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Conserving genetic diversity in animal populations is important for sustaining their ability to respond to environmental change. However, the “between-population” component of genetic diversity (biocomplexity) is threatened in many exploited populations, particularly marine fish, where harvest management regions may be larger than the spatial extent of genetically distinct subpopulations. Using single-nucleotide polymorphism data, we delineated the geographic limits of three population units of Atlantic cod (Gadus morhua) in northwest European waters. Two of the populations cohabit the North Sea, and trawl survey data showed differing trends in their abundances. We developed a spatial model of these units to simulate population dynamics under spatial patterns of harvesting. Competition between units during the pelagic juvenile stages in the model led to suppression of the more localized northern North Sea (Viking) unit by the more widespread (Dogger) unit, and its premature extinction under some spatial patterns of fishing. Fishery catch limits for cod are set at the scale of the whole North Sea without regard to such subpopulation dynamics. Our model offers a method to quantify adjustments to regional fishing mortality rates to strike a balance between maximizing sustainable yield and conserving vulnerable populations. [ABSTRACT FROM PUBLISHER]

In the last 20 years, new species, asexual reproduction, polyploidy and hybridization have all been reported within the genus Cobitis. An understanding of the current distribution and baseline phylogeographical history of ‘true’ nonhybrid Cobitis species is crucial in order to unravel these discoveries. In the present work, we investigated the phylogeography of the spined loach, Cobitis taenia, using 1126 bp of the mitochondrial cytochrome b gene from 174 individuals collected at 47 sites. In total, 51 haplotypes that differed at 49 positions (4.35%) were detected. We deduce that C. taenia survived European glaciations in at least three refuges in the Ponto-Caspian area. Two of these refuges each provided a major lineage that recolonized Europe in separate directions: one westward to England and the other spreading north into Russia before moving west. A third (minor) lineage that contributed little to the recolonization of Europe was also revealed — remaining near its Black Sea refuge. However, more recent history was difficult to resolve with colonization from a more western refugium during the last glacial maximum (LGM) a distinct possibility. Nested clade analysis indicates a pattern of restricted gene flow with isolation by distance at the first two levels and overall. Unlike many other European freshwater fish species, the Danube is not part of the current distribution of C. taenia, nor was it used as either a refuge or a source of colonization of Europe. Low genetic diversity within C. taenia suggests that its colonization of Europe is relatively recent. Demographic analyses revealed a history of recent expansion and isolation by distance. [ABSTRACT FROM AUTHOR]

Understanding the historical emergence and growth of long-range fisheries can provide fundamental insights into the timing of ecological impacts and the development of coastal communities during the last millennium. Whole-genome sequencing approaches can improve such understanding by determining the origin of archaeological fish specimens that may have been obtained from historic trade or distant water. Here, we used genome-wide data to individually infer the biological source of 37 ancient Atlantic cod specimens (ca 1050–1950 CE) from England and Spain. Our findings provide novel genetic evidence that eleventh- to twelfth-century specimens from London were predominantly obtained from nearby populations, while thirteenth- to fourteenth-century specimens were derived from distant sources. Our results further suggest that Icelandic cod was indeed exported to London earlier than previously reported. Our observations confirm the chronology and geography of the trans-Atlantic cod trade from Newfoundland to Spain starting by the early sixteenth century. Our findings demonstrate the utility of whole-genome sequencing and ancient DNA approaches to describe the globalization of marine fisheries and increase our understanding regarding the extent of the North Atlantic fish trade and long-range fisheries in medieval and early modern times. [ABSTRACT FROM AUTHOR]

Abstract: Quantitative trait loci (QTL) for age at smoltification and adult maturation have been mapped in several salmonid species but less is known about precocious male parr maturity. Phenotypic information on length at age, precocious male parr maturation (paedogenesis), early smoltification, and adult sexual maturation was recorded for four double-backcross families of F1 European/North American trans-Atlantic salmon that had been genotyped for 320 (family A) or 121 (families B, C and D) single nucleotide polymorphisms (SNPs). The locations of QTL for early smoltification and for precocious parr and adult maturation in Atlantic salmon (Salmo salar) were identified and then compared with QTL in homologous chromosomal arms of rainbow trout (Oncorhynchus mykiss). Novel QTL for precocious male parr maturation on Ssa05, Ssa07, Ssa09, Ssa10, Ssa12, Ssa16 and Ssa20 were significant at the genome-wide level as were QTL for early smolting detected on chromosomes Ssa05, Ssa08, Ssa13, and Ssa23. As predicted, precocious male parr were significantly less likely to become early smolts. Two QTL for adult sexual maturation on chromosomes Ssa21 and Ssa23 were significant at the chromosome-wide level as were QTL for adult length on Ssa05 and Ssa24. Separate analysis of family A resulted in novel QTL being detected on Ssa01q for early smolting, Ssa17 and Ssa22 for precocious maturation, and on Ssa03 and Ssa20 for length at the early smolt measuring period. The two chromosomes (Ssa21 and Ssa23) that contained QTL for adult maturation were homologous to two chromosomes (Omy22 and Omy4) that contain QTL for adult maturation in rainbow trout. [Copyright &y& Elsevier]