摘要:

Twenty-six body measurements and counts were made on the majority of 381 specimens of lake and Atlantic salmon. Adult lake and Atlantic salmon generally differ in coloration, spotting, and flesh color. Evidence is presented that indicates that these differences are not inherent but result from differences in the environment and diet. In the parr and in the spawning adult stages no consistent differences in body measurements could be demonstrated. Non-spawning adult lake salmon tend to have larger head parts and longer fins than fresh-run Atlantic salmon grilse. These differences are associated with a slower growth rate, maturation at smaller sizes, and a more pronounced retention of the secondary sexual characteristics in the lake salmon. The average counts for certain meristic structures tend to increase with increase in length. When lake and Atlantic salmon of approximately the same size were compared no consistent differences in these meristic characters could be demonstrated. Lake and Atlantic salmon may be inherently different with respect to migratory behavior but the evidence available to date fails to establish such a difference.

ISSN:1923-4287    

DOI:10.1139/cjr47d-013

出版商:NRC Research Press    

年代:1947

数据来源: NRC

摘要:

The red fox (Vulpes fulva) exists in the wild in three coat colour phases; red, cross, and silver or black. These three phases result from the action of one pair of alleles, the homozygotes being silver and red and the heterozygote being cross. At least two different mutations have occurred giving rise to the Canadian gene in eastern Canada and the Alaskan gene in western Canada. The mixing of these two mutant genes complicates the gene frequency analysis.The proportions of the three colour phases are shown to vary with (1) locality, (2) state of population cycle, (3) population trend, (4) migration pressure. Of these factors the variations with locality and population trend are fairly satisfactorily explained by selection but the fluctuation of colour phase proportions with the population cycle is not. On the other hand all the facts can be explained by a migration theory, with or without selection. By migration, a mixture of native and migrant populations with different gene frequencies is obtained. Such migrations tend to be rhythmic since they are connected with the population cycle. In the year that migration took place the pelt returns reveal aberrant gene frequencies or colour phase ratios. In the following years the gene frequencies quickly approach equilibrium that may be at the premigration level or at a new one depending upon the success of the migrants in establishing themselves in the breeding population.The marked diminution in the percentage silver and cross is due to the rapid population increase in an area of low frequency of the silver producing gene and the migration of this type into areas of higher frequency.

ISSN:1923-4287    

DOI:10.1139/cjr47d-014

出版商:NRC Research Press    

年代:1947

数据来源: NRC