Biochemical Geneticsof Lobsters: Genetic Variation and the Structure of American Lobster (Homarus americanus)Populations MenrrN L. Tnecev, 1 Kerru Ner-soN, DSNNrs Heocncocr, Ronenr A. Snr-Esen, eNo Meny Lou PnEssrcr University of California, Bodega Marine Laboratory, Bodega Bay, Catif. g4g23, USA Tucev, M. L., K. NEr-soN, D. Hrocecocr, R. A. Snlessn, eNo M. L. pnr.ssrcr. 1975. Biochemical genetics of lobsters: genetic variation and the structure of American lobster Qlomarus americanus) populations. J. Fish. Res. Board Can. 32: 2091-2101 . Eight populations of American lobsters, Homarus americanus, were surveyed for genetic variation at 44 loci encoding electrophoretically detectable proteins. Rather low levels ofgenetic variability were found, the average proportion of heterozygous loci per individual tein[l.A%. Genetic variation is concentrated at only eight loci, with just five loci - Acid phosphitase-1, Esterase-2, Phosphoglucose isomerase4, Phosphoglucomutase-1, andTetrazolium riductase-2 - having proportions ofheterozygotes greater than 207o. Interpopulation differences are small; the genetic identity averaged over all loci,1, is above 0.99 in all butihree comparisons. Differenti- ation between populations was found only at the Malit. enzyme locus, but the degree of this differentiation supports the suggestion from previous migration and morphological itudies that H' americanus is subdivided into a number of more or less geographicalty isolated inshore and offshore populations. These local populations are nonetheless genetically iimilar. TRAcEy, M. L., K. NBr-soN, D. Heocecocx, R. A. SHLespn, eNn M. L. pnessrcr. 1975. Biochemical genetics of lobsters: genetic variation and the structure of American Iobster QTomarus Tmericanus) populations. J. Fish. Res. Board Can. 32:2091-2101. Nous avons 6tudi6, sur huit populations de homards am6ricain, Homarus americanu.s.la variation gdn6tique ill4 loci encodant des prot6ines d6tectables par 6lectrophordse. Les niveau de variabilit6 g6n6tique observ6s sont plut6t bas, la proportion moyenne di loci hft6rozygotes par individu 6tant de 3.8Vo. Lavarialion g6n6tique n'est concentr6e qu'i huit loci, seulement-cinq - acide phosphatase-1, estdrase-2, phosphoglucose isomdrase-i, phosphoglucomutase-l ei titrazolium rdductase-2 - ayant des proportions d'h6t6rozygotes sup6rieures ;a 207o. Les diff6rences entre les populations sont faiblei; la similarit6 g6n6lique 6tabiie comme moyenne de tous les loci, 1, est sup6rieured 0.99 dans toutes les comparaisons,sauf trois. Nous n'avons trouve de diff6rence entre les populations qu'au locus de I'enzyme malique, mais le degrd de cette diff6rentiation appuie I'hypothdse d6coulant d'observations ant6rieures sur les migrations et la morphologie.i I'effet que H. americanus se subdivise en un nombre plus ou moins grand de populations littorales et hauturibres isol6es. Ces populations locales oni n6anmoins une 6troite similarite gdn6tique. Received October 3, 1974 AcceptedJune 17,1975 INsHonn populations of the American lobster, Homarus americanus, exist in commercial con- centrations from North Carolina to Newfound- land. Offshore popr-rlations, to depths in excess of 500 m, are found an the edge of the continental shelf from Ceorges Bank to North Carolina. In- creased fishing effort including the introduction of oflshore trawling has maintained lobster catches (Thor.nas 1973; Hollan<iet ai. 1972), but productivity declines have long been predicted (Herrick 19ll). With decreasins catch per unit 1P.*., ,ddress: Deparr.".r, of niological Sci- ences, Brock University, St. Catharines, Ont. L2S 3At. Printedin Canada(J3586) Imprim6 au Canada(J3586) R.egu le 3 octobre1974 Accept6 Ie l7 iuin 1975 effort, competition for the remaining resources intensifies the need for effective fishery manage- ment which in turn requires knowledge of popu- lation structure. ln particular, evidence that offshore lobsters rri'rate shoalward for egg extrusion and hatching (Ccoper and Lizmann l97l ) has recenrly pro- moted the suspicion ihat offshore trawling may be detrinrental to inshore stocks. Studies of moi- phology and migration, however, suggestthat in- shore stocks are distinct from offshore popula- tions. Saila and Flowers (1969) compare inshore and offshore animals matched by size and sex; they find definite conformational differences. Tagged inshore lobsters appear to be nonmigra- tory, but animals tagged offshore show extensive 2091 J. Fish. Res. Bd. Can. Downloaded from www.nrcresearchpress.com by Renmin University of China on 06/07/13 For personal use only.