Know more

About cookies

What is a "cookie"?

A "cookie" is a piece of information, usually small and identified by a name, which may be sent to your browser by a website you are visiting. Your web browser will store it for a period of time, and send it back to the web server each time you log on again.

Different types of cookies are placed on the sites:

  • Cookies strictly necessary for the proper functioning of the site
  • Cookies deposited by third party sites to improve the interactivity of the site, to collect statistics

Learn more about cookies and how they work

The different types of cookies used on this site

Cookies strictly necessary for the site to function

These cookies allow the main services of the site to function optimally. You can technically block them using your browser settings but your experience on the site may be degraded.

Furthermore, you have the possibility of opposing the use of audience measurement tracers strictly necessary for the functioning and current administration of the website in the cookie management window accessible via the link located in the footer of the site.

Technical cookies

Name of the cookie


Shelf life

CAS and PHP session cookies

Login credentials, session security



Saving your cookie consent choices

12 months

Audience measurement cookies (AT Internet)

Name of the cookie


Shelf life


Trace the visitor's route in order to establish visit statistics.

13 months


Store the anonymous ID of the visitor who starts the first time he visits the site

13 months


Identify the numbers (unique identifiers of a site) seen by the visitor and store the visitor's identifiers.

13 months

About the AT Internet audience measurement tool :

AT Internet's audience measurement tool Analytics is deployed on this site in order to obtain information on visitors' navigation and to improve its use.

The French data protection authority (CNIL) has granted an exemption to AT Internet's Web Analytics cookie. This tool is thus exempt from the collection of the Internet user's consent with regard to the deposit of analytics cookies. However, you can refuse the deposit of these cookies via the cookie management panel.

Good to know:

  • The data collected are not cross-checked with other processing operations
  • The deposited cookie is only used to produce anonymous statistics
  • The cookie does not allow the user's navigation on other sites to be tracked.

Third party cookies to improve the interactivity of the site

This site relies on certain services provided by third parties which allow :

  • to offer interactive content;
  • improve usability and facilitate the sharing of content on social networks;
  • view videos and animated presentations directly on our website;
  • protect form entries from robots;
  • monitor the performance of the site.

These third parties will collect and use your browsing data for their own purposes.

How to accept or reject cookies

When you start browsing an eZpublish site, the appearance of the "cookies" banner allows you to accept or refuse all the cookies we use. This banner will be displayed as long as you have not made a choice, even if you are browsing on another page of the site.

You can change your choices at any time by clicking on the "Cookie Management" link.

You can manage these cookies in your browser. Here are the procedures to follow: Firefox; Chrome; Explorer; Safari; Opera

For more information about the cookies we use, you can contact INRAE's Data Protection Officer by email at or by post at :


24, chemin de Borde Rouge -Auzeville - CS52627 31326 Castanet Tolosan cedex - France

Last update: May 2021

Menu Logo Principal


Zone de texte éditable et éditée

Reproductive Strategies

Reproductive Strategies
© Schulz.R
Although there are rare cases of parthenogenesis, such as in the Amazon molly (Poecilia formosa), the large majority of teleosts reproduce through sexual reproduction.

A reproductive strategy is defined as the way in which a species allocates or budgets energy to produce viable offspring. Energy is diverted into actual offspring and into parental care. One usually distinguishes the R-strategy, in which energy is invested in a multitude of offspring that receive little or no parental care, and the K-strategy, wherein energy is invested in a few, large offspring that require considerable parental care. Teleost fish have developed a large variety of reproductive strategies and reproductive behaviours, ranging from mass spawning to parental care, from strict gonochorism (separate sexes) to simultaneous hermaphrodism, and from oviparity to vivparity.
Gonochorism and sex change

Most fish are gonochoric, that is their sexes are separate and determined once, for life (e.g. rainbow trout, Onchorynchus mykiss). However, many fish exhibit sex change during their lifetime. This is called successive hermaphrodism, which can be protandrous if the fish changes from a male to a female, such as the gilthead seabream (Sparus aurata). Other species are protogynous hermaphrodites and change from a female into a male (e.g. orange spotted grouper). Simultaneous hermaphrodites also exist, which behave almost simultaneously as males or females with cross-fecundation taking place; indeed individuals can change within minutes from displaying male sexual behaviour, with sperm release, to female sexual behaviour, with egg laying (e.g. western Atlantic serranid black hamlet).
Release of offspring: Oviparous or Viviparous

In oviparous fish, eggs are fertilised externally, after spawning. In viviparous fish, such as the guppy (Poecilia reticulata) or the mosquito fish (Gambusia affinis), the fertilised and developing eggs remain inside the body of the mother for a certain period of time and the offspring are released as free-swimming young. In fact, it is more appropriate to speak of ovoviviparity as there are no real exchanges between the mother and the embryos.
Ovarian development: Synchronous, Group synchronous, Asynchronous

Synchronous fish reproduce only once each year, or once in their lifetime. In such species, all oocytes develop simultaneously and are at the same developmental stage at a given time. This is the case for salmonids, for example. Group synchronous fish have two or more distinct populations of oocytes present at the same time and ovulate once in a season, or undergo multiple ovulations over a few days or weeks within the spawning season. Asynchronous fish, such as the zebrafish, are capable of ovulating on a regular basis, sometimes every day, over a prolonged period.
Spawning strategies

Most teleost fish are are either determinate of indeterminate batch spawners. In determinate spawners, the potential annual fecundity is fixed prior to the spawning period. The total number of eggs spawned per female in a year is called the realised annual fecundity. For indeterminate spawners, the potential annual fecundity is not fixed before the onset of spawning. In such species, eggs can develop at any time during the spawning season.
Some fish species are single or total spawners. Total spawners release their eggs as a unique event, or over a short period of time but as part of a unique event (as opposed to being spawned in several batches). Single spawners release all their eggs in a single lifetime event.
Spawning type
Pelagic spawners allow their eggs to be carried freely by the currents, however spawning is precisely timed and takes place in specific locations; this is either to minimise egg predation, to maximise dispersal, or to provide the best conditions for the pelagic larvae to survive upon hatching.
Some fish are nest spawners, for example, the male stickleback (Gasterosteus aculeatus) builds a nest and attracts the female to this nest to spawn. Others are demersal spawners, attaching their eggs to a substrate such as the vegetation or the stream bed (e.g. cyprinids and salmonids respectively).
Mouthbrooders care for their eggs and / or larvae and protect them from predation by taking them into their mouths (e.g. tilapia). Some fish breed inside invertebrates, for example the European bitterling deposits its eggs into a living mussel. Other forms of parental care include egg brooding in special pouches, such as in the seahorse male ("pregnant" males); and skin brooding, which involves the attachment of eggs and developing embryos to the skin of one of the parents (e.g. pipefish).

This factsheet was prepared with the expert assistance of scientist Alexis Fostier.

See also

Jalabert, B. 2005. Particularities of reproduction and oogenesis in teleost fish compared to mammals. Reprod Nutr Dev 45:261-279.