Effect of Silver Carp Hypophthalmichthys molitrix and Freshwater Mussel Elliptio complanata Filtration on the Phytoplankton Community of Partitioned Aquaculture System Units

Abstract

Growers produce over 2.8 million kg of catfish (over $350 million wholesale revenue) annually in the United States. The microbiology of the phytoplankton community in culture water affects the growth and flavor of the catfish and is a consideration for growers. Filter feeders, like silver carp and freshwater mussels, in controlled growth systems are used to adjust the phytoplankton species. Our goal was to successfully control the algal populations with filter feeders in catfish production. We used silver carp Hypophthalmichthys molitrix as a filter feeder in Partitioned Aquaculture System (PAS) water. Silver carp completely eliminated the cyanobacteria Microcystis by size and biovolume reduction. This created the desired effect of small green algae dominating the algal community. A significant but opposite change was observed when freshwater mussels Elliptio complanata filtered PAS water resulting in Microcystis biovolume and size dominance in the PAS; a less desirable algal community. This study also showed an immediate shift in the phytoplankton community when silver carp and mussels were interchanged between PAS waters. The size‐selective filtration by the two filter‐feeding taxa was important in determining the composition of the PAS phytoplankton community, and it was apparent that filtration with silver carp successfully depleted undesirable algae.

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“…The ammonia level was higher in the control group than in the treatment groups containing mussels, but this difference was not significant (Table 1). Similar results were obtained in previous studies where lower concentrations of ammonia were recorded in ponds containing the mussel E. complanata (Mueller and et al, 2004) and the oyster C. gigas (Miranda et al, 2010), but no significant differences were observed between the treatment and control groups. McKenzie and Özbay (2010) also obtained results similar to ours but reported that ammonia levels occasionally increased significantly in the ponds containing mussels.…”

“…This supports the previous findings of Mueller et al, (2004) and Miranda et al, (2010). In contrast, McKenzie and Özbay (2010) recorded much higher concentrations of both nitrate and phosphate in the groups containing mussels than in the control group, although these differences were 99±1.00 Average mussel growth (mm) = Final lenght x width -Initial lenght x width Average mussel growth (g) = Final wet weight -Initial wet weight also not significant.…”

“…This indicates that the ammonia generated by the fish was converted into nitrite but that mussels removed this by filtering the particulate matter in the environment. Similarly, previous studies have found lower nitrite levels in tanks containing the mussel E. complanata (Mueller et al, 2004) and the oyster C. gigas (Miranda et al, 2010), although these concentrations were not significantly different from the control group. In contrast, McKenzie and Özbay (2010) reported higher nitrite levels in the treatment groups containing mussels, although these were also not significantly different from the control group.…”

“…Similar results were obtained for the Pacific oyster C. gigas (Miranda et al, 2010) and the freshwater mussel E. complanata (Mueller et al, 2004;McKenzie and Özbay, 2010), demonstrating that the water quality parameters are not affected by the taxon used for filtration (Mueller et al, 2004).…”

“…For example, Mueller et al (2004) previously examined the effects of the freshwater mussel Elliptio complanata and silver carp (Hypophthalmichthys molitrix) on water quality and plankton density in partitioned aquaculture systems housing growing catfish (Ictalurus punctatus), and McKenzie and Özbay (2010) examined the use of E. complanata as biomechanical filter in catfish ponds. Miranda et al (2010) also investigated the effects of Pacific oyster (Crassostrea gigas) and tilapia culture on TSS, ammonia, and plankton density in a recirculation system.…”