Linear decline in red snapper (Lutjanus campechanus) otolith Δ14C extends the utility of the bomb radiocarbon chronometer for fish age validation in the Northern Gulf of Mexico

Abstract

Radiocarbon (Δ14C) was analyzed in northern Gulf of Mexico (nGOM) red snapper (Lutjanus campechanus) otolith cores (n = 23), otolith edge samples (n = 12), and whole age-0 otoliths (n = 9), with edge samples and whole age-0 otoliths constituting known-age samples. There was no significant difference in the linear relationship of Δ14C versus year of formation between regional corals and known-age otolith samples, and a linear regression fit to the combined data from 1980 to 2015 extends the utility of the bomb radiocarbon chronometer for age validation. The entire regional coral and known-age otolith data set (1940 to 2015) was then utilized as a reference series to validate otolith-derived red snapper age estimates for cored otolith samples. A loess regression was fit to the reference data and then the sum of squared residuals (SSR) was computed from predicted versus observed birth years for cored adult otolith samples. This process was then repeated for ages biased ±1–4 years. Ages with no bias applied had the lowest SSR, thus validating red snapper age estimates and demonstrating the utility of the combined regional coral and known-age red snapper otolith Δ14C time series for age validation of nGOM marine fishes.

Bomb Radiocarbon Age Validation of Warsaw Grouper and Snowy Grouper

“…This radiocarbon chronology is consistent across multiple hermatypic coral reference series from the western Caribbean Sea and Gulf of Mexico: Belize (Druffel 1980), Flower Garden Banks (Wagner et al 2009), Florida Keys (Druffel 1989), and Puerto Rico (Moyer and Grottoli 2011). In addition, more recent work on fish otoliths shows that the radiocarbon decline rate has remained constant into the early 2000s (Cook et al 2009;Andrews et al 2013;Barnett et al 2018).…”

“…), and Red Snapper (Barnett et al. ) from 1978 through the early 2000s. Rate of decline was not significantly different among the three species (analysis of covariance [ANCOVA] slope test: F = 0.35, df = 2, P = 0.70); however, Warsaw Grouper had lower‐magnitude values than Red Snapper ( ANCOVA intercept test: F = 51.4, df = 1, P < 0.001).…”

“…Warsaw Grouper and Snowy Grouper Δ 14 C values were visually compared to a spline model (RStudio, package "mgcv") developed from reference radiocarbon chronologies for hermatypic corals between 10-and 20-m depth from the Flower Garden Banks National Marine Sanctuary (Wagner et al 2009) and the Florida Keys (Druffel 1989) and for two fish species, the Speckled Hind Epinephelus drummondhayi (Andrews et al 2013) and Red Snapper Lutjanus campechanus (Barnett et al 2018). The two coral radiocarbon chronologies were chosen based on their geographic proximity to our study area; the fish chronologies were selected to extend the reference series into the present.…”

“…) and Red Snapper Lutjanus campechanus (Barnett et al. ). The two coral radiocarbon chronologies were chosen based on their geographic proximity to our study area; the fish chronologies were selected to extend the reference series into the present.…”

Fisheries Volume 44 Number 11 November 2019

“…This radiocarbon chronology is consistent across multiple hermatypic coral reference series from the western Caribbean Sea and Gulf of Mexico: Belize (Druffel 1980 ), Flower Garden Banks (Wagner et al 2009 ) , Florida Keys (Druffel 1989 ), and Puerto Rico (Moyer and Grottoli 2011 ). In addition, more recent work on fi sh otoliths shows that the radiocarbon decline rate has remained constant into the early 2000s (Cook et al 2009 ;Andrews et al 2013 ;Barnett et al 2018 ).…”