Patterns of settlement of larvae and population dynamics
of juveniles are poorly known for coral reef fishes. During
1987 to 1989, I studied these phenomena in the domino
damselfish (Dascyllus albisella), a species endemic to the
Hawaiian Islands. Larvae settle onto branching coral heads
as new recruits (10-15 mm in length), usually with
conspecific groups, and remain on the coral heads through
juvenile life until maturity (70 mm total length). By
conducting experiments on natural patch reefs and on an
artificially distributed grid of coral heads, I found that
most larvae settle at night, and that they settle
preferentially on corals supporting large conspecific groups
compared to small groups or empty corals.
Within a group, juveniles form a linear dominance
hierarchy based on fish size; aggressive interactions are
mainly directed by larger fish towards smaller fish. Tagging
studies demonstrated that growth was retarded in larger
groups and for fish of low social status, but that survival,
especially of new recruits, was enhanced in larger groups.
Therefore, I identified both a growth cost and a survival
benefit to group living. I derived a measure of net benefit
of group living by combining size-specific growth and
survival data into an estimate of the probability of reaching
mature size. This estimate increased with group size in 1988
but not in 1987.
I developed a simulation model which used my field data
on settlement rate, settlement preferences, and juvenile
growth and survival to predict demography of juvenile groups.
The model successfully predicted seasonal fluctuations in
mean group size, and estimated the number of fish maturing in
1987 and 1988, as a function of settlement rate and
preferences and of juvenile growth and survival. Numbers
maturing were directly related to settlement rate in both
years, except at high rates in 1987, suggesting that primary
recruitment limitation of adult numbers could be occurring.
Settlement preferences also influenced numbers maturing. At
all settlement rates, numbers maturing differed between
years, suggesting that secondary recruitment limitation of
adult numbers may also occur. / Graduation date: 1991
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/37099 |
| Date | 25 January 1991 |
| Creators | Booth, David J. (David John), 1958- |
| Contributors | Hixon, Mark A. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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