Cyprinodon variegatus

From BKA Killidb
Jump to: navigation, search

(Lacepede 1803) B.K.A. Information Pamphlet No.79 March, 1972

Habitat: Cyprinodon variegatus: (The Sheepshead Minnow.) is a fish native to North America, and is found from Cape Cod in the north, down the length of the Eastern seaboard of the U.S.A., to the northerly extremes of Mexico. The population increases as one travels south along the coast until they become an extremely common species indeed in the Florida coastal regions. In nature they are frequently encountered in brackish water and even sea-water, and it is possible to acclimatise them to freshwater.

Description of the male: This is a chunky looking fish of about 8cm. maximum length and looks in outline not unlike the well known J.floridae. Ground colour is brownish, with a green sheen, and lovely gleaming zones. The upperside, nape and flanks down to the pectoral fins are a beautiful metallic blue, whilst the lower parts of the flanks are sea-green. Sides of the head, throat and belly are orange. Several dark transverse bars are sometimes observed on the flanks. Dorsal and anal fins are greenish-blue bordered with orange. Caudal fin greenish with dark base and jet-black border.

Description of the female: Generally of paler colour, more light brownish in appearance. Fins tinged yellow. The dorsal fin frequently has a very distinct dark blotch.

Maintenance: A number of authors recommend that this species be maintained at fairly low temperatures not exceeding 22C. (71F.) Sea salt at the rate of 2 tablespoons to 10 litres of water is normally added bearing in mind that the fish comes from brackish water in its natural habitat. During conditioning the pair require large amounts of live food and this should if possible be supplemented by green stuffs such as green algae or lettuce leaves. The normal live foods are taken avidly and the conditioning can take 3-4 weeks to get the pair into breeding trim. At this stage, the female is noticeably distended, and the male adopts his spawning colouration with the electric blue sheen forward of the dorsal fin insertion becoming even more intense.

Breeding: Speaking from purely personal experience, these fish generally need a fair amount of attention when preparing them for spawning. The pair I have were not separated during conditioning, and neither fish seemed to suffer during the occasional skirmishes when food was introduced. They certainly benefit from 3 good meals per day. Once in condition, the male is a persistent rather than rough driver, making constant attempts to persuade the female to join him at the spawning site. Both a floating and sunken nylon green wool mop were used, for this purpose. When not driving the female, the male spent a considerable period circling the sunken mop, biting at the strands as if rearranging things to his liking. Unfortunately the actual spawning was not observed, but some 90-100 small clear eggs were collected in 36 hours, some 20% being deposited on the floating mop, immediately under the cork. All the rest were found scattered amongst the nylon on the sunken mop. It is not known whether the female would have been damaged by remaining with the male as the pair were separated just in case. It is reported however that the pair may be put together again the next day providing both partners have been well fed. Egg development is rapid when compared to even most Aphyosemions, water incubated eggs maturing in only 8-10 days. It is important to note that collected eggs should be stored in water from the breeding tank in view of the saline content.

Light Intensity and Water Temperature: These two factors must be considered when conditioning North American killies. Genera from this part of the world normally have a winter rest period of short day lengths and lower temperatures. On receipt of this species late in November they were installed in water of pH 7.3 and hardness 6-7 German. Temperature for the first 4 weeks was kept at 66F. and the photoperiod (time of daily illumination) about 12 hours.

In order to simulate the onset of Spring, it was necessary to increase the photoperiod to 16-17 hours daily, and also step up the light intensity by installing a 30 watt strip light about 9" above the water surface. Water temperature was gradually increased to 74F. and spawning took place within 5 days of these changes.

Fry Care and Feeding: A number of peculiarities come to light when dealing with the eggs and fry of this species. After a couple of days, it may be thought that all the collected eggs are infertile, since they often take on a completely white appearance. The developing embryo however has very little pigmentation at this stage, and it is possible to confuse eggs of this species by judging on appearance.

Having got the fry to emerge safely, one is then confronted with the thought that they are all belly-sliders, due to their habit of bouncing off the bottom only to settle back down again. This is entirely natural, in fact the fry do not appear to swim in an orthodox manner until they reach a size of 1cm. (1/3rd" approx).

Sand on the base of the rearing tank can be provided to good advantage, the fry seeming to enjoy grubbing about therein. Growth is quite rapid when the usual fry-foods are used, though Artemia is strongly recommended as a starter food since it is quite likely that the original pair would have had this on demand in their natural environment. General: This is one of the North American species recently imported through Dick Armstrong our Species Controller. North American Killies are very much undernoted over here at the best of times, but I would strongly recommend members to have a go at this one as and when it becomes available. Incidentally it is one of the very few marine fish which have ever been bred in the aquarium.