Temporal and Ontogenetic Shifts in Habitat Use by Juvenile Pacific Cod (Gadus macrocephalus)
 

Figure 12.  Baited camera data showing the number of fish appearing over a 15 min set across depths over the course of a season (July-October).  Age-0 Pacific cod (P. cod) prefer the shallowest regions before moving into deeper water as age-1s.  Saffron cod (S. cod) were generally restricted to the nearshore as age-0 and age-1.

Figure 13.  Densities of juvenile cod caught in seine hauls by day and night.  No diel differences in catch were detected for age-0 Pacific or saffron cod.  Age-1 Pacific cod however did show a significant increase in catch during the night vs during the day.  Age-1 saffron cod increased in catch during the night as well, but the catch was not significantly greater than day catch densities.

Figure 14.  Results from the light gradient experiment indicated Pacific cod change their behavior in response to light with ontogeny.  The regression analysis indicated age-0 cod showed no change in distribution between gradient and non-gradient light treatments whereas age-1 juveniles demonstrated a strong avoidance of bright light.