Pilot Field Trial to Evaluate SLICE (0.2% Emamectin Benzoate)–Medicated Feed to Reduce a Natural Infestation of Salmincola californiensis in Freshwater‐Reared Rainbow Trout

Abstract

Salmincola spp. infestations can adversely affect freshwaterreared salmonids. Control methods tested to date have had limited success; consequently, we conducted a pilot field trial to evaluate SLICE (0.2% emamectin benzoate [EB])-medicated feed to reduce a natural infestation of S. californiensis in freshwater-reared rainbow trout Oncorhynchus mykiss. Before the trial started, 96 of 1,500 rainbow trout broodstock held in a flow-through raceway were impartially captured, sedated, uniquely tagged, and returned to the raceway. Pretreatment S. californiensis infestation prevalence and intensity were 97% and 10.4 ± 7.6 (mean ± SD) adult female parasites per fish, respectively. Treatment was administered at 50 µg EB·kg fish −1 ·d −1 for 7 d. By the end of the trial (43 d posttreatment), infestation prevalence and intensity had decreased to 32% and 1.6 ± 1.1 adult female parasites per fish, respectively. These results suggest that SLICE-medicated feed can be used to reduce natural infestations of S. californiensis in freshwater-reared rainbow trout.

Temperature effects on hatching and viability of Juvenile Gill Lice,Salmincola californiensis

“…Gill lice mainly attach on the gills of infected fish; however, they are also found on fins, opercula and the mouth cavity (Kabata & Cousens ; Gunn et al . ; Hargis et al . ).…”

“…The negative effects of S. californiensis threaten native fish and hatchery stocks of fish (Modin & Veek ; Gunn et al . ; Hargis et al . ).…”

“…Adverse effects from gill lice in hatcheries were observed in the 1990s in Colorado (Gunn et al . ). In 2007, the kokanee salmon population declined significantly in Elevenmile Reservoir (Park County, Colorado) concurrent with gill lice infestation (J. Spohn personal communication, 2014).…”

“…are parasitic copepods that commonly infect salmonids (Kabata 1969;Conley & Curtis 1993). Gill lice mainly attach on the gills of infected fish; however, they are also found on fins, opercula and the mouth cavity (Kabata & Cousens 1977;Gunn et al 2012;Hargis et al 2014). Gill lice have been associated with deleterious effects on salmonids including growth inhibition, decreased fecundity, limiting oxygen uptake, delaying sexual maturation, lowering resistance to high temperatures and increasing mortality (Gall, Mcclendon & Schafer 1972;Chigbu 2001;Gunn et al 2012).…”

“…Gill lice mainly attach on the gills of infected fish; however, they are also found on fins, opercula and the mouth cavity (Kabata & Cousens 1977;Gunn et al 2012;Hargis et al 2014). Gill lice have been associated with deleterious effects on salmonids including growth inhibition, decreased fecundity, limiting oxygen uptake, delaying sexual maturation, lowering resistance to high temperatures and increasing mortality (Gall, Mcclendon & Schafer 1972;Chigbu 2001;Gunn et al 2012). Salmonids of the genus Oncorhynchus (distributed throughout the Pacific Rim) are infected by the gill lice species Salmincola californiensis (Dana, 1852) which makes them one of the most broadly distributed gill lice species (Kabata 1969).…”