An ecological analysis of rockfish (Sebastes spp.) assemblages in the North Pacific Ocean along broad-scale environmental gradients

Environmental variability affects the distributions of most marine fish species. In this analysis, assemblages of rockfish (Sebastes spp.) species were defined on the basis of similarities in their distributions along environmental gradients. Data from 14 bottom trawl surveys of the Gulf of Alaska and Aleutian Islands (n=6767) were used. Five distinct assemblages of rockfish were defined by geographical position, depth, and temperature. The 180-m and 275-m depth contours were major divisions between assemblages inhabiting the shelf, shelf break, and lower continental slope. Another noticeable division was between species centered in southeastern Alaska and those found in the northern Gulf of Alaska and Aleutian Islands. The use of environmental variables to define the species composition of assemblages is different from the use of traditional methods based on clustering and nonparametric statistics and as such, environmentally based analyses should result in predictable assemblages of species that are useful for ecosystem-based management

The Absolute Magnitude of the Sun in Several Filters

This paper presents a table with estimates of the absolute magnitude of the Sun and the conversions from $vegamag$ to the AB and ST systems for several wide-band filters used in ground and space-based observatories. These estimates use the dustless spectral energy distribution (SED) of Vega, calibrated absolutely using the SED of Sirius, to set the $vegamag$ zero-points and a composite spectrum of the Sun that coadds space-based observations from the ultra-violet to the near infrared with models of the Solar atmosphere. The uncertainty of the absolute magnitudes is estimated comparing the synthetic colors with photometric measurements of solar analogs and is found to be $\sim$ 0.02 magnitudes. Combined with the uncertainty of $\sim$ 2% in the calibration of the Vega SED, the errors of these absolute magnitudes are $\sim$ 3--4%. Using these SEDs, for the three of the most utilized filters in extragalactic work the estimated absolute magnitudes of the Sun are $M_B$ = 5.44, $M_V$ = 4.81 and $M_K$ = 3.27 mag in the $vegamag$ system and $M_B$ = 5.31, $M_V$ = 4.80 and $M_K$ = 5.08 mag in AB.Comment: 17 pages, 2 figures, accepted by ApJS. Composite solar spectrum available for download at http://mips.as.arizona.edu/~cnaw/sun.htm