Ontogeny of dispersal-related behaviors in embryonic and larval burbot (Lota lota)

A common life history strategy of teleost fish is to produce planktonic larvae that rely on hydrodynamic forces for dispersal. As larvae develop, allometric growth patterns and larval behavior begin to play a significant role in dispersal. This study examines the ontogeny of dispersal behaviors in burbot (Lota lota) larvae in the Laurentian Great Lakes. Wild L. lota gametes were collected from Lake Superior tributaries and fertilized. L. lota were reared in a laboratory setting and monitored for embryonic buoyancy changes and larval phototaxis, startle response, and rheotaxis. Embryos remained negatively buoyant throughout but showed a significant increase in buoyancy as they approached hatching, with average sinking rates decreasing from 0.94 cm/s at 0 days post-fertilization (DPF) to 0.73 cm/s at 27 DPF. Larvae showed an increase in startle responses from 2.4 average responses per trial at 30 DPF to 6.0 average responses per trial at 70 DPF. Maximum velocity (cm/s) and proportion of startle responses increased significantly after swim bladder inflation. From 30 to 70 DPF, no phototactic light preference was detected. L. lota performed positive rheotaxis after swim bladder inflation. Rheotactic swimming bursts lasted between 0.21 and 34.42 s, with average positive bursts lasting 4.36 s and average negative bursts lasting 3.10 s. The inflation of the swim bladder may be critical for performing active dispersal-related behaviors. These results help elucidate the developmental timeline of L. lota dispersal behaviors that may inform conservation and management decisions for Great Lakes burbot populations.