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Exploratory sampling of the potential soft-shelled clam bottoms in the Potomac estuary was conducted to define the range and densities of the subtidal populations ofMya arenaria. Bottom samples were taken at depths ranging from 3 to 11 feet with the Maryland hydraulic clam dredge using a 3/8-inch mesh conveyor belt. Clam populations ranged from the mouth of the river to Popes Creek, approximately 40 miles upriver. The more dense populations of over 300 bushels per acre were found between Sandy Point and Swan Point, or 16 to 33 miles from the river mouth. Clam densities were extremely variable in this area, and were related to changes in bottom type and the instability of shoal water bottoms brought about by wind and wave action. Sixteen other benthic macro-invertebrates which were collected in 189 bottom samples are reported along with their relative densities and distribution in the river. The pelecypodsMacoma balthica andM. phenax were the most abundant and widely distributed invertebrates collected by the dredge throughout the sampled area. The number of species declined with the decreasing upriver salinity gradient, indicating the essentially marine elements in the benthic fauna.

Two cases of aspergillosis involving four adult cowbirds (Molothrus ater) collected during the nesting season are reported. Aspergillosis was found in house sparrows (Passer domesticus) on two occasions.

The food habits (1,773 individuals) and the distribution (2,056 individuals) of 9 families, 26 genera, and 32 species of fishes, were determined for Tuckahoe Creek, a lower piedmont tributary of the James River, Virginia. These species represent 41% of the freshwater fishes known for the entire river basin. Five species accounted for 69% of the collection:Etheostoma nigrum (20%),Lepomis macrochirus (18%),Hybopsis leptocephala (15%),Notropis cornutus (11%), andAphredoderus sayanus (5%). Within the upper twothirds of the creek there was a trend for the number of species to increase in a downstream direction. Stomach contents of 273L. macrochirus were mainly insects (65%) and crustaceans (29%). Tendipedids and copepods were particularly important food items although the bluegill consumed a wide variety of animal forms. The selection was a probable reflection of the general availability of potential food. Young fish (0 and 1 age-groups) fed more often on microcrustaceans and dipteran larvae while older fish consumed a higher percentage of coleopterans and hymenopterans. Analysis of stomach contents of other centrarchids showed significant differences. Hemipterans dominated the diet ofCentrarchus macropterus and were important food items forChaenobryttus gulosus. Entomostracans formed the bulk of the diet ofEnneacanthus gloriosus and decapods were eaten primarily byC. gulosus. The largest percentage of coleopterans was taken byLepomis auritus. The cyprinids were represented by all types of feeders.Notropis cornutus was a true omnivore (feeding equally on plant and animal matter) andH. leptocephala selected a diet primarily of plant material. Dipteran larvae dominated the diet of the percid,E. nigrum (78% of total items) and the pirate perch,A. sayanus (53%).Gambusia affinis fed mainly on Hemiptera (34%). The catostomids consumed predominantly microscopic plants. Specimens ofEsox niger less than 74 mm SL ate insects more often (48% as opposed to 16% in larger fish), whereas larger specimens fed on fishes (63% as opposed to 30% in the smaller forms).

Gonadal development and total gonadal DNA of M. manhattensis were studied. Evidence of atrophication and of phagocytosis of residual gametes was found during histological examination. Colorimetric estimations of gonadal DNA indicated that at least two spawning peaks occurred during the summer and suggested that egg release was suppressed by water temperatures above 20 C.

Male rock crabs,Cancer irroratus, were collected from the lower Chesapeake Bay during the winter dredge seasons of 1970–1973. Crabs migrate into Chesapeake Bay in late fall, molt extensively in January, remain in papershell condition until late March and April and leave the bay in May. Most crabs held in the laboratory molted in January, only 18% in February, thus confirming the pattern observed in the field. The molting season of male rock crabs appears to be related to decreasing seawater temperature. Signs of an approaching molt were determined by examining the mouth parts microscopically, and by testing the resiliency of the shell in the vicinity of the ecdysial suture line. Crabs larger than 100 mm carapace width did not molt. Progression of crabs through the intermolt cycle was dependent on temperature: crabs held at 17.5 C advanced from hardshell (C4) to papershell (B2) in one-third the time required for crabs held at 7 C. Most water uptake and weight change occurred between advanced peeler (D4) and soft crab (A2) stages; mean percent water content ranged from 67% for C4 to 87% for A2 stages. Mean percent increase in weight ranged from 52 to 59% in relation to size. Progressive growth occurred in length, width and weight; percent increment ranged from 18 to 23 for length, 19 to 27 for width and 52 to 82 for weight. Width-weight relationships of premolt and postmolt crabs were significantly different. Temperature-salinity tolerance experiments revealed that more crabs survived in 7 C than in 17.5 C. Stage B1–B2 crabs exhibited the highest survival and C1−C3 crabs the least. Maximum survival occurred within the salinity range 14–21‰. Papershell crabs were isosmotic to polyhaline salinities but were hyperosmotic at lower salinities. Those acclimated at 7 C approached isosmoticity near 28–30‰. Warm acclimated crabs were isosmotic near 24–26‰ but showed limited hyperregulation at salinities less than 20‰.

During the period December 17, 1974 through February 23, 1975 the author captured 27 cottontails (Sylvilagus spp.) a total of 110 times at elevations between 1800–2140 ft. The majority of these captures took place in a 6- to 7-year-old clearcut between 1880 and 1980 ft. elevation. Of the 22 cottontails captured at this location, 20 (91 percent) were identified asSylvilagus transitionalis (New England cottontail) and 2 (9 percent) asS. floridanus. Using the Krumholtz and Lincoln indices it was estimated that this clearcut was supporting a population density of greater than one cottontail per acre.

Pre-hard juvenile oyster crabs,Pinnotheres ostreum, were reared from the egg in the laboratory. A minimum of 18 days was required for larval development, after which the young crabs passed through several (up to 10) growth molts during 103 days. Survivors ranged from 0.82 to 1.61 mm in carapace width at the end of the experiment. Mean growth (measured as mean increase in carapace width) ranged from about 10 to 18% of the previous carapace width for each of the first six postlarval molts.

Forty-one invertebrate species were collected during two surveys of the soft-shelled clam,Mya arenaria, in Somerset County waters of the Chesapeake Bay area. Quantitative smaples taken with the hydraulic clam dredge were limited to bottoms in waters between 3 and 9 feet deep. Major bottom types, water temperatures, salinities, and dominant species in each of the twelve sampled areas are presented. The common synapta,Leptosynapta inhaerens, the ornate worm,Amphitrite ornata, and the stout razor clam,Tagelus plebius, were the most abundant and widely distributed species.

The vertical distribution of the polychaete Sabellaria vulgaris Verrill and its sandgrain tube material was studied on a sandflat near the mouth of the Mispillion River in Delaware Bay. Numbers of live worms, and amounts of tube material were determined for 13 exposure time zones on the sandflat. Exposure zones were established according to measurements made during an extreme low-water spring tide. Numbers of live worms declined sharply above the 126–150-minute exposure zone. Almost no live worms were found above 175 minutes of exposure. The largest amount of tube (colony) material was found in the area characterized as the 101–150-minute exposure zone. There was less colony material both above and below this level on the sandflat. An explanation as to why the 101–150-minute exposure zone is optimal for tube construction is proposed, and a comparision with the zonation of Sabellaria alveolata in England is made.