Dataset DOI: 10.5061/dryad.hx3ffbgts

Description of the data and file structure

Fish were collected by state agency personnel associated with the Long-Term Resource Monitoring element of the Upper Mississippi River Restoration Program. Personnel collected fish in accordance with all applicable laws and the ethical treatment of fish per state agency guidelines. Fishes were collected with low-pulse DC electrofishing, hoop nets, and mini fyke nets using standardized sampling techniques. I used fish collected in one field season between June 15, 2020, and October 31, 202,0 to reduce the chance of temporal diet differences affecting the stable isotope ratios of individuals.  In the field, fish were measured for total length (nearest mm) and then frozen until muscle tissue extraction. I targeted twenty of the largest individuals collected from each reach and species for stable isotope analysis to minimize variation in resource use due to ontogenetic diet shifts.

I prepared muscle tissue per the standard stable isotope analysis protocol. Briefly, I thawed fish, excised an American quarter-sized plug of dorsal muscle tissue, and dried the muscle in a drying oven at 50°C for a minimum of 48 hours. I ground dried tissue to a fine powder using a mortar and pestle and stored it in 1.5 ml microcentrifuge tubes. I weighed 0.300-0.400 mg of powdered muscle into 3.5 x 5 mm tin capsules and stored the samples in a desiccator.

Samples were analyzed for C and N stable isotope ratios and %C and %N of the samples using a Thermo Delta V Plus Isotope-Ratio Mass Spectrometer with a Costech Elemental Combustion System 4010 at Southern Illinois University’s Mass Spectrometry Facility. Isotope ratios are provided in standard delta (δ) notation:

(1)  δ¹³C or δ¹⁵N (‰) = [(Rsample / Rstandard) -1] * 1000.

Delta notation was relative to international reference standards of Vienna Peedee belemnite for δ¹³C and atmospheric N for δ¹⁵N using USGS 40 (L-glutamic acid) and USGS 41 (L-glutamic acid, enriched) as isotopic reference materials. Analytical precision was ±0.12‰ for δ¹³C and ±0.14‰ for δ¹⁵N.

Percent C and N quantified the C: N of each sample to assess if lipid correction was needed. A C:N of > 3.4 indicated need for lipid correction (Post et al. 2007). The max C:N was 4.1, and only 27 individuals had a C:N > 3.4 (1% of gizzard shad, 13% of emerald shiner, 6% of bluegill, 4% of freshwater drum, and 7% of bowfin). I corrected these δ¹³C signatures using the aquatic organism equation:

(2)  δ¹³C_corrected = δ¹³C_measured – 3.32 + 0.99 * C:N

Files and variables

File: Mississippi_River_Fish_Stable_Isotope_and_Demographic_Data.csv

Description: 

Variables

• ID: Individual identification number of each fish that was common between habitat and demographic data and stable isotope data
• Species.Code: Four-letter code that represents the species' common name
• Species: Species common name
• Site: One of five river reaches in the Mississippi River system. MMR means Open River Reach of the Middle Mississippi River
• Sample.Date: Date the fish was sampled from the river
• deltaN: Delta nitrogen value of the dorsal muscle tissue sample in relation to a standard
• deltaC:  Delta carbon value of the dorsal muscle tissue sample in relation to a standard
• WeightN: Percent weight of nitrogen in the dorsal muscle tissue sample
• WeightC: Percent weight of carbon in the dorsal muscle tissue sample
• C:N: Carbon to nitrogen ratio using percent weights
• deltaC.Corrected: Corrected the delta carbon value if the C: N ratio was above 3.4
• Corrected: Whether the delta carbon value was corrected (Y) or not corrected (N)
• stratum: Habitat type in the Mississippi River where the fish was sampled. MCB-U = unimpounded main channel border; MCB-W = main channel border wing-dam; SCB = side channel border; BWC-S = Backwater shoreline; IMP-S = impounded shoreline; TRI = tributary mouth, TWZ = tailwater zone of navigation dam
• gear: Type of gear used to collect each fish. D = DC pulsed electrofishing, M = mini fyke net, F = fyke net, HL = large hoop net set, HS = small hoop net set
• period: sampling period each fish was collected in. 1 = June 15-July 31; 2 = August 1 - September 15; 3 = September 16 - October 31
• utmzone: UTM zone each fish was collected in
• utm_e: UTM east coordinates within theUTMm zone
• utm_n: UTM north coordinates within the UTM zone
• fish.length: Length of fish to the nearest millimeter as measured in the field upon capture
• fish.weight: Weight of fish to the nearest gram as measured in the field upon capture
• NA: Missing data

Code/software

Any program that will open a spreadsheet, such as Excel, is recommended.

Access information

Other publicly accessible locations of the data:

• None

Data was derived from the following sources:

• https://umesc.usgs.gov/data_library/fisheries/fish_page.html