Equation-free mechanistic ecosystem forecasting using empirical dynamic modeling.

It is well known that current equilibrium-based models fall short as predictive descriptions of natural ecosystems, and particularly of fisheries systems that exhibit nonlinear dynamics. For example, model parameters assumed to be fixed constants may actually vary in time, models may fit well to existing data but lack out-of-sample predictive skill, and key driving variables may be misidentified due to transient (mirage) correlations that are common in nonlinear systems. With these frailties, it is somewhat surprising that static equilibrium models continue to be widely used.

Comment on "Declining wild salmon populations in relation to parasites from farm salmon".

Krkosek et al. (Reports, 14 December 2007, p. 1772) claimed that sea lice spread from salmon farms placed wild pink salmon populations "on a trajectory toward rapid local extinction.

An overview of effects of climate change on selected arctic freshwater and anadromous fishes.

Arctic freshwater and diadromous fish species will respond to the various effects of climate change in many ways. For wide-ranging species, many of which are key components of northern aquatic ecosystems and fisheries, there is a large range of possible responses due to inter- and intra-specific variation, differences in the effects of climate drivers within ACIA regions, and differences in drivers among regions. All this diversity, coupled with limited understanding of fish responses to climate parameters generally, permits enumeration only of a range of possible responses which are developed here for selected important fishes.

General effects of climate change on Arctic fishes and fish populations.

Projected shifts in climate forcing variables such as temperature and precipitation are of great relevance to arctic freshwater ecosystems and biota. These will result in many direct and indirect effects upon the ecosystems and fish present therein. Shifts projected for fish populations will range from positive to negative in overall effect, differ among species and also among populations within species depending upon their biology and tolerances, and will be integrated by the fish within their local aquascapes.

Macroscopic structure of the fin-rays and their annuli in pectoral and pelvic fins of Chinook Salmon, Oncorhynchus tshawytscha.

Light microscopy, enzyme clearing, and staining techniques were used to describe the structure of fin-rays in pectoral and dorsal fins of adult and juvenile chinook salmon,Oncorhynchus tshawytscha. In addition, several decalcification agents, fixatives, and staining methods were employed to demonstrate and determine the nature of the fin-ray annulus (yearly growth ring). Etched, transverse sections of fin-rays were examined by scanning electron microscopy (SEM).