Occupational therapists, physicians and others evince an appreciation

No abstract

Rapid evolution of pest, pathogen, and wildlife populations can have undesirable effects, for example, when insects evolve resistance to pesticides or fishes evolve smaller body size in response to harvest. A destructive invasive species in the Laurentian Great Lakes, the sea lamprey (Petromyzon marinus) has been controlled with the pesticide 3-trifluoromethyl-4-nitrophenol (TFM) since the 1950s. We evaluated the likelihood of sea lamprey evolving resistance to TFM by (i) reviewing sea lamprey life history and control; (ii) identifying physiological and behavioural resistance strategies; (iii) estimating the strength of selection from TFM; (iv) assessing the timeline for evolution; and (v) analyzing historical toxicity data for evidence of resistance. The number of sea lamprey generations exposed to TFM was within the range observed for fish populations where rapid evolution has occurred. Mortality from TFM was estimated as 82%–90%, suggesting significant selective pressure. However, 57 years of toxicity data revealed no increase in lethal concentrations of TFM. Vigilance and the development of alternative controls are required to prevent this aquatic invasive species from evolving strategies to evade control.

Rats were tested in an approach-avoidance situation using food and shock. Experiment 1 involved 72 Ss in a 2 X 2 factorial design comparing the effects of group or individual testing following group or individual shock at the goal. Experiment 2 involved 48 Ss in a 2 X 2 factorial design comparing effects of rearing Ss in groups or in isolation on 2 of the conditions from Experiment 1. Ss tested in groups approached significantly more than those tested individually, whereas group vs. individual shock made no difference. Ss raised in groups approached more and showed the "group effect" significantly more than Ss raised in isolation.

We reviewed responses associated with the invasion of dreissenid mussels by two eastern Lake Ontario fish populations and the fisheries they support. Resurging lake whitefish and walleye populations declined following dreissenid mussel invasion in the early 1990s. Impacts on whitefish were associated with the loss of a key diet item, Diporeia, and its replacement with diet items of lower energy value. Impacts featured a die-off, dispersal, declines in juvenile and adult condition and growth rates, delayed age-at-maturity, and several years of reproductive failure. Impacts on walleye were consistent with dreissenid driven ecosystem change, particularly, clearer water. The key response by the walleye population was a downward shift in recruitment levels. This shift appears to be due to a change in the stock-recruitment relationship caused by decreased survival during early life (i.e. egg to 4-months), and suggests that the carrying capacity for these early life stages has diminished. Currently, whitefish reproduction has resumed and walleye reproduction appears stabilized at a lower level. Recent (i.e. 2003 and 2005) whitefish year-classes were relatively large but the fish are growing slowly and annual survival rate is not yet known. The whitefish commercial harvest continues to decline in synchrony with the declining adult whitefish population. The walleye recreational fishery (i.e. effort and harvest) has stabilized at a smaller size consistent with lower walleye year-class strength.