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Results for “Journal of Applied Aquaculture”

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USGS2011

Occurrence of antibiotic resistance and characterization of resistant genes and integrons in Enterobacteriaceae isolated from integrated fish farms south China

Antibiotics are still widely applied in animal husbandry to prevent diseases and used as feed additives to promote animal growth. This could result in antibiotic resistance to bacteria and antibiotic residues in animals. In this paper, Enterobacteriaceae isolated from four integrated fish farms in Zhongshan, South China were tested for antibiotic resistance, tetracycline resistance genes, sulfonamide resistance genes, and class 1 integrons. The Kirby-Bauer disk diffusion method and polymerase chain reaction (PCR) assays were carried out to test antibiotic susceptibility and resistance genes, respectively. Relatively high antibiotic resistance frequencies were found, especially for ampicillin (80%), tetracycline (52%), and trimethoprim (50%). Out of 203 Enterobacteriaceae isolates, 98.5% were resistant to one or more antibiotics tested. Multiple antibiotic resistance (MAR) was found highest in animal manures with a MAR index of 0.56. Tetracycline resistance genes ( tet (A), tet (C)) and sulfonamide resistance genes ( sul2 ) were detected in more than 50% of the isolates. The intI1 gene was found in 170 isolates (83.7%). Both classic and non-classic class 1 integrons were found. Four genes, aadA5 , aadA22 , dfr2 , and dfrA17 , were detected. To our knowledge, this is the first report for molecular characterization of antibiotic resistance genes in Enterobacteriaceae isolated from integrated fish farms in China and the first time that gene cassette array dfrA17-aadA5 has been detected in such fish farms. Results of this study indicated that fish farms may be a reservoir of highly diverse and abundant antibiotic resistant genes and gene cassettes. Integrons may play a key role in multiple antibiotic resistances posing potential health risks to the general public and aquaculture.

Zhongshan↗

USGS2014

Survival of hatchery Gulf sturgeon ( Acipenser oxyrinchus desotoi Mitchill, 1815) in the Suwannee River, Florida: a 19-year evaluation

An experimental release of 1192 hatchery-reared, individually PIT tagged, 220 days old (296–337 mm TL) Gulf sturgeon, Acipenser oxyrinchus desotoi , was undertaken in 1992 in the Suwannee River, Florida. The original objectives of the 1992 release experiment were to: (1) evaluate survival rate of cultured Gulf sturgeon in the wild vs survival rate of their wild 1992 cohort counterparts, (2) determine the differential effect of release site within the river upon long-term survival, and (3) evaluate comparative growth rates of recaptured hatchery vs captured wild 1992 cohort Gulf sturgeon. The present investigation addressed those original objectives, plus an additional fourth objective: (4) evaluation of hatchery fish recapture rate change over the 19-year experiment. The primary objective was to determine efficacy of potential conservation aquaculture for this species in terms of long-term survival in the wild. Follow-up 1993–2011 gill net sampling in freshwater reaches (rkm 4–237) and the estuarine river mouth (rkm −6 to 4) yielded recaptures representing 13.0% of the total released. Mean annual hatchery fish mortality (including emigration) rate estimated for the 19-year period (1993–2011) was more than twice that for same cohort wild fish. Mark-recapture survival probability (phi) for hatchery fish, 1993–2011, was substantially lower (0.733) than for their wild counterparts (0.888). Mean annual hatchery fish recapture rate, as a percentage of all 1992 cohort fish recaptures, declined significantly after age-7, coinciding with age of onset of migration into the open Gulf of Mexico. Hypothesized causal factors may be differentially lower fitness in the marine habitat or permanent outmigration due to natal river imprinting failure. Hatchery fish recapture rates varied significantly for fish from the ten release sites, being highest near the river mouth, and lowest for the furthest upriver sites in the Suwannee River and its Santa Fe River tributary. Hatchery fish also displayed a significantly lower growth rate than their wild counterparts through age 3000 days. Cumulative hatchery fish mortality of 99.87% over 19 years predicts <3 individuals would have survived through 2011. From the results of the 1992 release experiment, hatchery supplementation as a Gulf sturgeon conservation measure does not appear to be an effective option.

Florida↗

USGS2024

Black carp Mylopharyngodon piceus (Richardson, 1846) mouth gape and size preference of a bivalve prey

Black carp Mylopharyngodon piceus (Richardson, 1846) have been widely used as biological control of snails in aquaculture and were imported to the United States in the 1970s and 1980s for this purpose. Prior research emphasizes the species’ propensity to control gastropods, but since subsequent escape and establishment of black carp in portions of the Mississippi River Basin, concerns now focus on the numerous endangered and endemic bivalve species upon which black carp may predate. Black carp mouth gape may limit predation on larger bivalves, but bite force is also a factor. We used regression of fish length to mouth gape of wild-caught black carp and compared these results to tank forage size preference trials with bivalve prey Corbicula fluminea clams. Wild-caught black carp ranged from 429 to 1580 mm total length, a size range larger than measured in previous studies. Regression of fish length and mouth gape indicated greater variability among sizes, as expected from wild versus cultured populations. Clam consumption was size-dependent. Black carp commonly engulfed but did not consume the largest clams in tank feeding trials. Shell width was a better predictor of successful consumption than length or height. Predation was restricted at sizes less than the mouth gape of test black carp as observed by individuals engulfing but failing to consume prey. This result indicates that either bite force or the pharyngeal apparatus gape (i.e., the distance between the pharyngeal teeth and keratinous pad) limited successful crushing of engulfed shells. Bivalve predation by black carp is limited by both a fish’s ability to engulf prey and the ability to fracture the shell of larger prey items that cannot be broken or swallowed whole. The results of this research may be used to assess potential prey sizes of wild black carp and anticipated effects of predation on bivalve communities.

Journal of Applied Ichthyology↗