560 



Abstract — The timing and duration 

 of the reproductive cycle of Atka mack- 

 erel (Pleurogrammus monopterygius) 

 was validated by using observations 

 from time-lapse video and data from 

 archival tags, and the start, peak, and 

 end of spawning and hatching were 

 determined from an incubation model 

 with aged egg samples and empiri- 

 cal incubation times ranging from 

 44 days at a water temperature of 

 9.85°C to 100 days at 3.89°C. From 

 June to July, males ceased diel verti- 

 cal movements, aggregated in nesting 

 colonies, and established territories. 

 Spawning began in late July, ended 

 in mid-October, and peaked in early 

 September. The male egg-brooding 

 period that followed continued from 

 late November to mid-January and 

 duration was highly dependent on 

 embryonic development as affected 

 by ambient water temperature. Males 

 exhibited brooding behavior for pro- 

 tracted periods at water depths from 

 23 to 117 m where average daily water 

 temperatures ranged from 4.0° to 

 6.2°C. Knowledge about the timing 

 of the reproductive cycle provides a 

 framework for conserving Atka mack- 

 erel populations and investigating 

 the physical and biological processes 

 influencing recruitment. 



Timing and duration of mating and 

 brooding periods of Atka mackerel 

 (Pleurogrammus monopterygius) 

 in the North Pacific Ocean 



Robert R. Lauth' (contact author) 



Jared Guthridge^-' 



Dan NichoP 



Scott W. McEntire' 



Nicola Hillgruber^ 



Email address for R. R. Lauth: Bob.Lauth(a)noaa.gov 



' National Oceanic and Atmospheric Administration 

 National Manne Fisheries Service 

 Alaska Fisheries Science Center 



Resource Assessment and Conservation Engineering Division 

 7600 Sand Point Way NE 

 Seattle, Washington 98115 



^ Alaska SeaLife Center 

 301 Railway Avenue 

 Seward, Alaska 99664 



5 School ol Fisheries and Ocean Sciences 

 University ol Alaska Fairbanks 

 11120 Glacier Highway 

 Juneau, Alaska 99801 



Manuscript submitted 23 February 2007 to 

 the Scientific Editor's Office. 



Manuscript approved for publication 

 24 July 2007 by the Scientific Editor. 



Fish. Bull. 105:.560-570 (2007). 



Atka mackerel (Pleurogrammus mon- 

 opterygius) is distributed along the 

 edges of the North Pacific Ocean and 

 adjoining basins in rocky shelf regions 

 near landmasses and archipelagos, 

 and in rocky reefs atop prominent 

 bathymetric features rising from the 

 sea floor (Rutenberg, 1962; Allen and 

 Smith, 1988). Atka mackerel is one 

 of the most abundant groundfish in 

 the central and western North Pacific 

 Ocean (Zenger, 2004) where it is a key 

 prey item for marine fishes, birds, and 

 mammals (Murie, 1959; Kenyon, 1965; 

 Sinclair and Zeppelin, 2002). Modern 

 large-scale commercial trawling by 

 U.S. and foreign fishing vessels began 

 during the latter half of the twentieth 

 century, and since the end of the joint 

 venture fishing in 1989, total landings 

 of U.S. fishing vessels have averaged 

 54,000 metric tons annually (Lowe et 

 al., 2006). 



Knowledge about the timing of the 

 reproductive cycle and temporal use 

 of nesting habitat is essential for un- 

 derstanding processes affecting the 

 recruitment and population dynam- 

 ics of Atka mackerel, and for mak- 

 ing management decisions regarding 



commercial fishing activity. Despite 

 Atka mackerel's relatively high abun- 

 dance and value to the ecosystem, 

 surprisingly little is known about 

 its life history and ecology. Access to 

 Atka mackerel is difficult and costly 

 because the species inhabits a vast 

 and remote region that is notorious 

 for inclement weather and rough seas. 

 Studies on the reproductive biology of 

 Atka mackerel are further limited by 

 a general lack of knowledge about the 

 location of spawning and nesting sites 

 in these remote areas. In the eastern 

 North Pacific Ocean off the coast of 

 Kamchatka Peninsula, there are only 

 a handful of known spawning and 

 nesting sites (Zolotov, 1993), and in 

 the central and eastern North Pacific 

 Ocean, the geographic and bathymet- 

 ric distribution of spawning and nest- 

 ing sites was completely unknown un- 

 til recently (Lauth et al., in press). 



Previously published studies have 

 used ovarian condition to determine 

 the start and end of the spawning 

 period (Gorbunova, 1962; Zolotov, 

 1993; McDermott and Lowe, 1997), 

 but very little has been done to in- 

 vestigate the time spent by males in 



