title: Mortality and recovery of runt white sturgeon (Acipenser transmontanus) in a commercial farm in California, USA.
abstract: We investigated the effect of raising runt white sturgeon (Acipenser transmontanus) separately from dominant fish during the initial stages of grow-out in a commercial farm. Runt fish are poor-growers, have underdeveloped muscle mass, swim slowly and are more-frequently found at the top of the water column. The objective of the study was to describe the mortality and recovery rates (and their determinants) of white-sturgeon runts after separating them from dominant fish. Runt white sturgeon were stocked into twelve 2 m x 2 m rectangular tanks and graded periodically during a follow-up of 46-102 days. Overall mortality rates ranged from 0.3 to 7 dead fish per 1000 sturgeon-days at risk and overall recovery rates from 3.9 to 13.5 recovered fish per 1000 sturgeon-days at risk. Period-specific mortality and recovery rates increased over time. The period-specific mortality rates for all three periods were significantly higher for tanks of runts originating from grow-out tanks with high mortality (p-values: first period = 0.06; second period = 0.09; third period = 0.03), but were similar for tanks of runts of high- and low-mean initial weight. The period-specific recovery rates were significantly higher in runts originating from high-mortality grow-out tanks only for the third period (p = 0.05) but not the first and second periods (p-values = 0.33 and 0.25, respectively). Recovery rates were significantly higher in the higher-mean-weight runts tanks for the first and third period but not for the second (p-values: first period = 0.02; second period = 0.65; third period = 0.06). We concluded that the proportion of runts that recover during a 46-89 day period is substantial (16-58%); therefore, it might be worthwhile growing such fish separately in a fish farm for about three months. Financial analysis showed that this practice was profitable, if the value of white sturgeon fish for the farm exceeded $2.05 per kg.
authors.affiliation: Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis 95616, USA. mmgeorgiadis@ucdavis.edu
authors.forename: M P
authors.initials: MP
authors.lastname: Georgiadis
authors.forename: R P
authors.initials: RP
authors.lastname: Hedrick
authors.forename: W O
authors.initials: WO
authors.lastname: Johnson
authors.forename: I A
authors.initials: IA
authors.lastname: Gardner
mesh_terms: D000820:Animal Diseases; D000818:Animals; D017756:Aquaculture / Q000191:economics*; D005376:Financial Management; D005399:Fishes / Q000254:growth & development; D009026:Mortality; D016019:Survival Analysis