William D. Youngs

Polychlorinated biphenyl residues: accumulation in Cayuga Lake trout with age.

The concentration of polychlorinated biphenyls was shown to progressively increase with maturity in a series of lake trout. The presence of these compounds was determined by column chromatographic isolation, specific detector gas chromatography and mass spectrometry. The relation between fish age and the concentration of polychlorinated biphenyls was highly significant.

Another Consideration of the Morphoedaphic Index

Abstract Ryders morphoedaphic index (MEI: Total dissolved solids, TDS/mean lake depth) was developed empirically as a predictor of fish yield. It generally accounts for 60 to 78% of the variation (corrected sums of squares) in fish yields observed in a set of data. However, no basis for these correlations has been proven or even generally accepted. We demonstrate that two mundane relationships may be the reasons the MEI appears to be valid. Quite simply, large bodies of water tend to produce greater fish yields than small ones, and large bodies of water tend to have greater mean depths than small ones. Mean depth acts as a surrogate for surface area in the MEI; however, surface area alone is a more powerful predictor. It accounts for 94% of the variation in fish yields observed in three combined sets of data reported in the literature. The variation accounted for by the regression only increased to 95% when TDS was added as a predictor.

Estimation of the Fraction of Anglers Returning Tags

Abstract The reciprocal of the slope of the regression of force of total mortality on force of reported fishing mortality provides an estimate of the percent of tags returned from tagged fish which are caught. Necessary conditions for the validity of this procedure are presented. An example of the technique is given.

Nickel and vanadium in foliage in the vicinity of an oil-fired power plant

Oil typically contains appreciable percentages of nickel and vanadium. When small amounts of fly ash are released from oil-fired, electric generating power plants, analysis for these metals contained in the ash in the vicinity of such facilities may serve as indicators of ash fallout. With prevailing winds toward the northeast, analysis of nickel and vanadium staghorn sumac (Rhus typhina L.) leaves sampled at increasing distances from the stacks in the vicinity of an oil-fired power plant showed consistently higher concentrations in all instances in foliage collected in an easterly direction versus that taken at the same distances west. Factors influencing the concentrations of nickel and vanadium in plants are discussed.

An Analysis of the Effect of Seasonal Variability of Harvest on the Estimate of Exploitation Rate

Abstract Five functional forms for the seasonal distribution of force of fishing mortality were used in determining expectations of death from fishing. Expectation of death from fishing calculated from E/F = A/Z was compared to the actual expectation of death from fishing determined by numerical integration. Bias results in the formula-calculated expectation of death from fishing if the force of fishing mortality is not a constant fraction of the force of total mortality. Bias is greater when the force of fishing mortality is more asymmetrical. Bias is positive when greater force of fishing mortality occurs early in the year; negative bias occurs when force of fishing mortality is greater later in the year. The magnitude of bias, for a given functional form of force of fishing mortality, is a function of the relative size of force of fishing mortality to force of total mortality.

Observed and Calculated Lengths of Lake Trout (Salvelinus namaycush) in Cayuga Lake, New York

Abstract Back-calculated lengths of lake trout (Salvelinus namaycush) in Cayuga Lake, New York, were compared with empirical values. The body-scale relationship was sigmoid over a range of fish lengths of 6 to 26 inches; the method of back-calculation involved preparation of a body-scale ruler adapted for use on a conventional direct proportion calculating device. When compared graphically, calculated and observed mean lengths (through age VII) were in excellent agreement. Calculated data showed a significantly lower variance than observed.