Invitation to Ph.D. Thesis Defence

Ph.D. thesis title: Individual Circadian Behaviour Variation in Wild Fish: Global Assessment, Environmental-Related effects, and Socio-Ecological Consequences.

Ph.D. Student: Martina Martorell, Department of Marine Ecology, IMEDEA (CSIC-UIB)

Supervisor: Dr Josep Alós, Department of Marine Ecology, IMEDEA (CSIC-UIB)

The defence will take place on monday February, 5^th at 11:00 at Sala de Grados B, Edificio Jovellanos, Universidad de les Illes Balears (UIB)

Abstract:

This thesis aims to comprehensively investigate the existence of chronotypes across different fish species and examines how environmental factors modulate them using cutting-edge fish tracking technologies. The thesis first investigates the presence of chronotypes in free-living fish species, clearly identifying these individual temporal patterns in several marine species. Fish behavior is known to be influenced by environmental factors. However, individuals within the same population can exhibit different responses to environmental gradients, referred to as behavioral reaction norms. Subsequently, the thesis describes a large-scale tracking experiment conducted to explore how those environmental gradients affect the expression of chronotypes in the pearly razorfish, Xyrichtys novacula. Behavioral traits typically covary, forming behavioral syndromes, yet few studies have explored chronotype-personality syndromes. This thesis proposes a novel methodological approach that combines laboratory and field experiments to quantitatively assess both classical and circadian-related behavioral traits in the pearly razorfish. Finally, it is well-established today that fishing exerts selective pressures on fish behavior. The final chapter of this thesis proposes a modeling approach to investigate whether exploitation by fishing may lead to directional selection on fish chronotypes. This PhD thesis introduces the field of marine eco-chronobiology, bridging gaps among three traditionally distinct disciplines: marine ecology, fisheries science, and chronobiology.

Link to zoom:

postgrau.uib.es/doctor.....tente

Abstract

In rainbow trout ( Oncorhynchus mykiss ) aquaculture a significant portion of the fish die (around 10%) or experience growth stunting (GS; around 10%), which represents an important profitability and welfare issue. In the presented study, we aimed at characterising the GS phenotype in seawater-transferred rainbow trout using untargeted and targeted molecular biology methods, discovering the implication of a variety of pathways. During this talk, each method used will be explained in detail, showcasing the capabilities of each one.

Asbtract

Seagrass meadows provide essential ecosystem functions and services. They serve as nursery habitats for fish, and the structural complexity is a key factor influencing this function. Despite their ecological importance, seagrasses are being degraded worldwide at an alarming rate, leading to a significant loss of habitat structure. In response to this trend, restoration projects have been developed in recent years, aiming to recover both habitat structure and associated functions We assessed the recovery of habitat structure and the associated nursery function within a restored Posidonia oceanica meadow. Additionally, we conducted habitat selection experiments with two species, Diplodus annularis and Symphodus tinca, to evaluate if they actively select seagrass habitats based on structural complexity. Our results revealed that, despite the presence of some fish species in the restored area, neither the structural complexity nor the nursery function had fully recovered. In the choice experiments, both species exhibited a clear affinity for seagrass habitats over unvegetated areas, demonstrating their ability to actively selected habitats based on visual cues. However, the response in occupancy patterns to increasing seagrass complexity was species-specific.Understanding how juvenile fish respond to changes in seagrass habitat features is crucial for quantifying the nursery service provision and for identifying effective measures to accelerate the restoration process.