mEthods for mass
rearing stages i-iv larvae of the american lobster, homarus americanus h.
milne edwards, 1837, in static systems
B.F. Beal, S.R. Chapman-2001
Journal of Shellfish Research, 20(1): 337-346
Abstract:
We conducted a series of five laboratory experiments
(7-18 days in duration) to test the interactive effects of stocking density,
aeration rates, and food types on survival of American lobster (Homarus
americanus) larvae through their first three planktonic stages (I-III) to
the postlarval stage (IV). Experimental units and culture protocols were
designed to replicate a 1:100 scaled-down version of equipment used in
association with a fishermen-sponsored, stock enhancement lobster hatchery
located in Cutler, Maine. The first four trials revealed that extremely high
rates of aeration (ca. 240 mL air/sec) were necessary to distribute larvae
and food sufficiently to reduce cannibalistic encounters; however, the best
survival from stage I-IV (at stocking densities of 7-26/L fed ad libitum
with enriched Artemia) was only 24%. The final experiment (stocking
density =20/L) yielded a mean survival rate (+/- 95% CI) of 75.8 +/- 10.2%
(range = 62.7% to 90.7%, n=6). One important difference between the last and
first four experiments was how stage I larvae were managed prior to their
culture. In the first four trials, unfed larvae were collected from a
relatively small (46cm x 30cm x 20cm), screened capture basket located near
the discharge pipe of a broodstock holding tank at the hatchery where they
may have resided for >12 hr. Larvae used in the final laboratory
experiment were collected directly from the broodstock tank within 30 min
after being liberated from the mother’s swimmerets. Larvae, at relatively
high densities within the screened box, likely had many more cannibalistic
encounters prior to their culture than those collected directly from the
broodstock tank and, therefore, suffered high rates of mortality during the
first four laboratory trials. Mass rearing methods for larval American
lobsters developed in conjunction with these laboratory experiments were
used successfully by staff at the Cutler Marine Hatchery from 1988 to 1992.
During this period, survival from stages I-IV averaged 44%, and
approximately 875,000 stage IV animals were released to the wild. These
culture methods have withstood the test of time as a private lobster
hatchery in Maine adopted our protocols in 1993, and they continue to be in
use. Further, the general techniques described here have been used since
1994 to culture European lobster (Homarus gammarus) at a commercial lobster
hatchery in the southeast of Ireland.
(University of Maine at Machias, 9 O’Brien Avenue,
Machias, Maine 04654, USA, e-mail: bbeal@acad.umm.maine.edu)