STOCK COMPOSITION IN NORTH-ATLANTIC POPULATIONS OF WHITING USING MICROSATELLITE MARKERS

A size-selected library constructed from DNA of the whiting Merlangius merlangus was screened. From about 3200 recombinant clones, 43 micros atellite loci were detected. Thirteen were sequenced in full. Primers were designed from the sequence of the flanking regions for six loci a nd used to test the allelic variability at these loci using the polyme rase chain reaction (PCR). In addition, five primer pairs developed fo r the stickleback and another seven for cod were tested. Only six prim er pairs revealed at least three alleles per locus. The three useful l oci Gmo2, Mmer-UEAW01 and Mmer-UEAW02, had 14-23 alleles per locus in 370 samples. Estimates of genetic structure (Phi(st)) were not statist ically significant. However, estimates of genetic differentiation (F-s t) were significantly different from zero. Heterogeneity chi(2)-analys is of allele frequencies among populations suggested relatively low le vels of differentiation among samples. Significantly different allele frequency distributions were found for Borgensfjord and northern and s outhern North Sea samples for at least one locus, and between the latt er samples for Mmer-UEAW02 and Gmo2. There were significant excesses o f homozygotes in all samples, over expectation for randomly mating pop ulations in Hardy-Weinberg equilibrium. The estimated frequencies of n ull alleles were 14.3%, for Mmer-UEAW01, 10.2% for Mmer-UEAW02 and 11. 6% for Gmo2. This result calls for a careful interpretation of the sig nificance of these microsatellite data. (C) 1997 The Fisheries Society oi the British Isles.