R.C. Summerfelt | USGS Science

USGS2007

Effect of relative volume on radio transmitter expulsion in subadult common carp

Expulsion of surgically implanted radio transmitters is a problem in some fish telemetry studies. We conducted a 109-d experiment to test the hypothesis that variation in relative volume of transmitters surgically implanted in subadult common carp Cyprinus carpio would affect transmitter expulsion. We also necropsied fish at the end of the experiment to evaluate histological evidence for the mechanism of expulsion. Survival rate was high during our experiment; all control fish and 88% of the fish subjected to the implantation surgery survived. Expulsion rate was low; of the 23 fish that received transmitters and survived the experiment, only two (9%) expelled the transmitters. One of these expulsions occurred through a rupture of the incision and the other occurred via the intestine. Retained transmitters were all encapsulated by tissue, and most exhibited multiple adhesions to the intestine, gonads, and body wall. Adhesions were more numerous in fish that received larger transmitters. ?? Copyright by the American Fisheries Society 2007.

North American Journal of Fisheries Management↗

USGS1995

Partial replacement of fish meal with spray-dried blood powder to reduce phosphorus concentrations in diets for juvenile rainbow trout, Oncorhynchus mykiss (Walbaum)

Feeds formulated with 5.7, 11.4 and 22.7% spray-dried blood powder, also called blood flour (88.1% protein, 0.2% total phosphorus), were compared with a control diet with 49% herring meal (64% protein, 2.1% total phosphorus) and no blood powder for rearing juvenile rainbow trout. Oncorhynchus my kiss (Walbaum). Diets with 5.7, 11.4 and 22.7% blood powder contained 1.22,1.03 and 0.84% phosphorus, respectively, compared with 1.36% phosphorus in the control diet. Over 12 weeks, differences in mean specific growth (range 2.23-2.35 day −1 ) or feed conversion (range 1.04-1.09) among the four diets were not significant ( P > 0.05). Apparent digestibility of phosphorus in the diet with 22.7% blood powder was greater (45.2%) than that in the control diet (31.6%). Increases in phosphorus concentrations in the water in which trout were fed diets with blood powder (range 16-20 μg −1 total phosphorus) were 33-47% less ( P <0.05) than in tanks where trout were fed the control diet (30μg −1 total phosphorus). Feed formulations for rainbow trout prepared with 22.7% blood powder and 17.0% fish meal would contain 65.3% less fish meal and 38% less total phosphorus than present in the control diet, which was a representation of a modern feed formulation for rainbow trout.

Aquaculture Research↗