That fish eggs develop faster at high temperature than at low temperature has been known at least since Dannevig (1895), and this theme has been amplified¾ and quantified¾ by many authors (see Pauly and Pullin 1988, and Fig. 46). The effect on egg development of factors other than temperature has been less studied: there are no datasets that could be used to identify such factors unequivocally and quantify their effects across a large number of fish species. The sole exception to this is egg size, which is usually documented as egg diameter.
Various authors have noted that large eggs develop¾ other things being equal¾ more slowly than small eggs (see, e.g., Breder and Rosen 1966). The first demonstration of this effect across a wide range of species may, however, be that of Pauly and Pullin (1988) whose compilation of fish egg development times, egg diameters and corresponding temperature for 84 teleost species from 50 references, provided the impetus for the development of the EGGDEV table, and its first entries.
The EGGDEV table has the following fields:
Egg development time: Duration from spawning/fertilization to hatching, in days; ideally this should refer to the time when 50% of the eggs have hatched, but often refers to a midrange.
Egg diameter in mm: This should be replaced by the diameter of a sphere equivalent to the volume of non-spherical eggs when such occur, e.g., in engraulids.
Water temperature in °C: Refers to the mean temperature to which the eggs are exposed.
Salinity: Given in two fields, one for ppt, the other a choice field. Options are seawater; brackish water; and freshwater.
Data type: A choice field with the options: based on field data; based on laboratory experiments; based on aquarium observations; other.
Remarks: a field for miscellaneous comments, e.g., on ‘egg diameter’ referring to a spherical equivalent, or a description of how estimates were obtained.
These fields are complemented by the Reference, Locality and Country fields such as used in other tables.
Pauly and Pullin (1988) derived a multiple (log linear) regression model to enable prediction of egg development time from knowledge of water temperature and egg diameter. An obvious use of the data in the EGGDEV table is to improve their model, based on the larger dataset now available. Such a model, possibly including dummy variables for taxonomic groupings, may help testing Pauly and Pullin’s contention that the taxonomic affinities of teleosts do not affect their egg development time, given the same temperature and egg diameter. Such testing may have important implications for the life-history theory.
Fig. 46. Relationship between the mean development time of fish eggs and the mean temperature of the water in which they develop. See Box 32 for a discussion of this graph.
It has been known to scientists for at least a century, and probably much longer to those involved in fish culture, e.g., of carp in ancient China, or medieval Europe, that the time required by fertilized fish eggs to hatch decreases with increasing temperature.
The two FishBase graphs dealing with egg development, based exclusively on the entries of the EGGDEV table, account not only for temperature but also for egg size – a factor that has received far less attention, though it also affects egg development (Pauly and Pullin 1988).
A plot of development time vs. temperature (see Fig. 46) differentiates eggs with diameters of 1 mm or less from larger eggs; it clearly shows that, at a given temperature, smaller eggs develop faster than larger eggs.
This theme is further explored in the second plot (Fig. 47), of ‘temperature-adjusted egg development time’ vs. egg diameter, which displays, as expected, an increasing trend, notwithstanding a simultaneous increase of variance. Note that this graph has a Y-axis roughly corresponding to the ‘degree-days’ of the practitioners, but with Kelvin (K = °
C + 273.16) being used to ensure linearity over a wide range of temperatures.
Reference
Pauly, D. and R.S.V. Pullin. 1988. Hatching time in spherical, pelagic, marine fish eggs in response to temperature and egg size. Environ. Biol. Fish. 22(4):261-271.
Daniel Pauly
Also, egg size and development time are very important in all captive breeding of fish because they can influence the design of hatchery equipment and the management and husbandry of all the life-history stages of fish held in captivity. Small eggs produce small larvae with small mouths that are often more difficult to feed than large larvae. Therefore, the EGGDEV table can provide some guidance for the requirements and likely success of breeding fish in captivity. This is important when considering potential new species for aquaculture.
Fig. 47. Temperature-adjusted development of fish eggs as a function of egg diameter. See Box 32 for a discussion of this graph.
You get to the EGGDEV table by clicking on the Biology button in the SPECIES window, the Reproduction button in the BIOLOGY window and the Egg dev. button in the next window.
On the Internet, you get to the EGGDEV table by clicking on the Egg dev. link in the ‘More information’ section of the ‘Species Summary’ page in either FishBase or LarvalBase (
www.larvalbase.org). You can create a list of species with available data by selecting the Egg dev’t. radio button in the ‘Information by Topic’ section of either FishBase or LarvalBase.
Breder, C.M., Jr. and D.E. Rosen. 1966. Modes of reproduction in fishes. T.F.H. Publications, Neptune City, New Jersey. 941 p.
Dannevig, H. 1895. The influence of temperature on the development of the eggs of fishes. Rep. Fish. Board Scotland 1894:147-152.
Pauly, D. and R.S.V. Pullin. 1988. Hatching time in spherical, pelagic, marine fish eggs in response to temperature and egg size. Environ. Biol. Fish. 22(4):261-271.