Ontogeny of Orientation during the Early Life History of the Pelagic Teleost Mahi-Mahi, Coryphaena hippurus Linnaeus, 1758

Abstract

Understanding the orientation behavior and capabilities in early life history (ELH) of fishes is critical for studying their dispersal but has, surprisingly, never been tested in any pelagic species. We here investigate the ontogeny of orientation and swimming abilities of the pelagic Coryphaena hippurus Linnaeus, 1758 larvae, hereafter mahi-mahi, through their ELH stages using the Drifting In Situ Chamber (DISC) in a laboratory setup. The DISC was deployed in a large (3 m3) circular aquarium in order to control the stimulus perceived by the fish and to identify behavioral response at the individual, developmental stage, and population levels. A total of 79 individual ranging from 7 to 23 days post hatch and from preflexion to early juvenile stages were exposed to a directional light mimicking the sun’s position. Orientation towards the light direction was tested by switching the light by 180° among trials. To compare the orientation among development stages, we scaled the directionality by the swimming ability, therein defined as “directionality competence”. The results show that while mahi-mahi directionality competence increases through ontogeny, they acquire a positive and directional phototaxis behavior at the flexion stage. This potential solar orientation is kept through the early juvenile stage. Mahi-mahi may thus be able to use the sun as a compass in the open ocean as observed in the larval stages of demersal species seeking for settlement habitats. This ability notably develops before the improvement of their swimming capabilities, suggesting that early orientation—even at micro-scale—and swimming capabilities may be equally important for the survival of the ELH stages of pelagic species.

Evidence for a consistent use of external cues by marine fish larvae for orientation

“…Previous implementation of oriented (e.g., BRW) 22 , 35 – 38 and unoriented (e.g., CRW) 22 , 32 , 39 movement patterns in biophysical models of larval dispersal, demonstrated a significant effect on dispersal trajectories, settlement success and connectivity patterns 22 , 32 , 35 – 37 . The mathematical methodology behind such implementation has been extensively described 11 .…”

Ontogeny versus environmental forcing off the Southwest Atlantic Ocean: Nutritional condition of Fuegian sprat (Sprattus fuegensis) early stages

“…As larvae grow, they may prey upon a wider range of zooplankters which could account for the increase in their sRD (Dickmann et al, 2007). Increasing swimming activity and sensory acuity (e.g., orientation behavior) have also been reported to occur from preflexion to postflexion in other fishes including clupeids such as Sardina pilchardus , leading to improved foraging activities for larger larvae which in turn allow them to achieve high growth rates and better nutritional condition (Faillettaz et al, 2020; Grorud‐Colvert & Sponaugle, 2006; Silva et al, 2014; Teodósio et al, 2016). Also, density‐dependent mechanisms such as food limitation are key determinants for growth at high latitudes (Houde, 1989) and are known to affect other sprat nutritional condition (Baumann et al, 2007).…”

Perspectives on Larval Behaviour in Biophysical Modelling of Larval Dispersal in Marine, Demersal Fishes

“…Most studies show that most individual larvae swimming in the ocean do so in a directional manner, and there is little ontogenetic improvement in orientation precision [31], however, these were in situ studies limited to postflexion larvae of demersal species. A recent laboratory study on larvae of an oceanic species using both pre-and postflexion larvae showed an ontogenetic increase in orientation precision [81]. Significant directionality among individuals is not as widespread, but even when it is absent, such behaviour can have a meaningful influence on dispersal outcomes [50].…”