Understanding the factors limiting migratory behaviour is fundamental to conservation of diadromous fish. Applications of indices of habitat suitability are problematic for diadromous fish because fish presence and abundance in relation to habitat quality are confounded by barriers to fish migration. An alternative approach is to assess diadromous fish distributions in proportion to distance in...

The predaceous cladoceran Leptodora kindti (Focke) became established in Third Sister Lake, Michigan, after individuals escaped from experimental enclosures in 1987. By 1988, the Leptodora population exhibited seasonal dynamics characteristic of natural populations. The maximum seasonal abundance of Leptodora increased to 85 individuals m23 3 yr following the introduction. After the appearance ...

The diversity and abundance of parasites vary widely among populations of the same host species. These infection parameters are, to some extent, determined by characteristics of the host population or of its habitat. Recent studies have supported predictions derived from epidemiological models regarding the influence of host population density: parasite abundance and parasite species richness a...

Animals show impulsiveness when they prefer a smaller more immediate option, even though a larger more delayed option produces a higher intake rate. This impulsive behavior has implications for several behavioral problems including social cooperation. This paper presents two experiments using captive blue jays (Cyanocitta cristata) that consider the effects of payoff accumulation and temporal c...

We present submillimeter continuum maps at 450 μm and 850 μm of a 12×8 region of the NGC 7538 high-mass star-forming region, made using the Submillimeter Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope. We used an automated clump-finding algorithm to identify 67 clumps in the 450 μm image and 77 in the 850 μm image. Contrary to previous studies, we find a positive corre...

Three dimensional (3D) hydrodynamical models of the evolution of marginally gravitationally unstable protoplanetary disks have shown that such disks are likely to form selfgravitating clumps that could become gas giant protoplanets, even when detailed thermodynamics is included [1]. Vertical convective motions appear to be crucial for providing a means of cooling the disk midplane sufficiently ...