| Artificial reefs are increasingly utilized in marine ecosystems to support biodiversity and provide refuge for fish species. To maximize the effectiveness of artificial reefs, it is crucial to understand how fish locate and aggregate around them. Sensory cues play a critical role in guiding fish navigation and aggregation behaviors. Among the primary sensory modalities, vision and the lateral line system are particularly important for detecting environmental features and predators. However, the specific contributions of these two sensory systems, and the potential interactions between them in guiding fish toward artificial reefs, remain poorly understood. This study investigates the effects of impairing the visual and lateral line systems, both independently and in combination, on the aggregation behavior of Sebastes schlegelii, a species that relies heavily on these sensory modalities for habitat selection.
The primary objective of this study was to assess whether impairments to the visual and lateral line systems affect the fish's ability to aggregate around artificial reefs. We designed six experimental groups to explore the impacts of various impairments on aggregation behavior. The groups were as follows: (1) Normal group, where no sensory impairments were applied; (2) Visual impairment group, where visual cues were blocked using opaque goggles; (3) Mild lateral line impairment group, where the lateral line system was partially disrupted using a gentle treatment; (4) Visual + mild lateral line impairment group, combining visual and mild lateral line impairments; (5) Severe lateral line impairment group, where the lateral line system was extensively disrupted; and (6) Visual + severe lateral line impairment group, where both sensory systems were impaired to a severe degree. Aggregation behavior was measured by observing the number of fish within a defined proximity to an artificial reef over a 12-hour period, which allowed us to examine both immediate and sustained responses.
Our findings demonstrated that fish in the Normal group exhibited the highest levels of aggregation, confirming that both visual and lateral line cues are essential for guiding fish towards artificial reefs. This supports the hypothesis that these sensory systems play a significant role in habitat selection and aggregation. Fish in the Visual impairment group and the Mild lateral line impairment group showed significantly reduced aggregation compared to the Normal group, suggesting that both visual and lateral line cues are critical for efficient navigation and habitat selection. Notably, fish in the Severe lateral line impairment group and the Visual + severe lateral line impairment group exhibited even lower levels of aggregation, indicating that more severe impairments to either or both sensory systems result in further decreases in aggregation behavior.
An important finding from this study was the absence of a significant interaction between the two sensory impairments. While impairing both the visual and lateral line systems (either mildly or severely) resulted in a greater reduction in aggregation compared to impairing either system alone, the effects were additive rather than synergistic. This means that impairing the two sensory systems did not result in a compounded or exaggerated loss of aggregation behavior. Instead, the loss of aggregation behavior due to sensory impairments occurred independently for each system. For example, fish with only visual impairments showed reduced aggregation, and fish with only lateral line impairments showed a similar reduction. The combined impairments led to a further decrease in aggregation but did not result in a proportionally greater reduction than would be expected from the sum of the individual impairments.
These results suggest that, while both visual and lateral line systems are crucial for fish aggregation behavior, the impairments to these systems do not interact in a way that amplifies the effects. In other words, impairing both sensory systems reduces aggregation behavior more than impairing either system alone, but the lack of an interaction effect implies that the two systems do not jointly influence aggregation in a compounded manner. This finding has implications for understanding how fish navigate toward artificial reefs and could guide the design of future reef structures. For example, artificial reefs that target the enhancement of one sensory modality (such as visual cues) may still be effective in supporting fish aggregation, as the loss of one sensory system does not appear to severely compromise aggregation behavior.
However, it is important to note that these conclusions are based on the behavior of Sebastes schlegelii in the context of this specific study. The lack of interaction between sensory systems in this species may not apply universally to all fish species. Some species may rely more heavily on one sensory modality over another, or they may exhibit different types of sensory integration. Thus, further studies are needed to explore the sensory preferences and behavior of other fish species in relation to artificial reefs.
This study also highlights the broader ecological implications of artificial reef design. Understanding the role of sensory systems in fish aggregation can inform strategies to optimize the placement and features of artificial reefs, making them more effective in supporting marine biodiversity. In particular, this research underscores the importance of considering the sensory ecology of target species when designing artificial habitats, and it provides valuable insights into how sensory impairments affect fish behavior and ecological interactions. |
