Smoltification

Abstract: An important requirement in the efficient use of artificially propagated juveniles for salmon enhancement programs is that the resulting smolts be fully prepared behaviorally and physiologically to migrate to sea and continue to grow and develop normally. In this paper,physiological criteria for identifying fully functional smolts are presented and environmental factors are identified which will influence smoltification, and thus early marine survival. Methods are describedfor optimizing time, age, and size at release, and data are presented on methods of environmental manipulation to alter smoltification to fit specific resource management needs. On the basis of our present understanding of the physiology of the parr-smolt transformation and of the influence of environmental alterations during rearing, guidelines are presented for management strategies to improve survival oj Pacific, Oncorhynchus sp., and Atlantic salmon, Salrno salar, and anadromous (steelhead) rainbow trout,

Abstract: Atlantic salmon Salmo salar, steelhead S. gairdneri, and several species of Pacific salmon Oncorhynchus spp. undergo transformation from stream-dwelling parr to seaward-mi- grating smolts. Physiological, behavioral, morphological, and biochemical changes occur in fresh water in preparation for marine life. The preparatory nature of these adaptations is reviewed and discussed with particular emphasis on osmomgulation, metabolism, and growth. Functional changes in gill, kidney, gut, and urinary bladder result in increased salinity tolerance and hypoosmomgulatory ability. Some or all of these preparatory physiological changes may reverse in the absence of exposure to seawater. Changes in lipid, protein, and carbohydrate metabolism, oxygen consumption, and aerobic respiratory enzyme activity suggest increased catabolism during parr-smolt transformation. These transient changes in catabolism may reflect energetic demands of the extensive differentiation occurring during transformation. Although them is increased growth during parr-smolt transformation, evidence for a hypothesized increase in scope for growth after transformation is not convincing. We suggest that different aspects of the transformation have different developmental patterns, the timing of which is species-dependent and responsive to environmental change. Phylogenetic comparison of the differentiation of salmonid hypoosmomgu- latory mechanisms and migratory behavior suggests that their evolution has occurred through heterochrony. Transformation of the stream-dwelling parr to the seaward-migrating smolt is a significant life history event in many salmonids. Various mor- phological, physiological, and behavioral changes occur seasonally (usually in spring), develop over a period of 1-2 months, and are presumably adaptive for downstream migration and residence in the marine environment (see Table 1 and re-

Abstract: Wild salmon stocks in the Pacific Northwest are imperiled by a variety of anthropogenic environmental modifications, not the least of which is increasing maximum water temperatures. While many reports have been written on physiological or population-level influences of temperature in terms of the decline of wild salmon, synthesis of these diverse sources is needed for evaluation of numeric temperature criteria and their potential in salmon recovery planning. Various sensitive life stages and biological processes are impacted differently for different salmon species. This article reviews the literature for chinook, coho, chum, and steelhead, which are currently listed in the Columbia River Basin under the Endangered Species Act. Spawning, incubation and early fry development, juvenile rearing and growth, smoltification, and migration are considered. Swimming speed, disease susceptibility, chemical considerations, and lethality are also reviewed. Regional population growth and climate change will e...