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Vol. 53 - Alaska Resources Library and Information Services

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sampling patterns within the St. George Basin covered similar areas<br />

(Table 6.4). Frequency of occurrence of p<strong>and</strong>alids in 1981 (PROBES) was<br />

relatively high compared to values from 1980 samples. P. borealis was<br />

taken at 38-45% of the stations from 1978, 1980, <strong>and</strong> 1981. P. stenolepis<br />

consistently showed the most variability in frequency of occurrence<br />

from a low of 2% in 1980 to a high of 20% in 1981. P. goniurus <strong>and</strong><br />

P<strong>and</strong>alopsis dispar larvae were taken rarely during 1980 <strong>and</strong> 1981 <strong>and</strong> not<br />

at all in 1978.<br />

Larval Duration.<br />

Zooplankton samples collected in February <strong>and</strong> March<br />

1978 contained no p<strong>and</strong>alid zoeae <strong>and</strong> thus first hatch was assumed to<br />

occur about April 1st. Stage I zoeae of P. borealis were present<br />

throughout the St. George Basin in early April during the first sampling<br />

days of the NOAA 1977, PROBES 1978, 1980 <strong>and</strong> 1981 cruises <strong>and</strong> continued<br />

to be taken as late as mid-May in 1978 <strong>and</strong> 1981. Figure 6.2 shows the<br />

duration of each stage during the PROBES 1981 cruise for P. borealis, P.<br />

tridens <strong>and</strong> P. stenolepis larvae. The intermolt period for P. borealis<br />

was calculated by taking the midpoints of each larval stage duration <strong>and</strong><br />

figuring the difference between adjacent midpoints. Thus 12-20 days<br />

(2-3 weeks) seems to be the average intermolt period for P. borealis<br />

larvae. These zoeae would require approximately 3 months of planktonic<br />

life to accomplish the 5 molts to the megalops stage (VI) <strong>and</strong> to settle<br />

to the benthos. Although the sampling periods of cruises from 1978-1981<br />

did not extend past mid-July, P. borealis larvae would apparently settle<br />

out by mid-August.<br />

Future examination of sameles from the NOAA 1982 summer<br />

cruise will help substantiate the exact length of the larval period.<br />

713

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