Adrien Bottarelli - Martin Jeanmonod - Sylvain Lanz
Introduction
The coral reef is an important shelter for many fish species or invertebrates. Indeed, the coral provide many refuges for the fishes which can hide from the predators, lay eggs in a safer place or use the coral to find food.
Therefore, in a team of three persons, we were wondering if the coral reef complexity could influence the diversity of fish species. We decided to create a project focused on the diversity of the damselfishes and the structural complexity of corals in the red sea on three consecutive days.
Method
The data were collected in two steps:
1st step (fish diversity):
Two persons were in charge to draw a lane of 1 meter wide with to strings of 5 meters long, (gal.1). After five minutes of none human disturbance on the coral, the number of damselfish species (gal.2) were counted in the lane.
2nd step (coral complexity):
After the fish diversity, we focused on the coral complexity. With a one meter quadrat containing sixteen squares, one person was in charge to determine which structural type of coral was present in each square (gal.3). Structural type were considered as complex for “branching”, “laminar” and “columnar” corals and simple for “massive” and “encrusting” corals (gal.4).
1
2
http://krupp.wcc.hawaii.edu/BIOL200/powerpnt/pdffiles/coralanatomy.pdf
http://krupp.wcc.hawaii.edu/BIOL200/powerpnt/pdffiles/coralanatomy.pdf
Results and discussion
The number of species was apparently not affected by the different types of corals. However, the number of individuals (all species together) was favoured by a higher proportion of complex corals (Figure 5). This could indicate that a complicated morphology of coral present more interest for fish to swim around.
Figure 5. Relationship between number of individuals and proportion of “complex” corals.
The place in the coral reef had also an effect on the number of individuals. Being in a small patch of corals or in a wide flat area of the reef may change the number of fish you can see.
Our project revealed that the impact of structural diversity on fish diversity is difficult to catch. The complexity of a structure is something not obvious to evaluate and lots of other factors are affecting the presence of fish at a certain place and at a certain time in a coral reef.