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Vol. 53 - Alaska Resources Library and Information Services

Vol. 53 - Alaska Resources Library and Information Services

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shallow water for breeding around Kodiak Isl<strong>and</strong> (NOAA 1981; Powell, et<br />

al. 1974; Weber 1967) <strong>and</strong> it is suspected that such migratory behavior<br />

occurs in the southeastern Bering Sea as well. Eggs carried from the<br />

previous year hatch about April 1-20 (Armstrong, et al. 1983b; Haynes<br />

1974; Weber 1967) <strong>and</strong> females soon undergo physiological changes leading<br />

to molt. By pheromone attraction (NOAA 1981) sexually mature males<br />

locate preecdysial females, embrace them for as long as 16 days, <strong>and</strong><br />

mate just after the female molts (Powell, et al. 1974). The nearshore,<br />

shallow water habitat is apparently selected in part for warmer water<br />

temperatures <strong>and</strong> also perhaps greater food supplies. The average<br />

temperatures associated with sexually mature males <strong>and</strong> females are 1.5°<br />

<strong>and</strong> 4°C, respectively (NOAA 1981). Stinson (1975) correlated male <strong>and</strong><br />

female abundance with temperature <strong>and</strong>, from NMFS survey data through<br />

1975, located most sexually mature females inside a 4 ° C isotherm nearshore<br />

off Unimak Isl<strong>and</strong> <strong>and</strong> directly in front of Port Moller. Weber<br />

(1967) summarized data on temperature-related hatchout time <strong>and</strong> development,<br />

noting both regional <strong>and</strong> annual differences in larval appearance<br />

<strong>and</strong> rate of development attributable to temperature variations. Larval<br />

development time can double with a decrease of temperature from 100 to<br />

5°C (Kurata 1960, 1961), <strong>and</strong> an average of 460 degree days (= cumulative<br />

average daily temperature) is required for development from hatch of egg<br />

to metamorphosis of megalops (Kurata 1961).<br />

After molting, a female must be located <strong>and</strong> mated within five days for<br />

viable eggs to be produced. Males are larger than females in 97 percent<br />

of all mating pairs (Powell, et al. 1974), <strong>and</strong> insemination of larger<br />

females by smaller males results in reduced clutch size (egg number).<br />

Any combination of events through natural <strong>and</strong> fishery mortality <strong>and</strong><br />

pollution that substantially reduce numbers of large males at some point<br />

in time could threaten the breeding potential of the species. Reeves<br />

<strong>and</strong> Marasco (1980) estimated that a male-female weight ratio of 1.7 is<br />

required for 100 percent copulation. This estimate is based, in part,<br />

on behavioral observations by Powell, et al. (1974). Below this value,<br />

decreasingly lighter males will have less success breeding large mature<br />

288

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