Breeding and Raising Marine Fishes – Part One
Many aquarists who have moved on to marines after keeping freshwater often wonder why it seems so difficult to breed marine species. Well for many species it’s not actually difficult! Any problems are more about raising the larvae or fry and most of these problems revolve around feeding. It’s probably true to say that the most difficult part of raising marine fish is not the fish themselves, rather the foods required to feed them.
For any aquatic animal to breed in captivity we need to first provide conditions conducive to breeding. This includes ensuring good water quality, a safe environment, optimum nutrition, and, of course, a compatible mate. Some species require additional cues to stimulate breeding behaviour; factors such as the lunar cycle, changes in salinity or temperature, along with other variables may need to be just right for breeding to commence. Species requiring additional cues are better off left to the more experienced breeder who’s prepared to devote time to research and experimentation so I’ll concentrate on comparatively easy, commonly available species.
The fishes that we’re able to successfully breed and raise tend to be those that demonstrate some form of parental care, either as demersal spawners or as mouthbrooders.
The most commonly raised demersal spawner is the ubiquitous clownfish, usually Amphiporon ocellaris, the common clown; most species of clowns are relatively easy to raise but may have their own idiosyncrasies. Other damselfish species readily spawn in the aquarium; there’s an undescribed species, sometimes referred to as “Gold Chromis”, probably and undescribed Amblyglyphidon species that’s even easier to breed than Clownfishes. Elacatinus evalanae and Elacatinus oceanops, – the gold and the blue neon gobies – are also relatively easy but they have the drawback that, unlike clowns, they can be intermittent, having brief periods of spawning activity interspersed with long periods of nothing! There’s evidence that they pair up to spawn seasonally, it may be wrong to expect them to reproduce continuously with the same partners without some manipulation of the environment to replicate what happens in the wild. Various species of Dottybacks are regularly captive bred although a bit of experience at breeding and raising easier species would be best before moving on to these; main difficulties appear to be in providing foods of the correct nutritional balance so more experience with live foods may be necessary to succeed.
When it comes to fish, the easiest of the commonly available species are Pterapogon kauderni, the Banggai cardinals. These fish differ from the aforementioned species in that they are mouthbrooders. In fact with this species, other than making sure you have a pair, feeding them well, and giving the young a safe, predator free environment the aquarist has very little to do! Unlike other species the young are released self sufficient, capable of feeding on newly hatched artemia nauplii. Before you rush out to buy yourself a pair there are a couple of drawbacks to consider. This species is endangered in the wild as it mostly comes from a very small collection area and owing to the manner of its breeding it doesn’t replace its population very quickly. Captive bred fished are your best choice. It can be difficult to correctly identify a pair, if you get it wrong it can be a death sentence for any smaller male supposed to be a female. Other species of cardinalfishes readily breed in the aquarium and can be raised successfully, however, as far as I know, they all appear to release their larvae at a stage of development roughly equivalent to a newly hatched clownfish larvae so need to be treated in the same way.
Note: for best results with Banggai cardinals keep them in a Caulerpa or sea grass environment. They’re not a reef species. A densely planted tank will benefit babies by providing plenty of safe hiding places and lots of natural food.
Shrimps of the genus Lysmata, commonly referred to as cleaner shrimps, are probably the easiest species of invertebrate that you’ll deliberately set out to breed. All you need with these are two shrimps of the same species and you have yourself a pair. Both shrimps will carry eggs on a regular basis, usually releasing larvae late at night. Lysmata wurdemanni or peppermint shrimp is by far the easiest of this group to gain success with due to the ease with which you can feed them. The set up described for fishes (see part 2 of this article) will work for raising these but you’ll need to pay extra attention to keeping the larval tank clean and preventing any build up of hair algae – tiny animals that are all legs can get easily caught up in hair algae and die.
The Importance of Live Food.
It’s commonly thought that getting fish to breed is the difficult part – not true! If your water conditions are satisfactory, the animals appropriately fed, not under undue stress from tank mates, and you have a male and a female then breeding should be inevitable. The real difficulties come in raising the larvae, the majority of these difficulties will stem from nutrition, and as the nutrition we require is derived from a combination of live foods in the form of phytoplankton and zooplankton I think it would be true to say that raising and maintaining these live food cultures is the key to the entire process of raising marine species.
Marine larvae are typically very small and spend their first few weeks living a pelagic existence amongst the rest of the zooplankton. They need food of a small particle size and, importantly, that food needs to be live. These larvae hunt by sight and need their food to be moving for it to catch their attention. You can see evidence of this after they’re a couple of days old and starting to become skilled in their hunting technique,
If you watch an individual larva hunt you’ll see it sights on its prey then pulls its body into an S shape that straightens out as it lunges forward.
If you can’t successfully raise and maintain the live foods your species requires in sufficient quantities, it’s very unlikely that you’ll ever manage to raise any larvae to adulthood!
First Culture Your Food.
Before going into detail about how to breed the various different species I’ll briefly look at the foods that need to be cultured. First you must bear in mind that it’s essential to have your food cultures up and running before you have any larvae to raise. If you’re not prepared in advance of a hatching you’ll lose the entire brood unless you know any friendly breeders who’ll take pity on you and help you out with cultures of their own.
As usual the base of the food chain when raising marine larvae is phytoplankton. Next up from phytoplankton are rotifers, then after rotifers there’s newly hatched artemia or brine shrimp. Rotifers are probably the most important link in the chain, marine fish larvae need a small particle size – far smaller than artemia nauplii – and they need something that’s moving too and is easily digestible. I reckon a good way to think about the relationship between these species is that the phyto supplies the nutrition a larva actually requires while the rotifers and artemia (older than twelve hours) are more the delivery system. By feeding rotifers and artemia with different strains of phyto we can fine-tune the selection of nutrients being delivered to the larvae according to that particular species requirements. This is because the different species of phyto all have different nutrient profiles i.e. different proportions of protein, fat, and carbohydrate; as adult fish of different species have different dietary requirements so do their larval forms. You may have noticed I specified artemia older than twelve hours, up until that time a newly hatched nauplii has a very good nutrient profile, after that time unless they are enriched they are nutritionally poor.
For more on live foods and nutrition see:
Note: Larval nutrition is going through a period of re-assessment with increasing use of copepods. Currently this article does not include practical references to copepods and is due to be updated in the near future. Nevertheless, the techniques described in this series of articles have been used to successfully raise marine organisms for many years.
Depending on how seriously you want to take your breeding project you can either keep your brood stock, the parents, in either your display tank or a dedicated brood stock tank. For a small-scale breeding attempt, perhaps you just want to have a go and see if you can raise a few clowns, you can be successful without having to set up the prospective parents in a separate tank by taking advantage of the fact that Clownfishes are demersal spawners.
A demersal spawner is one that spawns on a substrate, it’s useful to encourage the fish to spawn on or in a piece of material such as a tile, plant pot, length of plastic piping, etc. that can be transferred to a larval raising tank just prior to hatching. Do remember to make sure that whatever you use is of course made of a food safe material.
Sexual reproduction takes a great deal of energy so make sure you regularly feed your brood stock with foods of a high nutritional value, I’d suggest PE Mysis and CyclopEeze FreezerBar. If your water quality is good and there are no serious problems with any other of the tank’s inhabitants, by upping the quality and frequency of feeding (at least three times a day) you should shortly end up with a pair of fishes intent on breeding.
In part 2 of this article I’ll look at how to put together a larval raising tank and take you through the first few weeks of feeding and maintaining newly hatched larvae.
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