Here's what I know about captive propagation of Rhinichthys, from the
long-delayed NANFA Encylopedia of North American Native Freshwater Fishes.
Blacknose (R. atratulus) and longnose (R. cataractae) dace will spawn in the
aquarium if they are given a simulated winter cooling period followed by a
simulated springtime rise in light and temperature. Blacknose dace are
probably the easiest Rhinichthys to spawn. Maintain a group of five males
and five females in a well-aerated aquarium, 30 gallons or larger, with
moderate current (25 cm/sec) over sand or fine gravel. Situate plants, logs,
and rockwork to the sides and backs of the aquarium to create an open
spawning area in the middle. Condition with heavy feedings of live or frozen
foods. As temperature rises, watch for males to establish a territory over a
section of gravel. Once spawning occurs, either remove the eggs or the
adults immediately, as the adults will eat the eggs. Eggs hatch in 5-8 days.
The fry, after their yolk sacs disappear, require small live foods such as
rotifers, copepodites, and newly hatched brine shrimp, but may accept
Tetramin paste and flakes (Bartnik, 1970). For spawning longnose dace,
increase the current speed to 50 cm/sec and create an irregular bottom
consisting of various sized rocks and coarse gravel.
Speckled dace (R. osculus) are also easy to spawn. Valerie Burtson, writing
in American Currents, was surprised to find speckled dace fry feeding on
algae growing on the leaves of plants in a densely planted 55-gallon,
hexagonally shaped aquarium. Apparently, the five speckled dace she kept in
the tank (presumably collected near Burtson9s home in South Lake Tahoe,
California) spawned without her knowledge. Water conditions-in-the time were
as follows: 23-24C (74-76F), soft, pH 7.0, with one teaspoon of rock salt
added per gallon. Indirect sunlight and 12 hours of fluorescent light
contributed to plant and algae growth. The fry grew rapidly on microworms,
baby brine shrimp, and liquid fry food (Burtson, 1987). The fry were removed
when the adults, which usually stayed-in-the bottom of the tank while the
fry gathered near the top, began nipping the fry tails.
Details from Burtson's fortuitous spawning are consistent with those used by
a biologist raising speckled dace in the laboratory. Apparently, the dace do
not need live or frozen foods to reach spawning condition. Calvin Kaya,
working out of Montana State University, fed his speckled dace broodstock
commercial trout chow and flake food (Kaya, 1991). He kept them in aquaria
130 l (43 gal) and larger with 14 hours of light per day, and induced them
to spawn by gradually raising the temperature from 15C (59F) to 24C (75F) -
roughly the same temperature-in-which Burtson noticed her dace had spawned.
Fortunately, Kaya observed the spawning act: A single female was chased by
one or more males. Adhesive eggs were scattered in tank corners and crevices
in the gravel around undergravel filter standpipes. Since both sexes foraged
on the spawned eggs, Kaya placed a woven mat in the tank through which the
eggs could sink to safety. The fry were free-swimming 8-10 days later and
fed on powdered flake food, liquid fry food, and baby brine shrimp. The
first generation matured and spawned-in-almost two years of age.
The federally threatened loach minnow (R. cobitis has been raised at
Alchesay-Williams Creek National Fish Hatchery in Whiteriver, Arizona, as
part of the species' recovery effort (David and Wirtanen, 2001). Nonspawning
adults (8-10 per tank) were kept in 75 liter (20 gal) aquariums-in-15C (59F)
with gravel bottoms and broken clay pots to provide cover. Natural
illumination from a single southern exposure window provided primary light
and natural light cycles throughout the year. The fish were fed 3-4 times
daily a varied diet of frozen foods consisting of bloodworms, mosquito
larvae, brine shrimp, and krill. Although initially reluctant to accept
flake or freeze-dried foods, loach minnow can be trained to feed on flakes
and pellets after all other foods have been withheld for several days. The
loach minnow usually spent daylight hours hidden under the clay potsherds,
but darted in and out to retrieve food. The species is highly susceptible to
parasites, particularly Ichthyophthirius.
To induce spawning among captive loach minnow, aquarium conditions were
patterned after in the fish's natural habitat. Beginning in early October,
temperatures were incrementally lowered from 15C (59F) to 7.2C (45F) by
mid-November. This temperature was maintained throughout the winter until
mid-March when, in response to increasing stream temperatures, it was slowly
raised to 10C (50F) by mid-April. At this temperature loach minnow began
feeding more, females appeared slightly gravid, and males displayed a
gradual increase in reddish breeding hues. Two males and one female were
transferred to each of two 19-liter spawning aquariums. Temperature was
slowly increased to 17.2C (63F) by mid-June. Spawning began in late April
when temperature reached 12.2C (54F). Eggs were deposited in an adhesive
mass on the underside of the potsherd, usually where the shard came in
contact with the gravel. Egg masses, often still connected to a portion of
shard, were moved to a special incubator tank in which a rigid sheet of PVC,
containing three circular cutouts each mounted with a stainless steel screen
sieve, was placed just above the water surface. Many eggs were lost to
fungus, requiring frequent treatments of malachite green. A spray bar was
placed under the sieves to aerate the eggs and create a gentle upwelling
effect. Eggs hatched 12-16 days later. Fry were moved to small plastic
nursery tanks which were suspended in larger supporting aquariums to
maintain temperature. The fry began feeding on algae and rotifers 9-18 days
after hatching. Older, larger fry could take newly hatched brine shrimp
supplemented with small portions of krill shaved from frozen cubes.
Approximately 60% of the nursery tank water was siphoned off every 2-3 days
and replaced with water from the supporting aquarium. Fry were then moved to
the supporting tanks 29 days after hatching, where they began feeding on the
same diet as their parents.
Bartnik, V. G. 1970. Reproductive isolation between two sympatric dace,
Rhinichthys atratulus and R. cataractae, in Manitoba. Journal of the
Fisheries Research Board of Canada 27 (12): 2125-2141.
Burtson, V. 1987. An unexpected spawning of speckled dace. American Currents
Jun.-July-Aug. 1987: 10.
David, R. E., and L. J. Wirtanen. 1998. Artificial propagation of loach
minnow, Rhinichthys cobitis. American Currents 27 (3) [Summer]: 1-13.
Kaya, C. M. 1991. Laboratory spawning and rearing of speckled dace.
Progressive Fish- Culturist 53: 259-260.
Chris Scharpf
NANFA HQ
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