Lack of biochemical genetic and 

 morpiiometric evidence for discrete 

 stocl<s of IMorthwest Atlantic herring 

 Clupea harengus harengus 



Susan E. Safford 



U.S. Fish and Wildlife Service, P.O. Box 796 Turner's Falls, Massachusetts 01376 

 Present address. Graduate Center of Toxicology, 204 Funkhouser Building 

 University of Kentucky, Lexington, Kentucky 40506-0054 



Henry Booke 



us Fish and Wildlife Service, P.O Box 796, Turner's Falls, Massachusetts 01376 



Historically, herring stock delinea- 

 tion has been based on spawning 

 site because herring are presumed 

 to return to their natal beds to 

 spawn (Sindermann 1979). For ex- 

 ample, Wheeler and Winters (1984) 

 have estimated homing fidelity of 

 spawning herring at 90%. Further- 

 more, some recognition of these 

 historic stocks has been achieved 

 through meristic studies (Anthony 

 1972, Parsons 1975, Cote et al. 

 1980), though these meristic dif- 

 ferences disappear after several 

 years, probably from environmen- 

 tal perturbations (Sindermann 

 1979). These means of defining a 

 stock imply genetic differentiation, 

 but do not measure it. A valid stock 

 definition such as that in Booke 

 (1981), "a species group, or popula- 

 tion, offish that maintains and sus- 

 tains itself over time in a definable 

 area," should include both genetic 

 and geographic isolation. However, 

 for managerial purposes it is often 

 useful to divide large groups of a 

 species into smaller groups, even if 

 genetic or permanent geographic 

 isolation cannot be demonstrated. 

 Managerial units have sometimes 

 been defined as stocks as in An- 

 thony (1972), "a group of fish that 

 remain sufficiently isolated so it can 

 be managed as a unit separate from 

 another one." A population can sub- 

 divide itself into discrete groups, 



which can be individually managed 

 during the period of subdivision, 

 such as a spawning season, even if 

 these groups aren't genetically dif- 

 ferentiated. Therefore, the goal of 

 this study was to determine if the 

 two spawning groups investigated 

 constitute genetically differentiated 

 stocks, and whether these groups 

 could be identified either genotyp- 

 ically or phenotypically, regardless 

 of stock status, outside the spawn- 

 ing grounds. 



The first objective was to deter- 

 mine if herring which spawn in two 

 geographically well-defined areas- 

 Trinity Ledge, Nova Scotia, and 

 Jeffries' Ledge, MA— constituted 

 separate stocks through the demon- 

 stration of genetic differentiation 

 by starch gel electrophoresis of en- 

 zymes. Electrophoretic studies on 

 herring, including specimens from 

 the two spawning grounds sampled 

 in the present study, have been 

 published (Komfield et al. 1981 and 

 1982, Grant 1981 and 1984, King 

 1984). However, lack of standar- 

 dization in technique, which has led 

 to differences in the number and 

 frequency of alleles at the same 

 locus in different studies, makes it 

 difficult to assess the true amount 

 of electrophoretic differentiation 

 among spawning groups. The sec- 

 ond objective was to determine if 

 these same groups of herring were 



separable phenotypically, whether 

 or not genetic differences were 

 detected. Included in this objective 

 was the assessment of the temporal 

 stability of a set of phenotypic char- 

 acters measured over two years. 

 This was important, as most mor- 

 phometric and meristic studies 

 which have indicated that signifi- 

 cant phenotypic differences do exist 

 between spawning groups of her- 

 ring consist of only one year's data 

 (Parsons 1975, Cote et al. 1980, 

 Meng and Stocker 1984). The third 

 and most important objective was 

 to simultaneously measure the 

 amount of electrophoretic and mor- 

 phometric variation in the two 

 spawning groups. Simultaneous 

 performance of both kinds of anal- 

 yses, previously done only by Ry- 

 man et al. (1984) on Northeast 

 Atlantic herring, permits a better 

 understanding of the level of varia- 

 tion between herring spawning 

 groups. 



Materials and methods 



Sampling 



Trinity Ledge (TL) fish were col- 

 lected on 31 August 1983 and 5 Sep- 

 tember 1984, and Jeffries' Ledge 

 (JL) fish on 1 November 1983 and 

 11 October 1984. All fish were 

 taken on spawning grounds (Fig. 1) 

 by commercial fishermen. The fish 

 were transported frozen or packed 

 in ice, and stored at -20°C for 1 

 week to 9 months imtil white mus- 

 cle tissue samples were excised. The 

 tissue samples were stored at 

 -80°C until analyzed electropho- 

 retically. A sample of 100 fish from 

 each collection (400 total) was ana- 

 lyzed electrophoretically. These 

 same fish were also analyzed mor- 

 phometrically, except for 50 TL fish 

 collected in 1983. Poor packing con- 

 ditions made these 50 fish difficult 



Manuscript accepted 23 September 1991, 

 Fishery Bulletin, U.S. 90:203-210 (1992). 



203 



