Nano Gobies

Among the species caught
off the Long Island coast
in the summer, attractively
colored damselfishes like
this Cocoa Damselfish,
Pomacentrus variabilis,
are the most suitable for
domestic aquariums.
approach among invertebrates and fishes, and when it
is applied in a dynamic aquatic environment like the
ocean, it has tremendous dispersal value. Just look at the
diversity of marine life around even the most remote of
tropical islands, or the extensive geographic range of a
single successful species like the Moorish Idol, Zanclus
cornutus, in the Pacific.
Of course, this strategy has its drawbacks, most notably
a very low survival rate among offspring. Furthermore,
if a marine fish larva spawned in an ocean current
like the Gulf Stream is lucky enough to survive its planktonic
stage by avoiding predators and finding enough to
eat in the nutrient-poor tropical water, there is still another
big hurdle to leap, and whether it can do so or not
falls largely to chance. The probability of any individual
larva ending up in a suitable habitat is small. Keep in
mind that most fish species live in relatively shallow water
and maintain a close association with some benthic
substrate (reef, sand, grass bed), but the average depth
of the ocean is more than 12,000 ft (3,790 meters). So
when a larval fish, adrift on the open ocean, reaches that
critical point of settlement—when it needs to leave the
plankton community and head for the substrate to continue
its juvenile development—there’s a good chance it
will be riding on top of the dark, near-freezing waters of
the abyss. Even if a larva is lucky enough to come into
contact with an island, reef, or continental margin, it
still may not reach a place that can provide the requisite
habitat within a suitable climate zone. For the tropical
fishes that end up in the waters off New York, this is
where their luck runs out. Although they may be luckier
than the ones that become stranded over the abyss, in
that they have an opportunity to survive and grow for
at least part of a season, most of them will die when the
water temperature dips below their tolerance threshold.
As soon as the ocean water warms to about 68°F
(20°C), which usually occurs in late June or early July,
the first post-larval tropical fishes can be found in the
shallow waters of any bay that opens directly to the
ocean. Often the first arrivals include groupers (Serranidae),
goatfishes (Mullidae), and jacks (Carangidae).
Other species, including butterflyfishes (Chaetodontidae),
filefishes (Monacanthidae), and bigeyes (Priacanthidae),
tend to show up a few weeks later. As the summer
progresses, the abundance and diversity of tropical
species continues to increase until it reaches its peak
sometime in early September.
For local aquarium hobbyists this phenomenon presents
an opportunity to get a taste of
life on the opposite end of the supply
chain, and although many collectors
will tell you that they do it to save
money on stocking their aquariums,
they won’t think twice about spending
all afternoon (some using diving
and collecting gear worth thousands
of dollars) to outsmart a $3 damselfish
occupying a difficult crevice. At
some of the most popular collecting
sites you can see a steady stream of
bucket- and net-wielding fish col-
Juvenile Spotfin Butterflyfishes,
Chaetodon ocellatus, at Long Island
Aquarium and Exhibition Center,
formerly Atlantis Marine World.
88 CORAL