Birth of butterfly fish at the Aquarium La Rochelle

Scientific success at the Aquarium! After several attempts, our biology team sees its work rewarded by the birth of 16 Heniochus acuminatus, a species of the butterfly fish family.

A long and meticulous process

The Aquarium’s biologists have been working for several years on the larval rearing of numerous underwater species. Recently, their mastery of phytoplankton and zooplankton production has opened up the field of possibilities. In addition to the species for which they have mastered the pattern, biologists and divers are now focusing on fish for which there is a lack of scientific publications. Thus, the Aquarium’s experts are writing and implementing new protocols from behind the scenes. The first step is to collect fertilised eggs from the tanks. These eggs, which are less than one millimetre in diameter, are then isolated.

Mathieu Coutant, general manager of the Aquarium La Rochelle, explains:

"reproduction is one of the parameters that allows us to see that the animals' living conditions are close to optimum; the team's work focuses on larval rearing".

After a few hours, the eggs hatch and the larvae appear. Less than 1.5 mm long, they live for the first few hours on their yolk reserves. As soon as the mouth is formed, they must be presented with a sufficient quantity and quality of zooplankton to allow them to develop. These prey reared in the laboratories of the scientific structure measure 0.04 mm.

Many parameters and challenges to overcome

In order for the larvae to continue their development, the biology team creates a mesocosm, an environment with optimal conditions, similar to those found in the species’ natural environment. Each parameter is monitored daily: water salinity, pool lighting, pH, oxygen, water temperature, iodine, etc. Feeding is also essential. This, like the other criteria, evolves according to the progress of the protocol, as well as the size and nutritional needs of the larvae.

Moving research forward

There is no scientific publication today that mentions a larval rearing protocol for Heniochus acuminatus. Every 10 days, a new metamorphosis phase occurs. The environment set up and their nutrition must be continually reviewed. Guillaume, head of our biology department, concludes: “This success was built on our knowledge, our failures and our observations; it is a collective success that opens the way to scientific communication and new projects.

About two months into the process, the newcomers are on average two centimetres long. Under the watchful eye of the whole team, some of the juveniles have already joined the exhibition tanks!

First European scientific achievement

Birth of butterfly fish at the Aquarium La Rochelle

A long and meticulous process

Many parameters and challenges to overcome

Moving research forward