The introduction of top-minnows (natural enemies of mosquitoes) Into the Hawaiian Islands

Historic, Archive Document

Do not assume content reflects current scientific
knowledge, policies, or practices

Press Bul. 20, Issued July 25, 1907,

Hawaii Agricultural Experiment Station,

EES Ree 2 Se Be S|

JG] SMITH, Sprectat. AGENT IN CHARGE.

PRESS BULLETIN NO. 20.

THE INTRODUCTION OF TOP-MINNOWS
(Natural. Enemies of Mosquitoes)

INTO THE HAWAIIAN ISLANDS.

IN COOPERATION WITH THE BOARD OF HEALTH, TERRITORY OF HAWAII
AND LELAND STANFORD JUNIOR UNIVERSITY.

BY Dis Van’ DINE)

Entomologist, Hawaii Agricultural Experiment Station, United
States Department of Agriculture.

Fig. 1..—Top-Minnow, Mollienesia latipinna. (U.S. Fish
Commission. )

In December, 1902, a survey of Honolulu and vicinity was

begun to determine the character and location of the bodies of

water responsible for the great numbers of mosquitoes that

2

were common at nearly all seasons of the year. The places
in which mosquitoes were found to breed can be classed under
two general heads: (1) Such collections as in containers for
storing water (tubs, barrels, troughs, water-tanks, etc.) ; cess-
pools; surface sewers and the catch-basins; discarded tins,
bottles, and cans in vacant lots and on rubbish heaps; neg-
lected gutters and defective plumbing; and vessels holding
water in and about dwellings and out-houses (flower vases,
drinking cans in chicken yards, containers under table legs
and flower pots, etc.); and (2) the collections of water as taro-
patches; rice fields; reservoirs; irrigation ditches; swamps;
closed pools; ponds; temporary pools formed by storm water
on the lower levels; and pools in the beds of streams during
the dry seasons.

The breeding places included in the first class are responsi-
ble for the larger part of the number of mosquitoes in any
locality. They are entirely responsible for the mosquitoes in
the business section oi the city and in those residential por-
tions that are at any distance removed from the collections of
water enumerated tn the second class of breeding places. To
obtain relief from the mosquitoes that breed in the collec-
tions of water of the first class it is demanded that systematic
inspection work be carried on continuously throughout the
infested district. This inspection must be followed by active
measures of prevention, that is, preventing the development
of the mosquito larvae or wriggiers in any body of water dis-
covered that is capable of acting as a breeding place. The
preventive work implies screening, draining, oiling, hauling
away tins, bottles, broken crockery, etc., and periodically
emptying containers used for watering stock, or holding plants
or flowers about the house. Emphasis is given this phase of
mosquito control at this time to prevent a misconception on
the part of the people of this Territory in regard to the amount
of relief to be expected from the establishment of the top-
minnows in local waters.

The collections of water comprising the second class can-
not always be dealt with directly without a great expenditure
of money in drainage work or seriously interrupting such agri-
cultural operations as rice and taro culture. It is obvious,
then, that while any natural check or enemy of mosquitoes
is desirable, it is particularly to be desired in the case of mos-
quitoes developing in these bodies of water. Previous to tie

3

successful introduction and establishment of the top-minnows
in Hawaii no effective enemies of mosquitoes occurred.!. The
dragon-flies or mosquito-hawks and the gold-fish were their
only important enemies but neither are special mosquito
feeders, although the winged dragon-fly devours many aduit
mosquitoes in the air and the gold-fish feeds on the larvae to
a certain extent in the water, especially when confined in a
fountain, lily-pond, or aquarium.

The question of introducing the top-minnows into Hawaii
was first considered in the early part of 1903, these fish having
been reported as effective enemies of mosquito wrigglers else-
where.2 Dr. David Starr Jordan, to whom the problem was
referred, replied that these fish had never been transported
such a distance but, while the whcle undertaking would be an
experiment, the fish were extremely hardy and the greatest
consideration would be the cost of the work. Because of the
cost this phase of mosquito control did not receive further
notice at that time.

Fig. 2—Top-Minnow, Fundulus grandis. Enlarged. (U. S. Fish Com-
mission. )

During 1904 a Citizens’ Mosquito Campaign Committee was
organized in Honolulu and this body was instrumental in pro-
viding the means for the introduction of the fish. The writer

>

1 The species introduced were Mollicnesia latipinna Fundulus grandis,
and Gambusia affinis of the family Poeciliidae collected and transported
to the Islands from Seabrook near Galveston, Texas, by Mr. Alvin Seale.
See figures number I, 2, and 3.

2 L. O. Howard. Mosquitoes, New York, Igol.

A

had an opportunity to discuss the subject personally with Dr.
Jordan and in the interview Dr. Jordan offered to send an
expert from Stanford University. to collect the fish and bring
them to Hawai on condition that the Territory pay simpiy
the expenses of the undertaking. This offer was fully appre-
ciated by the Territory. On a recommendation from the
Citizens’ Mosquito Committee, the Governor presented an
item of $1500 to the Legislature of 1905 to cover the expenses
of the experiment. The communications on the subject were
as follows:

(Letter from the Citizens’ Mosquito Committee to the Governor.)

Honolulu, Hawaii, March 12, 1905.
Hon. George R. Carter,
Governor of the Territory of Hawai. Honolulu.

Sir: Dr. David Starr Jordan, of Stanford University. having offered to
send an expert of that institution to collect for these islands certain fish
of the Southern States and Mexico. at present entirely unrepresented here,
that feed upon the larve of mosquitces, providing the Territory pay the
expenses of such trip, the undersigned, at your request, beg to say that for
the expense of such a trip a sum of not less than $1,500 should be provided.
We suggest that, if appropriated for the above purpose. this sum, or as
inuch thereof as is necessary, be spent under the direction of the board
of health, since the president of that department of the government is the
chairman of the Citizens’ Mosquito Committee.

Very respectfully yours,

CHAS, By COORER Mie
Chairman Legislative Committee.

Wk eV AN Nee
Chairman Advisory Committee.
Representing the Citizens’ Mosquito Committee of Honolulu.

At the opportune time the above communication was trans-
mitted to the legislature with the following indorsement:

(Letter of May 10, 1905, from Governor Carter to the legislature. )
To the Legisiature of the Territory oi Hawaii:

Herewith, J transmit for your consideration copy of a letter of March
12, containing a proposal made by Dr. David Starr Jordan, of Stanford
University, to provide an expert, with the necessary apparatus, to under-
take the importation into these islands of a certain small and vigorous fish
found in Mexico that ieeds on the larve of the mosquito, provided the
Territory simply pays the expense of such an undertaking.

You are aware that the only fish we have at present exclusively occupy-
ing our fresh waters is a species of mud fish, commonly known as the oopu,
and the gold fish. You are also aware that there is known to exist here
the species of mosquito which carries the germs of yellow fever, which,
fortunately for us. has not as yet been inoculated, but with the completion
of the Panama Canal it will only be a question of time before cases of

5

this or some other disease will reach this port. Every interest in the
Territory would be advanced if this mosquito could in some way be
entirely eradicated, or at least reduced to the smallest possible number.
GR. CARER
Governor.

The subject was referred to the health committee of the
House. The committee reported favorably and the item
($1500.) was included in the general expense bill of the Ter-
ritorial Board of Health for disbursement. This money was
not available until July 1st, but as soon as possible thereafter
an advance was sent to Mr. Alvin Seale at Stanford University,
the man selected by Dr. Jordan to carry on the experiment.

The following report by Mr. Seale covers the work of coi-
lecting the fish and their transportation to Hawaii:

REPORT. OF ME SEALE.

Honolulu, Hawaii, September 23, 1905.
Mr. D. L. Van Dine,
Entomologist, U. S. Experiment Station,
Honolulu, H. T.

Dear Sir :—In accordance with the following letter to your-
self from Dr. David Starr Jordan, 1 was chosen to attempt
the introduction of “top-minnows” or “killifish’ into the Ha-
waiian Islands for the purpose of destroying the larvae of mo3-
quitoes: 7

LELAND STANFORD JUNIOR UNIVERSITY.

Office of the President.
Stanford University, Cal., April 18, 1905.
Mr. D. L. Van Dine,
United States Experiment ‘station,
Honolulu, Hawaii.

Dear Sir:—The best place to collect the fishes which you want would
doubtless be in Louisiana. It would probably take no longer time to bring
them from there than from any other places nearer. Perhaps an equally
good piace would be Tampico, on the edge of Mexico. You understand
that this would necessarily be an experiment. These little fishes feed
freely on mosquitoes. Some live in brackish water, some in fresh water,
and all of them are very hardy. But no one has ever tried to transplant
any of them, and the whole thing might turn out, for some reason or
other, to be a failure. Especially one would need to experiment on feed-
ing the little fishes during their transportation. The genera which I
would recommend are Mollienesia, Adinia, Gambusia, and Fundulus. Some
of these are viviparous, others lay eggs. Whoever undertakes this should
give a good deal of attention to the question of feeding the little fishes,

6

and for this purpose perhaps a tank breeding mosquitoes would be as good
as anything. ‘The best time to undertake it would be about the Ist of June.
I will select some one as soon as | hear from you.

Very truly yours,

DAVID S&S. JORDAN

On receipt of yours of July 11, 1905, with the advance of
$500 of the Territorial appropriation covering the expenses of
this undertaking, I started from Stanford University to the
Southern United States. It was my intention to secure the
top-minnows at or near New Orleans, but the rigid quaran-
tine in operation in Louisiana prevented my carrying out this
plan. Seabrook, near Galveston, Texas, was then selected as
the next place most available. At Seabrook I found the family
of top-minnows, Poeciludae, in large numbers. They: were
swarming in all the stagnant waters at sea-level as well as
in various ditches, ponds, and standing pools. Mosquitoes
are very plentiful in and about Seabrook, but after a study of
the situation I am convinced that their source is not the bodies
of water containing these fish but rather temporary and arti-
ficial breeding places, such as ciosed pools, tubs, tin cans, and
other refuse which are not accessible to these fish.

As per his letter to you, Dr. Jordan recommended the fol-
lowing genera: Moliienesia, Adima, Gambusia and Fundulus.
These are all members of the single family Pceciltidae or top-
minnows. i first made a careful examination of a number of
the stomachs freshiy taken from members of the above genera.
The stomach-contents was found to consist largely of larvae
of various insects, including those of mosquitoes; egg-masscs
of mosquitoes; minute crustacee and some vegetation. The
results showed that Gambusia were the best insect feeders.
Of 100 stomachs of this genus examined all contained many
insect larvae and eggs among which I noticed especially num-
erous egg-masses of the mosquito. However, Mollienesia,
Fundulus and Gambusia differed slightly in regard to their
capacity, for the various insect larvae and the difference was
probably due to the different food localities. The temperature
of the water in and about Seabrook in which these fish were
found ranged from 74° to 87°.

It now remained to determine under what conditions the
fishes could be most successfully transported to Hawaii. Six
ordinary ten-gallon milk cans were prepared by puncturing
the covers with numerous holes and placing the cans in bran
sacks, the intervening space being tightly packed with Span-
ish moss. his served to keep the water at an even tempera-

lad
/

ture. Two hundred fish were placed in each can. The foi-
lowing morning so many were dead that it was evident the
cans were overcrowded and I reduced the numbers to one
hundred.

Experiments were conducted as follows:

Can No. 1. Allowed to stand undisturbed. Water un-
changed and unaerated. Temperature normal. The first
morning six fish were dead. The second day, two died. The
third day the fish were perfectly lively and were taking food
freely. The fifth day five died and by the eighth twenty had
died. The experiment was not carried further.

Can No. 2. Water changed once each day. Temperature
normal (ranged irem=74--10 75). 4 Wurine the first three days
there were four deaths. The eighth day two died. After this
time there were no more deaths. Fish fed freely on mosquito
Jarvae, and prepared fish food.

Can No. 3. Water changed.twice each day. Temperatu-.e
normal. Yhree deaths the first night. After this time thers
were no more deaths. Tish fed freely on mosquito larvae aad
prepared fish food.

Can No. 4. Water changed every two days. Temperature

anormal. Five deaths the first three days, after which no fish
died. Fish fed freelv, keeping constantiv at top of the water.

Can No. 5. Water slowly and very gradually reduced in
temperature to 40°. Fish would not feed at the end of six
days. During this time eighteen had died. Experiment dis-
continued.

Can No. 6. Water reduced slowly to freezing point, then
can packed in ice. At the end of six days all but three of the
fish were dead. Experiment discontinued.

The above experiments deimonstrated that the fish shoul
be transported in water at the normal temperature and gave
the necessavy information in regard to the frequency of chang-
ing the water.

"phe three most abundant species, (eee afinis, Fundulus
grandis and Mollienesia latipinnoa, were collected and approxi-
mately sevcnty-five placed in zach can. On Sept. 4, 1905, I left
Seabrook, Texas, on the long journey to Honolulu. A 20-gal-
lon tin tank was taken along as a supply reservoir.

The following routine work was observed during the entire
trip: At 8a. m. the fishes were fed sparingly on prepared fish
food, finely ground liver or hard boiled eggs; at 9:30 half the
water in each can was siphoned off from the bottom, this
cleaning out the cans and removing all uneaten food an

8

excrement, and an equal amount of fresh water added; at noon
the cans were all aerated by means of a large bicycle-pump,
a sponge being tied over the end of the hose to separate the
air into fine particles; at 4 p. m. two gallons of water were
siphoned off from the bottom and two gallons of fresh water
were put in; just before retiring the cans were again aerated
by means of the air-pump.

At each place en route where the water was changed it was
frst tested by placing two fish in a bucket containing the
new water at the proper temperature. At El Paso, Texas,
only, did the water kill the fish thus treated. After ten
minutes the two fish were dead, probably due to the alkaii
it contained. The water at Los Angeles was good as also the
San Francisco water, which was used from the latter place
to Honolulu, an abundant supply being carried on the steamer.
The water used from El Paso to Los Angeles was taken from
the supply tank, filled at San Antonio, Texas.

Twelve fish died between Galveston and San Francisco ar
only fifteen between San Francisco and Honolulu.* The fish
were landed in Honolulu from the S. S. “Alameda” on Sep-
tember 15, 1905, the trip from Texas occupying 12 days and
27 of the approximate 450 fish were lost.

The fish were in fine condition on-arrival and as preay-
ranged by yourself were placed in the breeding ponds pre-
pared for them. The temperature of the water about Hono-
lulu is almost identical with that where the fish were col-
lected, and the appearance of the fish at this writing indicates
that they should thrive on the [slands. The fish should be con-
fined in the present breeding ponds, where they can be pre-
vented from going out to sea or falling prey to other fish until
their increased numbers permit general distribution to other
localities in the group.

Very truly yours,
ALLA DNL See
Assistant, U. S. Fish Commission.

Upon the arrival of the steamer the fish were taken at once
to Moanalua near Honolulu where, through the courtesy of
Hon. S. M. Damon. a series of four ponds had been prepared
for their reception and breeding. An irrigation ditch led clear
’ water to the ponds through a gate-way guarded by wire cloth
of a fine mesh. The outlet was guarded in a similar manner.
The water was allowed to circulate through three of the ponds
but no outlet was provided for the fourth in order that the
water might remain standing. Two of the ponds were about

eae

2

two feet in depth with one free from vegetation and two were
from two to six inches in depth, with one also free from vege-
tation. These varying conditions represented somewhat the
shallew waiters of the Islands as regards depth, temperature,
presence or absence of vegetation and standing or running
water. Abcut equal numbers of the fish were placed in each
of the four ponds.

ae 2: : = = = =
i = —S_ =

Fig. 3.—Top-Minnow, Gambusia affinis. Male above, female below. En-
larged. (U.S. Fish Commission. )

The fish thrived in all of the ponds almost equally well, the
main advantages of their confinement being the prevention cof
their being carried out to sea by a freshet and the protection
irom other predaceous fish? It was determined, however, by

* Dr. Jordan informed the writer that the Hawaiian fish likely to prey
upen the top-minnows were Sphyracna snodgrassi (Kaku) in the mullet
ponds, Elops (Awa-Aua), and Kuhlia (Aholehole).

10

observation at the ponds and in other locations where the ton-
minnows were liberated later that they thrived best in shallow,
standing water ait a temperature ranging from 76° to 82° F.
The fish show no inclination to go out to sea and avoid the
deep water, iessening the probability of their being eaten by
the larger predaceous fish.

Thev have multiplied rapidly and from the few hundred
introduced, several hundred thousand have been bred and dis-
tributed. - Where they occur ihey effectively clear the water
of the mosquito larvae, feeding likewise on the egg-masses of
Culex pipiens on the surface. In the absence of mosquito larvae
or eggs the top-minnows feed upon the smaller aquatic insects
of other species, as the nymphs of the water boatman, Coriva
blackburni, eating also various small insects that fall into the
water and are drowned. In an aquarium the larger fish have
been observed making way with the very small of their own
kind in the absence of other food.

Under the direction of the writer, the Territorial Board of
Health has made the following distribution of the top-min-
nows irom the funds appropriated for their introduction an¢l
distribution by the Legislature:

{sland of Oahu: Honoluiu and vicinity generally, Aaea,
Pearl City, Waialua, Maunawai, Wahiawa and Waimanalo.

Island of Hawaii: Hilo and vicinity, and Paauhau.

Island of Maui: Kahului, Wailuku and Lahaina.

Island of Molokai: Kalaupapa.

Island of Kauai: Jihue, Eleele, and Waimea.