In situ swimming and orientation ability of larval cod and other plankton. Parameterizing models of prey availability to top predators

Larval transport from spawning grounds to nursery grounds is a key processes that needs to be addressed if attempting to quantify spatiotemporal availability to top predators. However, larvae are not entirely destined to follow ocean currents. They can af fect their dispersal both through vertical and horizontal movements and this will change the prey availability to their predators. While existing NFR-projects already model seabird-fish interactions under various climatic states with state-of-the-art mode l components, they would greatly benefit from improved model parameterizations of larval behavior. Here we propose to combine a unique field and laboratory observation platforms that, together, will add substantially to our knowledge of these critical asp ects of the early life history of a keystone fish species in Norwegian waters, Atlantic cod. Specific objectives are to (1) provide and analyze in situ measurements of swimming and orientation of the early life stages and (2) elucidate the in situ behavio ral responses of cod larvae, as individuals and in groups, to a combination of proximal cues. This information is complementary to observations on the sensory capabilities and behavior of cod larvae that are generated in the laboratory and/or from acousti c measurements. Furthermore, we will 3) communicate through publications how new knowledge on larval behavior gained through the experiments described above may be included in existing coupled physical-biological models involving early stages of cod. Key questions to address: Are cod larvae orienting vs. swimming at random when in open water? If larvae do orient, when during development does this begin? Where do they orient, i.e. towards what location? Are multi-modal stimuli providing useful information for detection, navigation and nursery habitat localization? What are these stimuli? How do swim speed and swim time compare in the field vs. laboratory observations? The study answered these questions, as follows: Most individual larvae exhibited directed swimming regardless of species and developmental stage. The swimming speed of Atlantic haddock increases with age only in-situ. In the laboratory the swimming speed remains low. Population-level orientation in Atlantic haddock (18-36 dph) is generally to the SW, the orientation is better during sunny days than during overcast days. This indicates goal-oriented swimming. Glass eels have directional swimming and show a preference in the orientation in coastal environments with a significant orientation during the ebb tide in situ and in the MagLab. Glass eels have a geomagnetic compass. Tides drive the orientation of glass eels at this migrating phase. This is the first study of ontogeny of orientation in a temperate fish This is the first evidence of magnetic orientation in the early life history of a fish.

Larval transport from spawning grounds to nursery grounds is a key processes that needs to be addressed if attempting to quantify spatiotemporal availability to top predators. However, larvae are not entirely destined to follow ocean currents. They can af fect their dispersal both through vertical and horizontal movements and this will change the prey availability to their predators. While existing NFR-projects already model seabird-fish interactions under various climatic states with state-of-the-art mode l components, they would greatly benefit from improved model parameterizations of larval behavior. Here we propose to combine a unique field and laboratory observation platforms that, together, will add substantially to our knowledge of these critical asp ects of the early life history of a keystone fish species in Norwegian waters, Atlantic cod. Specific objectives are to (1) provide and analyze in situ measurements of swimming and orientation of the early life stages and (2) elucidate the in situ behavio ral responses of cod larvae, as individuals and in groups, to a combination of proximal cues. This information is complementary to observations on the sensory capabilities and behavior of cod larvae that are generated in the laboratory and/or from acousti c measurements. Furthermore, we will 3) communicate through publications how new knowledge on larval behavior gained through the experiments described above may be included in existing coupled physical-biological models involving early stages of cod. Key questions to address: Are cod larvae orienting vs. swimming at random when in open water? If larvae do orient, when during development does this begin? Where do they orient, i.e. towards what location? Are multi-modal stimuli providing useful information for detection, navigation and nursery habitat localization? What are these stimuli? How do swim speed and swim time compare in the field vs. laboratory observations?