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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.

The breeding behavior and biology of black ducks,Anas rubripes, were observed from 1953–1958 on the upper Eastern Shore of Chesapeake Bay in Maryland. Ducks were trapped, banded and marked during the study in an essentially estuarine habitat, which was frost-free from mid-April to early November. The general habitat adjoining the Bay consisted of cultivated fields, pine woods with dense underbrush, extensive marshes in some areas, and duck blinds. Resident black ducks began to pair in the late summer and reached a peak in early April just before the height of the breeding season. Few if any young were observed to pair in the early fall. In the spring the male defended a territory for each clutch, generally using some promontory along the shore. The male remained nearby while the female built her nest, gradually deserting his mate during incubation. Eventually the pairing bond disappeared, although some males probably paired again with renesting hens. Females renested one or more times when the eggs were destroyed or even when the ducklings disappeared on the first day after hatching. At least eight out of 51 marked ducks were known to have renested. The dates of first laying varied from March 9 to March 27. The nesting peaks occurred about April 20. The first hatching occurred in early April; the last in early August. The date by which 50 percent of the nests were started was significantly earlier in 1953 than in 1957 or 1958 but no other differences were significant. Comparison of the peaks of hatching and of laying showed that in 1958 a loss of early clutches occurred. Nests were built most extensively in woods, less so in fields and marshes and markedly on duck blinds. They were constructed from adjacent material (leaves, grass, twigs, pine needles) in shallow basins, which were occasionally used by renesting females. Usually the nest site was covered by honeysuckle, poison ivy, brush, or grasses. Spacing between nests was determined by available cover; sometimes they were placed within a few feet of each other. The density varied from 0.6 to 15.2 nests per acre. The average number of eggs in a clutch declined from 10.9 to 7.5 during the season (360 clutches). Young females laid smaller average clutches (9.2) than adults (9.7). Primary clutches were larger (9.1) than secondary clutches (8.1) for the same females. The incubation period averaged 26.2 days (51 clutches). Neither size of clutch nor season had a significant effect on incubation period. About 5.6 percent of the eggs did not hatch. The fate of nesting was determined for 574 nests. During the six years, 38.0 percent hatched at least one egg, 11.5 percent were abandoned, and 50.0 percent were destroyed (34.0 percent by crows). Although complete and incomplete clutches were equally susceptible to predation, over half (51.8 percent) of the destruction of complete clutches occurred in the first week of incubation. An average of 9.6 percent of eggs in successful clutches was taken by crows. Estimations of production indicated that 100 females would raise 510 young to flying age and that the population in the area would decline if the mortality rate of females from flying age to breeding exceeded 78 percent.

It is possible to make statistically significant comparative measurements of similar sections of subestuaries under conditions where the large natural variations would mask all but drastic changes in the systems if they were studied individually. The comparative study is proposed as a modification to the baseline study of a single system for the assessment of the effects of man’s activities in an estuary. We have made temporally coincident measurements of phytoplankton production, standing crops and a range of physical and chemical parameters in comparable sections of the Rhode and West rivers and in an adjacent section of the Chesapeake Bay for the 3-year period 1970–1972. We analyzed the data for standing crops and demonstrated that at least at the trophic level of phytoplankton, the judicious application of a paired comparative sampling protocol to the Rhode and West rivers is superior to a study of either system alone. We calculate that the paired comparison sampling protocol requires approximately one tenth the sample size of the single-system sampling technique to achieve the same significance level.

Transforming clingfish larvae 4–12 mm. T.L. are illustrated. Meristic and morphometric data for 50 larvae are examined. Fin ray counts were verified from stained specimens. Counts were: pectoral 22–24, pelvic 4, dorsal 10–12, anal 9–10 and caudal 22–23. Differentiation and total fin ray complements were achieved at 9.0 mm T.L. or greater. The distinctive clinging disc was first observed in 4.5 mm specimens and was complete at 12.0 mm. Lack of pigmentation over the posterior quarter of the larvae was obvious for larvae less than 12.0 mm.

The locomotor activity cycle of the American eel (Anguilla rostrata) was studied in a light-proof shelter. Measurements of activity were registered by a mechanical assembly triggered by the eel’s movements. The results demonstrate that the eel posses a locomotor cycle with greater activity in dark than in light and activity peaks in response to light changes at dawn and dusk. The latter is significantly higher than any of the peaks during the night or the one at dawn. The one at dawn is frequently not any higher than some peaks of activity occurring throughout the night. The presence of peaks at dawn and dusk appears to be a more generalized condition than the period of maximum activity. Both frequency and phase of the eel’s cycle were shown to vary directly with the light conditions, and the cycle was totally obliterated under constant conditions of either light or dark. It is concluded that this locomotor activity cycle is essentially exogenous, under the control of the environmental light cycle, with the preference for dark activity being the only endogenous component.

Cyathura polita is a benthic, estuarine isopod found in restricted habitats, but normally tolerant of salinities between 0.5 and 32 ‰. Established populations ofC. polita are not found in the oceanic habitat or in fresh water. Their absence from these two habitats may be the result of the failure of some stage in the life cycle to osmoregulate. Measurements of freezing point depressions of the body fluids of juvenile and adultC. polita which had been subjected to salinities of 0.0 to 40 ‰ (NaCl) for 3 hours were used to show that both stages in the life cycle osmoregulate. At low salinities the juveniles and adults were equally able to osmoregulate. At the highest salinity, higher than in normal habitats ofC. polita, adults were better able to osmoregulate than juveniles. Part of the animals were subjected to 44,000 r of gamma irradiation from a Cs137 source and were then subjected to the various salinities. At low salinities the juveniles and adults of the irradiated group were equally able to regulate, and their ability was equal to that of the animals subjected to salinity changes alone. At the highest salinity, however, juveniles and adults that were irradiated had less ability to osmoregulate then the non-irradiated animals. Juveniles were more strongly affected by irradiation than adults. Irradiation, then, decreases the ability to osmoregulate only at the highest salinity.