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.

110. Controlling fish Frankengenes
Cloning and expression analysis of an inducible HSP70 gene from tilapia fish. 2000. Molina, A. , F. Biemar, F. Muller, A. Iyengar, P. Prunet, N. Maclean, J.A. Martial, and M. Muller. FEBS Letters 474:5-10.
        One of the most useful tools for the molecular dissection of biological function is a gene that can easily be switched on or off under human experimental control. The authors of this paper have isolated and characterized an O. mossambicus gene which dramatically increases its rate of mRNA transcription (i.e. turns on) when whole animals are exposed to a transient heat shock.
        The gene encodes an enzyme which plays an essential role in protein metabolism. However, the importance of this work is the genetic engineering involved in identifying the regulatory sequence of the gene and then experimentally splicing it onto other genes to control their function. "Reporter constructs [i.e. special genes that send out a signal to show they're working] were tested for transient expression in carp cells and in microinjected zebrafish embryos. The entire isolated regulatory region ... was able to mediate heat shock inducible expression of the reporter gene, with no preference for a particular tissue. Our studies [reveal] ... a powerful tool to direct controlled, tissue-independent gene expression in fish."
        Heat shock is a simple and non-toxic treatment. Can heat-shock controlled maturation of salmon and tilapia be far behind? (Actually it hardly matters how far behind at this point. Genetic engineering is a big drift net and sooner or later everyone's gills are going to get caught in it.) m.muller@ulg.ac.be 

109.  At what age should you select shrimp or fish?
Correlation between two size classes of Pacific white shrimp Litopenaeus vannamei and its potential implications for selective breeding programs. 2000. Argue, B.J., S.M. Arce, and S.M. Moss. Jour. World Aquaculture Soc. 31 (1):119-122.
        When selecting for rapid growth it would be nice to select as early as possible to reduce grow-out costs and squeeze more generations into a year. However, if age at selection, age at breeding and the age at which harvestable size is attained are not exactly the same, then relative size at the earliest stage may not be a reliable indicator of relative size later on, and vice versa. Growth curves of individual animals may cross each other repeatedly during the grow-out of the population. Whether crossing does occur depends on genetic and environmental factors, especially the intensity of size-dependent competition for food, which tends to magnify early size differences and make them permanent whether or not they originally had a genetic basis.
        The authors of this paper measured the correlation between market weight (21-25 g) and breeding weight (35+g) in 120 tagged L. vannamei grown in an earthen pond. "There was a significant relationship between market and broodstock weight (P < 0.001) but it was not highly correlated (r = 0.42). ... Of the largest 20 broodstock, only seven were among the top 20 at market weight. If the goal of a breeding program is to select the fastest growing individuals to market, shrimp should be individually selected at market weight and not [much later] as broodstock." This is a timely and useful observation which, as mentioned above, is highly environment-dependent.
        The question when to select is also influenced by assumptions about the underlying genetics of growth. You might want to think of the relative size of a shrimp (or fish) at different ages as being repeated expressions of the same underlying genotype, namely its "true" growth rate. (Technically, we are looking at the physical size of the animal  as an indicator of its "breeding value" for growth). Measurements at either time could be rather uninformative; weight at harvest might be the better indicator but it might not -- for instance if relative size at marketing time were temporarily dominated by some random factor like PL quality or age-at-stocking, so that breeding value is more evident after a longer grow-out period. If indication of the breeding value becomes more accurate later on, this "repeated-measure" view of growth would indicate that selection should occur later, i.e. at the time of breeding.
        As an alternative viewpoint you might want to think of the relative market and broodstock sizes as two different genetic traits (see for example March list #20) and ask about the genetic correlation (technically, breeding value correlation) between them. This can be no more than the phenotypic correlation, which according to this paper is 0.4. The indicated selection strategy would then be cumulative, once at market size and then again at breeding, so that selected broodstock are in the top category twice, not just the first time. From this viewpoint, the extra correlated selection exerted on market size by two successive selections, the second one coming at broodstock size, is worth weighing against the extra effort. oignet@lava.net  [Argue]

108. Would you like to stop pretending your endangered population is in equilibrium?
Zygotic associations and multilocus statistics in a non-equilibrium diploid population. 2000. Yang, R-C. Genetics 155:1449-1468.
        As the authors say, the complexity of the possible disequilibria between multiple loci and alleles can quickly increase "beyond comprehension".  "The purpose of [their] study is to develop a set of summary statistics that can be used to characterize and estimate the multilocus associations in a non-equilibrium population. .... The method presented here is a generalization of the well-known development for the Hardy-Weinberg equilibrium population and thus may be of more general use in elucidating the multilocus organizations in non-equilibrium and equilibrium populations."
        The authors note that their methods are especially useful in hybrid populations where various problems including outbreeding selection against hybrids may maintain strong disequilibria. This is exactly what is postulated to occur when invading farmed salmonids mate with the natives. A sample size of 30 seems to be sufficient for analysis. rongcai.yang@agric.gov.ab.ca 

107. Genetic variation in the basic population variables
Genetic influences on experimental populations of the Least Killifish. 2000. Leips, J., J. Travis, and F.H. Rodd. Ecological Monographs 70 (2):289-309.
        For at least four decades the more abstract flavours of population ecology have relied on a few, simple variables to explain and categorize the broad outlines of the living world. Familiar concepts like "intrinsic rate of increase", "K-selected", "reproductive value" are in this explanatory tradition. Ecological and evolutionary geneticists use closely related concepts like "life history trade-offs" to predict the fitness and evolutionary trajectory of a mutation. Resource managers and conservation geneticists use "carrying capacity" in discussing the recovery or survival potential of endangered populations such as Newfoundland codfish and Atlantic salmon in Maine.
        The authors of this paper have conducted field experiments to analyse the extent to which classic population variables such as these are under genetic control in a species of fish. To do this they took samples from two populations that have very different life histories and population densities, hybridized them in different proportions, and stocked the hybrids in replicated experimental ponds. The populations were then grown out for several generations until the densities reached equilibrium. The experimental design is reminiscent of the replacement series used by plant ecologists to analyse competition.
        "The mean offspring size differed among stocks by as much as 50%. At low densities, offspring size exhibited a trade-off with brood size. ... Stocks differed in realized population growth rate by as much as 70%; the rank order differences among stocks with respect to population growth rate appeared to match the genetic relatedness among stocks. ... The stocks differed in their response to the depressant effects of density on life history trait expression. .... Differences in population growth rate appeared to be due to differences in brood size among stocks at low density. Stocks did not differ in the equilibrium population size, which indicated the absence of a trade-off between population growth rate and carrying capacity in this environment." jwleips@unity.ncsu.edu 

106. IHHNV – resistant strain of shrimp
Postlarvae and juveniles of a selected line of Penaeus stylirostris are resistant to infectious hypodermal and hematopoietic necrosis virus infection. 2000. Tang, K.F.J., S. V. Durand, B. L. White, R.M. Redman, C.R. Pantoja, and D.V. Lightner. Aquaculture 190: 203-210.
        A company in Yuma, Arizona called Maritech has selected IHHNV resistance in a line of shrimp they are marketing under the name Super Shrimp®. In this study, done in the laboratory at the University of Arizona, postlarval and juvenile Super Shrimp were challenged with IHHNV and their response compared with a specific pathogen free strain of P. vannamei. The authors confirmed through both histology and in situ hybridization that the Super Shrimp PLs did not become infected with IHHNV while the other strain (which was not, technically speaking, a selection control) did. The IHHNV apparently did not replicate and the shrimp were resistant in the absolute sense discussed in August list #96.  "In contrast, P. vannamei juveniles, which were used as a positive control, showed a more intense IHHNV infection, as determined by PCR detection, beginning at 6 days postchallenge and increasing throughout the remainder of the study. ... Our studies show that Super Shrimp® are resistant to IHHNV infection. This is the first unequivocal demonstration of resistance to viral infection in shrimp." fengjyu@u.arizona.edu 

105. Tempo and mode in viral pathogen evolution
Are RNA viruses adapting or merely changing? 2000. Sala, M, and S. Wain-Hobson . Journal of Molecular Evolution 51:12-20.
        RNA viruses and retroviruses evolve approximately 1,000,000 times faster than their hosts. The question is whether this rapid evolution represents random drift or whether it is driven selectively by the "evolutionary arms race" between pathogen and host. According to the latter theory the evolutionary changes in the viral genome allow it to stay ahead of the defenses of the individual host during the course of a disease, and of the host population during the course of an epidemic. (See August list #96.)
        The authors of this paper review the RNA sequence of a variety of viruses and, using a statistical argument that "spans quasispeciation following clonal infection, to variation among different isolates of the same virus, to viruses from different species or those associated with different diseases", conclude that most of the viral evolution (fixation of mutations) does represent drift. "This held for both mammalian and plant viruses, indicating that adaptive immunity doesn't necessarily shape the relative accumulation of amino acid substitutions. When compared to their hosts RNA viruses evolution appears conservative."
        Note that this finding does not imply that adaptive evolution of RNA viruses is slow; it means that the observed rapid evolution of RNA substitutions is not adaptive; these statements are not equivalent. One significant aspect for aquaculture is that the essentially random nature of the vast majority of substitutions should make it easier to track the origin and spread of disease epidemics using molecular markers. simon@pasteur.fr 

104. Ex situ fisheries conservation
Social studies. 2000. Anonymous. Toronto Globe and Mail, July 31.
        "The world's first museum dedicated to fermented herring will be opened in northern Sweden next year. The museum, outside Ornskoldsvik [upwind of most places], will explain the ancient technique ... for preserving herring by adding small amounts of salt and then letting the fish ferment."

103. How many markers will you need?
Individual-based genotype analysis in studies of parentage and population assignment: how many loci, how many alleles? 2000. Bernatchez, L., and P. Duchesne. Canadian Journal Fisheries and Aquatic Sciences 57:1-12.
        "Given sufficient allelic diversity, a relatively low number of loci is required to achieve high allocation success [to full-sib families] even for relatively large numbers of possible parents. In contrast. ... there appears to be no significant gain in increasing allelic diversity beyond approximately 6-10 alleles per locus in population assignment studies." This study should help decide which, and how many, marker loci are needed to tackle a particular problem in aquaculture or conservation genetics. louis.bernatchez@bio.ulaval.ca 

102. Useful tool for choosing marker loci
A computerised algorithm for selecting a subset of multiplex molecular markers and optimising linkage map construction. 2000. Charmet, G., P.F. Bert, and F. Balfourier. Theoretical and Applied Genetics 101:90-95.
        "A computer algorithm is presented which allows selection of a subset of multiplex markers based on the minimisation of an optimality criterion for a genetic linkage map. The goal is to achieve a saturated map of evenly spaced markers, using as few primers as possible to minimise cost and labour... Genetic diversity studies may also benefit from using such a subset of less-redundant markers in genetic distance estimation." (But see caution in the March list #29 about choosing markers non-haphazardly.) charmet@valmont.clermont.inra.fr 

101. Resistance traits depressed by inbreeding are uncorrelated
Stress resistance and environmental dependency of inbreeding depression in Drosophila melanogaster. 2000. Dahlgaard, J., and A.A. Hoffmann. Conservation Biology 14:1187-1192.
        One of the most controversial questions in conservation genetics is whether it is advisable to deliberately inbreed small, captive populations to get rid of their inbreeding depression. This would be done by deliberate inbreeding accompanied by selection for fitness. After the recessive alleles that reduce the fitness of inbred animals (under some models of this phenomenon) have been purged out by selection, population managers will never have to worry about the effects of inbreeding again. Selective purging could potentially be applied to aquaculture broodstock as well.
        The authors of this paper addressed the question whether the effects of environmental stress and inbreeding are independent of each other in Drosophila. They found that the deleterious effect of all the types of stress they examined were indeed increased by inbreeding. However, "... resistance traits were uncorrelated in the inbred as well as in the outbred flies. Recessive, deleterious alleles therefore did not appear to have any general deleterious effects on stress resistance. Inbreeding within a specific environment and selection for resistant genotypes may therefore purge a population of deleterious genes specific to only one environmental stress." The purged, inbred populations would be just as susceptible as ever to the next stress that comes along.  jesper.dahlgaard@biology.au.dk 

100. Sorting out individuals and populations
Inference of population structure using multilocus genotype data. 2000. Pritchard, J.K., M. Stephens, and P. Donnelly. Genetics 155:945-959.
        This is a new and potentially useful method for inferring population structure and assigning individuals to populations. "We assume a model in which there are K populations (where K may be unknown). ...Our model does not assume a particular mutation process. ... Applications of our method include demonstrating the presence of population structure, assigning individuals to populations, studying hybrid zones, and identifying migrants and admixed individuals. We show that the method can produce highly accurate assignments using modest numbers of loci—e.g., seven microsatellite loci in an example using genotype data from an endangered bird species." The software is incorporated in a package called STRUCTURE which is available at http://www.stats.ox.ac.uk/~pritch/home.html The author's e-mail address is pritch@stats.ox.ac.uk 

99. Frankensalmon growth data for aquaculture and biosecurity
Growth rate, body composition and feed digestibility/conversion of growth-enhanced transgenic Atlantic salmon (Salmo salar). 2000. Cook, J.T., M.A. McNiven, G.F. Richardson, and A.M. Sutterlin. Aquaculture 188:15-32.
        Two additional papers in the same issue of Aquaculture by these authors are entitled Metabolic rate of pre-smolt growth-enhanced transgenic Atlantic salmon (pp. 33-45) and Effect of food deprivation on oxygen consumption and body composition of growth-enhanced transgenic Atlantic salmon (pp. 47-63).
        These three papers from the AF Protein /Aquabounty experimental facility at Souris, Prince Edward Island, Canada, are an interesting and important contribution to our understanding of how transgenic salmon are likely to perform in aquaculture environments -- as well as their probable fate if they escape into the wild. The transgenic salmon are F2 fish carrying a salmon growth hormone gene which is attached to a foreign promoter; this promoter causes it to be continuously expressed in the liver. See the note on the US patent application for this transgenic fish in the July list #85.
        The essential results are as follows: (1) The growth-enhanced transgenic fish grew 2.62- to 2.85-fold faster over the size range 8 - 55 g. (2) They exhibited a 10% improvement in gross feed conversion efficiency. (3) Moisture content was significantly higher, relative to protein and ash, than in the normal controls. (4) The transgenic fish had higher metabolic rates but they consumed 42% less total oxygen between hatching and smolt size. "The added cost to smolt producers for the short-term delivery of more water or oxygen to support the elevated metabolism of such growth-enhanced fish would appear to be justified in light of the benefits in reducing smolt production time." (5) When starved, the rate of oxygen consumption declined more rapidly in the transgenic fish. The starved transgenic fish also lost protein, dry matter, lipid and energy more quickly than controls.
        The authors conclude that these results should reduce public anxiety about the genetic impact of escaped transgenic salmon. " [The persistence of transgenic salmon] in maintaining a higher metabolic rate, combined with their lower initial endogenous energy reserves, suggests that the likelihood of growth-enhanced transgenic salmon achieving maximum growth or even surviving outside intensive culture conditions may be lower than that of non-transgenic salmon. " todd_cook@hotmail.com 

98. Internet discussion group for fisheries biotechnology
Electronic Forum on Biotechnology (Fish). 2000. FAO. Internet website.
        The Food and Agriculture Organization of the UN has organized an open, but moderated, forum on biotechnology in the fisheries sector. The particular emphasis is on the suitability or otherwise of this technology for developing countries. The forum is a lively one and will run from August 1 - October 1, 2000. http://www.fao.org/biotech/Conf4.htm 

97. Salmonids, sex and maps
A microsatellite linkage map of rainbow trout (Oncorhynchus mykiss) characterized by large sex-specific differences in recombination rates. 2000. Sakamoto , T., R.G. Danzmann, K. Gharbi, P. Howard, A. Ozaki, S.K. Khoo, R.A. Woram, N. Okamoto, M.M. Ferguson, L.-A. Holm, R. Guyomard, and B. Hoyheim. Genetics 155:1331-1345.
        The authors constructed a genetic linkage map for rainbow trout using 208 markers in three backcross families and several gynogenetic diploids. The authors comment that the "Parental origins of chromosomes involved in meiotic pairings may have a very large influence on the resulting gametic vector of alleles." For instance, "Extreme differences in female:male map distances were observed (ratio F:M, 3.25:1). Females had much lower recombination rates (0.14:1) in telomeric regions than males, while recombination rates were much higher in females within regions proximal to the centromere (F:M, 10:1). Quadrivalent formations that appear almost exclusively in males are postulated to account for the observed differences." rdanzman@uoguelph.ca