The hypothesis that traits closely associated with fitness will generally possess lower heritabilities than traits more loosely connected with fitness is tested using 1120 narrow sense heritability estimates for wild, outbred animal populations, collected from the published record. Our results indicate that life history traits generally possess lower heritabilities than morphological traits, and that the means, medians, and cumulative frequency distributions of behavioural and physiological traits are intermediate between life history and morphological traits. These findings are consistent with popular interpretations of Fisher's (1930, 1958) Fundamental Theorem of Natural Selection, and Falconer (1960, 1981), but also indicate that high heritabilities are maintained within natural populations even for traits believed to be under strong selection. It is also found that the heritability of morphological traits is significantly lower for ectotherms than it is for endotherms which may in part be a result of the strong correlation between life history and body size for many ectotherms.

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Natural selection and the heritability of fitness components

Electrophoretic data were analysed from 49 species of freshwater fish, 57 species of marine fish, and seven anadromous species. For each species, at least 15 individuals had been assayed for at least 15 loci in two or more subpopulations. The results showed that while average total heterozygosity (HT) was approximately equal in freshwater and marine species (0·062 and 0·064 respectively), subpopulation heterozygosity (Hs) was significantly less in the former group (0·046 and 0·059 respectively). Consequently the average degree of genetic subpopulation differentiation (HST) was significantly greater for freshwater species (0·222 v. 0·062). On average, it is likely that marine subpopulations exchange between 10 and 100 times more migrants per generation than freshwater subpopulations, presumably because of the relative absence of barriers to dispersal in the marine environment. The reduced values of Hs in freshwater species are likely to reflect reduced effective subpopulation sizes relative to marine species. The few andromous species that have been analysed show intermediate levels of GST.

A comparison of genetic diversity levels in marine, freshwater, and anadromous fishes

http://auburn.edu/academic/agriculture/fisheries/genomics/FISH7660%202006/DNA%20marker%20review%20paper-Aquaculture.pdf

DNA marker technologies and their applications in aquaculture genetics.

http://digital.csic.es/bitstream/10261/44729/1/Taranger%20et%20al_%2c%20GCE.pdf

Control of puberty in farmed fish

Polyploid fish and shellfish: Production, biology and applications to aquaculture for performance improvement and genetic containment

Bluesac disease is one of the major causes of post-hatching embryo mortality in salmonids. The incidence of bluesac is strongly inherited in splake (Salvelinus fontinalis × S. namaycush hybrid) under hatchery conditions. Lake charr, F2 splake, F6 splake, and lake charr backcrosses of F6 splake had incidences of 7%, 23%, 5% and 40% respectively. For the backcrosses, which are of practical interest because they are used for experimental plantings in the Great Lakes and northern Ontario inland lakes, the variation among families in the incidence of bluesac is primarily determined by the splake parent. Hence the incidence of bluesac disease in the progeny of splake and lake chair is considered to be a character of the splake parent. The heritability of this character in the splake is about 0.74. The level of bluesac in the backcrosses can, therefore, be significantly reduced in one generation by selecting as breeders those splake that produce low levels of bluesac in test backcrosses to lake charr.

Inheritance of bluesac disease for hatchery charr of the genus Salvelinus.

Rainbow trout Oncorhynchus mykiss native to the Athabasca River of the Arctic Ocean drainage differed at several allozyme loci from rainbow trout and anadromous steelhead populations in the adjacent Fraser River and Columbia River drainages. A dendrogram of genetic distances suggested that the rainbow trout from the Athabasca River drainage are genetically distinct from other inland and coastal rainbow trout and steelhead. Principal component analysis of meristic data supported the allozyme analysis and indicated two main groupings, inland and coastal, that both were distinct from the Athabasca fish. The Athabasca rainbow trout appear to have been reproductively isolated for at least 64,000 years, since the recession of the early-Wisconsin glaciation, possibly in an inland refuge in southwest Alberta.

Rainbow Trout of the Athabasca River, Alberta: A Unique Population

In an attempt to distinguish between parr of ouananiche (freshwater) and those of anadromous Atlantic salmon Salmo salar, we undertook a study of meristic and morphometric variation among populations from rivers along the Quebec north shore of the Gulf of St. Lawrence. We sampled parr from six locations in 1984; two 1983 samples were used to estimate year-to-year variation in the Watshishou River. Based on the characters examined, no practical method was found for distinguishing between the two types of parr. Morphologically, ouananiche and anadromous parr exhibited significant heterogeneity and could be classified according to origin by discriminant analysis with 71.0–84.6% accuracy. Very little variation in meristic characters was evident among the populations examined.

Meristic and Morphometric Variation in Parr of Ouananiche and Anadromous Atlantic Salmon from Rivers along the North Shore of the Gulf of St. Lawrence

We investigated effects of starvation on acid tolerance of young-of-year smallmouth bass Micropterus dolomieui in the laboratory. Juvenile smallmouth bass, held under simulated winter conditions for up to 5 months, experienced losses in ash-free dry weight of up to 30%. However, consecutive tests failed to demonstrate any decline in the short-term (≤7 d) tolerance of these fish for pH levels in the range from 3.0 to 4.5. We discuss the implications of these findings for northern populations where young-of-year fish experience significant winter starvation, followed by short-term exposure to low pH in spring. Calcium and sodium concentration of the water and fish body size (fork length) were all positively related to acid tolerance. A doubling of fork length increased survival time at any pH by 100%. At pH 3.0, a doubling of calcium concentration increased survival time by 13% and at pH 4.0 it increased survival time by 50%. Over the pH range 3.75 to 4.0, a doubling of sodium concentration increas...

Chemical and Biological Factors Affecting Acid Tolerance of Smallmouth Bass

The distribution of variation at 37 enzyme coding loci was determined in six samples of rainbow trout (Oncorhynchus mykiss) from hatchery and natural sources. Significant heterogeneity in allele frequencies was detected among samples of Lower Laurentian Great Lakes rainbow trout. Geographical proximity was a poor predictor of genetic similarity among samples. The adaptive significance of two loci was examined in 16 experimental families. Rainbow trout homozygous for an allele at a phosphoglucomutase structural gene (Pgm1-s), which results in no detectable activity of phosphoglucomutase (PGM1) in all tissues where this locus is normally expressed (e.g. muscle), were larger than those heterozygous or homozygous for the active allele. However, no significant differences in asymmetry of four bilateral meristic traits were detected between fish with different PGM1 phenotypes. Rainbow trout with PGM1 in liver because of a regulatory gene, Pgm1-t(b), were marginally larger than those without the allele. These da...

Peter E. Ihssen

Papers

Inheritance of bluesac disease for hatchery charr of the genus Salvelinus.

Rainbow Trout of the Athabasca River, Alberta: A Unique Population

Meristic and Morphometric Variation in Parr of Ouananiche and Anadromous Atlantic Salmon from Rivers along the North Shore of the Gulf of St. Lawrence

Chemical and Biological Factors Affecting Acid Tolerance of Smallmouth Bass

Distribution and Phenotypic Correlates of Variation at Enzyme Coding Loci in Rainbow Trout (Oncorhynchus mykiss) from the Lower Laurentian Great Lakes