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34 Rethlnking the Stock Concept greater (D =' 0.0826) than that within the North Pacific, to the extent that the differences were far greater than those between the separate sibling species B. borealis (sei) and B. bryde (Bryde's). This suggested that north- ern and southern minkes were separate species, or at least separate subspecies. DNA nuclear probes suggest significant differences between the Antarctic, North Atlantic (West Green- land), and the western North Pacific (Sea of Japan) pop- ulations (Amos & Dover 1991). The results could be translated into migration rates between regions. The high level of migration between adjacent Areas IV and V was enough to make separate stock identity question- able (Hoelzel & Dover 1991). In the Norm Atlantic, Palsboll (1990) reported on restriction fragment analysis of ribosomal DNA of minkes from the Northeastern Atlantic (Barents Sea) and West Greenland, He found that there was a proba- bility of less than 0.001 that the two stocks were from a ,single random-mating population-good reason for identifying the stocks as separate. Amason and Spilliaert (1990) reponed evidence of stock differences between minkes from the Norway (Northeastern stock-Barents Sea), Iceland,(Central stock), and West Greenland. Us- ing genomic, DNA probes, they found the greatest dif- ferences between West Greenland and the others. Dif- ferences were also found between Iceland and the Barents Sea populations. They concluded that existing management 'stock divisions were valid. Danielsdottir et at (1990) also found supporting evidence using elec- trophoretic analyses on the separation of these three stocks. Using restriction fragment analysis of mtDNA, however, PalSboll ( 1990) found conflicting and contra- dictory resu16 for these three regions. Bakke and EI- Gewely (1990) reported stock differences between northern Norway and the west coast of Svalbard using the same techniques. IV. Classification The minke' whale has been comparatively well inves. tigated and defined in terms of stock identity, probably because the species has been exploited on an interna- tional scale. The evidence seems strong that the North. em and Southern Hemisphere populations are clearly distinct and in category I blabcd status, and the subspe- cies category' seems valid. The North Atlantic and North Pacific stocks also appear distinct and in category I sta. tus. In the Southern Hemisphere, clearly it seems that populations in Areas III, IV, and V are not easily discern- able and probably should be afforded category IV abed/a status--veryweak stock definition, if any. However, compared to. the southern bonaerensis subspecies, the dwarf form also could be afforded subspecies status, but it would be aScribed to category II because of sympatric distribution. The final categorization might be II alcd. Coaservatlon Biology Volume 6, No, 1, March 1992 DIzon et aI, The North Atlantic stock definitions appear to be largely supported by genetic analyses, 'and the majority when compared would be given category III c/acd sta- tus. --- This species is of particular interest in stock analysis because of multiple representations in each stock cate- gory, I-IV. The recent genetic investigations have brought to light the fact that speciation, not just subspe- ciation, may be occurring in the minke whale popula- tions. In the future, the whole question of what consti- tutes a species may have to be reconsidered for the family Balaenopteridae. Literature Cited Aguayo, LA, 1974, Baleen whales off continental Chile, Pages 207-217 in W, E. Schevill, editor, The whale problem: a status report. Harvard University Press, Cambridge, Massachusetts, Amos, W., and G, A. Dover. 1991. The use of satellite DNA sequences in determining population differentiation in the minke whale. Pages 235-244 in A, R Hoelzel, editor. Genetic ecology of whales and dolphins, Reports of the International Whaling Commission. Special Issue 13, International Whaling Commission, Cambridge, UK' Anonymous. 1987. United States marine mammal regulations. 1986 and beyond A reference of tuna seiners, Southwest Re- gion. National Marine Fisheries Service, San Diego, California Amason, A" and R A. Spilliaert, 1990. Study of variability in minke whales (Balaenoptera acutorostrata) in the North At- lantic using a human hypervariable region probe, alpha- globulin 3'HVR!WC Document SCl42/NHMi 23. International Whaling Commission, Cambridge, England. Arnold, P., H. Marsh, and G. Heinsohn. 1987. The occurrence of two forms of minke whales in east Australian waters with a description of external characters and skeleton of the dimin- utive and dwarf form, Scientific Reports of the Whales Re- search Institute, Tokyo 38:1-46, Avise, J. C. 1989, Gene trees and organisma1 histories: a phy- logenetic approach to population biology. Evolution 43(6): 1192-1208, Avise, J. c., J. Arnold, R Martin-Ball, et al. 1987, Intraspecific phylogeography: the mitochondrial DNA bridge between pop- ulation genetics and systematics, Annual Review of Ecology and Systematics 18:489-522. Avise, J. c., and R M. Ball, Jr. 1990, Principles of genealogical concordance in species concepts and biological taxonomy, Pages 45-67 in D. Futuyma and J. Antonovics, editors. Oxford Surveys in Evolutionary Biology Volume 7. Oxford University Press, Oxford, UK Baker, A. N, 1983. Whales and dolphins of New Zealand and Australia An identification guide, Victoria University Press, Wellington, New Zealand. Baker, C. S., S. R Pa1umbi, R H. Lambertson, M, T. Weinrich, J. Calambokidis, and S. J. O'Brien. 1990. Influence of seasonal migration on geographic distribution of mitochondrial DNA haplotypes in humpback whales. Nature 344:238-240.