Lauth et aL: Timing and duration of mating and brooding periods of Pleurogrommus monopterygius 



563 



Values for the total incubation time of a collected egg 

 mass (Z),) were calculated with a best-fit regression equa- 

 tion derived from the laboratory incubation experiments. 



Temperature data sets used for determining a low and 

 high range of D, were obtained from buoys operated by 

 the Eastern Pacific Investigation of Climate Processes 

 (EPIC) program of the NOAA Pacific Marine Environ- 

 mental Laboratory (PMEL; Table 1; Fig. 1). There were 

 two EPIC temperature data sets available for the Am- 

 chitka and Tanaga Island area and five for the Seguam 

 Island area (Table 1). The depths for the EPIC buoy data 

 ranged from 39 to 147 m, which are close to the depth 

 limits where Atka mackerel nesting sites were observed 

 (Lauth et al., in press). In addition to the EPIC data sets 

 for the Seguam Island area, two more temperature data 

 sets were available from a shallow (22 m) and deep (92 

 m) Atka mackerel nesting site (Table 1). The tempera- 

 ture data from the shallow nesting site were collected 

 from the data logger attached to the time-lapse camera 

 and the data from the deep nesting site were collected 

 from an archival tag on a male that exhibited nesting 

 behavior. Daily water temperatures were pooled by area 

 for calculating an average daily water temperature and 

 standard deviation. The minimum and maximum aver- 

 age daily water temperatures from each area for the 

 period 1 July to 15 January were used in the incubation 

 model for the low and high Z),. 



Egg mass spawning and hatching dates were pooled 

 by week and ogives of the pooled data were made for a 

 low and high range of Z), for each egg collection area. 

 To estimate the timing of spawning and nesting periods 

 across the entire geographical region, pooled data for 

 both low and high temperatures from all three areas 

 were proportioned equally, combined, and plotted by 

 relative frequency over time. 



Results 



Direct observation of nesting behavior 



Time-lapse camera The time-lapse camera was used 

 for documenting the arrival of male Atka mackerel at 

 a nesting site near Seguam Island in 2002 (Fig. II. 

 Divers at the site observed no males or Atka mackerel 

 egg masses when the camera was deployed on 31 May, 

 nor were males observed in the camera footage for the 

 first five days. On 5 June, a bright yellow male with 

 black vertical stripes (male nesting coloration) swam 

 across the screen during a 10-second period. There 

 was a similar observation on 6 June. Neither of these 

 males exhibited territorial behavior toward a specific 

 patch of rocky substrate. On 9 June, two males hovered 

 close to the bottom at mid-screen in the background for 

 the entire minute, and on 10 June, one male pursued 

 another Atka mackerel of unknown sex, followed it (off 

 screen), and then returned to mid-screen and hovered 

 for the remainder of the minute. Atka mackerel were 

 not observed with the time-lapse camera for the next 

 two days. On 13 June, a group of three males swam 

 across the screen in the distance. On 14, 15, and 17 

 June, males were observed hovering in the distance 

 or swimming across the screen. On 18 June, a bright 

 yellow male with dark black vertical bands was posi- 

 tioned in front of the camera. The same male was 

 observed in the same area in front of the camera every 

 day after that through 31 August (74 days). Between 

 18 June and 31 August, other males were periodically 

 observed in the background exhibiting nesting behavior. 

 During all three recoveries of the time-lapse camera, 

 divers observed two egg masses within aim radius of 

 the camera mooring. 



