ALBERT

Notes: Anadromous Atlantic salmon swim-up fry were stocked into a small pond (surface area 4.0 ha; maximum depth 3.6 m; mean depth 1.9m) in urban St John's, Newfoundland, Canada. The outlet from the pond was placed underground about 15 years ago. The growth rate of young salmon in this pond was two to five times as fast as in populations in insular Newfoundland. Females matured after a size at which they should have smolted and emigrated to sea. Growth, fecundity, and egg size of transplanted females are compared with those of the donor stock and with those reported for populations of landlocked salmon in insular Newfoundland. The evolutionary implications of the study are discussed.

Notes: Migrations of juvenile Atlantic salmon between habitats (both fluvial and lacustrine) were studied in a Newfoundland river system from May through September. Salmon parr showed poor site fidelity in fluvial habitats, and high rates of migration, especially in spring-early summer. Most habitat shifts were upstream from fluvial habitats to a lake at the head of a small tributary. In September, 10% of the salmon parr caught in the lake (n=275) had been marked in the main stem of the river or in the tributary stream (total n=641). The abundance of parr in the lake increased in May-June, then declined gradually to September. Most of the lacustrine immigrants were 1+ parr. Mature males were found amongst the autumnal emigrants. Salmon parr in the lake grew larger than those in the river, and lacustrine smolts captured in the lake were larger than those caught at the mouth of the river.

Notes: Abstract – The required freshwater habitats of juvenile Atlantic salmon (Salmo salar) are, in general, well known, but vary in quality, related to interacting effects of several variables, which may depend on different parts of a river system. Examples are given of ranges of densities and growth that can be found at various sites in eastern Canada, illustrating the biological and physico-chemical factors affecting production of juvenile salmon. Relative growth rates can indicate habitat quality and population densities. Salmon parr have negative effects on brook trout in riffle habitats. The effects of migrations within the river and of changes with stream succession on juvenile salmon production are illustrated with examples from a Newfoundland river. Migration of age-classes can be quantified from ‘self-thinning’ curves. Lakes have enhancing effects on downstream fluvial habitats, and, at least in Newfoundland, and probably in many boreal areas, the lacustrine proportion of the basin can be used as an index for deriving estimates of required spawning escapement. The factors described should be taken into account for more refined estimates of river production and management of the salmon resource.

Notes: [Auszug] IN a recent number of NATURE (December 11, p. 141), Prof. T. J. Parker gives three suggestions in biological terminology, on which you will perhaps permit me to make one or two remarks, as his notes are à propos of some criticisms of mine on his paper on that subject (Proc. Austr. Assoc. Adv. ...

Notes: [Auszug] HAVING frequently observed in your columns accounts of remarkable instances of reasoning power in animals, I am tempted to send you the following notes, which may perhaps be not without interest to the readers of NATURE. A young canary belonging to our family is in the habit of receiving ...

Notes: [Auszug] WHILST dissecting the leech in the class of practical zoology, one of my students directed my attention to an apparent abnormality in the specimen which it fell to his lot to dissect. On careful examination it was found that the vesicula seminalis of the right side had moved forwards into the ...

Notes: Summary Fluvial salmonids have evolved to use the diversity of habitats in natural streams for different life history stages and at different seasons. Required freshwater habitat of Atlantic salmon can be classified generally as that suitable (i) for spawning, (ii) for feeding during the major growing period, and (iii) for overwintering. Spawning habitat of salmon is usually in rapid water at the tail of pools on the upstream edge of a gravel bar, ideally with depths about 25 cm, in mean water velocities of about 30–45 cm s-1, with maximum velocities about 2 body lengths s-1, and with a substrate of irregularly shaped stones of cobble, pebble, and gravel. Underyearling salmon (〈7 cm TL) are most common in shallow (〈15 cm) pebbly riffles, whereas older and larger parr (〉7 cm TL) are usually in riffles deeper than 20 cm with a coarse substrate. Depth preference increases with size. Multiple linear regression models quantifying parr habitat have identified substrate as an important variable, with a positive relationship to an index of coarseness. Negative relationships were found with mean stream width, range of discharge, and overhanging cover. Water chemistry, especially alkalinity, nitrates, and phosphates, are important regulators of production. Although similar variables had importance, coefficients among rivers differed. Interactions occur among variables. Further studies are required to quantify productive capacity of habitat for parr. Results suggest that useful models can be derived and if a river system is mapped, and stratified by habitat, then smolt yield could be predicted and the required egg deposition could be estimated. In winter, young salmon shelter among coarse substrate or move to pools, but continue feeding, with larger parr being more active. Feeding is in general opportunistic. Food consists mainly of insects, taken primarily in the water column, but also from the surface and at the bottom. Young salmon in flowing water are highly territorial but are less so in slow or still waters. In fast water, parr use their large pectoral fins to apply themselves to the substrate, allowing them to occupy this type of habitat with little expenditure of energy. Height above the substrate decreases with water velocity, but increases with temperature and social status. Although riffles are preferred habitat, and are relatively more productive, lentic waters can be occupied where there are few predators or severe competitors and may provide significant smolt yield in some systems. Selective segregation minimizes competition between salmon and brook charr or brown trout, but brook charr and brown trout may have negative effects on underyearling salmon, and on parr in pools, whereas salmon have negative effects on small brook charr and brown trout in riffles and flats. Competition by both interference and exploitation results in interactive segregation when the resource, mainly food, becomes limiting. Limited downstream movement of underyearling salmon may occur during the summer. Older juveniles may make upstream movements, but generally migrate downstream, with most movements in the spring, and a lesser peak of activity in the autumn. Dispersal tends to be mainly downstream, indicating that for full distribution, spawning areas are best located upstream. High densities of yearling parr may have negative effects on growth and survival of underyearlings in some river systems, but apparently not in others, so that future research is required in this regard. Density-dependent growth is evident where food is limiting, and can provide an indicator of densities of cohorts so that if a quantitative relationship has been derived, mean size from a sample can give an estimate of the density at that station, with minimum size occurring at carrying capacity. Such regressions vary between habitats with differing productive capabilities, so that future research could provide useful models for assessing productive capacity of a habitat, and optimum densities. Life history strategies can change with changes in density-dependent growth rates. Present stock-recruitment functions do not take environmental variables into consideration, and have limited applicability. Further research is required to determine optimum spawning requirements for salmon in different types of river systems in different geographical areas.