The complexity of seagrass meadows is key to habitat selection in juvenile fish.
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Recent research led by scientists from the Institut Mediterrani d’Estudis Avançats (IMEDEA, CSIC-UIB) has shed light on the importance of the structural complexity of seagrass meadows for habitat selection by juvenile fish in the Mediterranean.
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The study, which focused on two common species in Posidonia oceanica meadows, the peacock wrasse (Symphodus tinca) and the annular seabream (Diplodus annularis), demonstrated that these fish actively prefer vegetated habitats, although the two species respond differently to changes in complexity, highlighting the need to preserve and restore these vital ecosystems.
Seagrass meadows, especially those formed by the species Posidonia oceanica, play a crucial role in the survival of numerous marine species. These ecosystems not only provide shelter and food but also act as nursery habitats for various fish and invertebrates. A recent study by the Marine Ecology Institute has revealed key details about how the structural complexity of these meadows influences habitat selection by juvenile fish. In this study, experiments were conducted with juvenile peacock wrasse (Symphodus tinca) and annular seabream (Diplodus annularis) in an experimental aquarium simulating different habitat configurations. The results showed that both species prefer vegetated habitats compared to non-vegetated areas, using visual cues exclusively to identify their environment. However, the annular seabream showed a greater affinity for habitats with higher structural complexity, while the peacock wrasse did not show significant variations in its selection based on complexity.
These findings suggest that the annular seabream may be more vulnerable to the loss or simplification of P. oceanica meadows due to its preference for complex habitats to find refuge. In contrast, the peacock wrasse may adapt better to changes in habitat structure, allowing it to use restored P. oceanica meadows as nursery areas more quickly than the annular seabream. This is particularly relevant given the slow growth of P. oceanica and the low structural complexity of restored meadows in their early stages.
Photo: Specimens of Diplodus annularis, one of the species included in the study.
An Ecologically Important Finding
Understanding these habitat preferences is crucial for developing more effective conservation and restoration measures for seagrass meadows. Posidonia oceanica meadows, which extend from the surface to 40 meters deep in the Mediterranean, are declining at an alarming rate and are threatened locally and globally by factors such as boat anchoring, coastal erosion, climate change, and the invasion of exotic species. In many regions, these impacts have led to the reduction and fragmentation of P. oceanica meadows, resulting in structural changes that can affect the survival or habitat choice of the juvenile fish that depend on them.
This study highlights the need for restoration efforts that consider structural complexity to maximize their function as nursery habitats. Protecting and restoring these habitats not only helps maintain marine biodiversity but also ensures that juveniles of important species can find refuge and food, contributing to the sustainability of fish populations.
Reference:
Castro-Fernández, J; Hinz, H; Castejon-Silvo, I; Catalán, I.A.; Disdier-Gómez, J-M; Moranta, J; Ruiz-Frau, A; Grau, A; Terrados, J.