Vol 2 #4 - Gobioid Research Institute

JIGS Vol. 2 No. 4
July 2003
Round Gobies in Captivity
Before working with live round gobies, consult local state or
provincial laws. In North America, it is generally illegal to
possess live round gobies, either as bait or for aquarium use.
The reason for these laws is to prevent accidental or intentional introductions to areas where they do not yet occur.
However, if you would like to see captive round gobies, they
may be observed at public aquariums such as the Shedd
Aquarium in Chicago, Illinois.
Patricia Arseneault lives in Windsor, Ontario and is a wildlife
rehabilitator for the Canadian Ministry of Natural Resources.
Someone turned in a live round goby to her organization,
which she kept in a 75 gallon community aquarium. (This was
legal because of her state permit - assuming of course, that she
not release the goby.) She found the new acquisition to be a
delightful and endearing aquarium specimen; easy to feed with
flake food, frozen brineshrimp and bloodworms. She was most
highly impressed by its awareness to its surroundings, ability to
recognize her as a food source, and ability to change color and
pattern rapidly.
She wrote: “When I first received him, he was a light olive
green with a very striking darker pattern (similar to the checkerboard pattern on a fox snake). My tank bottom is sand with
tons of plants. Within a few hours of placing him in the tank,
he changed to a light brown with a green undertone and the
pattern was pretty well gone. It happened so fast I wasn't even
sure afterward that he had been a different color.”
Unfortunately, an electrical mishap caused an early demise to
some of Pat’s favorite fishes, including her round goby.
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The Journal of the
International Goby Society
Vol. 2 No. 4 July 2003
JIGS Vol. 2 No. 4
July 2003
JIGS Vol. 2 No. 4
July 2003
Why Control Round Gobies?
ISSN 1543-7744
————————————————————————–
The Journal of the International Goby Society (JIGS) is the
quarterly publication of the International Goby Society (IGS).
Non-profit organizations may reprint articles, however we ask
that you contact the editor before doing so.
Editor: Naomi R. Delventhal
[email protected] or [email protected]
International Goby Society, P.O. Box 329, Richland Center,
WI 53581, USA
—————————————————————————
Our scientific advisors:
Dr. Helen K. Larson Indo-Pacific and Australian Gobies
Dr. Richard Winterbottom Indo-Pacific Reef Gobies
Dr. James L. Van Tassell Atlantic and Eastern Pacific Gobies
Dr. Robert A. Patzner Mediterranean Gobies
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Contents
Editor’s Introduction……………………………………….3
Goby Queries………………………………………………4
Mudskippers: The Periophthalmus species, Part 3………..9
By Richard Mleczko
The Round Goby…………………………………………..13
By Naomi Delventhal
2
There are at least two major potential problems with the round
goby’s presence in the Great Lakes. One is their competitive
advantage over native species. Round gobies are more
efficient feeders and also more aggressive than native darters
and sculpins. The also reproduce more quickly. Unlike
native sculpins, female round gobies spawn more than once
per season. In some places, they have been shown to reduce
the populations of these small native fishes.
Another major problem of round gobies is their affect on the
food web. As I mentioned earlier, round gobies are efficient
consumers of zebra mussels. Larger fish eat round gobies,
which sounds like a good situation, since zebra mussels are
not usually available in useable form to native fishes.
Unfortunately, this may cause serious problems because zebra
mussels are filter feeders that take in large quantities of fine
suspended material. Pollutants (such as mercury and PCBs)
ingested by these mollusks build up in the bodies of the round
gobies and are further concentrated in the piscivorous fish that
eat them. Eventually these pollutants may be taken in by
water birds or humans that eat the larger fish.
Because of these negative effects, most ecologists and
fisheries biologists believe it is important that the round goby
not spread to other areas - particularly the Mississippi river
and its drainage basin.
For more information on round gobies, including many
technical papers from which information for this article was
drawn, visit the Sea Grant Nonindigenous Species Site:
http://www.sgnis.org/update/goby.htm
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JIGS Vol. 2 No. 4
July 2003
Life History of the Round Goby
In both their native and introduced habitats, round gobies
typically migrate to deeper water during the winter and
shallow water during the spring to spawn. Each female
spawns several times per season; males select cave-like
structures as nests. Males attract the females by a mating call
- not what most of us usually expect of a fish, although round
gobies are not unique in this regard. Males take on a dark
coloration during breeding season, when they are
spawning and guarding eggs. It is thought that the males die
after one breeding season.
Round gobies lay large (about 3.5 mm) eggs which hatch in
2-3 weeks, depending on temperature. Unlike with most
gobies, there is no planktonic larval stage - the newly hatched
fry are already more than half a centimeter long and
immediately hop about on the bottom like the adults. They
stay in the nest, however, for a few days before moving on.
Round goby development before hatching is indeed amazing.
While still an embryo, the goby’s digestive system becomes
functional, and while in the egg it actually swallows yolk
material, digests some of it, and excretes the remainder! No
other gobies are reported to have such a development.
Round gobies are primarily carnivores that consume a range
of bottom dwelling organisms - including insect larvae,
crustaceans, small fish, fish eggs, and mollusks. This last
item is especially important in their diet, because round
gobies are efficient predators of another nonindigenous
nuisance species, the zebra mussel.
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JIGS Vol. 2 No. 4
July 2003
Editor’s Introduction
This issue marks the end of the second year of JIGS, and looking
back it has been a very interesting experience being editor. But it
takes much more than an editor to make a good newsletter. I am
indebted to all of my readers - both gobiologists and aquarists for comments, questions, articles, and for simply reading this
modest publication. It’s not always easy to publish a goby newsletter, and sometimes I wonder how I manage to balance it with
family, friends, 20 tanks of gobies, and my education. I thank all
of you readers for your support - and for helping to make the
International Goby Society and this publication a reality.
Naomi Delventhal
31 July 2003
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Cover photos: (Top) Gobiodon rivulatus, with its host coral.
Photo by Phil Munday. (Bottom) Gobiodon histrio, in
aquarium. Photo by Takahiko Mukai.
Regarding the mix-up of the two species, Rick Winterbottom,
who studies Gobiodon taxonomy, explains the history: “The
confusion of G. rivulatus with G. histrio (a later name, and valid)
came about because in the original description of G. rivulatus,
Rüppell stated that it was green with red bars - and juveniles can
be that, although I have never seen a green and red adult. This
was picked up by Jack Randall, who identified his photo of G.
histrio as G. rivulatus in his book on Red Sea fishes (both occur
there). But Tony Harold has examined Rüppell’s type specimens
of G. rivulatus, and they are the species with wavy thin bars on
the head and the body. I went back to Rüppell’s original description (in German), and the translation relating to the colour pattern
reads: ‘Ground colour of whole body emerald green, with a carmin-red labyrinth-like pattern of lines, all fins grass-green.’ So
you can see how easy it is to go wrong!”
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Goby Queries
Q.
I really like clown gobies, and want to set up a tank just
for them. Should they be kept with live corals? If I keep the
red, green, and yellow ones together will they hybridize? Can
they be bred easily in captivity, like neon gobies?
A. The variously colored coral gobies (Gobiodon spp.) are
comprised of 16 valid species, with several additional species
awaiting formal description. Most aquarium dealers in the
USA sell them as inexpensive beginner’s fishes, lumping them
all together under the name “clown gobies.” This lack of attention is a pity, since they are a fascinating group of reef
gobies. Species I’ve seen offered for sale include G. axillaris
(brownish with somewhat indistinct red bands on the head),
G. citrinus (various shades of yellow to almost black with
narrow, well-defined “electric blue” bands on the head and
similarly colored stripes at the bases of the dorsal and anal
fins), G. histrio (green with wide red bands on the head and
red stripes/spots on the body), G. okinawae (bright yellow
with no stripes or bands), and G. quinquestrigatus (red with
pale, narrow vertical lines on the head and a darker body and
fins). G. rivulatus is similar to G. quinquestrigatus, but has
narrow wavy lines on the body, as well. This species has been
confused with G. histrio (see note under introduction). Other
species may also show up from time to time in the trade.
In nature, these small, highly compressed gobies are usually
associated with branching corals of the genus Acropora. If
you are a skilled reef aquarist, a coral set-up is possible,
although the gobies may irritate the corals by constantly
sitting on them and there is some evidence that the natural
diet includes tissue from the host coral itself. Otherwise, the
4
Above: Inside of the Round Goby Watch Card, an example of
the efforts being made to increase public awareness of the
round goby’s presence as an invasive species.
All images used by permission of Minnesota Sea Grant.
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Gobiodon okinawae, the most popular of the coral gobies in the hobby.
Compared with other Gobiodon species, they are bolder and more likely to
live in groups. Photo by Takahiko Mukai.
Top: Cover side of the Round Goby Watch Card, which is
often displayed in libraries and distributed free by Sea Grant
in the Great Lakes region.
Below: Back side of the Round Goby Watch Card, showing
how to identify round gobies.
16
fish should be provided with artificial corals, coral skeletons,
or branching type rock. These gobies will learn to accept a
range of small drifting foods, but if they seem reluctant to eat
at first, they should be offered live brineshrimp.
It’s not easy to say whether different Gobiodon species would
hybridize in aquaria. I have never heard a report of this
happening and no hybrids have yet been identified in the wild.
Coloration is usually important in goby courtship, and most
Gobiodon species are distinct in coloration. According to
Phil Munday, who studies the ecology of these gobies, another
thing working against hybridization in the field is that species
of Gobiodon have distinct patterns of habitat use (i.e. which
coral colonies they inhabit), which means some species
combinations are unlikely to ever occur in nature. Furthermore, a number of species might prefer the same species of
corals but it is uncommon to find mixed species groups. This
means the opportunities for interbreeding are not great. For
example, G. histrio and G. axillaris both prefer to live in
Acropora nasuta but you rarely find them in the same coral
colony even in places where both species are very abundant.
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There only is one species, G. unicolor, that is commonly found
to inhabit coral colonies with other species of Gobiodon.
Like many other reef fishes, these gobies are hermaphrodites,
and several species have been shown to be capable of sex
change in both directions. In most species there is one
mature breeding pair per coral colony, with immature fish
being females. The ability to change sex is advantageous to
the wild gobies - if one of a pair dies, the remaining individual does not need to travel as far to find another potential
mate, thus reducing the risk of predation.
The ability of Gobiodon to change sex is also advantageous to
aquarists who wish to breed them in captivity, since
(theoretically, at least) any two fish will become a malefemale pair. In captivity they can be kept either as pairs or in
a harem, although in some species only the dominant pair
spawns. Coral gobies reproduce readily in aquaria, laying
their eggs on corals (or in the absence of corals, on rocks, or
even on the aquarium glass). Raising the young is another
matter. The larvae are small and the best rearing success has
been reported using large, microalgae filled tanks and rotifers
as first food.
Q.
What can you tell me about sexual dimorphism in
bumblebee gobies? Also, I’ve been using “aquarium grade”
rock salt for their water, but guessing at the quantities. How
much (spoonfuls or weight) per 10 gallons? I’ve recently
added a “dragon fish” (Gobioides broussoneti). The only info
I can find says they’re from North America (where?), grow to
19 inches and eat worms, etc. Anything you can add?
J.R. Erickson
Gavilan Hills, California
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The tubenose goby (Proterorhinus marmoratus), a smaller
goby species (endangered in the Black and Caspian Seas) has
also recently been found in the St. Clair River. However, it
has not spread as quickly as the round goby, and being a less
aggressive fish, has not caused as much concern among
ecologists and fisheries biologists.
In North America, round gobies are often found in habitats of
larger stones and rubble. In Chicago, Illinois, I observed
numerous round gobies in rocky areas less than a meter deep.
Local fishermen reported that they are easy to catch if bait is
allowed to sink. In some parts of their introduced range round
gobies are extremely abundant, but in other areas maintain
only low populations. In Green Bay, Wisconsin, I fished for
round gobies but did not catch any (only one was reported
caught in the bay during the three days I was there). But
farther north in Sturgeon Bay anglers catch so many round
gobies they find them quite annoying!
Interesting Facts About the Round Goby
Like many other gobies, the round goby has fused pelvic fins
and lacks a swim bladder. It therefore maintains a bottom
dwelling lifestyle, generally resting on the substrate. Also
typical of gobies, it has a canal system on the head, but only
superficial neuromasts on the body (instead of a true lateral
line where the neuromasts are enclosed in a canal system).
This sensory system is ideal for night feeding, and helps give
the round goby a competitive advantage over native benthic
fishes with similar habitat needs, including sculpins (family
Cottidae) and darters (Etheostoma and Percina spp.). It is
large for a goby, with the maximum size reported about 30
cm, but usually remains significantly smaller.
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Stowaway!
The round goby is native to Eurasia, where it is found in areas
of the Caspian Sea, the Black Sea and other bodies of water
including larger rivers. It has a high tolerance for a range of
environmental conditions such as salinity and temperature. In
many parts of its native range, the waters have become highly
polluted due to industry.
Like many other invasive aquatic species, the round goby is
thought to have arrived in the Great Lakes as an accident - in
this case, as a stowaway in the ballast water of ships traveling
from Eurasia, probably during the late 1980s. The fish (or
their eggs) most likely were taken in with the ballast water of
a transatlantic vessel, and survived the journey across the
ocean to be dumped into a new habitat. As with other organisms, an obvious responsibility of individual round gobies is
to survive and multiply, which is exactly what they did,
having found the new habitat to be quite suitable for both
activities.
In North America, round gobies were first captured in the St.
Clair River (between Lake Huron and Lake St. Clair) in 1990.
Within a space of five years, the round goby had found its
way to each of the five Great Lakes. What hastened the speed
of its spread is thought to be the same mechanism which
brought it to North America in the first place. Ships traveling
within the Great Lakes also take in large quantities of
(sometimes goby-laden) water, discharging it in other
locations along with its piscine passengers. The same year
round gobies showed up in the St. Clair River, they were
discovered for the first time in the Gulf of Gdansk in the
Baltic Sea (Poland) - again showing their ability to establish
themselves in new locations.
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A.
The most reliable way to distinguish the male and
female of most goby species (including bumblebee gobies) is
by observing the shape of the urogenital papilla. This small
structure is located just after the vent and in front of the anal
fin. In males, it is pointed and often curved; in females it is
shorter, thicker, and blunt. Unfortunately, it is not always
easily visible until spawning time is near. In female bumblebee gobies, the developing eggs are often visible through the
yellow band on the belly, and a highly gravid female is easy to
identify. In my experience, the males of Brachygobius doriae
(the species most often sold) tend to be more orange in the
yellow bands, while the females are paler yellow. During
courtship, the dark bands of both sexes become pale, leaving
the male with an overall yellow-orange appearance, and the
female looking faded yellow and gray.
Regarding the ideal salt concentration for bumblebees,
B. doriae can survive in water that is entirely fresh to over 1/4
strength seawater. Usually, I prefer to keep them in the lower
range, since in nature they are found primarily in freshwater.
A little salt does help prevent disease, especially in softer
water; 1-3 teaspoons per gallon is appropriate.
Gobiodes broussoneti (known by several common names,
although “violet goby” is preferred) has a wide distribution
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JIGS Vol. 2 No. 4
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Gobiodes broussoneti is known by several names, including violet goby,
dragon goby, and dragon eel.
JIGS Vol. 2 No. 4
July 2003
The Round Goby:
When a Good Fish Ends Up In the Wrong Place
By Naomi Delventhal
[email protected]
There aren’t any gobies native to my home state, Wisconsin.
on the Atlantic side of the Americas, ranging from South
Carolina in the north to Brazil in the South. It has been
known to grow to about 20 inches, but rarely exceeds 12
inches in captivity. Violet gobies do better in more strongly
brackish water than do bumblebee gobies, about 1/3 strength
seawater. They also should be kept in cooler water (about
65—75 degrees); bumblebees do best at warmer temperatures
in the mid 80s. For these reasons they do not make ideal tank
mates.
Violet gobies are best kept in larger (at least 48 inch) tanks
with a soft, sandy substrate and rocks or pipes for burrowing.
Probably the most common problem people have keeping violet gobies in captivity is starvation. Violet gobies don’t feed
by sight, but rather by shoveling the substrate for edibles and
gulping mouthfuls of water. In community tanks, the other
fish usually find all the food before the violet gobies come out
of hiding. This can be prevented by feeding the violet gobies
after the lights have gone out. Violet gobies learn to eat a
range of sinking foods, but newly introduced individuals often
require blackworms.
8
And, until a few years ago, we didn’t have any gobies at all in
Wisconsin waters. This changed, however, when the round
goby (Neogobius melanostomus) came to the Great Lakes.
Now, in Wisconsin as well as the other states and provinces
that border the Great Lakes, the round goby has become a
permanent resident, and it is closely studied and monitored for
possible negative effects on native fishes.
In some of these Great Lakes areas, the word “goby” alone
means one thing – the round goby. In fact, the round goby’s
infamous reputation has gone far beyond those places where it
has colonized. Try doing an Internet search using Google,
and you will find more “hits” for the round goby than any
other goby species. (This is in part due to the efforts of
agencies such as Sea Grant, which publicize information on
invasive species.)
Biological invasions have been a normal part of history, but in
recent centuries they have increased in frequency because of
human activities. It is unlikely that the round goby will cause
an ecological disaster on the magnitude of that caused by the
Nile perch in Lake Victoria in Africa. But what has made the
round goby a successful invader? And what will be the long
term effects of its presence in the Great Lakes? These are fascinating and important questions, and we don’t have all the
answers yet.
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King, R.P. and M. T. Udo. 1997. Vegetational succession - mediated
spatial heterogeneity in the environmental biology of Periophthalmus Barbarus (Gobiidae) in the estuarine swamps of Imo estuary, Nigeria. International journal of surface mining, reclamation and environment,
Volume11.
Steeger, H.U. and C. R. Bridges. 1995. A method for long-term measurement of respiration in intertidal fishes during simulated intertidal conditions. Journal of Fish Biology, volume 47.
Udo, M.T. 2002. Trophic attributes of the mudskipper Periophthalmus
barbarus (Gobiidae: Oxudercinae) in the mangrove swamps of Imo estuary, Nigeria. Environmental Sciences (China), 14(4).
JIGS Vol. 2 No. 4
July 2003
Mudskippers The Periophthalmus Species
Part 3
Periophthalmus barbarus
By Richard Mleczko
[email protected]
Udo, M.T. 2002. Morphometric relationships and reproductive maturation
of the mudskipper Periophthalmus barbarus from subsistence catches in
the mangrove swamps of IMO estuary, Nigeria. Environmental Sciences
(China), 14(2).
Udo, M.T. 2002. Intersexual plasticity in aspects of the biology of the
mudskipper Periophthalmus barbarus (Gobiidae) in the mangrove swamps
of IMO Estuary, Nigeria. Environmental Sciences (China), 14(1).
Photo by Richard Markham
Species identification: Linnaeus 1766.
P. barbarus in captivity. Photo by Marli Tanobe
About the Author
Richard Mleczko is a hobbyist who knows what he’s talking
about. Visit his Mudskipper and Goby Website at
http://members.ozemail.com.au/~thebobo/goby.htm
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Species name: The name barbarus is from the Greek
barbaros, meaning foreign, possibly referring to the marked
differences between this species and other gobies.
Other used names: Gobius barbarus, Gobius koelreuteri,
Periophthalmus koelreuteri, Periophthalmus papilio,
Periophthalmus papillon, Periophthalmus gabonicus,
Periophthalmus erythronemus.
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JIGS Vol. 2 No. 4
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Common names: Atlantic
mudskipper, Butterfly mudskipper, Tokouintokouin
(Benin), Adi, Soetsi, Lamole
(Ghana).
July 2003
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Periophthalmus barbarus featured in the literature.
Compiled by Richard Mleczko
Etim, L., T. Brey and W. Arntz. 1996. A seminal study of the dynamics
of a mudskipper (Periophthalmus papilio) population in the Cross River,
Nigeria. Netherlands Journal of Aquatic Ecology, 30(1).
Distribution: Known only
from West Africa; Gambia,
Senegal, Benin, Nigeria, Angola and the Gulf of Guinea
Islands.
Photo by Marli Tanobe
Distinguishing features: One of the only two Periophthalmus species to have blue in the first dorsal fin. Brilliant blue
spots on face and some blue vertical stripes on the body.
Physical characteristics: Typical
length range 10 to 20 cm. First dorsal
fin has 10 to 14 spines, second dorsal
fin has 11 to 14 elements. Anal fin
has 9 to 11 elements.
The pelvic fins of
P. barbarus
JIGS Vol. 2 No. 4
Sexual dimorphism: The genital papilla is broader and the free end more
rounded in females, on average the
height of the first dorsal fin is greater
in males.
Aquarium suitability: Very good, most often exported to
Europe and the United States.
10
Etim, L, R.P. King and M.T. Udo. 2002. Breeding, growth, mortality and
yield of the mudskipper Periophthalmus barbarus (Linneaus 1766)
(Teleostei: Gobiidae) in the Imo River estuary, Nigeria. Fisheries Research, 56(3).
King, R.P. 1996. Population dynamics of the Mud Skipper Periophthalmus
barbarus (Gobiidae) in the Estuarine Swamp of Cross River, Nigeria.
Journal of Aquatic Sciences, volume 11.
King, R.P. and M. T. Udo. 2001. Fecundity of the mudskipper Periophthalmus barbarus (Gobiidae) in Imo River, Nigeria. Archive of Fishery and Marine Research, 49(2).
King, R.P. and M. T. Udo. 1998. Dynamics in the length-weight parameters of the mudskipper Periophthalmus barbarus (Gobiidae), in Imo River
estuary, Nigeria. Helgolander Meeresuntersuchungen, 52(2).
King, R.P. and M. T. Udo. 1998. Ovarian morphogenesis, breeding cycle
and fecundity of the mudskipper Periophthalmus barbarus in the Imo
River estuary, Nigeria. African Fishes and Fisheries Diversity and Utilisation, FISA, Grahamstown, South Africa.
King, R.P. and M. T. Udo. 1998. Seasonality in diet and foraging performance of the mudskipper, Periophthalmus barbarus (Gobiidae) in the
Imo River estuary, Nigeria. Fish and Fisheries of Southeastern Nigeria.
King, R.P. and M. T. Udo. 1997. Some aspects of the reproductive biology of the endangered mudskipper, Periophthalmus barbarus (Gobiidae),
in Imo River estuary, Nigeria. Trans. Nig. Soc. Biol. Conserv, Volume 50.
11