Aquatic animal tracking is offering a new panoramic view to study wild fish behaviour at unprecedented levels of detail. The most recent example of its benefits is the discovery of fish chronotypes; consistent intra-specific variation in behavioural traits related to the circadian rhythm measured in free-living fish (morning larks or evening owls chronotypes). Similar to personality traits, fish chronotypes may play a relevant role in many ecological and evolutionary processes occurring in wild populations. CLOCKS aims to provide novel insight into the causes and consequences of such circadian behavioural variation.

            In work-package (WP) one, we will investigate whether fish chronotypes are a global property of marine fish populations using an existing multi-species behavioural data-set from different fish species. This data-set will be complemented by data from other species around the globe taking advantage of a recently launched Pan-European biotelemetry network, of which the CLOCKS team is an inherent part of the research group.
    In WP two, we will provide novel insight into the causes of fish chronotypes using a cross-disciplinary approach. Our theoretical hypothesis is that chronotypes are the behavioural expression of an endogenous oscillation rhythm of about 24 hours (circadian rhythm) interacting with the aquatic environment. Therefore, we will first control the effects of the environment and study whether the daily biological rhythm in a model marine species (Xyrichtys novacula) under laboratory conditions meets the three conditions to be defined as circadian rhythm: the rhythm is endogenous and has a free-running period, is entrainable, and exhibits temperature compensation. We will study the circadian rhythm in our model species across different ontogenetic stages (larvae and adult). After laboratory assays, fish will be secondly tracked in the open ocean using electronic devices to study whether our theoretical prediction is true - fish chronotypes emerge from the circadian rhythm interacting with the environment. The effect of multiple environmental variables shaping circadian behavioural variation will be evaluated using high-resolution tracking and statistical patterns. A recent review suggests that half of the observed intra-specific behavioural variation across taxa is generated from additive genetic variation in addition to the environmental effects. Accordingly, we will in parallel provide novel insight into the genetic basis of fish chronotypes through a combination of hypothesis-driven candidate gene approaches and next generation molecular tools for genome-wide expression.
     In WP three, we will explore the consequences at individual level of fish chronotypes. We will develop a new individual framework that integrates circadian behavioural variation and life-history (growth, age of maturation and reproduction investment) based on bio-energetic models. Our main aim is to make predictions of the consequences of fish chronotypes on life-history and physiology at the individual level. We will validate our new framework using fish otoliths and novel approaches to estimate the fish metabolic field using Isotope-ratio mass spectrometry.
    CLOCKS has a specific WP four dedicated to the transference of the new knowledge generated and results dissemination. CLOCKS will provide the most comprehensive view of the causes and consequences of fish chronotypes in the new research field of eco-chronobiology.