Bowhead whales (Balaena mysticetus) summering in the eastern Beaufort Sea in 1983 were measured through aerial stereophotogrammetry. Photos were taken from a turbine Aerocommander 690 with wingtip‐mounted, calibrated 35‐mm cameras. Photos were measured on an analytical plotter with scale data provided by radar altimeter and focal length of the lenses. Coefficient of variation of known‐sized targets 12 m long was 1.7 percent (n= 25). Potential duplicate photographs of whales were removed from consideration through an algorithm based on whale swim speed and elapsed time between sightings. Significant segregation by bowhead whale length was found between four broad regions (P < 0.001, ANOVA, Chi square). Also an inverse correlation appeared between longitude and size of animals (P < 0.001), with the larger animals occurring farther east. This unequivocal size‐class segregation confounds an accurate assessment of overall size‐class composition of the population as well as recent attempts to determine calving rate from aerial survey data.
We examined the mortality rates and causes of death of harbor seal (Phoca vitulina) pups in three regions of the inland waters of Washington (USA) in 1984. One hundred eight pups were collected during 239 searches of the shoreline areas near harbor seal haulout sites or through public reports. Minimum neonatal (up to 1 mo after birth) mortality rates at these regions ranged from 12% to 26% of the pups born. Neonatal mortality was highest in the Strait of Juan de Fuca; 33 of the estimated 105 (31%) pups born at the primary site died. Causes of death varied by location. In southern Puget Sound predation by coyotes (Canis latrans) was the primary cause of death, accounting for eight of 43 (19%) of the dead pups examined; starvation was the next most common cause of death. Mortality at study sites in the Strait of Juan de Fuca was related to premature parturition; 19 of 49 (39%) of the pups found dead were born prematurely. Nine species of bacteria were identified in samples taken from 42 pups; Proteus sp. and Escherichia coli were the most common.
Abstract-The relative abilities of sediment concentrations of simultaneously extracted trace metal : acid-volatile sulfide (SEM: AVS) and dry weight-normalized trace metals to correctly predict both toxicity and nontoxicity were compared by analysis of 77 field-collected samples. Relative to the SEM:AVS concentrations, sediment guidelines based upon dry weight-normalized concentrations were equally or slightly more accurate in predicting both nontoxic and toxic results in laboratory tests.
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