Energy Requirements Of Migration Research Articles

AGE-RELATED DIFFERENCES IN FORAGING EFFICIENCY, MOLT, AND FAT DEPOSITION OF GRAY CATBIRDS PRIOR TO AUTUMN MIGRATION

Abstract The ability to satisfy the energy requirements of migration and to cope with problems that arise en route is likely to be age dependent. We studied hatch-year (HY) and after-hatch-year (AHY) Gray Catbirds (Dumetella carolinensis) to determine if differences in foraging efficiency and molt affected fat deposition prior to autumn migration. Hatch-year catbirds were less efficient foragers than AHY catbirds; however, efficiency improved with age to the extent that many HY catbirds are probably as efficient as AHY birds by the time they commence migration. We discovered age-dependent patterns of fat deposition, which probably resulted from differences in foraging efficiency and molt timing. Hatch-year catbirds began to deposit fat sooner than AHY catbirds but did so more slowly throughout the postbreeding and premigratory phases of the annual cycle. Adult catbirds did not become hyperphagic until they neared the completion of their molt, then deposited fat rapidly. Diferencias Relacionadas con la Eda...

Biology of the North American Anadromous Sea Lamprey, Petromyzon marinus

The sea lamprey (Petromyzon marinus) in the western Atlantic Ocean adjacent to North America is usually found within a depth of 200 m between latitudes of 30 and 53°. Spawning size lampreys have been recorded in 116 rivers between 32 and 48° latitude. The upstream spawning migration which may extend to several hundred kilometres, takes place between March and September, the actual time varying directly with latitude. Fecundity of the anadromous P. marinus (approximately 124 000–305 000) is the highest for any lamprey species. Energy requirements for migration and reproduction are discussed in the context of parental investment. The larval phase lasts 6–8 yr and is followed by a highly synchronous period of metamorphosis. On completion of metamorphosis in late autumn some juveniles migrate downstream to the estuary or ocean and commence feeding. In at least some rivers, a portion of the young juveniles overwinter in the natal stream without feeding. Subsequent to a short feeding period in May these young juveniles leave the river for the sea. Sea lampreys attack a variety of marine elasmobranchs and teleosts. Only swordfish, Xiphias gladius, and striped bass, Roccus saxatilis, are reported to eat lampreys. During the marine interval, which lasts from 23 to 28 mo, the calculated instantaneous growth rate is 0.645–0.785 g∙d−1. Lamprey scarring frequency on Atlantic salmon, Salmo salar, in the St. John River, New Brunswick, increased from 2.6 to 15.0% between 1972 and 1975 coincident with a dramatic rise in the number of migrant salmonids. Scars were most prevalent on larger salmon, particularly females. Most scars were recorded on the right side of salmon, particularly in the ventral regions.Key words: sea lamprey, Atlantic Ocean, distribution, life cycle, growth, energetics, fecundity