This article originally appeared in Freshwater and Marine Aquarium magazine (FAMA), Volume 19 Number 6, June 1996. All rights reserved by R/C Modeler Corporation. Permission to reproduce is granted by the publisher and the author to The Breeder's Registry and is not transferrable.
By Robert Brons
Research Department Red Sea Fish pHarm Ltd., Eilat, Israel
P. fridmani: adult female. |
The recent widespread attention for minireef aquaria and the exciting progresses achieved in growing hard corals, have shifted the interest in fishes. Many spectacular reef fish species can indeed be detrimental to a coral reef aquarium, either by loading the system with their wastes or by feeding on polyps. Small and colorful fishes that harmlessly blend with the invertebrate fauna have, however, greatly increased in popularity. Possession of these positive qualities combined with lively and interesting behavior, have made the Dottybacks (genus Pseudochromis) very popular among reef aquarists. Most species occur in the Indo-Pacific region, but in the Red Sea, the genus Pseudochromis species, five of which are endemic in the area. While is represented by seven nature conservation laws in Israel forbid collection of reef specimens entirely, the export of wild caught Red Sea fishes is restricted in most other countries on the Red Sea. Therefore, these endemic species are, unfortunately, rarely encountered in the aquarium shops, and if they are available, the price is very high. The two most colorful Red Sea Dottybacks, Pseudochromis fridmani (Orchid Dottyback) and P. flavivertex (Sunrise Dottyback), were the subjects of an intensive Research and Development project in order to search for methods to breed these fishes in captivity. The experiments were performed as part of the ongoing reef fish breeding program at Red Sea Fish pHarm Ltd., in Israel.
P. fridmani: male tending the eggs (as described in the text). |
The Laboratory where this work takes place is located near the city of Eilat on the Gulf of Aqaba, the most northern part of the Red Sea. Eilat is well known among European divers, snorkelers, and marine aquarists for its excellent opportunities to observe reef fish and invertebrates in their natural habitat. Despite the close proximity of the Red Sea, the wet laboratory has closed systems with artificial seawater made from the company's Coral Reef Red Sea Salt dissolved in reverse osmosis water. The water quality is maintained by biological filtration, protein skimming, carbon filtration, and regular partial water changes. Although the Red Sea has a high salinity (40 ppt), our Red Sea species (including the larval stages) are successfully maintained at 30 ppt (s.g. 1.020-1.022, 250C-770F).
The stunningly deep-violet colored Pseudochromis fridmani is quite a common reef fish near Eilat and can also be spotted in shallow water by snorkelers. The Orchid Dottyback has a wide depth distribution and can be found between 1 and 60 meters. The fish are usually seen in groups of several individuals around coral heads, rocks, against vertical rock faces, or beneath rock overhangs. They are in continuous agile movement and dash into coral crevices when disturbed.
P. fridmani: egg balls of two different pairs. Scale below in inches. |
Pseudochromis flavivertex is a beautiful blue fish with a white belly and a yellow stripe extending from head to tail down the back. The dorsal fin and the tail are transparent yellow with contrasting blue edges. It is more robust than P. fridmani and not as easily encountered in this part of the Red Sea. The fish are usually observed at a depth of 15-25 meters on sand bottoms with scattered coral rocks. They live solitary or in pairs, each fish occupying its own burrow under a rock. When observing paired specimens, the presumed male and female reside at approximately a 2 meter distance from each other. The fish curiously observe the diver, while they swim or hover actively in the immediate proximity of their shelter.
Though occasionally it is possible to observe aspects of Pseudochromid reproductive behavior in the sea, this is largely a matter of chance, while the actual spawning takes place in secrecy. The observations below have been made in our "wet lab" where we maintain several pairs of both species among a collection of reef fish species from all over the world. Although our main task is directed towards fish production, that is to develop methods that ensure an economic production of the fishes involved, some time can be spent on purely ecological or behavioral aspects.
P. fridmani: Photomicrograph of the eggs after 4 days development. Magnification: 7X. Note the fine threads that hold the eggs together. |
Captive specimens of P. fridmani and P. flavivertex do not show the dramatic color losses known of Pseudochromis species like P. diadema and P. paccagnellae. Still, it is highly recommended to regularly supply feeds that are rich in natural pigments, such as krill or planktonic copepods. This is especially important in the case of P. flavivertex, the colors of which tend to become slightly drab in older specimens.
To bring both species into spawning condition, a varied diet consisting of quality feeds as chopped clam, squid, Artemia, krill, and high quality dry foods is required. Spawning pairs should be fed heavily: Between spawnings, females can devour astonishing amounts. Balanced foods are not only important for the general condition of the broodstock, but also influence the quality of the eggs and probably the initial survival of the larvae. Wild caught specimens generally require time to adapt to feeding on nonlive foods. Well established specimens will even take food from the bottom and readily accept a wide variety of frozen and dry foods, including flakes.
A very important factor is the water quality. Despite the constant nest care of a male Pseudochromis, an unfavorable water quality can negatively influence the hatching result of the eggs. Spawning tanks should be kept meticulously clean, while the dissolved organic carbon level should be maintained as low as possible by siphoning uneaten food and applying mechanical filtration, protein skimming, carbon, and biofiltration.
P. fridmani: Photomicrograph of the eggs 7 hours after fertilization. Magnification 15X. |
Effective water circulation in the spawning tank is significant to prevent areas with standing water and to maintain oxygen saturation throughout the tank.
Data aiding to successful pairing of individual fishes form relevant basic information for the fish culturist or hobby breeder. For the genus Pseudochromis, the factors involved are the following:
(1) Distinguishing characteristics between male and female.
Sex based differences in coloration, size, and body shape are described by the term sexual dimorphism.
P. fridmani: first day larva. Note that stomach and gut are filled with ingested food organisms. Photomicrograph, magnification: 7X. |
(2) Genetically fixed sexes versus occurrence of sex reversal
Being closely related to the hermaphroditic Serranidae (Groupers and Sea Basses), Pseudochromis species are likely to be protogynous hermaphrodites (Thresher, 1984), meaning capable of sex reversal from female to male. Pairs, therefore, consist of a large dominate male and smaller submissive female. The female can develop into a male if the dominant fish is removed. Although specific knowledge for the genus is largely lacking, the fish breeder can, in principle, use this information by pairing a large specimen with a juvenile or significantly smaller specimen.
(3)Aggressivity.
Most Pseudochromis species are highly territorial fishes. While several species can be classified as moderately aggressive, others will viciously attack any member of the same species including smaller or submissive specimens, often until death follows. Pairs combined out of individuals should, therefore, always be closely monitored, even if the process is facilitated by the presence of sexual dimorphism or the occurrence of sex reversal.
Pseudochromis fridmani forms a fortunate exception to point 3, as it is one of the least aggressive species in the genus. If supplied sufficient space and shelter sites, theses fish can be maintained in a group; however, more than four specimens in a 500 liter (125-gallon) tank cannot be recommended. The fish will defend their territory and occasionally chase each other, but seldom is any serious damage inflicted. Although this quality facilitates obtaining at least one good breeding pair out of a group, it is of course more efficient to be able to combine, with a high degree of certainty, males and females in a one to one ratio.
P. fridmani: 40 day old, completely metamorphosed, juvenile. |
After combining a significant number of pairs out of wild caught and tank raised individuals, we have come to the conclusion that sexing Pseudochromis fridmani is not as easy as several authors suggest (Thresher, 1984; Michael, 1990; Paletta, 1993). The difference in the lower part of the caudal fin, which is described as on average more pointed in the male, proved to be not reliable enough for our purpose. We failed to completely observe a clear color difference in the anal fin. We achieved far better results by using the experience that an adult female is slightly, but clearly, smaller and plumper in the abdominal region, compared to the slimmer and more elongate male. This difference has been consistent until now.
Being able to sex individuals gained more relevance after we collected indications that led us to assume that in P. fridmani the sexes are fixed. On two occasions, we noticed that in a batch of tank reared juveniles, the largest (fastest growing) specimen was a female, which became evident after it shed an egg ball. The eggs remained unfertilized since there was no mature male present. Likewise, combining a large fish with a juvenile, the previously discussed procedure for spawning hermaphroditic fishes, proved unsuccessful several times as the fish later turned out to be members of the same sex.
P. flavivertex: 35 days old, completely metamorphosed juvenile, near 1 inch PVC pipe cutting. |
The observation that the female is smaller than the male, however, seems to contradict the existence of fixed sexes (gonochorism). Now that sufficient tank reared specimens can be available for experimentation or dissection, we will hopefully be able to give a definite answer to this intriguing question.
Pseudochromis flavivertex occupies an intermediate position on the genus aggressivity scale. However, more than one mated pair cannot be maintained in a normal sized aquarium. Even in an established pair that is spawning regularly, the female is often chased and bitten, so the spawning tank should be provided with sufficient shelter sites. Also, regular monitoring for increased aggressivity of the male is important. At the end of a spawning period, the attacks by the male can become increasingly severe and, consequently, there is a high risk of losing the female. The female should in this case be allowed a rest period, preferably by separating it from the male by a glass tank divider.
There are no distinguishing characteristics between male and female except for a moderate size dimorphism. The male is slightly larger and overall more robust than the female, which also has a rounder abdominal region. The color dimorphism described by Baensch & Debelius, (1992), whereby the female is grey-blue colored with dark blue spots, lacking the characteristic yellow back, is questionable. We noticed this color variation in wild caught juvenile specimens imported from Egypt's Sinai region. In the aquarium, however, these juveniles gradually attained the normal coloration and developed into both males or females.
P. flavivertex: 35 day old, juveniles. Transfer to grow-out tank. |
The occurrence of this natural color variety remains unexplained. All our tank reared specimens, however, show the normal pigmentation from settlement and metamorphosis to adulthood.
We have reasons to assume the Pseudochromis flavivertex is a protogynous hermaphrodite (capable of sex reversal) since the fastest growing and dominant juvenile in a batch of tank reared specimens invariably developed into a male. Likewise, a combination of a large (dominant) specimen with a juvenile fish to form a new breeding pair is usually successful.
The spawning behavior of both Pseudochromis species is basically similar. Spawning is imminent as the female swells with eggs, which may sometimes lead to grotesque proportions, especially in P. flavivertex. Spawning usually occurs during the morning. The male chases the female and displays "leading behavior," during which he repeatedly approaches the female, stops and turns in front of her, then swims towards his burrow with accentuated undulations of the body. This sequence is often alternated by a chase followed by a new leading sequence. This behavior is observed for a maximum of one hour, after which the female eventually follows the male into its hole and spawning takes place.
P. flavivertex: adult male (tank raised specimen). |
The actual spawning lasts approximately one hour, during which the female gradually produces a ball-shaped egg mass while upside down in the burrow. While the P. flavivertex male remains inside the burrow during spawning, the P. fridmani male appears regularly in the entrance, as if guarding it. We observed an even greater activity on the part of male while the female spawns with the Indo-Pacific species, P. diadema. In this species, the male regularly leaves the nest and female for a short excursion through the spawning tank until the female completes oviposition. As the egg ball finally falls to the bottom of the nest, the male chases off the female and will tend the eggs until hatching.
A mature Pseudochromis fridmani female produces a more or less spherical egg ball with a diameter of approximately 2.5cm (1 inch), consisting of roughly 500 eggs. The P. flavivertex spawn is elliptical, 3-3.5cm (1.2-1.4 inches) long, containing over 1000 eggs. Egg balls can be considerably smaller in young specimens and at the start of a spawning period. The egg diameters differ slightly, being 1.0mm for P. fridmani and 1.2mm for P. flavivertex. The eggs of both species are interconnected by fine threads, giving stability to the egg mass. The egg ball is, however, not attached to the substrate, like for example in the related Calloplesiops altivelis (Wassink & Brons, 1990), but remains free inside the burrow.
P. fridmani spawns in rather narrow cavities that can be provided by adding PVC pipes to the spawning tank. P. flavivertex requires more space and prefers to spawn under a large rock or in the cavity formed by several stacked rocks.
The male's nest care in both species is intensive until hatching of the larvae, while often little or no food is accepted. The nest care behavior of P. fridmani is especially noteworthy. During the day, the male is observed swimming frequently in and out of the nest. It enters the nest as often as every two minutes and remains inside for up to one minute, circling several times around the egg ball and lifting it from the nest bottom with its tale or snout. At night, the male appears to be continuously inside the nest. During regular nightly checks, and while using a narrow light bundle to look inside the nest, we observed an intriguing behavioral aspect. Many times the male was observed pressed against the roof of the burrow, holding the egg ball in the arch of its curved body, whereby it seemed to successfully prevent direct illumination and observation of the egg ball.
The nest care of a P. flavivertex male can be described as less sophisticated than P. fridmani. The number of "nest visits" per time unit is lower, while the technique of agitating the eggs occurs rather violently, so that sometimes the egg ball is fragmented or swept out of the burrow.
Several wild caught pairs of Pseudochromis fridmani have currently spawned uninterruptedly for one and a half years at a frequency of 3-4 times per month. Two wild caught pairs of P. flavivertex spawned for 8 months at a frequency of 2-3 times per month, after which the reproductive cycle was interrupted. This interruption occurred, however, after a three day decrease in the mean water temperature from 250C to 230C which, nevertheless, did not halt the spawning activity of P. fridmani.
In both species, hatching occurs in the evening of the 5th day after spawning (incubation time approximately 4-1/2 days at 250C-770F). The larvae hatch almost synchronously within one hour after darkness. The male is with the eggs during hatching and presumably aids in the process by agitating the eggs. Egg masses removed from the nest to be hatched out "artificially," give a significantly lower hatching percentage compared with eggs left with the male.
As is the case with newly hatched larvae of many marine fish species, both P. fridmani and P. flavivertex larvae are photo positive, so they are easily collected using a strong light bundle. Directly after hatching, fridmani and flavivertex larvae have a total length of respectively 3.7 and 3.9mm. Apart from a few scattered pigment cells, the body is completely transparent and contrasts sharply with the well pigmented eyes. The jaws are well developed while only a remnant of the yolk sac is visible.
Feeding starts the following morning at first light. The larvae are very active swimmers that utilize the entire water column, although usually an assembly of larvae is found near the water surface. Initially, the larvae feed well on the rotifer Brachionus, but since this is basically a low quality food organism, improving the nutritional value by proper enrichment is vital.
If provided suitably nutritious feeds and an appropriate rearing tank environment, the growth rate of the larvae is very fast. While growth is already apparent at day 2 or 3, the larvae double their length in a week to 10 days. From day 9, the larvae develop diffuse red body pigmentation, giving them a pink appearance. From day 20, we can no longer speak of larvae but rather of presettlement juveniles. Adult coloration, however, does not develop until several days after settlement.
P. flavivertex juveniles start settling to the substrate from day 25, P. fridmani from day 29-30. In this stage, juveniles of both species have a total length of approximately l2mm. Except for settling to the bottom, the juveniles also change their swimming mode, which transforms from a rather continuous swimming motion to the typical Pseudochromis style, which characteristically includes frequent hovering. The still pinkish-transparent juveniles tend to hide in narrow and dark places to complete their metamorphosis. At this stage, PVC cuttings are added to the larvae tank. This behavior is comparable with that of settling Calloplesiops altivelis juveniles (Wassink & Brons, 1990). While Calloplesiops juveniles readily aggregate together underneath a cover, Pseudochromis juveniles already display territorial behavior and chase other settling juveniles out of their hiding place. The larvae tank, therefore, has to be provided with many small "cells" to prevent aggression and possible damage in this sensitive development stage. Settlement of many such juveniles, places the breeder before a practical problem, comparable with, for example, settling Opisthognathus aurifrons (yellow headed jawfish) juveniles, that each require a few square cm of bottom substrate for settlement.
The Pseudochromis juveniles complete their metamorphosis inside their hiding place. The coloration intensifies gradually within seven days to the full adult pigmentation. Recently settled juveniles remain feeding on prey that flows past their shelter, but in this stage they do not venture outside. Fully colored juveniles (35-40 days old) have a total length of approximately 15mm and start to actively hunt for prey in the larvae tank. In this stage, they are transferred to a grow-out tank.
Although territorial behavior is already observed immediately after settlement, juveniles, fortunately, do not yet display the problematic aggressivity of adults. Pseudochromis flavivertex, the most aggressive species, can be maintained until the half-grown stage (total length 5cm), in reasonable density, which is gradually decreased to 20 fish per 50 liters as the fishes grow. Sufficient shelter sites as well as a tank cover should be provided since the fish tend to jump as they chase each other. Until half-grown, the fish do not seriously damage each other. P. fridmani requires even less precautions.
The growth of the juveniles is rapid in both species. P. fridmani reaches adult size in 5 months, P. flavivertex in 10-12 months. At present, we have several pairs combined out of tank raised specimens, have recorded spawnings, and are working on a second captive generation.
Achieving this will hopefully bring us another step closer to the final goal that any serious captive breeding program should embrace: To achieve complete independence of wild specimens caught from the reef. With this project we hope to have contributed (and to remain contributing) to what must, indeed, be the future of the marine aquarium hobby: independence of the world's threatened reef ecosystems.
Baensch, H.A. & H. Debelius, 1992: Meerwasser Atlas, Mergus Verlag, Melle. (in German; English version: Marine Atlas).
Brons, R., 1995: Nachzucht von Pseudochromis fridmani und P. flavivertex. DATZ 1/95, p.7 (in German).
Michael, S.W., 1990: An aquarst’s guide to the Dottybacks, Part I & II. FAMA Oct.1990, pp 8-15; Nov.1990, pp 16-24.
Paletta, M., 1993: The Orchid Dottyback Pseudochromis fridmani. Sea Scope, Vol.10, summer 93.
Randall, J.E., 1986: Red Sea Reef Fishes. Immel Publishing, London.
Thresher, R.E., 1984: Reproduction in Reef Fishes. TFH Publications, Neptune City.
Wassink, H. & R. Brons, 1990: A successful cultivation of the Comet Calloplesiops altivelis. Sea Scope, Vol.7, spring 1990.
