POSTLARVAL SETTLING BEHAVIOR, SUBSTRATE PREFERENCE, AND TIME TO METAMORPHOSIS FOR RED KING CRAB PARALITHODES CAMTSCHATICUS

Swimming behavior was observed and substrate preference determined for glaucothoe stage postlarvae of the red king crab Paralithodes camtsch aticus in the laboratory. One hundred 1 d old glaucothoe were placed i nto each of 3 replicate 10 l aquaria, each containing a choice of 3 su bstrates: sand. gravel, or synthetic fiber mesh. Glaucothoe began sett ling on the first day, and <10% remained swimming after Day 6. Glaucot hoe showed a significant preference for the structurally complex mesh substrate. Occupancy of mesh increased from 49% on Day 2 to 75% by met amorphosis to the first crab (C1) instar, with a mean of 62 +/- 11%. G laucothoe rejected sand, and only 1% were observed on it. Settlement w as also tested in aquaria with only sand, gravel or mesh substrates. G laucothoe in gravel- or mesh-only aquaria settled rapidly, whereas 40% of glaucothoe in the sand-only aquarium continued swimming until meta morphosis to C1 instar. In addition, mean time-to-metamorphosis in the sand-only aquarium (17.6 d) was significantly greater than in other e xperimental aquaria (16.8 d). Glaucothoe in the sand-only aquarium exh ibited marked diurnal swimming behavior; 66% were swimming at 14:00 h (vs a maximum of 12% in other aquaria), but only 5% (vs 1%) were swimm ing at 02:00 h. Daytime swimming probably allows glaucothoe to avoid n octurnal predators while searching for preferred substrates, i.e. thos e which are structurally complex, can be easily grasped, and provide a high degree of interstitial space.