Hatching Strategies of Coral Reef Fish
Nest of Sergeant Major fish in Florida.
In all fishes, hatching from the eggs takes a negligibly short time compared to the remainder of their lives. However, it is a crucial event, and when, and under what conditions it occurs influence considerably the survival, development and success of the fish larvae. Furthermore, for coral reef fish, hatching not only marks the beginning of life, but also of the dispersal phase. The timing of hatching dictates the conditions that the larvae will encounter, potentially influencing their survival and dispersal. Despite this importance, very few studies looked at hatching in the natural environment because of important technical constrains. Yet, it is necessary to study the characteristics of the hatching events and the surrounding environmental conditions to better understand the larval phase.
Adult sergeant major fish in Florida
Observing the hatching events in situ is particularly challenging because this process occurs mostly at night and underwater. Furthermore, the minute size of the eggs and larvae complicates direct observations. In order to overcome these constrains, we developed infra-red underwater video cameras and remotely monitored the clutches of fish eggs for the entire night. Our approach allows for long observation times, without being limited by safety or resources, and the use of infra-red lights avoids disturbances to the fish. Using this method, we successfully documented for the first time the hatching events of three coral reef fish species, all benthic brooders (Abudefduf saxatilis, Elacatinus lori, and Stegastes partitus).
Myself deploying an infrared camera in front of a nest of bicolor damselfish in Florida.
Using the observations, we show that the timing, rate, and duration of the hatching events are different for the three species, but consistent within each species, highlighting different hatching strategies. The analysis of the fish behaviors shows that the males display parental cares beyond the incubation period of the eggs and play an active role in the hatching events. With this study, we can finally relate the hatching events to the environmental context. This gives us a better understanding of the factors influencing the beginning of the larval phase. It also opens to speculation about the consequences of different hatching strategies for the survival and dispersal of fish larvae.