Particle retention during respiration and particulate feeding in the suspension-feeding blackfish,Orthodon microlepidotus

Abstract

Juvenile blackfish (Orthodon microlepidotus) retained styrene microspheres (30–90 μm) during respiration in the absence of food. The fish retained significantly more microspheres when particulate feeding on Artemia adults, suspension feeding on Artemia nauplii, or in the presence of Artemia extract than when respiring in the absence of food. The frequency distribution of microsphere sizes retained during respiration did not differ significantly from that retained during feeding, a result that is consistent with the hypothesis that the site and method of particle retention during respiration and particulate feeding do not differ from those operating during suspension feeding. There was significant interindividual variability in the number of particles retained. Some individuals retained consistently fewer microspheres than other individuals of similar size and age, suggesting that further study is needed to quantify interindividual variation in other factors (e.g., stroke volume, ventilation rate, or mucus secretion) that have the potential to affect particle retention rates. Our results have implications for the energetics of suspension-feeding fishes, the impacts of suspension-feeding fishes on plankton communities, and the exposure of these fishes to toxic phytoplankton strains and particle-bound organic chemicals.