SURVIVAL AND GROWTH OF THE AMERICAN LOBSTER HOMARUS-AMERICANUS FED FORMULATED FEEDS

There may be an opportunity to culture American lobsters (Homarus amer icanus) in Japan using warmed seawater from thermal effluent of power generating stations. Growth parameters for culture lobsters were compa red between groups fed two artificial diets (feed A and feed B) or a s tandard rotational diet. The rotational diet consisted of frozen shrim p, lugworm, and pelleted kuruma prawn feed given on alternate days. Th e principal protein sources for formulated feed A were squid meal, fis h meal, salmon roe meal and prawn meal (in the proportions 43:29:14:14 ), and for formulated feed B the sources were squid meal, fish meal an d shrimp meal (in the proportions 35:29:36). Each diet was given to 14 individually reared juvenile lobsters (13th-14th stage, wet body weig ht ca. 10 g), maintained at 18 +/- 2 degrees C for 150 d. Survival in all three treatments was high (ca. 80%) and not significantly differen t. There were no significant differences between lobsters fed feed A o r B in molting frequency (mean +/- SD: 2.5 +/- 0.5 vs. 2.2 +/- 0.5); w eight gain ration per molt (1.44 +/- 0.05 vs. 1.40 +/- 0.10); total pe rcent weight gain (150 +/- 59% vs. 116 +/- 44%); or, feed conversion r atio (2.0 +/- 0.6 vs. 3.0 +/- 1.1). However, both diets proved inferio r to the rotational diet for all of these factors. Lobsters fed the ro tational diet had an average of 2.9 +/- 0.5 molts, weight gain ration per molt of 1.56 +/- 0.06, total percent weight gain of 376 +/- 67%, a nd a feed conversion ratio of 1.4 +/- 0.3. Lobsters fed feed B develop ed a whitish-blue exoskeleton after 4 - 5 wks, probably due to a carot enoid deficiency, so from day 58 onward, feed B was supplemented with carotenoid oil. The original exoskeleton color recovered after three m olts. Lobster given feed B also seemed to take longer than those recei ving feed A to harden the new exoskeleton after molting. Neither of th e formulated feeds is adequate to replace the rotational diet.