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.

261.  Conserve broodstock diversity and minimize inbreeding depression
        A comparison of management strategies for conservation with regard to population fitness. 2001. Fernández, J., and A. Caballero. Conservation Genetics 2 (2):121-131.
        The authors examine, through computer simulation, several broodstock-management procedures which are intended to maximize the retention of genetic diversity in a captive population. All the procedures use the minimal kinship criterion for choosing breeders (July-August list #212), which increases the retention of genes that are not identical by descent. Pedigree records of relatedness, or possibly a surrogate measure of relatedness derived from microsatellite marker data (see September list #227), are required for this procedure.
        The simulated management procedures differ in the way the breeders are mated with each other after they have been chosen (e.g. excluding matings between close relatives, mating related males with unrelated females etc.), and thus differ in their implications for short term loss of fitness due to inbreeding depression in the captive population. jesusfm@uvigo.es

260.  Genetic impact of stocking brown trout eventually fades away
         Distribution of individual inbreeding coefficients, relatedness and influence of stocking on native anadromous brown trout (Salmo trutta) population structure. 2001. Ruzzante, D.E., M.M. Hansen, and D. Meldrup. Molecular Ecology 10 (9):2107-2128.
        Microsatellite data were used to calculate Ritland's estimates of individual inbreeding coefficients and pairwise relatedness coefficients on more than 4000 Danish brown trout. Relatedness, but not inbreeding, appears to differ among locations within rivers, suggesting the existence of local population structure. The authors can detect the presence of both native and hatchery stocks at most locations -- more hatchery individuals where stocking has been more intense -- but conclude that "the relatively high proportion of locally assigned trout in populations where stocking with domestic fish no longer takes place suggests limited long-term success of stocking". (See July-August list # 214.) dr@dfu.min.dk

259.  Cause of sex, depression & everything
         High genetic load in the Pacific oyster Crassostrea gigas. 2001. Launey, S., and D. Hedgecock. Genetics 159:255-265.
        The analysis of microsatellite data from inbred and crossbred C. gigas has enabled the authors to elucidate the life history strategy known as the "elm-oyster model", while managing to shed light on several other puzzles as well.
        Oysters (and elm trees -- George C. Williams) rely on sexual recombination and high fecundities to respond adaptively to environments which are highly heterogeneous in space and time. They broadcast millions of highly varied offspring in the hope that at least one, on average, will make it. These and other organisms that have similar life-history strategies exhibit strong heterosis in nature; offspring that are homozygous at marker loci die out more quickly as a cohort of offspring ages. The same kinds of organism often show unusual, non-Mendelian inheritance of allozyme and microsatellite marker loci.
        The breeding and grow-out experiments in this interesting paper show that these phenomena have a common cause. Heterosis and segregation distortion are due to linkage between the (neutral) markers and deleterious recessive alleles at nearby loci. Heterosis in bivalves is here shown conclusively to be due to linkage, not to the intrinsically higher fitness of animals that are heterozygous for the markers. Furthermore, non-Mendelian inheritance of markers in this elm-oyster oyster is due to the selective purging of deleterious homozygotes at linked loci (September list #228).
        For a complete list of the topics illuminated these experiments you will have to read the paper itself. It might also be noted that the results agree nicely with a recent Drosophila experiment (Rice & Chippendale, Science 294:555-559 October 19th) which showed that evolution proceeds in sexual organisms because, through recombination, favourable genes are able to shake off unfavorable genetic backgrounds. The oysters carry a high load of deleterious mutations, but with sexual reproduction and millions of recombinant offspring every season they do very nicely anyway. dehedgecock@ucdavis.edu

258.  Optimal pedigree assumptions when you add new animals to a broodstock
        Unpedigreed populations and worst-case scenarios. 2001. Willis, K. Zoo Biology 20 (4):305-314.
        Zoo geneticists are ahead of fish-hatchery geneticists in thinking about inbreeding and diversity loss during the prolonged cultivation of captive populations. Of course, zoo biologists usually have pedigree records to help them make decisions about which matings to make. Fish hatcheries rarely have such records (as yet). In zoo populations animals with unknown pedigrees are occasionally brought in from outside and are added to a pedigreed broodstock. This also happens in hatcheries. What assumptions should be made about the unknown pedigree of these breeder "immigrants" when they are incorporated into the existing pedigree? This is question which will soon confront aquaculturists and fisheries conservationists as routine hatchery practice become more sophisticated.
        Standard zoo practice is to assume that the immigrants are highly related to each other, i.e. are full sibs. This is considered to be a conservative assumption: sibs will not be mated with each other and short-term inbreeding depression will be minimized.
        The author of this paper shows, however, that this is not the optimal assumption if the objective is conservation of gene diversity in the captive population. A calculation is presented which enables estimation of the relatedness which should be assumed in the unknown pedigree in order to minimize the loss of founder genome equivalents (FGE) when immigrants are added. FGE is a measure of equivalent allele number or gene diversity. Relatedness estimators (see September list #227) may be one of several possible ways to estimate the quantities required for this calculation using microsatellite marker data.
        If, following this advice, you don't assume the immigrants are full sibs, inbreeding remains a potential problem in the next generation. Apparently in zoos "the rule of thumb is that inbreeding coefficients of potential offspring should be kept at a value less than the current average mean kinship". This could be a useful rule in fish hatcheries as well. kwillis@mail.mnzoo.state.mn.us

257.  Coho strains differ in their immune response to Vibrio
         Coho salmon Oncorhynchus kisutch strain differences in disease resistance and non-specific immunity, following immersion challenges with Vibrio anguillarum. 2001. Balfry, S.K., A.G. Maule, and G.K. Iwama. Diseases of Aquatic Organisms 47:39-48.
        The authors measured mortality rates as well as the immune-response variables plasma lysozyme activity and anterior kidney phagocyte respiratory burst activity. Two coho strains were challenged with Vibrio at various treatment levels. "The more disease-resistant strain was found to have higher levels of plasma lysozyme and anterior kidney phagocyte respiratory burst activity. ...The results of this study suggest that the basis for strain differences in innate disease resistance is related to the ability of the fish to respond quickly to the initial infection and to maintain the response until the infection is quelled." balfry@interchange.ubc.ca

256.  Ayu mitochondrial sequence
         Complete mitochondrial DNA sequence of ayu Plecoglossus altivelis. 2001. Ishiguro, N., M. Miya, and M. Nishida. Fisheries Science 67 (3):474-481.
        "... the genome (16 537 bp) contained the same 37 mitochondrial genes (two ribosomal RNA, 22 transfer RNA, and 13 protein-coding genes) as those found in other vertebrates, with the gene order identical to that in typical vertebrates." The putative control region (D-loop) of 857 non-coding base pairs was also identified. ishiguro@ori.u-tokyo.ac.jp

255.  Another instance of outbreeding enhancing fitness
        Outbreeding increases offspring survival in wild greater horseshoe bats (Rhinolophus ferrumequinum). 2001. Rossiter, S.J., G. Jones, R.D. Ransome, and E.M. Barratt. Proceedings of the Royal Society (Ser. B..) 268 (1471):1055-1061.
        There have been a few studies that have shown that inbreeding in small, natural populations increases the extinction rate (September list #230, June list #210, March-April list #185). There have been many studies that have shown that individual heterozygosity (assumed to indicate lack of inbreeding) is associated with increased fitness, especially under harsh conditions (See #259 above, also February 2000 list #9) .
        This paper shows that outbreeding -- the converse of inbreeding -- is associated with the survival of young males in a colony of bats studied over a period of seven years in Britain. Heterozygosity per se was not associated with fitness, however. "The influence of mean d2 [a measure of outbreeding] was not due to a single locus under selection but a wider multilocus effect and probably represents heterosis as opposed to solely inbreeding depression. ... Mean d2 may reflect immunocompetence, which influences mortality. Protection of mating sites in order to facilitate gene flow and, therefore, outbreeding may help to promote population stability and growth."
        The possible role of immunocompetence is interesting; see July-August list #221 on mate choice in salmon in order to increase MHC diversity. The mate choice would presumably show up as outbreeding by the d2 measure. See also March-April list #179. s.j.rossiter@qmw.ac.uk

254.  Domestication changes feeding behaviour
         Selection for surface feeding in farmed and sea-ranched masu salmon juveniles. 2001. Reinhardt, U.G. Transactions of the American Fisheries Society 130:155-158.
        Feeding and aggressive behaviour was compared among offspring of wild, farmed and sea-ranched populations of this Japanese salmon species. Hatchery and sea-ranched strains had been propagated for approximately 30 and 90 years, respectively. The domesticated strain tended to feed higher in the water column than the other strains. The fish with sea-ranched parents were intermediate in the water column. Levels of aggression were about the same in all three strains. "New hatchery techniques that teach fish to avoid the surface or prevent selection for surface-seeking behavior promise to bolster the survival of postrelease ranched salmon." ureinhardt@online.emich.edu

253.  Performance of triploids proportional to genetic variation
         Separate effects of triploidy, parentage and genomic diversity upon feeding behaviour, metabolic efficiency and net energy balance in the Pacific oyster Crassostrea gigas. 2000. Hawkins, A.J.S., Magoulas A., M. Heral, S. Bougrier, Y. Naciri-Graven, A.J. Day, and G. Kotoulas. Genetical Research 76:273-284.
        Triploidy was induced by suppressing either the first or second polar body. The authors compared these two types of triploid with ordinary diploids. Feeding rate, absorption efficiency, net energy balance and growth efficiency were measured in a large numbers of individuals in which microsatellite and allozyme allelic variation were also estimated.
        "Comparison of meiosis I triploids, meiosis II triploids and diploid siblings established that improved physiological performance in triploids was associated with increased allelic variation, rather than with the quantitative dosage effects of ploidy status." Because genetic variation was highest in individuals triploidized at meiosis I the authors suggest "that it may be preferable to induce triploidy by blocking meiosis I, rather than meiosis II as has traditionally been undertaken during commercial breeding programmes". ajsh@ccms.ac.uk

252. Population supplementation: not perfect, but helpful
         Captive breeding and reintroduction evaluation criteria: a case study of peninsular bighorn sheep. 2001. Ostermann, S.D., J.R. Deforge, and W.D. Edge. Conservation Biology 15 (3):749-760.
        Fish are not sheep, but (by analogy) this study provides a good example of how an aquatic stock supplementation program might be evaluated. The authors used several criteria to evaluate a bighorn sheep (Ovis canadensis) supplementation program: "(1) survival and recruitment rates in the captive population, (2) survival of released animals, (3) recruitment of released animals, (4) growth rate of the reintroduced or augmented population, and (5) establishment of a viable wild population".
        The analogy with salmonids is rather good: the sheep recruited and survived well in captivity but poorly in the wild. Deteriorated environmental conditions in the wild did not help the supplementation and recovery of a self-sustaining wild population was not achieved. However, the stock supplementation program certainly helped prevent local extinction and helped maintain the metapopulation web. "Standard evaluation criteria for ongoing reintroductions allow for informative assessments and facilitate comparisons needed to refine reintroduction science as a recovery tool for threatened or endangered populations." sdostermann@ucdavis.edu

251.  Lords of the Harvest
         Seeds of discontent. 2001. Charles, D. Science 294 (5543):772-775.
        Everyone knows of the struggle between those who want open access to the world's indigenous genetic resources and those who want to restrict ownership so that benefits can return to the developing countries where useful genes commonly originate. The protagonists include multi-national agro-biotech firms and some international agricultural development agencies on the one hand, and national governments, environmentalists and native rights groups on the other. What may not be so well known is that the struggle has been turning out badly for both sides. This well-written and somewhat frightening paper should interest anyone concerned with the long-term sustainability of ex-situ genetic conservation.
        What appears to have changed things was the International Convention on Biological Diversity which has, since 1993, inspired the enactment in more than 50 nations of laws restricting the export of plants, seeds, and other local genetic materials (including in some instances human genes). The laudable motive was to restrict exploitation of developing countries by multinational "bio-pirates". The unfortunate result, however, is that non-profit research and gene-banking which greatly benefits the development of agriculture in poor countries is grinding to a halt.
        Charles writes that "After spending most of his life railing against the evils of multinational corporations, [Pat Mooney, a major figure in agricultural activist circles] now finds himself condemning the legal walls that Third World governments are building around seed banks. "Forcing farmers and other researchers to reduce their options and [restrict] their access to diversity is irresponsible. It is the flip side of intellectual property monopoly and equally immoral," ".
        Charles illustrates this point with the tale of the construction of a strain of drought-resistant maize, in Kenya, by Marianne Bänziger, a geneticist at the International Center for the Improvement of Maize and Wheat. This strain will soon be distributed free to farmers in southern Africa, but her work relied on free access to seed from local maize landraces in Latin America, access which Charles says is now impossible.
        "Moreover, says [another researcher quoted in Charles's article] genetic resources now flow mainly from "North" to "South" rather than the other way around. In one recent typical year, for every single seed sample that developing nations sent to international gene banks, those gene banks sent about 60 samples back. Farmers in poor nations now depend on seeds held by gene banks located in or funded by rich nations." It is hard to escape the conclusion: "If poor nations create a world in which they have to bargain for access to the genetic resources in these banks, they lose."
        Charles expands on these and other issues, especially the development of transgenic Frankenfoods -- in which dirty linen is a primary ingredient -- in a new book "Lords of the Harvest: Biotech, Big Money, and the Future of Food" Perseus Publishing, September 2001, which is getting rave reviews. No e-mail address available.