Breeding Orchid Dottyback - Part 1

Introduction

Breeding marine aquarium fish in captivity is one of the best ways to supplement the supply of livestock. However, there has only been a limited supply of marine aquarium fish available to the hobbyist with much of the knowledge of raising these fish kept secret. In a 2 part article I will explain how I successfully raised the Orchid dottyback (Pseudochromis fridmani) through to adulthood. The articles will describe each brood I attempted to raise and provide an insight into the effective and not so effective techniques that I used. It has not been an easy task but I have now found a method for the small scale breeding and raising of these wonderful fish that with time and effort can be replicated by the hobbyist.

Orchid Dottyback

Pseudochromis fridmani, the Orchid dottyback is one of the groups of Pygmy basslets originating from the Red Sea. Naturally they are very shy but highly territorial fish. In the wild they feed on small crustaceans and drifting plankton, once settled in captivity they are hardy and readily take most foods offered making them a good choice for the reef aquarium. I had a pair of P. fridmani in my reef tank for about six months before I realised they were breeding. The first bundle of eggs I found by accident, a ball about 15 to 20mm in diameter nestled in a tropical barnacle shell covered with Xenia. After a short dilemma (where could I put a new tank?), I decided to try and raise some future broods. After a failed attempt to remove a batch of eggs from inside a piece of live rock and a missed hatch, the parents spawned again. Luckily this time the male had taken up residence in a piece of live rock conveniently located at the bottom of the aquarium. Not for the first time I noticed that the female had tattered and torn fins after spawning so it would seem that mating is a bit of a rough affair! After spawning the female takes no part in the care of the eggs and is kept at bay by the male who guards the clutch. As the time gets closer to hatching the male spends more and more time with the eggs. The larvae emerge four days after spawning, about an hour or two after the lights go out.

Brood One

A small new hatchery was now complete, consisting of a 50 litre sump containing some live rock and two small tanks above lit by two 30w fluorescent tubes. The eggs were removed from the reef tank three hours before lights out on the night they were due to hatch. I had constructed a hatching device for the eggs as it is known that the males vigorous shaking helps the fry to emerge. Using an air valve I could control bubbles moving up through a piece of pvc pipe. Through the top of the pipe I added the eggs, the idea being that the slow emergence of bubbles would rise and bump the egg bundle without running too fast and carrying the eggs up and out. It worked perfectly! As soon as I turned on the airflow the egg bundle was bumped and the fry began to emerge. Over the next 20 minutes the fry continued to hatch and in the end there were only six fry out of 1000 that did not emerge. The fry were about 2-3mm long and looked like little slivers of glass. Unfortunately I did not have any rotifer cultures ready for this brood yet and so all I could offer was newly hatched Artemia. Although they ate a small number, these proved to be too large for the fry and they starved to death over the next 3 days. It was clear that I was going to need rotifers for at least the first week of development and maybe longer.

Brood Two

I had finally received some rotifers and set up cultures which were doing well. I was feeding them on yeast and Martin Moe's V8 method. The parents had spawned again but I was unsure as to which day. I removed the eggs at about 11.00pm, unsure as to whether they were 3 or 4 days old and had decided to leave the eggs until the next night to be certain they were ready to hatch. Unfortunately in the morning the majority of eggs were dead, only about one hundred or so had hatched during the night and were now swimming about the hatchery. This obviously meant I had got the dates wrong. I added a few thousand Rotifers to the brood tanks and by the end of the day many of the fry could be seen with rotifers in their stomachs. There was about 40 - 50 percent mortality by the end of the next day but quite a few were still darting around. Some of the fry didn't seem to have much food in their stomachs but others looked full and were really active. To begin with the fry seemed to take the rotifers as they were swimming along but by day three I was starting to notice a more definite strike from the fry. The fry would stop in front of it's tiny victim and pull it's body into an S-like posture and then strike out at the rotifer, swallow it and then motor off looking very proud of itself! I was feeding rotifers twice a day and enriching them with bottled phytoplankton but it seemed that the amount that I was feeding to the fry was still far too low and I was concerned about the nutritional quality of the rotifers. By day four there were still about 40 babies alive. Numbers were dropping each day but some seemed to be doing well with full stomachs and looking very active. There always seemed to be some fry that were just drifting around with empty stomachs and I was not sure if this was due to low food concentrations, poor nutritional quality of the food or some other factor. I was now using sterile, spray dried phytoplankton for the rotifers, using Nannochloropsis for culturing the rotifers and Isochrysis for enriching them for a couple of hours before feeding them to the fry. By the sixth day there were only a few fry left and I was sure that the problem was lack of food. Those that were left had grown to about 6mm in length and their bodies had become thicker with the straight digestive tract easily seen. The last of the fry made it to seven days old which I didn't think was too bad for only the second batch. Thankfully I now had larger rotifer cultures ready for the next brood.

Brood Three

I removed the eggs of this brood from the parents a day before hatch. On the night they were due to hatch the eggs were showing the reflective eyes of the fry and there was plenty of movement. At around 10:30pm I started agitating the eggs using the hatcher but they did not seem inclined to come out. Only after the eggs had been in the dark for at least an hour did the fry start to emerge. I agitated the eggs in the dark for at least 30 minutes but only about 15-20% hatched. Others could be seen struggling inside the eggs but the majority did not make it out. It seemed that they either had not developed as quickly as those left with the parents or there was something missing needed for hatching. Perhaps the male helps to keep the eggs clean and soft, or maybe something else is done to aid hatching. I colleced and enriched around 70,000 rotifers from the culture vessels and added them to the hatchery. By the end of the next day there were around 300 fry, most of which were feeding. By the end of day seven there were about 80 fry left. Mortalities had been at a fairly steady rate but most of those left looked strong. I was concerned however about the nutritional quality of the rotifers in the hatcheries. Once out of the culture medium, rotifers lose the vast majority of their nutritional value. I was also concerned about head bumping behaviour the fry were starting to show and a tendency to congregate in the corners. On day eight I started adding a few newly hatched Artemia which the fry readily took however, much of the food in the hatcheries seemed to have been recycled through the sump and back into the tank, this food was certainly nutritionally poor. By day 10 the stomachs of the fry had developed a more complicated digestive tract. First the digestive tract started to lengthen and develop a u-shape and then as development continued, it formed a complete loop. As the fry grew the looping of the digestive tract continued. Unfortunately by the time the fry reached thirteen days old there were only 25 left. The largest of these were about 10mm long and had started to develop whitish heads due to the laying down of calcium in the skull and some slight red colouring to the fronts of their mouth. Heavy mortalities continued until there were only 6 fry left by day 15. Tests on the water quality had shown that nitrites and ammonia levels were too high and so I performed some large water changes. It was becoming clear that I would need to change the hatcheries to provide consistent nutritious food and cleaner water. The last of this brood made it to 18 days old. I was not sure if the mortalities were due to too low a food concentration, nutritiously poor food, poor water quality or bacterial infections. I needed to work on the low food concentrations and the nutritional quality of the food and so I came up with my next fry rearing technique.

Brood Four

The new method for this batch consisted of a 230 litre black plastic vat lit with three 30w fluorescents. I had used a fluidised sand filter that circulated around itself and a powerhead that drew a slow feed from the vat. Rotifers were added to the vat to reach the concentration of 4-5 per ml and phytoplankton was added directly to the vat meaning that I could keep the rotifers constantly enriched. Quite a lot of research has been done into the DHA:EPA (fatty acid ratio) requirements of larval fish (particularly species farmed for food), and giving 2 parts DHA to one part EPA was the recommended balance. To achieve this I used 12 parts of Isochrysis to one part Nannochloropsis. This was very different to the last brood where I was feeding mostly Nannochloropsis. Around 500 fry hatched from this batch. The fry were growing well and I still had around 500 fry on day 13, unfortunately by then there were some problems. The filter was not coping with the biological load of the system and the ammonia levels had climbed to over 0.5mg/l. Also the fry were consuming vast amounts of rotifers and I was only now able to maintain the concentration around 1/ml. I held off starting to use Artemia until day 13 as they are a poorer nutritional food source for the fry. Newly hatched Artemia (instar 1) do not feed until they have gone through their first moult at about 12 hours old, however after hatching they quickly lose their nutritional value and don't regain it until they start feeding at the instar 2 stage. As instar 2 Artemia still seemed too large for the fry I had to try and only offer Artemia that were less than three hours old. By day 20 there was about 50% mortality but I still had 240 fry left. The rotifers had almost all gone and the fry were now feeding on instar 2 and 3 Artemia that had been fed on the same ratio of phytoplankton as the rotifers. The fry had started to take on a more fish-like appearance and there was the slightest red pigmentation on their sides. Physical damage was becoming a problem now. I had lost at least 80 fry from either being trapped under equipment or in the water meniscus between an airline and the side of the vat. I was also worried about the fry congregating in the corners with many of them head bumping against the side of the vat. Things did not get any better and I was down to 130 fry on day 23. By now the fry had reached the post-larval stage, the head was narrower, the body deepened and the eyes darker and they had also taken on a more opaque appearance. Unfortunately many of the fry appeared to have mouth deformities. It looked as if all the mouth parts were there but the mouth was permanently agape. I was not sure if the cause was a vitamin deficiency (probably vitamin C) or due to the excessive head bumping where the fry would continually swim against the side of the vat or appear to bite at it. P. fridmani start to go through metamorphosis around day 26 and by day 24 I still had around a hundred fry. The largest fry were 12mm long, pigmentation was increasing along the sides and they had started to behave more like adult dottybacks and less like larvae. However by day 29 still none of the fry had gone through metamorphosis and I was starting to get worried. I removed the remaining 30 odd fry and put them into a small glass tank. They did not look particularly good as most had mouth deformities while the others looked weak or stunted. I was not sure if the problem was due to them not being able to catch so much food due to the mouth deformities or nutritionally poor food itself. Many of the fry would drift around before they died with empty stomachs, others seeming to go into panicked spins before dieing rapidly whilst showing very high respiration rates. None of this batch made it through. They were 36 days old and up to 15mm long before the last ones died. Although they should have gone through metamorphosis over a week earlier none of them did. The mouth deformities and nutritional deficiencies seemed to be the main problem although I was loosing a lot of fry to what I now thought were bacterial infections. I had kept the fry alive long enough but I now had to find out what was missing. I had another brood on the way and I was sure I would solve the problems soon.

Glossary

• Nannochloropsis - A species of marine phytoplankton (that has a high EPA profile).
• Isochrysis - A species of marine phytoplankton (that has a high DHA profile).
• DHA and EPA - Essential fatty acids of the omega 3 family.
• DHA - Docosahexaenoic acid.
• EPA - Eicosapentaenoic acid.

By Clayton Smith

Photos By Robert Brady and Derek Scales