15 



Abstract — Fecundity was estimated 

 for shortspine thornyhead (Sebas- 

 toiobus alascanus) and longspine 

 thornyhead (S. altivelis) from the 

 northeastern Pacific Ocean. Fecun- 

 dity was not significantly different 

 between shortspine thornyhead off 

 Alaska and the West Coast of the 

 United States and is described by 

 0.0544 xFL 3978 , where FL=fish fork 

 length (cm). Fecundity was esti- 

 mated for longspine thornyhead off 

 the West Coast of the United States 

 and is described by 0.8890 xFL 3249 . 

 Contrary to expectations for batch 

 spawners, fecundity estimates for 

 each species were not lower for fish 

 collected during the spawning season 

 compared to those collected prior to 

 the spawning season. Stereological 

 and gravimetric fecundity estimation 

 techniques for shortspine thornyhead 

 provided similar results. The stereo- 

 logical method enabled the estimation 

 of fecundity for samples collected ear- 

 lier in ovarian development; however 

 it could not be used for fecundity esti- 

 mation in larger fish. 



Fecundity of shortspine thornyhead 

 (Sebastoiobus alascanus) and longspine 

 thornyhead (5. altivelis) (Scorpaenidae) 

 from the northeastern Pacific Ocean, determined 

 by stereological and gravimetric techniques* 



Daniel W. Cooper 

 Katherine E. Pearson 

 Donald R. Gunderson 



School of Aquatic and Fishery Sciences 



University of Washington 



1122 NE Boat Street 



Seattle, Washington 98105 



Present address (for D W Cooper, contact author): Alaska Fisheries Science Center, F/AKC2 



7600 Sand Point Way NE 

 Seattle, Washington 98115-0700. 



E-mail address (for D W Cooper) dan.cooper@noaa.gov 



Manuscript submitted 15 July 2003 to 

 the Scientific Editor's Office. 



Manuscript approved for publication 



20 September 2003 by the Scientific Editor. 



Fish. Bull. 103:15-22 12005). 



Shortspine thornyhead {Sebastoiobus 

 alascanus) is distributed from the 

 Bering Sea to Baja California (Orr et 

 al., 2000). Longspine thornyhead (S. 

 altivelis) is distributed from the Gulf 

 of Alaska to Baja California (Orr et 

 al., 2000), and a few specimens have 

 recently been collected in the eastern 

 Bering Sea (Hoff and Britt, 2003). 

 Both species are commercially impor- 

 tant (Piner and Methot, 2001; Gaichas 

 and Ianelli, 2003) and inhabit deep 

 waters over the continental shelf and 

 slope. Both shortspine and longspine 

 thornyhead are determinate spawn- 

 ers (Wakefield, 1990; Pearson and 

 Gunderson, 2003), and spawn pelagic, 

 gelatinous egg masses (Pearcy, 1962; 

 Best, 1964; Wakefield, 1990; Wake- 

 field and Smith, 1990). Shortspine 

 thornyhead spawn between April and 

 July in Alaska, and between Decem- 

 ber and May along the West Coast of 

 the United States, whereas longspine 

 spawn between January and April 

 along the West Coast (Pearson and 

 Gunderson, 2003). 



Annual fecundity is used as a mea- 

 sure of reproductive output in fishery 

 population models and life history 

 studies. Accurate annual fecundity 

 estimates require identifying oocytes 

 to be spawned in the current spawn- 

 ing season. For iteroparous spawn- 

 ers, developing oocytes are often 



distinguished from reserve oocytes 

 by diameter or yolk presence (Macer, 

 1974). Collection date for samples is 

 important. If samples are collected 

 too early in oocyte development, some 

 developing oocytes will be indistin- 

 guishable from reserve oocytes, and 

 fecundity will be underestimated. 



In shortspine thornyhead, oo- 

 cyte stages 4-8 are maturing to be 

 spawned in the current spawning sea- 

 son, whereas oocyte stages 1-3 are 

 reserve oocytes to be spawned in fu- 

 ture spawning seasons (Pearson and 

 Gunderson, 2003). Early vitellogenic 

 oocytes (stage 4) overlap in size with 

 late perinucleus (stage 3) reserve oo- 

 cytes (Pearson and Gunderson, 2003). 

 Late vitellogenic oocytes (stage 5) are 

 easily distinguished from reserve oo- 

 cytes. In whole oocytes, neither oo- 

 cyte size nor appearance can be relied 

 on to distinguish stage-3 and early 

 stage-4 oocytes; however stage-3 and 

 stage-4 oocytes can be visually dis- 

 tinguished from histological samples 

 (Pearson and Gunderson, 2003). Em- 

 erson et al. (1990) developed a stereo- 

 logical method to estimate fecundity 



: Contribution 929 from the Joint Insti- 

 tute for the Study of the Atmosphere 

 and Ocean (JISAO), 4909 25 th Ave NE, 

 Seattle, WA. 



