The Fry Nursery Table

After completion of metamorphosis, fish larvae are usually transferred to a new environment such as concrete tanks, small ponds or lakes. The conditions applied here are often more natural than within the larval nursery. The table Fry nursery system holds information on all important aspects for this larval stage, from transport to feeding.


The field Nursery system gives a broad classification of the appropriate culture system for the selected species. The field Details is a free text field and gives additional information about on-growing facilities, their preparation in cases of, e.g., outdoor ponds, indication on handling of fry, and details about water supply and turnover rate.

The field Number of fry indicates the actual number of larvae released into an on-growing unit, whereas the Stocking density gives a number per unit for optimal stocking of the on-growing facilities (e.g., kg/m3).

The field Main water source indicates the most common water source used for water supply or the place (e.g., pond) where the fry were released. A water source which can be used alternatively is mentioned in the field Supplemental water source.

The fields Temperature, Salinity, pH, Oxygen, Hardness and Illumination give the range of optimal abiotic values for fry. Illumination in case of natural light in outdoor cultures (e.g., ponds, tanks) may indicate that shading against sunlight is required.

Biotic values are presented in the next table section: Production. The Time to alevins in day-degrees and in days gives information on the time needed for fry to reach the stage of alevins (or fingerlings). Because this period depends among others (e.g., feeding) on the temperature regime, the values presented here relate to the indicated water temperature in the on-growing facilities.

Morality after metamorphosis

The Mortality field indicates the range of fry mortality encountered during the period from larvae (end of the larval stage, i.e., from metamorphosis) to alevins, in percent.

Production/cycle indicates the amount of fry produced per cycle and rearing unit (e.g., number/m3), the field Production/year indicates the total production in amount of fry per year per unit (e.g., number/m2). Notes about the growth rate may be shown in the free text field Growth rate, where growth of the fry can be described in relation to the actual environmental conditions and feeding regime.

The next section Nutrient inputs refers to the food and feeding regime for the fry. The Main food field indicates the different food needed throughout the fry period. Description of nutrient input is a free text field and describes in detail, e.g., the diet sequence, the different sizes of formulated feeds, food quality (e.g., the need for certain fatty acid profiles for normal development) and density of food organisms or amount of formulated feed to apply.

The free text field Comments may be used for further relevant notes about specific requirements of the species, such as sorting, grading and transportation, stunting, critical periods, quality control measures, or treatment against infection and parasites.


The literature about larval rearing is very diverse, with data for the same species varying between geographic regions, and there are sometimes considerable differences with the biotic and abiotic factors among experimental rearing and commercial hatchery operation. It was often found difficult to present a rearing protocol in a concise and standardized table format valid for all purposes and localities. Thus, we decided to produce additional comprehensive essays about each species in LarvalBase. These essays can be accessed by clicking on the button Mini-Essay which is present in each table but only active if a mini-essay is availaible for the respective species.


Only a few mini-essays are available at present. Please volunteer to cover species of which you have a good knowledge. Please contact the project leader of LarvalBase for more information (

Water Quality Button

Within all LarvalBase tables, a button Water Quality is present and opens a table showing values about optimal water quality (by species) and indications on harmful concentrations of a wide variety of organic and inorganic substances (e.g., nitrite, nitrate, ammonia, ozone, chlorine, polychlorinated biphenyls, DDT, etc.) which are of concern in larval rearing and aquaculture of fish.


If data about Water Quality are availaible for a species, the respective button is active (black). At present, these records are available only for a few species.

Picture Button

Larval photos as well as drawings of developmental stages of eggs and larvae are important for identification or to check if regular development occurs. Thus, LarvalBase intends to add these kinds of illustrations for each species in LarvalBase. The Picture button is active (black) if an image is availaible for a certain species.


Larval photos are very difficult to obtain, nevertheless LarvalBase aims at the presentation of at least one photo for each species. Just a few photos come with the present version of LarvalBase. Please help if you have photos about fish larvae and juveniles in your collection. The same is true for drawings of developmental stages.


While this version of LarvalBase on CD-ROM is rather a preview of forms than a complete collection of data, the www-version of LarvalBase will be completed continuously (updates about every 4 weeks; visit to see our progress).

How to get there

All tables described above can be accessed from the SPECIES table. From there, click on the Biology button and from there choose Reproduction. You will see buttons for Broodstock, EggNursery, LarvalNursery and FryNursery. The buttons are active (black) if related information is available. Mini-Essays about larval rearing are accessible from within the LarvalBase tables.

Bernd Ueberschär