Allen and Franklin Settlement patterns of Atractoscton nobtlis in the Southern California Bight 



641 



control white seabass settlement in the Southern 

 California Bight. Parrish et al. (1981) demonstrated 

 that seasonal effects of the California Current and 

 upwelling in central California had a major effect on 

 the distribution patterns of marine fish. The spawning 

 activities of most fishes coincide with the onshore flow 

 which is characteristic of the late winter and early 

 spring months and transports eggs and larvae into 

 shallow waters. The effects of major hydrographic 

 events on the abundance and distribution of YOY white 

 seabass remain largely unknown. 



The main geographic source of white seabass larvae 

 that settle successfully in southern California is also 

 unknown. Southern California populations of adults 

 may be reduced to the point that they may be only a 

 minor source of larvae. Since larvae remain in the 

 plankton as long as 4-5 weeks, population centers of 

 adults off northern Baja California may constitute the 

 major source of southern California YOY seabass. 

 Thus, successful settlement to southern California 

 waters may depend largely on the northward-flowing, 

 warm-water currents best developed in the summer 

 months. Satellite infrared-imagery data indicated that 

 such a large, warm-water mass moved north along 

 the southern California coastline in early July 1988 

 (Jan Svedkowsky, Ocean Imaging, San Diego, pers. 

 commun.). The resulting dramatic rise in surface and 

 bottom temperatures may have accounted for the 

 marked increase in settlement of white seabass be- 

 tween June and Juiy of that year if the water mass also 

 contained a sufficient number of premetamorphic 

 larvae. Studies of subpopulation structure utilizing 

 restriction fragment length polymorphism (RFLP) 

 analysis of nuclear DNA are currently underway in our 

 laboratory in an attempt to identify the source of 

 newly-settled white seabass in southern California 

 coastal waters. If the main parental population of these 

 fish is located in more southerly waters, joint U.S. and 

 Mexican management efforts may be necessary to pre- 

 vent the decline of these major breeding stocks in the 

 south. 



Acknowledgments 



A study of this magnitude could not have been ac- 

 complished without the support of many people. We 

 thank those who ably assisted with the demanding field 

 work, especially Jan Cordes, Monica Lara, Julia Sears- 

 Hartley, Phyllis Travers, and Lisa Wooninck. The crew 



of the RV Yellowfin, Jim Cvltanovich, Danny Warren, 

 and Dennis Dunn, assisted greatly through their 

 capable handling of vessels in shallow and often tur- 

 bulent waters. Al Ebeling and three anonymous 

 reviewers greatly improved this paper through careful 

 readings and numerous, helpful comments. We also 

 gratefully acknowledge the assistance provided by 

 Steve Crooke and Paul Gregory of the California 

 Department of Fish and Game. This research was sup- 

 ported through contracts with the Ocean Resource 

 Enhancement and Hatchery Program (OREHP) and 

 the Bay, Estuarine, and Nearshore Ecosystem Studies 

 (BENES) program, administered by the California Fish 

 and Game. 



Citations 



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 Donohoe, C. 



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