LIFE AQUATIC
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FALL 2014
and waiting, might be momentarily confused with
so many identical fish packed into a living, moving
wall. Late in the afternoon the predators become
more active, and their anxious prey pack even closer
together. In contrast to the quickly moving prey fish,
motionless adolescent longfin spadefish frequently
hover above the wide-eyed scad, watching the parade
and perhaps wondering what all the hurry is about.
Each locale offers slightly different environmental
factors — varying depths, light intensities, currents,
plankton availability, nutrient levels, water chemistry,
etc. — that affect which marine life colonizes a
structure. When new pilings are put in place, they
act as open territory, fit for colonization by hundreds
of sessile organisms. In a matter of days, marine life
begins to claim territory upon the thick wood or metal
supports. Barnacles, hydroids, bryozoans, crinoids,
mussels and innumerable barely visible creatures settle
onto the pilings, where certain cues signal for them to
metamorphose into thriving, mature communities. The
quick succession of life shows how prolific larvae are in
the overall tropical marine environment. Evolutionarily,
it pays obvious dividends for a species’ planktonic larvae
to be able to settle and metamorphose immediately
upon sensing the right environmental factors.
In some areas where coral reefs are not profuse,
docks and piers can potentially increase fishery
resources, either by drawing in dispersed populations
of fish or by creating a more suitable habitat for the
escalation of fish populations. Many organisms that
typically live in cavern environments are also found in
the dark cavities of piers and docks.
Considerable variation may be expected in different
portions of one set of docking facilities and certainly
between docks placed in ecologically different situations.
No two docks are ever alike in terms of their aggregated
marine life. Most illuminated spaces will tend to be
monopolized by photosynthetic organisms, and partly
or completely shaded areas are apt to have assemblages
of more unusual animals. Many of the organisms living
under floats or on pilings are those normally found at
deeper parts of the intertidal or subtidal zones. On a
pier or dock, they can live close to the surface without
danger of exposure to intense sunlight.
Just about any structure under which divers (and their
gear) can slither will present strange, bottom-dwelling
critters and unique environmental scenery vastly different
from that of coral reefs. While the Pacific offers any
number of exhilarating dives over bottomless drop-offs,
along deep pinnacles and through swift channels where
large fishes roam, piers and docks are consistently rich in
bizarre, photogenic inhabitants. For photographers these
man-made marine habitats are almost always productive
for both macro and wide-angle photography. Pier pilings,
dock moorings and surrounding habitats are loaded
with the odd creatures for which divers have a special
affinity — from tiny harlequin shrimp to lumpy frogfish
to leaflike waspfish. While many divers focus on a pier’s
smaller critters, larger predators such as resident giant
moray eels or tassled wobbegongs, who appreciate the
culinary abundance at these locations, will also frequently
patrol the waters around these man-made structures.
Each marine ecosystem, each underwater habitat,
each niche with its associated wealth of generalist or
specialist inhabitants is part of the all-encompassing
biosphere. No trophic level or species exists in
isolation. Even piers and docks, which bear various
collections of odd and intriguing creatures and their
own distinctive food webs, are intricately tied to the
open ocean. These structures of wood, concrete, nails,
ropes and tires are merely part of a dynamic puzzle
whose pieces extend from DNA molecules to entire
ecosystems and whose effects radiate through the
world’s oceans.
AD
Caught in the open, schooling
scad are easy targets for
marauding trevally and small
sharks. These silvery prey-fish
often seek refuge under
docks or piers, which attracts
larger predators.
