Bottles as models: predicting the effects of varying swimming speed and morphology on size selectivity and filtering efficiency in fishes

Abstract

SUMMARYWe created physical models based on the morphology of ram suspension-feeding fishes to better understand the roles morphology and swimming speed play in particle retention, size selectivity and filtration efficiency during feeding events. We varied the buccal length, flow speed and architecture of the gills slits, including the number, size, orientation and pore size/permeability, in our models. Models were placed in a recirculating flow tank with slightly negatively buoyant plankton-like particles (~20-2000m) collected at the simulated esophagus and gill rakers to locate the highest density of particle accumulation. Particles were captured through sieve filtration, direct interception and inertial impaction. Changing the number of gill slits resulted in a change in the filtration mechanism of particles from a bimodal filter, with very small (≤50m) and very large (>1000m) particles collected, to a filter that captured medium-sized particles (101-1000m). The number of particles collected on the gill rakers increased with flow speed and skewed the size distribution towards smaller particles (51-500m). Small pore sizes (105 and 200m mesh size) had the highest filtration efficiencies, presumably because sieve filtration played a significant role. We used our model to make predictions about the filtering capacity and efficiency of neonatal whale sharks. These results suggest that the filtration mechanics of suspension feeding are closely linked to an animal's swimming speed and the structural design of the buccal cavity and gill slits. Supplementary material available online at

Area-restricted searching by manta rays and their response to spatial scale in lagoon habitats

“…Owen 1989), hence ARS behavior should lead to increased foraging rates (Sims & Quayle 1998). Furthermore, filtering rates and even prey selection (small versus large plankton) are going to be closely linked to the filter feeders' swimming speed (Paig-Tran et al 2011). For the mantas tracked in areas where plankton measurements were also taken, movement tortuosity increased with increasing plankton concentration, reaching a plateau at approximately 0.1 to 0.2 g m −3…”

“…Basking sharks did not respond to plankton patches < 0.48 g m −3 , suggesting that they have a higher feeding threshold. The higher threshold for basking sharks may be related to differences in size, swim speeds, and gill-raker morphology (Sims 1999, Paig-Tran et al 2011. While there are locations with predictably higher abundance of plankton (particular ledges), patches are likely to be found throughout the lagoons, and feeding has been observed at more central lagoon locations.…”

“…Mobile filter-feeding marine planktivores are unique in that movements of these animals are intimately coupled to their foraging; they must move in order to filter prey from their environment and thus their patterns of movement very closely reflect the ecology of their foraging (Paig-Tran et al 2011). Furthermore, with the capacity to directly measure the abundance of the planktonic prey of filter feeders, we can empirically examine whether postulated differences in forage do indeed create the patterns of movement we observe (e.g.…”

Diet of whale sharks Rhincodon typus inferred from stomach content and signature fatty acid analyses

“…However, considering the overwhelming observational evidence (e.g. Nelson & Eckert 2007, Motta et al 2010) and a mouth morphology adapted to filter feeding (Gudger 1941, Paig-Tran et al 2011, whale sharks clearly are not herbivores. The high occurrence of macroalgae in stomach contents is likely due to incidental ingestion of brokenoff floating pieces that do not get digested as quickly as invertebrate or fish prey.…”

Spatial and Temporal Variation of the Gill Rakers of Gizzard Shad and Silver Carp in Three Midwestern Rivers

“…In crossflow filtration, ingested water travels parallel to the gill rakers and collects a concentrated slurry of food particles destined for the esophagus (Sanderson et al 2001). In vortex filtration the slurry spins parallel to the gill rakers via centrifugal forces, rejecting filtrate out the gill rakers while concentrating food particles near the esophagus or resuspending them (Paig-Tran et al 2011). Hydrosol filtration, crossflow filtration, or vortex filtration are the likely means of retention of food particles in Silver Carp based on their ability to consume particles much smaller than the pores of their gill rakers (Adamek and Spittler 1984;Xie and Liu 1994).…”