Milo E. Richmond

CORMORANT PREDATION AND THE POPULATION DYNAMICS OF WALLEYE AND YELLOW PERCH IN ONEIDA LAKE

Double-crested Cormorants (Phalacrocorax auritus) increased dramatically in North America during the 1990s, providing the opportunity to study the effects of an increase of a top predator on an existing predator–prey system. In Oneida Lake, New York, USA, Double-crested Cormorants were first observed nesting in 1984 and had increased to over 360 nesting pairs by 2000. Concomitant with this increase in piscivorous birds was a decrease in the adult walleye (Stizostedion vitreum) and yellow perch (Perca flavescens) populations. Analysis of a 40-yr data series shows higher mortality of subadults (age 1–2 yr perch and age 1–3 yr walleye) for both species in the 1990s compared to the previous three decades. Cormorant diet was investigated from 1995 to 2000 using a combination of cast pellets, regurgitants, and stomach analysis. Walleye and yellow perch were a major portion of the cormorant diet during these years (40–82% by number). The number of subadult walleye and yellow perch consumed by cormorants suggests...

Requirement of Rainbow Trout for Dietary Phosphorus and Its Relationship to the Amount Discharged in Hatchery Effluents

Abstract Fingerling rainbow trout Oncorhynchus mykiss with initial mean weights of 9 g (small fish) and 35 g (large fish) were fed diets adequate in all known nutrients except phosphorus (P). In two experiments, triplicate lots of rainbow trout were fed basal diets containing either 0.14 or 0.41% non-phytin P, with or without graded levels of supplemental P. Deficiency of P reduced growth, feed efficiency (weight gained/weight fed), bone ash, and whole-body ash contents. The requirement for non-phytin P by small trout for maximum growth and feed efficiency was not more than 0.41% of diet: The requirement by large trout was between 0.34 and 0.54% of diet. The requirement of non-phytin P for maximum bone ash development was about 0.51% of diet for small trout and more than 0.54% for large trout. Whole-body phosphorus content of small trout suggested a requirement above 0.51% but not more than 0.61% non-phytin phosphorus. Although an effect of size of trout on the requirement was not clearly demonstrated, th...

Field determination of optimal dates for the discrimination of invasive wetland plant species using derivative spectral analysis

Mapping invasive plant species in aquatic and terrestrial ecosystems helps to understand the causes of their progression, manage some of their negative consequences, and control them. In recent years, a variety of new remote-sensing techniques, like Derivative Spectral Analysis (DSA) of hyperspectral data, have been developed to facilitate this mapping. A number of questions related to these techniques remain to be addressed. This article attempts to answer one of these questions: Is the application of DSA optimal at certain times of the year? Field radiometric data gathered weekly during the summer of 1999 at selected field sites in upstate New York, populated with purple loosestrife (Lythrum salicaria L.), common reed (Phragmites australis (Cav.)) and cattail (Typha L.) are analyzed using DSA to differentiate among plant community types. First, second and higher-order derivatives of the reflectance spectra of nine field plots, varying in plant composition, are calculated and analyzed in detail to identify spectral ranges in which one or more community types have distinguishing features. On the basis of the occurrence and extent of these spectral ranges, experimental observations suggest that a satisfactory differentiation among community types was feasible on 30 August, when plants experienced characteristic phenological changes (transition from flowers to seed heads). Generally, dates in August appear optimal from the point of view of species differentiability and could be selected for image acquisitions. This observation, as well as the methodology adopted in this article, should provide a firm basis for the acquisition of hyperspectral imagery and for mapping the targeted species over a broad range of spatial scales.

Foraging location and site fidelity of the Double-crested Cormorant on Oneida Lake, New York

Abstract We studied the foraging behavior of the Double-crested Cormorant (Phalacrocorax auritus) on Oneida Lake, New York, by monitoring the activities of 27 radio-tagged birds in July and August of 1999 and 2000. A total of 224 locations were obtained of cormorants actively diving, and presumed foraging, at the time of detection. A geographic information system was used to examine foraging distances from the nesting island, the water depth and type of substrate at preferred foraging sites, and to estimate kernel home ranges for analysis of individual foraging site fidelity. An explanatory model was developed to determine parameters affecting the distance to cormorant foraging sites. The mean distance to foraging locations of tagged cormorants from the colony site was 2,920 m (SE ± 180 m, max = 14,190 m), and 52% of the locations were within 2,000 m of the nesting island. No cormorant was observed making daily foraging trips to outside water bodies. Mean foraging distance was greater during morning than in the afternoon, and there was a significant effect of the time of day on distance. There was no significant effect of sex date, a seasonal measure on distance to foraging location. Individual cormorants exhibited fidelity to specific foraging sites. Most cormorants foraged in close proximity to the nesting island much of the time, while those detected further from the island tended to return repeatedly to the same locations. Ninety percent of the foraging locations were in water depths ≤7.5 m, and most were in water 2.5-5 m deep. Compositional analysis of habitat use revealed a preference for these depths, along with substrates of cobble with rubble, and silt with clay.

Prevalence of Patent Baylisascaris Procyonis Infection in Raccoons (Procyon Lotor) in Ithaca, New York

The prevalence of patent Baylisascaris procyonis infection in raccoons was determined by examining fecal samples collected between July 1986 and May 1987 in Ithaca, New York. September, October, and November had the highest prevalence of infection (35-48%). Significant differences (P less than 0.001) were found when months were grouped by season to test the hypothesis that a fecal samples probability of being positive does not vary from month to month. Fall was the season contributing most to the overall chi-square statistic. Host sex/age class and prevalence of patent infection were investigated. The raccoons were aged as either juveniles or adults. A significantly higher prevalence of patent infection (P less than 0.001) was found in juveniles when compared to adults. No statistically significant difference was found in other comparisons of host sex and age. Contingency analysis tested the independence of sex/age class/season and presence of eggs. The results of the test were significant (P less than 0.001).

Influence of Soil Texture, Moisture and Temperature on Nest-site Selection and Burrowing by the Pine Vole, Microtus pinetorum

The influence of soil temperature on nest-site selection by the semifossorial pine vole (Microtus pinetorum) was examined by presenting the voles with a dichotomous choice in soil temperature (19 C vs. 25 C, 30 C or 35 C). In this instance, the number of nests constructed in heated soil decreased with increasing soil temperature; no subsurface nests were built in soil maintained at 30 C or 35 C. These findings may be related to an inability of these voles to effectively regulate body temperature in a heated subsurface environment. When presented with a choice among three soil types consisting of a base mixture of loam and peat moss (3:1 volume/volume), or the base mixture to which was added gravel (3:2 v/v) or stone (1:1 v/v), a significantly larger number of voles selected the loam/peat moss mixture in which to construct subsurface nests and tunnel systems than the other two soil mixtures. The soil/stone mixture was always avoided completely. Similarly, voles confined to the soil/stone mixture, and subsequently released, re-established themselves in an alternate soil type. The majority of voles selected the loam/peat moss mixture. Lastly, when a moisture gradient was imposed on each of the three soil types, voles continued to select the loam/peat moss mixture, but significantly more voles were located in an area of intermediate soil moisture content than in the wet or dry regions of each soil type. These results are discussed with regard to both the energetic costs of burrowing and the water conservation requirements of this species;

Clinal Variation and Morphology of Woodrats (Neotoma) of the Eastern United States

We examined the cranial and external morphology of putative specimens of Neotoma floridana from the eastern United States to investigate the morphological distinctness of N. f. magister and clinal variation in size of woodrats. Significant differences in quantitative morphologic characteristics between N. f. magister and non- magister specimens were detected using both univariate and multivariate analyses. Although most morphometric characteristics demonstrated distinct clinal variation, covariate analyses indicate that differences between N.f. magister and non- magister specimens cannot be attributed to patterns of clinal variation alone. Specimens of N. f. magister also differ from non- magister specimens with respect to the presence of a maxillo-vomerine notch and, unlike non-magister specimens, none possessed a strongly bifurcated anterior palatal spine. We contend that this pattern of morphologic variation, in conjunction with previous genetic studies, indicates that resurrection of the taxon N. magister is warranted.

ALLOCATION OF INNER CELL MASS AND TROPHECTODERM CELLS TO THE PREIMPLANTATION BLASTOCYST OF THE DOMESTIC FERRET, MUSTELA PUTORIUS FURO

The growth of ferret preimplantation blastocysts in vivo, collected between 156 and 240 hr post coitum, was investigated. A technique, combining immunosurgery and differential fluorochrome staining, was used to discriminate between inner cell mass (ICM) and trophectoderm (TE) cells. Using the stains propidium iodide and bisbenzimide (Hoechst 33342), the ICM was stained blue and the TE was stained pink. The ICM and TE counts for 90 blastocysts, respectively, averaged 25 and 63 at 156 hr and increased exponentially to 2077 and 4137 at 240 hr. The Box-Cox procedure was used for choosing a transformation that minimized the error sum of squares for a linear regression of Y (cell count) on X (time in hr). Logarithmic transformations of the ICM, TE and total cell count gave a good fit, but the following equations obtained by the Box-Cox procedure provided the best fit, where Y is cell count and X is time in hours. For inner cell mass: Y = [(176.06 + 2.45X)/-899.44 + 1]-3.33; trophectoderm: Y = [(301.38 + 14.48X)/-6863.42 + 1]-10; and total: Y = [(2266.97 + 17.0X)/-7837.21 + 1]-5. The R2 values were 0.73, 0.84, and 0.84, respectively. The exponential growth of the ferret embryo during the time interval that measurements were made fits the general pattern described for other mammalian embryos. This report is the first to characterize the pattern of cell allocation and growth in preimplantation blastocysts of the ferret, and the first such report for a carnivore. The pattern of in vivo development provides a standard for judging the quality of in vitro produced and matured ferret embryos and, concomitantly, a means to evaluate culture systems.

Track plate enclosures: Box designs affecting attractiveness to riparian mammals

Abstract We examined the efficacy of four track plate enclosure designs for monitoring the abundance of small and medium-sized mammals along 10 streams in New York State. Box size and clarity of view through the box were evaluated as factors affecting visitation. We checked track plate stations weekly from September 1999 to March 2000. Eleven mammalian species or species groups visited the track plate stations. Raccoons (Procyon lotor) (P = 0.020) and feral cats (Felis catus) (P = 0.008) visited large enclosures significantly more than small enclosures. Feral cats visited clear-view enclosures significantly more than obstructed-view enclosures (P = 0.025). Enclosure size and view did not significantly affect visitation by other species; however, a large box with a clear view was the most effective design.

Daily Foraging Patterns of Adult Double-crested Cormorants During the Breeding Season

Abstract We recorded the daily presence of Double-crested Cormorants (Phalacrocorax auritus) at the nesting island on Oneida Lake, New York, by monitoring the activities of 15 radio-tagged adults from July through September, 2000, using an automated data-logging receiver. A total of 24,464 acceptable detections was obtained for adult cormorants actively attempting to nest on the lake. Tagged cormorants had a bimodal daily activity pattern during the first month, with the fewest birds detected on the island at 09.00 h and 15.00 h Eastern daylight time. The pattern of activity appeared to change slightly in the second month of the study, representative of a post-breeding period for the colony, with a shift from a less synchronous pattern of departures to a greater focus on morning activity also centered around 09.30 h. These results correspond with daily observations of Great Cormorant (P. carbo) foraging activities reported for colonies in Africa and Poland. The data also support the possibility of nocturnal foraging activity, not previously reported for this species on their summer breeding grounds. No correlation was found between total number of daily detections and climatalogical factors or events.