Periodontal diseases are Gram-negative anaerobic infections that can occur in women of childbearing age (18 to 34 years). In the present investigation we sought to determine whether the prevalence of maternal periodontal infection could be associated with preterm low birth weight (PLBW), controlling for known risk factors and potential covariates. A case-control study of 124 pregnant or postpartum mothers was performed. PLBW cases were defined as a mother with a birth of less than 2,500 g and one or more of the following: gestational age <37 weeks, preterm labor (PTL), or premature rupture of membranes (PROM). Controls were normal birth weight infants (NBW). Assessments included a broad range of known obstetric risk factors, such as tobacco use, drug use, alcohol consumption, level of prenatal care, parity, genitourinary infections, and nutrition. Each subject received a periodontal examination to determine clinical attachment level. PLBW cases and primiparous PLBW cases (n = 93) had significantly worse periodontal disease than the respective NBW controls. Multivariate logistic regression models, controlling for other risk factors and covariates, demonstrated that periodontal disease is a statistically significant risk factor for PLBW with adjusted odds ratios of 7.9 and 7.5 for all PLBW cases and primiparous PLBW cases, respectively. These data indicate that periodontal diseases represent a previously unrecognized and clinically significant risk factor for preterm low birth weight as a consequence of either PTL or preterm PROM. J Periodontol 1996;67:1103-1113.
Historical and contemporary data on lake whitefish (Coregonus clupeaformis) from the Ontario waters of Lake Huron were examined for evidence of stocks with the objective of defining population boundaries. We delineated the spatial distribution of five stocks from tag–recapture data and the general location of six additional stocks on the basis of population parameters such as growth rate, age structure, and abundance trends.Samples of fish collected (summer and fall) from 5 of the 11 potential stocks were evaluated on the basis of 11 morphometric and 7 meristic characters. We also examined osseometric features such as shape of scales and otoliths, and electrophoretic characteristics at 32 loci associated with 12 enzyme systems.The summer and fall samples for each group were generally not significantly different. For the phenotypes examined electrophoretically, each stock was in Hardy–Weinberg equilibrium; 12 of the 32 loci considered were polymorphic and 4 of the 10 possible genetic distances differed significantly from zero.The Inner Basin stock was distinctly different from all other stocks. The Blind River stock was also found to be different by osseometrics, but not by morphometrics or electrophoresis. Osseometrics separated the stocks by basin of origin. Two stocks, Outer Basin and Burnt Island, appeared to be the most similar and could be separated from each other only on the basis of growth rate and tagging data. These two stocks are adjacent to each other in the main basin of Lake Huron, along the south shore of Manitoulin Island.Whitefish stocks of Lake Huron represent groups of fish that differ phenotypically and genotypically in varying degrees, are spatially separated, and behave as cohesive units. We conclude that they should be regarded as functional units for management purposes.Key words: lake whitefish, Coregonus clupeaformis, Lake Huron, stocks, tag–recapture data, population structure, morphometrics, meristics, osseometrics, scale and otolith shape, starch gel electrophoresis, biochemical genetic variation
A population of lake whitefish (Coregonus clupeaformis) in the waters off eastern Manitoulin Island in Lake Huron was sampled from 1950 to 1982 by an experimental pound net in the outer basin of South Bay. Year-class strength increased markedly from 1947 to 1977; the increase began with the decline of the 1943 year-class. The fork length attained by age 1–3 fish decreased during the study, but no trend was apparent for older fish. Natural mortality of year-classes varied considerably, and was probably related to the abundance of lamprey. The annual exploitation rate increased from 1 to 37% between 1960 and 1977. Year-class strength was not correlated with the thermal regime during spawning and hatching. Recruitment was a function of parental stock size, and there was evidence that survival from the egg to juvenile stage was inversely correlated with parental stock size. Instantaneous growth rates (G) during the 2nd year of growth were inversely related to year-class strength. Growth (G) in the 1st year was positively correlated with estimated surface water temperatures. The sizes attained by ages 2 and 3 were inversely related to total population abundance. Catchability coefficients in 144-mm-mesh gill nets were inversely related to estimated population sizes. An intrinsic mechanism of population regulation is proposed whereby recruitment is a function of parental stock size, juvenile survival is inversely related to stock size, and growth is inversely correlated with population abundance.
This paper describes the depth distributions and numeric abundance of fishes in the Canadian waters of Lake Huron based upon size‐corrected results of experimental netting from 1958 through 1968. Gill‐net catches were corrected for encounter probabilities based on the positive correlation between fish size and swimming speed and for retention probability offish of different sizes once they encounter the net. A 3‐parameter gamma function was used to fit net‐selectivity curves for 13 Great Lakes species. Comparison of raw with corrected catches for Georgian Bay showed that the former exaggerated the relative abundance of deep‐water coregonines Coregonus spp. in the deepest strata and overrepresented the abundance of yellow perch Perca flavescens and lake chub Couesius plumbeus in the shallowest waters. Corrections resulted in status changes for several species that are major segments of the fish community. Nearly two decades after the collapse of the top‐level native piscivores, Georgian Bay retained much of the character of the fish fauna prevailing before establishment of exotic species. Deep‐water coregonines dominated the community at depths below 50 m. The main basin and North Channel supported major populations of rainbow smelt Osmerus mordax and alewives Alosa pseudoharengus; rainbow smelt abundance increased with depth. Deep‐water coregonines formed a substantial proportion of the fauna in all basins of the lake, Smaller benthic and littoral‐zone species were well represented in the shallower areas (less than 20 m deep) and were gradually dominated by rainbow smelt, alewives, and coregonines as depth increased. The three basins differed in fish species composition to a greater extent than would be predicted on the basis of their bathymetries. None of the larger species of piscivores characteristic of North American oligotrophic lakes were present in large numbers during the term of this study.
In the early 1970s Lake Huron fishermen converted their gill nets from multifilament to monofilament nylon web in the lake whitefish (Coregonus clupeaformis) fishery. Catch comparisons in the two gears showed that monofilament nets were 1.8 times more efficient (but varied seasonally), resulting in biased commercial catch statistics. The use of monofilament web has probably increased exploitation pressure on whitefish. Both gears selected whitefish of the same size despite stock differences in individual size and shape. Catches in both gears declined during the full moon phase, possibly due to increased net visibility. Key words: mono-multifilament gillnet efficiency, selectivity, lunar illuminance, Coregonus clupeaformis, Lake Huron
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