or below this depth. Regardless of seasonal changes, sharp tions when estimating biodegradation rates (Johnson separations were seen between the depth of O 2 penetration from the and Perrott, 1991; Fischer et al., 1996;. ground surface and the depth of penetration of the vapors upwardWe present the results of field research and modelfrom the hydrocarbon-contaminated zone. Modeling of steady-state ing to quantify the role of a fine-scale moisture-retentive O 2 profiles indicated that a number of simple O 2 consumption models layer in a soil profile in changing the subsurface distribumight apply, including point-sink, distributed zero-order, or distribtion of gasoline vapors and the major gases due to seauted first-order models, each leading to different biodegradation rates. sonal changes in moisture contents. Simple analytical Combining independent data with modeling helped determine the and numerical modeling was performed to assess the most appropriate model, and hence estimates of O 2 consumption and impact of moisture variability on estimates of the biohydrocarbon biodegradation. Also, reliable estimates of the biodegdegradation rate based on depth profiles. Coring, depth radation rate could only be calculated after consideration of the layered features.

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Abstract.-The high variability in reported lengths of larval yellow perch Perca flavescens at hatching, dietary shift, and morphometric transformation may be partly caused by shrinkage that occurs after preservation. Larval yellow perch were captured, randomly assigned to one of six preservative treatments (100%, 95%, 80%, and 50% ethyl alcohol and 5% and 10% formalin), and measured (before preservation) for total length (TL). Larval yellow perch total lengths were then recorded on days 1, 7, 14, and 21 after storage in each of the six preservatives. Significant reductions in TL (11.5-14.3%) occurred during the first 24 h after fixation and larvae continued to contract at a lesser rate through day 7 in all four ethyl alcohol treatments. Total length reductions of up to 2.5% also occurred during the first 24 h in each formalin concentration. Our findings report the total length reductions of larval yellow perch at a length range used by some biologists when indexing year-class strength and during studies of early life history. The length reductions of larval yellow perch that are associated with storage in different concentrations of preservative appear to be inconsistent with those noted for other species; therefore, our findings support the need to obtain species-specific data for larval shrinkage.

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Declining burbot (Lota lota) abundance across some portions of North America has prompted a search for additional evaluation tools, including a measure of condition. Weight–length data were compiled for 10 293 burbot from 79 North American populations. These data were used to develop a 75th percentile standard weight (Ws) equation using the regression-line-percentile technique. The proposed equation is log10Ws = −4.868 + 2.898 log10 TL, where Ws is the standard weight in grams, and TL is the maximum total length in millimetres. The equation is valid for burbot ≥ 20 cm and will allow calculation of relative weights (Wr) for this species. Based on the length of the longest burbot in our data set (104.3 cm), we propose minimum standardized length categories of 20, 38, 53, 67, and 82 cm for stock, quality, preferred, memorable, and trophy length, respectively. The standard length categories will allow determination of mean Wr by length group, as well as calculation of stock density indices. Differences in Wr values were present between lentic and lotic burbot populations, suggesting variation in body shape and a need for establishment of different Wr objective ranges.