These aquaculture- and conservation-oriented commentaries are not abstracts written by the original authors.  They reflect the opinions of someone else -- usually Roger Doyle.  Direct quotations from the papers or abstracts are marked with inverted commas.

250.  New, large, cloning vectors for three important aquacultural species
        Construction and characterization of BAC libraries for three fish species; rainbow trout, carp and tilapia. 2001. Katagiri, T., S. Asakawa, S. Minagawa, N. Shimizu, I. Hirono, and T. Aoki. Animal Genetics 32 (4): 2000-204.
        Bacterial artificial chromosomes (BACs) are constructed by transferring DNA from a target organisms into the fertility factor plasmids of E. coli. Fertility factor plasmids, which are DNA molecules separate from the main bacterial chromosome, are involved in bacterial conjugation and have only one copy per bacterial cell. This permits cloning and analysis of very large pieces of foreign DNA (up to about 300 kilobases) free from the confusing effects of recombination within the host. Libraries of BACs containing target DNA from a variety of plant and animals species have become essential in large scale genomic sequencing and chromosome- walking programs.
        The authors of this paper report the construction of BAC libraries for carp, trout and tilapia with fairly good coverage of the genome of each species. "The libraries can be screened by conventional colony hybridization and provide a starting point for the construction of high-density filtres or polymerase chain reaction (PCR) screening approaches. These BAC libraries will facilitate the positional cloning of quantitative trait loci (QTLs) for a variety of economically important traits in these species." aoki@tokyo-u-fish.ac.jp 

249.  Equalizing family sizes does not greatly increase loss of natural fitness
        Accumulation of deleterious mutations and equalization of parental contributions in the conservation of genetic resources. 2001. Fernández, J., and A. Caballero. Heredity 86 (4):40-488.
        Standard texts on aquaculture broodstock management  recommend equalizing family sizes; that is, trying to arrange one-on-one mating of males and females while retaining equal numbers of offspring from all matings. This procedure will reduce the rate of accumulation of inbreeding and random loss of genetic variation. There are known to be some problems with the procedure, however, including the reduction in the intensity of natural (actually domestication) selection that occurs when fitness is managed in this way (See December 2000 list #149, February 2000 #11). Furthermore, mutational load will accumulate.
        This paper reports the results of computer simulations which take into account mutation as well as fitness considerations. "Our results suggest that equalization of family sizes does not produce a particularly high threat to small conserved populations, at least in the short term (up to about 20 generations), and the more efficient preservation of genetic variability seems to be a clear advantage of the procedure." See also July-August list #212. armando@uvigo.es 

248.  Genetics of the physiological stress response in fish
        Heredity of stress-related cortisol response in androgenetic common carp (Cyprinus carpio L.). 2001. Tanck, M.W.T., K.-J. Vermeulen, H. Bovenhuis, and H. Komen. Aquaculture 199 (3-4):283-294.
        One of the more interesting aspects of this paper is the use of androgenic individuals in a quantitative genetic analysis. Androgenesis was performed by fertilizing eggs, which had previously been UV sterilized to eliminate the haploid maternal genome, then using heat shock to diploidize the male genome. Six wild carp were used as sperm donors, and the heritability estimates presumably refer back either to those fish or the population from which they were captured.. Androgenesis doubles the additive variance in the population of zygotes, because they are all homozygous although not identical.
        The zygotes were grown for 110 days before the experimental stress (a 9-degree cold shock) was administered. The amount of cortisol released into the blood in response to this shock was the stress variable studied. The heritability estimate was 0.6, which is very high, in fact higher than the previously-estimated repeatability of this trait. The authors discuss various explanations for this theoretically impossible result. The androgenesis procedure provides a means to develop highly stress-resistant homozygous lines very quickly, which may be of aquacultural importance because of the association of the stress response with disease resistance and growth. michael.tanck@alg.venv.wag-ur.nl 

247.  Can maladjusted immigrants destroy an endangered population?
        Effects of releasing maladapted individuals: a demographic-
evolutionary model. 2001. Tufto, J. American Naturalist 158:331-340.
       How dangerous is the escape of domesticated salmon which carry genes unfavorable for survival in the wild? Is it possible to re-establish an extinct population using animal bred in captivity, if those animals have evolved away from the local fitness optimum? Does supplementation of wild stocks by release of domesticated "gene-banked" animals seriously damage the genetic survival capacity of the remnant wild population?
        The authors of this paper have produced a model which joins the evolutionary dynamics of a quantitative trait under stabilizing selection with Lotka-Volterra-like population dynamics. In essence, selection becomes a partial function of population size and vice-versa. The model sheds light on how genetic load (a function of the variance of maladaptation, i.e. deviation from the fitness optimum, and the rate of immigration) affects the carrying capacity and intrinsic rate of increase of the population. Not surprisingly, even in this deterministic model the results are complex and depend on selection intensity, immigration rate, recombination rate, the presence or absence of competitors, the basal intrinsic rate of increase and the carrying capacity.
        When immigration and selection are both small the population is reduced below carrying capacity only if the immigrating ("maladapted") animals are far from the optimum. Conclusion for gene banks: try to reduce domestication. It's worth it.
        When selection is strong but density dependence is weak, as it might be in the early stages of re-introduction, it is feasible to use maladapted individuals to initiate a population. If the ongoing supplementation (immigration) continues at a low, constant rate the new population adapts sufficiently quickly and reaches a stable population equilibrium. See March-April list #187 for a natural situation in which the success of colonization seems to have been strain-dependent. jarlet@math.ntnu.no 

246.  Salmon Bacchanalia is confirmed
        A genetic evaluation of mating system and determinants of individual reproductive success in Atlantic salmon (Salmo salar L.). 2001. Garant, D., J.J. Dodson, and L. Bernatchez. Journal of Heredity 92:137-145.
        Salmon mating is not monogamous. As in other papers already noted here (July-August list #216 and June list #211), the authors of this study used microsatellites to determine parent/offspring and sib relationships, and came to the conclusion that polygynous and polygamous mating behaviour is the norm. Interestingly, they also found that the number of offspring ( a major component of fitness) is correlated with the number of mates, but not with body size. (It was not correlated with body size in cod either, in paper #242.) considering the three papers together, it appears that the prevalent assumption that salmon mating is monogamous has been effectively overturned. This has obvious connotations for calculating effective population number and modeling such genetic processes as introgression. louis.bernatchez@bio.ulaval.ca 

245.  Simultaneous evolution of correlated fitness traits
        Inbreeding changes the shape of the genetic covariance matrix in Drosophila melanogaster. 2001. Phillips, P.C., M.C. Whitlock, and K. Fowler. Genetics 158:1137-1145.
        The many morphological, behavioural and physiological traits of aquacultural species usually do not evolve independently, either in hatcheries or in the wild. When the value of one trait increases another trait often changes as well, and perhaps for the worse. This correlation may merely be the consequence of directly selecting more than one trait at the same time. Simultaneous changes in several traits can also arise, however, when selection on one trait induces a change in others because the traits are genetically correlated.
        One source of genetic correlation, although not the only one, is variation in genes that affects more than one trait. This give rise to a genetic "common cause" which produces correlated genetic effects. The pattern of common causes in a population is described by a genetic covariance matrix, which is just an extension of the concept of genetic variance which is used in relation to traits considered one at a time.
        In theory, if a population undergoes random genetic drift because it is very small (e.g. in a hatchery or an endangered population), the terms in the genetic covariance matrix will remain in a constant proportion to each other. This implies that although the rate of genetic adaptation may slow down because of random loss of genetic diversity, the overall pattern of evolution of different traits affected by the genetic covariance matrix should be preserved. However, this theoretical expectation is just an average and very little is known about how particular, small populations might behave.
        The authors of this paper set up a large number of small populations of Drosophila in such a way as to generate random drift and then looked at the genetic covariance among traits.
        "Although the average G [variance-covariance matrix] of the inbred lines did not show change in overall structure relative to the outbred controls, separate analysis revealed a great deal of variation among inbred lines around this expectation, including changes in the sign of genetic correlations. Since any given line can be quite different from the outbred control, it is likely that in nature unreplicated drift will lead to changes in the G matrix. Thus, the shape of G is malleable under genetic drift, and the evolutionary response of any particular population is likely to depend on the specifics of its evolutionary history."
        This paper has a number of implications (by analogy) for aquaculture and genetic conservation. For one thing, it suggests that when people carry home a few breeders from a larger population they may see evolutionary changes which are qualitatively as well as quantitatively very different from those in the source broodstock. These can occur even if the culture environment replicates nature exactly. pphil@darkwing.uoregon.edu 

244.  Identifying families of offspring when you don't know the parents
        Accurate partition of individuals into full-sib families from genetic data without parental information. 2001. Smith, B.R., C.M. Herbinger, and H.R. Merry. Genetics 158:1329-1338.
         It is often very useful to be able to identify full sibs in a broodstock, either to prevent accidental production of inbred offspring or to maximize founder diversity. The authors of this paper have devised a new method to identity full sibs and applied it to data on a hatchery population of Atlantic salmon for which microsatellite scores and independent pedigree analyses were available. Their procedure works by calculating the ratio of likelihood that pairs of individuals are full-sibs vs. the likelihood that they are unrelated, for all pairwise combinations in the population. Groups of full sibs are then assembled by maximizing the overall score or the full joint likelihood of the proposed groupings. Note that this is an exercise in identifying full-sub groups, not identifying particular parents. The difficulty of identifying parents when uncles and aunts are also present in the population therefore does not arise.
         Groups identified as full sibs rarely include animals which are not full sibs, but erroneous grouping of unrelated individuals occurs somewhat more frequently. In any case the overall success rate of classification is very high even with as few as four microsatellite loci. The current version of the program which runs on Unix computers is available from the authors. A PC version is in preparation. bruce.smith@dal.ca 

243.  Genetic variation in salmon migratory traits
        Genetic differences in physiology, growth hormone levels and migratory behaviour of Atlantic salmon smolts. 2001. Nielsen, C., G. Holdensgaard, H.C. Petersen, B. Th. Björnsson, and S.S. Madsen. Journal of Fish Biology 59 (1):28-44.
        When the authors released 1+ smolts of five hatchery strains into a Danish river in 1996, three of the strains went to sea almost immediately, but two strains waited for more than two weeks before migrating. In the following year the timing of various enzymatic changes associated with smoltification was studied in the same five strains. "Differences in the timing of gill enzyme development matched the observed migration pattern well. [Early migrating] strains reached high enzyme activity earlier than the [late migrating] strains, and strains with delayed enzyme development and migration showed a delayed regression of seawater tolerance compared with the early strains. ...The study gives evidence of genetic influence on the timing and intensity of smolting and subsequent migration in Atlantic salmon. steffen@biology.sdu.dk 

242.  Size does not matter in male cod
        Male reproductive success and body size in Atlantic cod Gadus morhua L. 2001. Rakitin, A., M.M. Ferguson, and E.A. Trippel. Marine Biology 138 (6):1077-1085.
        Eight replicate tanks were maintained throughout the spawning season, each containing two males of different body size and one female. Every male fertilized at least one of the 51 batches of eggs. Allozyme and minisatellite scores were used to sort out the parentage of the offspring. "Male size, condition factor, and total or relative body-weight loss over the season were not correlated with the estimated proportion of larvae sired by each male during the spawning season. [It was not correlated with body size in salmon either, in paper #246.]  ... Male reproductive success was affected by female size, with males much larger (>25% total length) than females siring a smaller proportion of larvae." mmfergus@uoguelph.ca 

241.  Inbreeding depression of salinity tolerance
        Temporal changes in allele frequency, genetic variation and inbreeding depression in small populations of the guppy, Poecilia reticulata. 2001. Shikano, T., T. Chiyokubo, and N. Taniguchi. Heredity 86 (2):153-160.
        Three closed lines of guppies (N=10) were propagated for six generations. The calculated inbreeding levels achieved at this point were 0.186, 0.321 and 0.414 and the corresponding salinity tolerances were 82.5%, 71.7% and 67.6% of their original values. This represents a linear inbreeding depression of approximately 8.4% per 10% increase in inbreeding. Various measures of allozyme diversity did not correlate well with the inbreeding estimated from the demographic effective population number in this particular experiment, as is often the case. shikano@bios.tohoku.ac.jp 

240.  Major histocompatability genes in trout
        Association between DNA polymorphisms tightly linked to MHC class II genes and IHN virus resistance in backcrosses of rainbow and cutthroat trout. 2001. Palti, Y., K.M. Nichols, K. Waller, J.E. Parsons, and G.H. Thorgaard. Aquaculture 194 (3-4):283-289.
        This is a good example of the use of a broad cross (species level hybridization) in an association study between a quantitative trait and a candidate gene or set of genes. "The results suggest that MHC polymorphism can contribute to linkage and association studies of immunity to infectious diseases in rainbow trout." (See July-August list #221, apparent breeding strategy of salmon to enhance MHC diversity.) nichols@wsunix.wsu.edu, 

239.  You may as well stop worrying about Frankensalmon
        Imperial college fined over hybrid virus risk. 2001. Pickrell, J. Science 293 (5531): 779-781.
        Experimenters at Imperial College London have succeeded in creating a chimeric virus containing all the best features of Hepatitis C, which is transmitted by blood, etc. and dengue fever, which is transmitted by mosquitoes. The experimental objective was to develop a strain of hepatitis that grows really, really well in the laboratory. "But the experiment ended after inspectors from the Health and Safety Executive (HSE) filed a devastating report on safety violations, following a laboratory inspection in 1998. Specialist Inspector Simon Warne says HSE found inadequate safety cabinets, a lack of proper equipment to fumigate the laboratory, poor facilities for waste disposal, and "confused, inadequate, and apparently untested" onsite lab rules. ... Imperial College issued a statement expressing regret and emphasizing that no one was hurt." (no e-mail available).