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Vol. 53 - Alaska Resources Library and Information Services

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Bay <strong>and</strong> west to Cape Newenham. The 1983 population was centered over<br />

Bristol Bay between 50 to 70 m <strong>and</strong>, in general, reflected closely the<br />

abundance of larvae in the water column.<br />

4.1.3 Vertical Distribution<br />

The May time series demonstrated the presence of diel vertical migration<br />

in first stage red king crab zoeae. This behavior had been suggested<br />

previously (Takeuchi 1962, trans. 1967; Haynes 1977), but not quantitatively<br />

documented. Kurata (1960) has suggested that if larval red king<br />

crab vertically migrate, there should be less vertical migration in the<br />

later stages as they adopt a more benthic behavior. No support was<br />

found for any changes in vertical migration for the first three zoeal<br />

stages.<br />

Diel vertical migration in larval decapods may have an important effect<br />

on the horizontal distribution of these stages, particularly in areas<br />

where current direction <strong>and</strong>/or velocity change with depth. Larval blue<br />

crabs (Callinectes sapidus) vertically migrate <strong>and</strong> are thus retained in<br />

Atlantic Coast estuaries where habitat is suitable instead of being<br />

dispersed into the open ocean (Sulkin <strong>and</strong> Van Heukelem 1982). Epifanio<br />

<strong>and</strong> Dittel (1982) hypothesize that successful recruitment of C. sapidus<br />

is due to "the evolution of behaviorial traits (i.e., rhythmic vertical<br />

migration) that allow larvae to take advantage of . . . advective<br />

flows." Cronin <strong>and</strong> Forward (1982) further argue that such rhythmic<br />

behavior may be widespread among estuarine planktonic larvae, particularly<br />

where tides exert strong dynamic effects.<br />

Rhythmic vertical migration in larval red king crabs may have similar<br />

biological significance. Hebard (1959) reported that currents in the<br />

shallow Bristol Bay region are strongly influenced by tides. He further<br />

learned that surface <strong>and</strong> bottom currents there flow in different directions.<br />

Since red king crabs dwell primarily in <strong>and</strong> apparently evolved<br />

in shallow <strong>Alaska</strong>n coastal waters (Makarov 1938) which are characterized<br />

388

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