At. Palma et al., DIFFERENT EARLY POSTSETTLEMENT STRATEGIES BETWEEN AMERICAN LOBSTERS HOMARUS-AMERICANUS AND ROCK CRABS CANCER IRRORATUS IN THE GULF-OF-MAINE, Marine ecology. Progress series, 162, 1998, pp. 215-225
The abundance of many invertebrates with planktonic larval stages can
be determined shortly after they reach the benthos. In this study, we
quantified patterns of abundance and habitat utilization of early bent
hic phases of the American lobster Homarus americanus and the rock cra
b Cancer irroratus. These 2 decapods are among the most common and abu
ndant macroinvertebrates in coastal zones of the Gulf of Maine, with s
imilar densities of larger individuals. Settlement and early postsettl
ement survival indicate that lobsters are highly substrate-specific ea
rly in life, settling predominantly in cobble beds. Crabs appear to be
less selective, setting both in cobble and sand. Cumulative settlemen
t of crabs, inferred from weekly censuses over the summer, was an orde
r of magnitude greater than that of lobsters over the same time period
. However, only crabs showed significant postsettlement losses. Althou
gh the identity of specific predators is unknown, predator exclusion e
xperiments and placement of vacant uninhabited nursery habitat suggest
ed that post-settlement mortality rather than emigration was responsib
le for these losses. The selective habitat-seeking behavior and lower
post-settlement mortality of lobsters is consistent with their lower f
ecundity and later onset of reproductive maturity. The patterns observ
ed for crabs, however, suggest a different strategy which is more in a
ccordance with their higher fecundity and earlier onset of maturity. I
t is possible that lower fecundity but greater per-egg investment, alo
ng with strict habitat selection at settlement and lower post-settleme
nt mortality, allows adult lobster populations to equal adult populati
ons of crabs. This occurs despite crabs being more fecund and less hab
itat-selective settlers but sustaining higher postsettlement mortality
.