A New PCR-Based Method Shows That Blue Crabs (Callinectes sapidus (Rathbun)) Consume Winter Flounder (Pseudopleuronectes americanus (Walbaum))

Abstract

Winter flounder (Pseudopleuronectes americanus) once supported robust commercial and recreational fisheries in the New York (USA) region, but since the 1990s populations have been in decline. Available data show that settlement of young-of-the-year winter flounder has not declined as sharply as adult abundance, suggesting that juveniles are experiencing higher mortality following settlement. The recent increase of blue crab (Callinectes sapidus) abundance in the New York region raises the possibility that new sources of predation may be contributing to juvenile winter flounder mortality. To investigate this possibility we developed and validated a method to specifically detect winter flounder mitochondrial control region DNA sequences in the gut contents of blue crabs. A survey of 55 crabs collected from Shinnecock Bay (along the south shore of Long Island, New York) in July, August, and September of 2011 showed that 12 of 42 blue crabs (28.6%) from which PCR-amplifiable DNA was recovered had consumed winter flounder in the wild, empirically supporting the trophic link between these species that has been widely speculated to exist. This technique overcomes difficulties with visual identification of the often unrecognizable gut contents of decapod crustaceans, and modifications of this approach offer valuable tools to more broadly address their feeding habits on a wide variety of species.

Piscivory in age-0 summer flounder Paralichthys dentatus with a focus on predator-induced mortality of post-settlement winter flounder Pseudopleuronectes americanus

“…DNA quality values (A260/A280) were comparable across tissue types (1.94 ± 0.27; range = 0.88−3.20). The speciesspecific primer set used in this study (WF208; Collier et al 2014) consistently amplified DNA from fieldcollected (non-consumed) winter flounder, and conversely, no amplification occurred for field-collected summer flounder or non-target fish and invertebrate prey. With respect to prey recovered from summer flounder stomachs, PCR products were observed in 58.8% of the consumed winter flounder (10 of 17 samples), and 3.3% of the unidentified fish prey resulted in amplification of target DNA (2 of 60 samples).…”

“…For example, in this study, the majority of fishes encountered in the stomachs of summer flounder were unrecognizable to a detailed taxon, and 'unidentified fish' routinely accounted for the largest component of the summer flounder diet (% weight or volume dietary contribution ~12−21%; Festa 1979, Link et al 2002, Sagarese et al 2011. The molecular genetic technique used in this study offers a supplementary approach to analyzing predator stomach contents by testing for the presence of intraspecific genomic DNA (Collier et al 2014). The efficacy of this approach is contingent on minimizing errors in analysis associated with false-positive and false-negative results.…”

“…A species-specific polymerase chain reaction (PCR)based method was used to amplify a 208 bp sequence of winter flounder DNA from prepared samples. The oligonucleotide primers implemented in this study (WF208) were first identified by Collier et al (2014) and were synthesized by Integrated DNA Technologies (Coralville, Iowa, USA). The WF208 primer set targets the mitochondrial non-coding control region (D-loop) of the winter flounder genome (GenBank accession number U12068), with 4 sections of the D-loop used to create the forward and reverse primers (Collier et al 2014).…”

“…The oligonucleotide primers implemented in this study (WF208) were first identified by Collier et al (2014) and were synthesized by Integrated DNA Technologies (Coralville, Iowa, USA). The WF208 primer set targets the mitochondrial non-coding control region (D-loop) of the winter flounder genome (GenBank accession number U12068), with 4 sections of the D-loop used to create the forward and reverse primers (Collier et al 2014). The PCR-based and gel electrophoresis methods described herein follow the protocol of Collier et al (2014) with minor modifications.…”

“…The WF208 primer set targets the mitochondrial non-coding control region (D-loop) of the winter flounder genome (GenBank accession number U12068), with 4 sections of the D-loop used to create the forward and reverse primers (Collier et al 2014). The PCR-based and gel electrophoresis methods described herein follow the protocol of Collier et al (2014) with minor modifications. A 12.5 µl small-scale PCR reaction was initiated by combining 10.5 µl of 2× MyTaq Red DNA polymerase (Bioline USA), 0.5 µl of each 10 µM WF208 primer, and 1 µl of template DNA.…”