[Coral-List] fish and algae

Bill Allison allison.billiam at gmail.com
Tue Feb 18 08:07:12 EST 2014

Hi Dennis,

No doubt damsels kill coral. As you suggest, it is most likely that
underlying causes such as bleaching, pollution, and overfishing tilt the
playing field too allow more coral destruction, or less construction, or
both, but it's much more satisfying spiritually and economically to have a
critter to blame and kill, non?

On several reefs that I have surveyed over time corals survived only in
Stegastes nigricans territories after repeat COT outbreaks (I also noticed
coral survival in damsel territories after the 1998 bleaching). During the
second COT outbreak all the preferred COT prey were gone and the COT were
eating whatever was left. Some coral colonies within but near the periphery
of S. nigricans territories were damaged along their outer edges but apart
from that, corals in S. nigricans territories survived these invasions
unscathed. I am not the first to have noticed this (e.g., Glynn and Colgan,

Glynn, P. W. and M. W. Colgan (1988). "Defense of corals and enhancement of
coral diversity by territorial damselfish." Proc. 6th ICRS, Townsville 2:

On Sun, Feb 16, 2014 at 5:56 PM, Dennis Hubbard
<dennis.hubbard at oberlin.edu>wrote:

> When I was a young reef geologist, I was told by most biologists visiting
> West Indies Lab that Damselfish "farm" the algal turfs and actually crop
> them for maximum yield. As such, they help maintain this autotrophic system
> which transforms organic carbon and nutrient into a form (algal tissue)
> that can work its way up the food chain. Walter Adey used turfs to maintain
> balance in his "microcosms" at the Smithsonian, has been a valued
> consultant to aquaria (including the large GBR tank) and has received
> patents for "algal scrubbers". So my sense was that the service provided by
> both the turfs and the fish that regulated them is still recognized.
> I was just looking for photos to shamelessly use for class and came across
> an NPR piece (*Tiny Damselfish May Destroy a Ree*f) dated August 11 in
> which Richard Harris (who regularly appears on *Morning Edition* and *All
> Things Considered*) described a "war going on between corals and 'a
> creeping menace'.... algae". This crux of the story is that parrotfish are
> the "allies of coral" and 'damselfish promote algal growth by killing coral
> to create new space for algal colonization'. Enter the fishermen who have
> taken out the predators who used to "keep the damselfish in check". The
> result is that damselfish are disproportionately opening up more space by
> killing corals while scaring off the "coral-friendly" parrots by shear
> tenacity.
> Might anyone put this into perspective for me so I don't tell a story that
> is no longer true? Each of these points has a ring of truth... overfishing
> is real and algae can inhibit coral recruitment. However, the
> transformation of damsels from fish "tending their gardens" to "the primary
> ally of the creeping manace" seems a bit dramatic. It also seems to
> conflate algal turfs (which I understand the damsels are cultivating) and
> macroalgae (which can be equally damaging to both corals and turfs by
> shading and a host of other pathways).
> As I hope to get to this in about a week in class, I'd appreciate it if
> folks who are closer to this can give me a sense of whether eradicating
> algal turfs and the scurrilous damselfish that encourage them is the new
> reef paradigm. If there is a place I can send a smart undergraduate (not
> necessarily a NS student) to read about this new balance, that would be
> even better. What I have read has argued that there are ties between
> macro-algal proliferation and both overfishing and increased nutrient
> input. While there have been numerous thoughtful discussions about the
> details of these interactions, I have understood that both of these
> possible linkages are are still considered to act at some level. I can also
> imagine a delicate balance between the benefits of encouraging turfs and
> clearing space by chomping on live coral.... and that fishing has impacted
> this. My question is whether situation portrayed in this NPR interview is
> correct and that the damselfish/turf ralationship shas gon awry to the
> point that we need to stop worrying about lionfish and focus on what I
> agree is, "pound-for-pound", the meanest fish on the reef.
> Dennis
> --
> Dennis Hubbard
> Chair, Dept of Geology-Oberlin College Oberlin OH 44074
> (440) 775-8346
> * "When you get on the wrong train.... every stop is the wrong stop"*
>  Benjamin Stein: "*Ludes, A Ballad of the Drug and the Dream*"
> _______________________________________________
> Coral-List mailing list
> Coral-List at coral.aoml.noaa.gov
> http://coral.aoml.noaa.gov/mailman/listinfo/coral-list

"... the earth is, always has been, and always will be more beautiful than
it is useful." - Ophuls, 1977

More information about the Coral-List mailing list