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often exceed rates of fishing mortality (Tyrrell et al., 
2011). Despite the importance of diet data to ecosystem 
modeling, collection and analysis of such data are fraught 
with challenges, and incorporation of diet data in fishery 
management plans and ecosystem-based fisheries man- 
agement efforts has been limited. 
One challenge is that prey found in stomachs can be 
difficult to identify because of loss of distinctive features 
from digestion and overlapping meristics among closely 
related taxa. For example, fish prey consumed by gag 
(Mycteroperca microlepis) can be 50-75% digested within 
8 h of ingestion (Berens and Murie, 2008). Similarly, in 
other studies, species-level resolution for fish prey of 
red lionfish (Pterois volitans) (Harms and Appledoorn?) 
and gray snapper (Lutjanus griseus) (Longley and 
Hildebrand, 1941) could not be attained visually just 
5 h after ingestion. Capture of predators immediately 
following predation is difficult; therefore, prey items are 
commonly in advanced stages of digestion upon exam- 
ination. Calcified fish structures, such as otoliths, are 
less digestible than flesh and have been used to confirm 
species identification and even to infer prey size; how- 
ever, otoliths of many species are difficult to discern, and 
small otoliths can be digested rapidly (Granadeiro and 
Silva, 2000). 
For the reasons described in previous paragraphs, 
visual methods of diet analysis rarely provide complete 
taxonomic resolution and, as a result, are poor indicators 
of the species composition of the diets of piscivorous fish 
species. Poor taxonomic resolution of prey in stomachs 
of fish can obfuscate estimates of dietary specialization 
and overlap with concomitant species, which are known 
drivers of reef-fish community structure (Longenecker, 
2007). 
Results of recent studies indicate that taxonomic reso- 
lution in analysis of the diets of piscivorous predators can 
be improved significantly by using DNA barcoding that 
sequences the cytochrome oxidase I mitochondrial gene of 
prey items (Aguilar et al., 2017; Dahl et al., 2017). The 
main objective of our study was to improve resolution of 
diet composition for red snapper (L. campechanus), a com- 
mercially and recreationally valuable piscivorous predator 
along the Atlantic coast of the southeastern United States, 
by using DNA barcoding and visual methods of taxa iden- 
tification. Until now, the diet of red snapper in this region 
has been poorly known. Although there have been sim- 
ilar studies in the Gulf of Mexico (e.g., Szedlmayer and 
Brewton, 2019), predator—prey interactions are known to 
be ecosystem-specific (Hanson and Chouinard, 2002) and 
often are not comparable across regions. Improving the 
resolution of diet composition for red snapper will eluci- 
date potential effects of this species as a predator on other 
managed species and identify prey resources that could 
? Harms, C. A., and R. S. Appeldoorn. 2013. Digestion rate anal- 
ysis of fish prey items in lionfish (Pterois volitans). Poster pre- 
sented at the 66th annual meeting of the Gulf and Caribbean 
Fisheries Institute; Corpus Christi, 4-8 November. Gulf Caribb. 
Fish. Inst., Marathon, FL. 
potentially limit population growth along the Atlantic 
coast of the southeastern United States. 
Materials and methods 
Collection of predator samples 
During 2017 and 2018, samples of red snapper were col- 
lected through routine sampling of the Southeast Reef 
Fish Survey, a fishery-independent sampling program 
for which multiple organizations collaborate. The pri- 
mary sampling gear used by the Southeast Reef Fish 
Survey during this collection period was a chevron 
trap (Smart et al.°), baited with Atlantic menhaden 
(Brevoortia tyrannus). Chevron traps were deployed 
for ~90 min during daylight hours in sets of 6 traps, at 
least 200 m apart along live bottom habitat. Samples for 
diet analysis were selected by using a size class (total 
weight: 0—2500 g, 2501-7500 g, or >7500 g) and a lati- 
tude (1° bins from 31°N to 34°N) in a stratified sampling 
design. The first 3 specimens in each combination of size 
class and latitude whose stomachs were not everted or 
visibly damaged and that contained prey items were 
retained from each trap. Similarly, additional samples 
were opportunistically collected with unstandardized 
hook-and-line gear. 
Red snapper were weighed to the nearest gram and 
measured to the nearest millimeter in total length (TL), 
fork length, and standard length. Stomachs were excised 
at sea from the esophagus to the pyloric sphincter, individ- 
ually labeled and bagged, and placed in a freezer (—20°C) 
to halt digestion. 
Processing of stomach contents 
Frozen stomachs were immersed in water to thaw uni- 
formly. Once thawed, all contents from individual stom- 
achs were removed, with care taken to avoid scraping 
cells from the stomach itself. For examination of stom- 
ach contents of all fish captured in chevron traps, 
Atlantic menhaden were regarded as bait and discarded. 
Prey items of known bait species found in stomachs of 
fish captured with hook-and-line gear were also dis- 
carded (usually squid species or round scad, Decapterus 
punctatus). The remaining stomach contents were 
examined under a dissecting microscope and identified 
to the lowest taxonomic level possible, counted, and 
weighed (by wet weight to 0.001 g) by using a Sartorius* 
CPA228S analytical balance (Sartorius AG, Goettingen, 
Germany). A digestion code was assigned to each fish 
3 Smart, T. L., M. J. M. Reichert, J. C. Ballenger, W. J. Bubley, and 
D. M. Wyanski. 2015. Overview of sampling gears and standard 
protocols used by the Southeast Reef Fish Survey and its part- 
ners. Mar. Resour. Monit. Assess. Prect. Progr., MARAMP Tech. 
Rep. 2015-005, 14 p. [Available from website.] 
4 Mention of trade names or commercial companies is for identi- 
fication purposes only and does not imply endorsement by the 
National Marine Fisheries Service, NOAA. 
